Lowering 351W based 427 - what things to consider

[EBarnes]

I have a 351W based 427 going into my coupe.

This is a track car. I want to lower the engine as much as practicable for CG first, and to limit/eliminate he hood modification.

I would like advice/input to make sure I understand what I need to think through before doing this. And any suggestions on parts to make this work best for the track. That said, I don't want to make any follow on modifications to be anal, but only if it will avoid a durability problem without the mod (pinion angle and IRS may illustrate this).

* Actual fabrication of the engine mounts - suggestions as to how to accomplish the lowering, and should the OFFSET to the pax remain?

* Bell housing - make & model suggestions? TKO600 Trans, or I may get a G-force or Astro

* Trans mount changes? IRS should reduce the impact of an angle change... But the pinion angle is also fixed... Right? Or would a modification to the front mount be best? Or..?

Car particulars:
- IRS
- aviaid dry sump (5.50" pan)
- KAASE P-38 heads
- Super Victor manifold
- Levy's Quartermaster 8.5" clutch and flywheel
- exhaust will be custom, although I may modify the FFR 351 headers initially.

Also... What am I missing?!

Eric

[crossle45f33cf]

I see that you've stated that you're using an Aviaid dry sump pan.
I'm assuming that you'll be using a dry sump oil pump and external oil reservoir, too.
Having said that, it is imperative that the oil pan not extend below the 4" diameter frame tubes.
If you lower the engine sufficiently to put the bottom of your oil pan even with the bottom of the frame tubes, then your bell housing will probably be significantly lower than the frame tubes.
It is a really bad idea to have anything you value be the lowest thing on the chassis.
When I'm on the race track my motto is: Nothing bad happens until it does...

[HCP 65 COUPE]

Lowering the engine any more than where it is now will require a smaller diameter flywheel and new starter location as the bell housing is currently the lowest part of the car, while
not imposable it will be quite expensive to accomplish and I don't know if anybody makes a bell housing to accomplish this goal the starter would most likely need to be turned
around 180 deg and placed on the transmission side seeing there is not a ton of space along side the block now. If this is going to be a pure race car you may want to consider
a close ratio 4 speed like a Jerico. The 4 speed is smaller lighter and is available in alot of racing configurations for the circle track folks and they may also have the smaller
diameter setup your after.
Quarter master does in fact make a setup look at this

http://www.quartermasterusa.com/qm/m...-clutcheshtml/

or

http://www.quartermasterusa.com/qm/f...ing-16901html/

As far as pinion angle is concerned if it where a 3link rear lowering the drive train would improve the drive shaft angle alot but I don't have knowledge of the current IRS drive line angles.
I'm not sure it would hurt the drive shaft angle it may very well improve it.

[CES55N]

I am also doing a similar set-up,all aluminum 427 W with P38 heads, Quartermaster 153 tooth flywheel 7.25 triple disc clutch & mag bellhousing with a richmond road race 5 speed. After mocking everything up I decided I needed to move motor ahead aprox 1 1/2 for transmission to work out and I could lower motor aprox 1 inch with a 7 1/2 deep oil pan and smaller flywheel. With a 5.5 pan and a LGC bellhousing you should be able to lower everything at least 2.5 inches although depending on trans you may need to notch trans xmember tube. Roush Yates used racing parts usually has reverse mount 110 tooth set-ups from their Nascar teams. With my 9" floater set-up driveline angle improved not sure on an IRS. Best to mock everything up. Also if you decide to remove motor mounts from 4" tubing be very careful to not put to much heat to the tubing it WILL warp! Good luck & keep us posted Coupe 665

[Hankl]

Here's a picture of Carl Critz's coupe that we used the small clutch and bell housing combination on.
In the lower right corner you can see the access panel removed to access the starter. We found out from our
own experience, and from others, that this is not the best combination of parts to use. Better to stick with more
conventional parts, lower cost and ease of procurement if needed in a pinch.



Hank

[nicknitro71]

I'm in the same boat as I'm planning to put a 460 cui, 351 based.

I think I'm just gonna cut a hole in the hood and put a ram-air intake...

[CraigS]

W/ all the things pointed out above I wonder if it is worth the effort. If you could do back to back testing w/ engine/trans in stock location vs say, 2.5 inches lower, what would the effect on lap times be. I am thinking very little. It would be nice to find some software where you could move the CG and see the effects. I wonder what the effect of lowering the engine trans 2.5 inches would be on CG height lowering? 1 inch? 1.5 inch?

[Hankl]

Here's a point that needs to be brought up. When FFR added the 5 inches to the wheel base of the roadster to the coupe, it was all in the area in front of the firewall. So if you think about balance between the roaster and coupe, you'll see that were not talking apples to apples. If I recall correctly, we move the engine in my coupe forward 2.5 inches. This allowed us to modify the foot boxes and the trans tunnel. Just an additional item to look at.

Hank

[CHOTIS BILL]

W/ all the things pointed out above I wonder if it is worth the effort. If you could do back to back testing w/ engine/trans in stock location vs say, 2.5 inches lower, what would the effect on lap times be. I am thinking very little. It would be nice to find some software where you could move the CG and see the effects. I wonder what the effect of lowering the engine trans 2.5 inches would be on CG height lowering? 1 inch? 1.5 inch?

The only experience I have of lowering components to get the CG lower and then testing the difference was on my DSR many years ago. I lowered the rear wing that weighed around 6 pounds about 2-3 inches lower and the difference was a lot more than I expected. I don’t remember what the lap time difference was but the feel of corner entry was huge and the entry speed was definitely higher. I am sure the wing being pretty high to start with had something to do with the large change but the weight was also pretty small. I am sure lowering the complete engine and trans a few inches would make a major change in lap times.

Bill Lomenick

[HCP 65 COUPE]

Another thing to consider with lowering the CG is what effect this Has on the roll centers of the suspension as well as instant center.

The change could make the car better or worse.

[EBarnes]

Bill, the problem with lowering the wing is, you probably effected the angle of attach via the different relative wind at the lower point. While I am for changing small parts so the sum has a measurable effect, I have a hard time believing lowering 10# alone 6" has a measurable affect. Do it for 10-15 6# items and maybe.

Lowering the CG will always be better EXCEPT for the potential negative effect on roll center. More engineering than I have the knowledge to do. Also, moving mass INWARD toward the center should help rotational forces. Think 3 dimensional.

Not sure if this is helpful or not though in terms of lowering lap times.

But...

Too late - already bought the mounts and QT bell housing. We'll see!