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Thread: GTM roll cage modifications and race car build log

  1. #41
    Senior Member mikespms's Avatar
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    Quote Originally Posted by kabacj View Post
    More solid progress this weekend.

    I tell you I must have spent 3 hours staring at this problem over the past two weeks. My goal is to add SCCA and NASA legal door bars to a car that can be street driven. Ideally I should be able to cover the bars and make them look less race car and more street car. Finally I don’t want the bars to make entry or exit any harder.

    The ideal way to attach door bars to the stock frame would put the bars right in the same plane as the current window and interior door frame. With this situation the door bars occupy the same space as the stock door frame. If you want working windows and doors this option is out. Several racing bodies also prohibit removal of the stock door framework. In order to install door bars you either need to make a bar that squiggles it way around the obstructions and spans a large distance, or you need to create new landing areas for the door bar structure.

    After considering all of the pros and cons I decided new structure to attach the door bars would be easier and stronger.

    The first problem was the rear verticals. I did not want to break the plane of the firewall and I also needed to avoid blocking my fuel tank install. The tank is so tight, I have no more then 1/8 clearance at the pinch points. I can just glue some rubber on to the frame to cushion the tank and it does not need any other mounting. (but I will mount it firmly)

    Now the verticals. The bottom of the tube lands right where stock corvette seat belts attach. I will not use those seat belt mounts so I cut off the plate. In order to make attaching the tube easier, I used the cut off pieces of seat belt mount to weld up a continuous horizontal plate to attach the vertical bar. It makes it easier to slide the bottom of the bar in from the front. It wedges in when its too long. This way I can sneak up on a tight fit.


    I cut and bent two symmetrical but mirror image vertical bars for the driver and passenger side.



    What’s cool is the vertical clears the stock cross brace but is just touching. I Debated cutting the cross brace out , but there is not much gain and its possible that the frame would pretzel if I took out that support. The frame is jig welded and I found it to be pretty symmetrical, however when its cut apart it will spring to relieve any pent up stresses.



    I ended up using the cross brace as another point to attach and stiffen the rear vertical.



    Next was the front vertical. I attached the bottom to the 2x2 square that runs across the foot box and the top of the tube to my window frame gusset. The gusset was an easier attachment point because I could more easily run a bead around the joint. I think it looks cool there too. With all this new structure the frame is starting to look like a fortress.



    In keeping with my street car/ stealth race car theme I can also hide these supports under the dash .

    Finally the whole point of adding the vertical bars is to add the horizontal door bars.

    The lower bar is a simple straight bar. It runs just slightly inside the door shell. The top bar is the tricky one. I am going to mock that one up because I think if done properly it might not obstruct the entry into the car at all and yet still meet the safety requirement. I have seen corvette bars where the top bar is an S bend allowing the front half of the door bar to be lower. This is key in the GTM because swinging your feet out is a little tricky. A high set of door bars in this area is going to make it very difficult to get out.



    Getting out with the X style door bars would be very hard. Basically you would need to crawl out or be very good at yoga.

    All the vertical elements were welded up. Next weekend is mock up, cutting,and fitting the horizontal elements.


    John
    003.JPG
    Hi John,
    Looking at the strings running along the door, and cant tell how high they are. Did you check if the seat is going to fit in the passenger side? In my car on the passenger side I had less than a 1/4 in. clearance between the seat and the door and the tunel panel. I made a new tunel panel and gained almost 2 in.,it allowed me to move the seat to the center so that I could operate the power seat switch on the side of the seat. It may give you the room you need to run that tube and be able to fit your seat.
    Mike
    Attached Images Attached Images

  2. #42
    Member kabacj's Avatar
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    Talking about a tall guy not fitting in a racing gtm.

    A tall guy needs a GT 43

    http://m.youtube.com/watch?feature=mhee&v=UzC-mQoY3aI

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  3. #43
    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    003.JPG
    Hi John,
    Looking at the strings running along the door, and cant tell how high they are. Did you check if the seat is going to fit in the passenger side? In my car on the passenger side I had less than a 1/4 in. clearance between the seat and the door and the tunel panel. I made a new tunel panel and gained almost 2 in.,it allowed me to move the seat to the center so that I could operate the power seat switch on the side of the seat. It may give you the room you need to run that tube and be able to fit your seat.
    Mike
    Good point Mike. I have not tested the passenger seat honestly. The lower bar is under the widest part of the seat so I was guessing that it would be fine. Im surely going to check it out. Thanks for the tip.


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  4. #44
    Member kabacj's Avatar
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    Quote Originally Posted by Hankl View Post
    John,

    It looks like you're going towards the SIB's we have in the Coupe, NICE WORK!!

    Hank
    Yep Hank, I think your coupe design slightly modified will work well in the gtm. Like what you guys have done, I still want to maintain the stock door function.

    Ill post a mock up side view to get everyone's opinion of my plan.

    John
    XTF #2
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    GTM # 344
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  5. #45
    Member kabacj's Avatar
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    Ok here is my attempt at door bars that are both safe for the track and also easy to exit and enter the car.



    and from the other side



    obviously these are rough mock ups, and i did not adjust the seat for ideal placement, however I was pretty happy with the outcome.

    Exit and entry is basically the same as without the bars. Just a little higher to get your first foot out.

    I have seen racing corvettes with the same setup as they also have the problem of exit and entry when the front half of the door bars are much higher.

    ill add verticals that tie the bars into the lower frame and to each other.

    What do you guys think? I am going to run the design by my local safety director as well.

    John
    XTF #2
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    GTM # 344
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    First track day April 2013

  6. #46
    Member kabacj's Avatar
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    I added the lower door bars on both the passenger and driver side. Both bars are as far outboard as possible while not intersecting with the diagonal square tube.

    Here is a view from the top



    here is a view from the side.



    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  7. #47
    Senior Member mikespms's Avatar
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    Quote Originally Posted by kabacj View Post
    I added the lower door bars on both the passenger and driver side. Both bars are as far outboard as possible while not intersecting with the diagonal square tube.

    Here is a view from the top



    here is a view from the side.



    John
    Hi Jonh,
    Are you going to put the other tubes in also?
    Drivers side looks good, where you able to fit the seat on the passenger side with the tunel panel in ?
    Mike

  8. #48
    Senior Member VD2021's Avatar
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    John,
    More very impressive work.

    How tall is the Gentlemen in the picture?
    R/s
    Vidal
    CURRENT STATUS: Interior Rework and Bodywork.
    GenII GTM #331. Delivered (23/9/10)
    BUILD LOG AND WEBSITE:
    http://gtmbuild.weebly.com/ .

  9. #49
    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    Hi John,
    Are you going to put the other tubes in also?
    Drivers side looks good, where you able to fit the seat on the passenger side with the tunnel panel in ?
    Mike
    Hey Mike,

    Yes I do plan on putting a top tube in. I am experimenting with configurations that sill allow you to enter and exit without lifting your foot so high it would hit the dash. I noticed the issue with the passenger side and the tunnel. I have not tried to fit the seat in. Its on today's list of things to do.




    Quote Originally Posted by VD2021 View Post
    John,
    More very impressive work.

    How tall is the Gentlemen in the picture?
    Hi Vidal.

    The driver (me) is 5'7". I am going to have my dad 5' 11' also try out the adjustable seat to see if we can also fit him in with required 2" to the upper roll cage.

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  10. #50
    Member kabacj's Avatar
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    After lots of thinking, I realized that the S bend top bar would be less strong then a straight tube. (see post 45 for a picture) Of course the S would bend over instead of pulling the verticals in.
    I spoke with "Hank" from the forum here who has much more experience at this than I. He pointed out that the top of the S would be near my helmet and its better to hit your head on a net then a bar.

    So change of plans. I decided to go back to basics. I built a cage in tape to see how it would relate to other parts.



    That looked pretty good so i made the top bar out of steel. I decided to go up to .120 wall tubing for the door bars. A few extra lbs here are worth the extra stiffness in my book.




    The front tips down so I can still exit in a dignified manner when driving on the street.

    I was thinking of making the passenger bar even lower. I will not have passengers on the track and for street use this bar is easy to get over. The last thing I want to hear is my wife complaining that its hard to get in and out of the car.

    note the front of the passenger bar nearly intersects with the lower door bar.



    I am not sure if this is NASA or SCCA legal. If anybody knows I wold be glad to hear it.

    I will run both sides by my local scrutineer to make sure he is happy with it before I weld it in.

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  11. #51
    Trick Tool Maker, Super Moderator Hankl's Avatar
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    John,

    I think you're pretty safe, they might just comment on the height difference between the driver and passengers side, but you are complying with the intent of the rules, looks GREAT!!

    Hank
    “If you didn’t have enough time to do it right the first time. How come you always have time to go back and do it again?” FFR1000186CP

    Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car.
    Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

  12. #52
    Senior Member flotowngtm's Avatar
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    John,

    Is it possible to make the top door bars removable? Or would it not pass inspection?

    And that straight bar looks much stronger!

  13. #53
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    Definitely looks better than the S bar.

    I would consider leaving the passanger side upper bar out entirely. You have tons of crush space between you and the passanger door, and including the lower frame rail in the equation, you already have two side bars there. If they say anything, just run a couple of stringers from upper to lower and you are good.

    Still not sure if the main hoop flies, but if the scrutoneer says it's good...then it's good!
    www.myraceshop.com

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  14. #54
    Member kabacj's Avatar
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    Quote Originally Posted by Hankl View Post
    John,

    I think you're pretty safe, they might just comment on the height difference between the driver and passengers side, but you are complying with the intent of the rules, looks GREAT!!

    Hank

    Thanks Hank. I could not have done it without your help.


    Quote Originally Posted by flotowngtm View Post
    John,

    Is it possible to make the top door bars removable? Or would it not pass inspection?

    And that straight bar looks much stronger!
    Yes I was originally planning on making the bars removable. Here is the problem. To make the bars removable you compromise strength and I was not able to come up with a mounting method that allowed for a clean removal and be as strong as welded in bars. To make a very strong removable bar you need to have both the horizontal bars and the vertical stringers as one piece. This needs to mount to the uprights around the door frame. I was not able to come up with a solution that was both strong and elegant. I think the door bars actually add to the car. They look no nonsense and hardcore. I like that. They are actually not hard to enter and exit over. Yeah the whole S bend thing was an idea that was given to me by the chief scrutineer. It works well for the corvette, but after seeing both in the GTM I think the straight bars both are strong and look nicer.

    Quote Originally Posted by crash View Post
    Definitely looks better than the S bar.

    I would consider leaving the passanger side upper bar out entirely. You have tons of crush space between you and the passanger door, and including the lower frame rail in the equation, you already have two side bars there. If they say anything, just run a couple of stringers from upper to lower and you are good.

    Still not sure if the main hoop flies, but if the scrutoneer says it's good...then it's good!

    Good idea to leave the passenger bar out. The lower bars sorta form an X and might pass as they are. I agree its not a safety thing.

    Ill let you know on the main hoop deal.

    Thanks for the feedback guys.


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  15. #55
    Member kabacj's Avatar
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    Nearly done.

    I finished constructing and welding both the passenger and driver door bars.


    My concern on the passenger side was that entry and egress would be nearly as easy as stock. Although I most likely could have gotten away with a less structure on the passenger side, I am a sucker for symmetry. Having door bars on the driver side and nothing on the passenger side would bother me. Since they actually are very easy to get over I was pleased how they looked when added. Regarding entering and exiting. The bars don't actually get in the way. The car is so low the passenger can just sit in the seat then swing their legs in. My grandma could do it.


    passenger



    and with the body on.



    The driver side.



    and with the body.



    Funny how these things go. Now that its done I look at it and say of course you would do it that way. Prior to starting I was really unsure how the whole thing would go together.

    Since it has been so humid I coated the whole cage with POR 15 metal prep. A great idea I borrowed from the competition coupe build. The metal prep keeps the bare tubes from rusting while the final welding is completed.


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
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    First track day April 2013

  16. #56
    Trick Tool Maker, Super Moderator Hankl's Avatar
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    SWEET!!

    Hank
    “If you didn’t have enough time to do it right the first time. How come you always have time to go back and do it again?” FFR1000186CP

    Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car.
    Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

  17. #57
    Member kabacj's Avatar
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    Unfortunately vacation has gotten in the way of the build.

    I was able to make a bit of progress today however with the addition of 1 inch square tube that re enforces the area that I needed to remove in order to install my single passenger side fuel tank. This braces the frame and I think reasonably equates to the strength of the structure as designed by factory five.



    My goal with the tank was to get as much capacity as possible with the goal of 18 gallons. Because of that I made the tank as high as I could and still allow filling using the stock filler location. The shape of the tank got in the way of the 1 inch tube I needed to add. I sorta knew this was going to be a problem, however I hoped I was going to come up with some way to re enforce the frame but not notch the tank. I could not think of anything that was as strong as the method I used so I needed to cut the tank.

    I bent up a little plate and welded it in.



    Ill loose a few ounces of capacity with that little cut out, but the 18 gallon number was just a target.

    I also cut the interior aluminum panels to fit around the new roll cage structure.

    John
    XTF #2
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    GTM # 344
    Build Start December 2010
    First track day April 2013

  18. #58
    Senior Member flotowngtm's Avatar
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    John,

    Looking back in your post I see that you upped that side door bars to .120 tubing. What is the FFR tubing thickness? And did you go with the same size as FFR on all the other bars?

  19. #59
    Member kabacj's Avatar
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    Quote Originally Posted by flotowngtm View Post
    John,

    Looking back in your post I see that you upped that side door bars to .120 tubing. What is the FFR tubing thickness? And did you go with the same size as FFR on all the other bars?

    Hey Jason

    FFR use .120 wall tubing on their cage elements. I only used .120 wall on the door bars and foot protection as they obviously will need to resist a side load. Thicker is stronger.

    For all other parts I used .095. DOM. Most of the additional structure I added is not side loaded so I did not see much benefit from over sizing the tubing.

    095 DOM is the requirement for SCCA and NASA for cars up to 2500 lbs. Many street GTMs come in under this weight so I figure I'm pretty safe from the weight standpoint.

    Just to be clear since I left all of the FFR 1.5" round tube and only added tubing to meet SCCA/ NASA spec. I will end up with a cage thats mostly 120 wall with the support structure under the rear hoop in 095.



    John
    Last edited by kabacj; 07-23-2012 at 11:38 AM.
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  20. #60
    Member kabacj's Avatar
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    It was Christmas in August on Friday as my motor arrived. I had ordered a lift gate delivery but when the trucking company called and asked to schedule delivery next week I asked if I could pick it up. Sure they said. So I picked it up after work. Hmm small problem. How Do I get this giant box out of my truck without any help. Well I made like the pharaohs and got the box out of my truck . The engine crane was not high enough and it was too dark to build a gantry outside. Sure I could wait till Saturday when some buddies could help me carry it out of the truck but who has time to wait for that.

    After getting the motor out of the crate and installing all the parts needed to check clearance with my rear hoop supports, with the help of my 8 year old son we dropped the motor and tranasxle in.

    Boy is that nice to see.

    I have been waiting for quite a while for all the parts to arrive and I am pretty happy with how everything turned out.







    I had assumed that the motor mounts from my ls1 donor pallet would fit right on to the LS3 block. Nope. The right side hit one of the mounting bosses on the block behind the AC mounts. That was unexpected. So I modified the motor mount to clear the boss on the block and dropped the motor in. Seems to me like the motor is really far forward.

    I figured that if i put the transaxle in and if that fit properly the motor was in the right place.

    Well the transaxle mount has two sets of holes. One set forward (I used those) and one set about an inch father back. The motor fit perfectly with the mendiola transaxle attached.

    See how far forward my motor is? Nothing hits, but it sure is tight.



    Notice how close the top of the thermostat housing is. Sure there is plenty of room, (1/4 inch) but seems pretty close.

    Is this normal?

    John
    XTF #2
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  21. #61
    Senior Member Kempo's Avatar
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    Congrats John. That intake looks amazing.
    GenII GTM #354
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  22. #62
    Senior Member VD2021's Avatar
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    Very Nice! A work of art.
    R/s
    Vidal
    CURRENT STATUS: Interior Rework and Bodywork.
    GenII GTM #331. Delivered (23/9/10)
    BUILD LOG AND WEBSITE:
    http://gtmbuild.weebly.com/ .

  23. #63
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    Quote Originally Posted by kabacj View Post

    Notice how close the top of the thermostat housing is. Sure there is plenty of room, (1/4 inch) but seems pretty close.

    Is this normal?

    John
    John,

    My LS3 is exactly the same. Just a bit of clearance. I used much stiffer Pfadt motor mounts to minimize motor rocking because the clearance was so small.

    -Michael

  24. #64
    Senior Member flotowngtm's Avatar
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    cage WIP.jpeg
    Dosent even look like you could remove that Thermostat housing without jacking up the motor or something.
    Also I noticed that the horizontal bar that you had added to the center of the rear hoop is missing. Is the motor in the way. Or you just going to add it in latter. From the pics it looks like that bar would have to pass through the motor.

    It all looks great! Your engine bay is going to look spectacular!

  25. #65
    Trick Tool Maker, Super Moderator Hankl's Avatar
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    WOW! WOW! WOW! WOW!!!!

    Hank
    “If you didn’t have enough time to do it right the first time. How come you always have time to go back and do it again?” FFR1000186CP

    Understeer is when you hit the wall with the front of the car and oversteer is when you hit the wall with the rear of the car.
    Horsepower is how fast you hit the wall and torque is how far you take the wall with you.

  26. #66
    Member kabacj's Avatar
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    Quote Originally Posted by flotowngtm View Post
    cage WIP.jpeg
    Dosent even look like you could remove that Thermostat housing without jacking up the motor or something.
    Also I noticed that the horizontal bar that you had added to the center of the rear hoop is missing. Is the motor in the way. Or you just going to add it in latter. From the pics it looks like that bar would have to pass through the motor.

    It all looks great! Your engine bay is going to look spectacular!

    With help from folks on the forum here I was pretty sure that the cross bar was going to be close. I was also pretty sure it would fit with a standard intake, but I was concerned that the hillbornes would interfere. Turns out they do. there is a little linkage on the drivers side that would hit that cross bar. I could move the linkage on the intakes move the bar lower or I can move the motor back an 3/4 inch. Right now I am leaning toward moving the motor back a bit. It would most likely take less time then making a new cross bar with the compound cut on each end. I need to think about it for a week and do some more research.

    Moving the motor back will change the CG of the car slightly. Dont know if this is a good idea.


    Thanks for the compliments on the motor guys. The ITBs are surely more work then the stock GM intake, however I think they will be worth in both on the track and how they sound.. and how they look of course. Mast motorsports sorted them all out and tuned them for great drive ablity both on the street and track. Im going to thrash on this thing as hard as i can to get a first start as soon as possible.

    John
    XTF #2
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    GTM # 344
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    First track day April 2013

  27. #67
    Senior Member Kempo's Avatar
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    What power was Mast able to get out of that set up?
    GenII GTM #354
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  28. #68
    Member kabacj's Avatar
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    Quote Originally Posted by Kempo View Post
    What power was Mast able to get out of that set up?
    They built the motor to be bullet proof and got a nice power curve

    XTF #2
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  29. #69
    Senior Member Kempo's Avatar
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    That's a very nice power band. You should have one fast care there. I can only imagine how incredible that intake must sound at WOT.
    GenII GTM #354
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  30. #70
    Member kabacj's Avatar
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    Quote Originally Posted by Kempo View Post
    That's a very nice power band. You should have one fast care there. I can only imagine how incredible that intake must sound at WOT.
    Thanks Hugo.

    Yeah I grew up on individual throttle bodies on motorcycles. They were far less sophisticated then the mast/hillborne solution. But I just love how they look, sound, and drive.

    I also like the classic throw back.

    Of course I could have gone with even bigger hp and torque, but I don't know how much more could be used on a road course. And more importantly I'm pushing the mendiola transaxle power rating as it is.

    Sometimes it's easier and more fun to drive a car that has enough hp but is not too much. As if there is such a thing as too much hp.

    Can't wait to get out on the track with this setup.

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
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  31. #71
    Member kabacj's Avatar
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    With my motor and transaxle installed I had lots to consider regarding the cross brace under the rear hoop as well as the common ls3 install concerns. AC plug etc

    I briefly considered just calling the install good and moving on.. But knowing that a decision to leave things alone would bother me till I'm dead, I decided to move the motor back a bit.

    How hard could that be right? I considered my options. Modify the cast section of the mount that connects to the motor. Too time consuming. I considered modifying the rubber elastomer /vibration isolator from the donor. I purchased new ones so I cut the old ones apart.

    They are filled with oil! That was a surprise. Too bad because moving the mounting stud would be an easy way to move the motor a small amount. . I love how over engineered parts like this are. I figure its a blob of rubber. Wrong.

    The only reasonable option was to change the frame mounting point. The new position is only 7/16ths back and there is almost enough room to fill old hole and reddrill the mount. However the nut that mounts from the bottom would land on the inside corner radius of the cross brace edge.

    The easiest way to solve this was to cut a hole in the brace using a 1.5 inch hole saw. Install a 1.5 inch pipe scrap from the cage with a piece of plate welded to the top. Drill the plate and weld it in the cutout.



    This was very easy. I installed the new hole plugged the old hole and moved the outer edge of the stock frame outboard in one easy step. I think it's most likely stronger then the old setup.






    Next was the transaxle mount.

    This was easy. Cut some plugs from bar stock and welded the old holes closed.





    Re installed the motor and transaxle ( I'm getting good at it now with so much practice.) whew the holes lined up and the motor dropped right in.

    With everything in position I checked that the drive line was centered and used the sleeves that hold the transaxle mounting bushings from compressing as the bolts are tightened as drill guides. With this method the holes are perfect.



    After a three hours of experimenting the maybe 2 hours of fabrication my motor was 7/16ths more rearward

    This will give me clearance for my AC plug but more importantly it gives me more room for my fuel rail plumbing and un shrouds the intake bell mouths a bit. They were pretty close to the cage and might have had a negligible interaction from an airflow standpoint. Trivial you say? Maybe. I like to eliminate problems I don't even have. It's a mental problem .

    Next step was the cross brace. I flipped the valve covers from left to right. Took off the drivers side coil packs which are currently mounted with the stock ls3 mount. I mocked up and bent a new cross brace with radius bends at each end. I think I can make it all fit. It was late on Sunday and I was running short on patience. Time to put down the tools and step away from the build

    Sitting at a desk for 5 days will allow me to recharge for final sprint to finish of the cage mods.

    John
    Last edited by kabacj; 08-13-2012 at 08:51 PM.
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  32. #72
    Member kabacj's Avatar
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    The before and after shots of my motor relocation explained in the prior post.


    Before



    After


    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  33. #73
    Senior Member Kalstar's Avatar
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    What a work of art. Can't wait for that beast to be on a track.

  34. #74
    Member kabacj's Avatar
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    The final element of the cage that I needed to finish was the cross bar that spans the motor.

    My original plan was to make the bar cross right in front of the intake. Unfortunately my intake is bigger and higher then the stock ls intake. My first attempt made before the motor arrived did not fit.


    I installed the motor and decided to move it back almost 1/2 inch.

    Next was fitting the cross bar. Turns out with the motor back 1/2 inch I had plenty of room to install the cross bar. There were still obstructions from the fuel rail plumbing and throttle body linkage, but I was able to put small bends in each end of the cross bar and make it fit with miles of room to spare.






    I resisted my normal urge to make things as tight as possible to make removing and installing the motor easier.

    This weekend I also made an aluminum battery box/ hold down. Welded tabs on to the frame to securely mount the battery. I installed the gas pedal , installed the kooks exhaust (mounts need a bit of modification) installed the engine accessories, and planned out the removable V that goes over the motor.

    The key with this V structure above the motor is that I need to leave enough room to install an air box above the intakes as well as make the whole thing as light and strong as possible.

    Still lots and lots to do, but getting closer.

    John
    Last edited by kabacj; 08-22-2012 at 08:20 PM.
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  35. #75
    Senior Member mikespms's Avatar
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    Hi John,

    Awsome drive line and that roll cage looks to be very strong as is . Is that cross bar needed? It looks like is going to interfere with the window bulkhead and engine cover.

  36. #76
    Member kabacj's Avatar
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    Quote Originally Posted by mikespms View Post
    Hi John,

    Awesome drive line and that roll cage looks to be very strong as is . Is that cross bar needed? It looks like is going to interfere with the window bulkhead and engine cover.
    Hey Mike.

    Thanks for the compliment.

    Is the cross bar needed?... well for practical purposes. Probably not. For NASA/SCCA approval it does not hurt.

    From stress analysis of the frame with the added parts, the cage is much stronger then needed compared to the SCCA and NASA spec.

    The bar just adds a bit more strength and definitely increases the stiffness that prevents the rear hoop from racking sideways. That is the whole point of the SCCA and NASA cross brace that runs diagonally across the car.



    Much of the scrutineers decisions have some subjective element. The more overkill the solution looks the easier time I will have getting this thing approved. Thats my theory anyway.

    Regarding the window bulkhead and engine cover. It JUST fits over the bar. The lower bend in the bulkhead sits right on the bar and the engine cover fits on top pretty easily.

    That part of the fit is super tight... but since its easy to make it all fit it works.

    Good thing you pointed out how tight the first cross bar was. I would have ended cutting that one out if I welded it in.

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  37. #77
    Member kabacj's Avatar
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    Spent some quality time with the lathe today. I am working on the v shaped braces that go above the motor between the center of the rear roll hoop and the shock towers. I wanted to make my braces out of aluminum and I could not find aluminum ends that I liked so I decided to make them.

    I got some hex bar stock and spent a few hours removing metal.





    After quite a while I have 4 ends. Each brace will get one end with a hex and one smooth. The ends have left and right hand threads so I can simply spin the brace and add a bit of preload.

    As usual it took much longer then I planned. Tomorrow i will cut the steel tabs in order to attach the braces to the frame.





    John
    Last edited by kabacj; 08-30-2012 at 06:14 PM.
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  38. #78
    Senior Member Kempo's Avatar
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    Awesome job John!!! You really are a fabrication artist. Those are some impressive abilities you have there.
    GenII GTM #354
    Delivered (02/09/11)

  39. #79
    Member kabacj's Avatar
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    Thanks Hugo. I just get carried away sometimes.

    Wrapping up the welding projects I needed to modify the kooks exhaust mount. The Kooks comes with a bracket that wraps around the polished muffler.



    It hurt me to clamp on to the muffler so I considered other ways.

    Turns out that using the 3 inch dynomax auccuseal clamps that come with the setup I could fabricate a mount off the transaxle support.



    I took it apart and added a bigger stainless steel block that I could weld a stud onto. Turned out I needed to cut out about a half inch of the clamp band in order to allow it to tighten on the exhaust tubing.



    here it is all ready to install. I was interested in making the mounts somewhat flexable so they don't fatigue and break over time so I found a cool neoprene bushing with a captured stud on one end an a threaded section on the other.




    I added a slotted bracket on to the transaxle support which allows me to move the exhaust left to right for final alignment.



    And installed everything.



    I can screw the stud out about 5 threads and or shim the vibration damping mount to raise or lower the exhaust tips.

    With both sides attached its very sturdy, but still allows the whole exhaust to flex slightly if pushed hard.

    Now back to work...

    John
    XTF #2
    build start date June 19 2023

    GTM # 344
    Build Start December 2010
    First track day April 2013

  40. #80
    Member noother's Avatar
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    Nice solution John!

    Can you pass on the source for the neoprene bushing when you get a chance?

    Thanks, Mark

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