EFI to Carb conversion

[glastron351]

Hi Everyone...I am in the process of converting a 408w from EFI to Carb and have a chance to pick up a BLP BX4 750cfm carb at an attractive price... Any thoughts/input on this carb set up. Carb was only used for a couple of hours before seller found a period correct carb for an old Ford Cougar he restored. Will probably use an Edelbrock Performer RPM intake and have AFR 1450 Heads.

Here is a link to the specific carb itself..

http://blp.com/cart/index.php?main_p...oducts_id=1584

Am also looking for a distributor and fuel pump set up....like the idea of an MSD setup with adjustable rev limit but don't really want a separate ignition box. Also noticed Summit has there own line of stand a lone distributors that are priced fairly reasonably. Again thoughts? Anybody have anything they want to sell? Will post a WTB soon.

Thanks again..

[GoDadGo]

Glastron,

You may want to look at an HEI from Performance Distributors.
They will set up a custom curve for you, plus you won't need an MSD box; however, they only offer a plug-in module style rev limiter.

http://performancedistributors.com/p...1-289-302-cid/

The good news is if you run an HEI setup, then you can get a cool little limiter from MSD specfically designed for the HEI distributor.
This unit adjusts from 3000-to-9,900 in 100 RPM increments, plus it holds your highest RPM logged once the engine has shut down.

https://www.summitracing.com/parts/msd-8727ct/overview/

For the record, I've got the DAVIS HEI and the MSD pieces on my Dark Side MK-4.
The two combined makes for a very simple installation.

Good Luck From The Dad Side!

Steve

[JRD56]

I used the in tank fuel pump (190 liter/hour Walbro) from Breeze and a Holley 12-803BP bypass regulator. With a bypass regulator you have to run a return line to tank, but if you are converting from fuel injection you may already have that. I'm running a 302, but with a 408 you may need more than 190 liter per hour. There are some calculators on line that can help you determine volume needed. My setup works great.

[skidd]

For me, budget an simplicity drove my conversion. I went with a distributor out of a '85 mustang since it has a magnetic pickup, steel cam gear, and a vacuum advance canister. I wired the distributor to a GM HEI (Echlin TP45) and an Echlin E-Core coil. I installed the HEI module just behind my dash, on a small HEI Heat-Sink firewall mount (ACDelco 10474610). But, for a few more dollars, and an even cleaner install, you could get the Pertronix module that wires directly inside the distributor. They even have one with a rev-limit built in. Something I might need since my little 302 likes to wind up past 6500 really easy. Another step up from there, the read-to-go pertronix distributor. None of the above is expensive, or hard to wire.

As for fuel pump, again.. I went simple. I installed a Spectra Premium SP1138 in-tank fuel pump with a Spectra Premium STR01 strainer. It's a low pressure electric fuel pump. Not sure it's free-flow capacity, but it's more than enough to handle my mild 302 with a Summit Racing 600cfm carb. Easy to retro-fit the pump into the FOX mustang fuel tank hanger. This pump makes just shy of 7psi at my carb dead-headed. No return. I have the return line installed and plumbed, but I just capped it off at the engine-bay. That way, I could go EFI in the future, if I really felt like it.

[glastron351]

Hi Guys - Thanks for the information greatly appreciated!

GoDadGo...Those distributors look nice! I will have to do some research, hate to admit it but cosmetics will also play into my build, looking for a (preferably) black or red rotor cap...can't see myse,f doing a yellow one but it may just be their promo pic. Really like the simplicity of the entire set-up though......Happy Fathers Day!!

JRD56-Thanks for the great pics! Is the mechanical throttle linkage setup you have from Breeze as well or did you custom make it? What PSi are you seeing at you carb? I like the guage and was thinking of getting one myself...where is yours from?

skidd-thanks for the info on the distributor and fuel pump...I think my requirements are around the same....7psi sounds about perfect. I may switch to a fuel injection system in the future but for now just want to get a running and driving car, am trying not to over think it. I have a 68 mustang fastback running a 750 vacuum secondary carb with a mechanical fuel pump..never had an issue with it. If I was smart I'd just go with this setup but I never claimed to be a mensa student

thank again guys!

[glastron351]

Hi Guys - Thanks for the information greatly appreciated!

GoDadGo...Those distributors look nice! I will have to do some research, hate to admit it but cosmetics will also play into my build, looking for a (preferably) black or red rotor cap...can't see myse,f doing a yellow one but it may just be their promo pic. Really like the simplicity of the entire set-up though......Happy Fathers Day!!

JRD56-Thanks for the great pics! Is the mechanical throttle linkage setup you have from Breeze as well or did you custom make it? What PSi are you seeing at you carb? I like the guage and was thinking of getting one myself...where is yours from?

skidd-thanks for the info on the distributor and fuel pump...I think my requirements are around the same....7psi sounds about perfect. I may switch to a fuel injection system in the future but for now just want to get a running and driving car, am trying not to over think it. I have a 68 mustang fastback running a 750 vacuum secondary carb with a mechanical fuel pump..never had an issue with it. If I was smart I'd just go with this setup but I never claimed to be a mensa student

thank again guys!

[JRD56]

Glastron351,

I custom made the throttle linkage. Bought the levers and linkage from Speedway and made everything else including the throttle pedal. If you are a good fabricator its easy to make otherwise I've seen several kits out there.

I've set the regulator to provide 6-1/2 PSI at the carb. I did put a temporary gauge on the inlet side of the regulator and it measures about 7-1/2 PSI. At that flow rate the pump only draws about 3 amps and should last a long time. I don't remember where I got the gauge but any speedshop will carry them. Mine is liquid filled, but that's probably not really necessary.

Good Luck,

Jim

[CraigS]

Two years ago a friend installed an MSD that allowed him to tailor the spark curve. Seemed like a really neat piece and worked fine. For maybe 3 months. I commented at breakfast about why he was in his street car and it was because the MSD was at MSD. That and MANY threads about dead MSDs and I wouldn't install one on my car if it was free.

[glastron351]

Haha yes i've heard that from a few people. Some people have no problems with there MSD while others have many, many issues. I contacted a friend of mine who is an engineer at Ford in Dearborn and his comment was that MSD should stand for 'May Suddenly Die'. Other then that he recommended I call the Ford Performance Tech Line and see what they recommend and gave me some contact info for some of the techs who work on the 'older technology'. I will try to call them tomorrow and see what they have to say.

I have also been asked why am I converting from EFI to carb....long story short I bought a SN95 mustang with a nice 408 build in it. Unfortunately with the massive Trick Flow intake on it and the fact that is was using the factory ECU with a diablo tune made it not very practical for a cobra build. There is no way I could stuff that intake in a roadster build. That plus (at least for now) I wanted to go with a bit more of a period correct look. I may change to an FI Tech fuel injection system at some point but for now I'm trying to simplify things until I get a running a driving car. Am probably going about things entirely the wrong way but it won't be the first time I've taken the bumpy road of lessons learnedIMG_3186.JPG.

Here's a pic of the motor before I pulled it from the mustang....

[GoDadGo]

Since you wanted a "Period Correct Look / Not A Period Correct Setup" then have you considered going with an Edelbrock Dual Quad System?
It would likely fit under the hood of your MK-4, but might poke up into the scoop.
If you are able to handle the tuning chore it might be a viable option.

https://www.summitracing.com/parts/e...view/make/ford

I've got a single 800 AVS on a Team-G Single plane intake, but only 383 CID, and it was extremely easy to tune so a pair of 500's might be worth looking into.
It ran great until my block spung a leak and I had to replace it, but that's another story.
Shown below was my last good drive before I replaced the block:

https://youtu.be/PCngiKoopkA

[JRD56]

Just a quick comment on MSD ignitions. I've used them for many years when I drag raced in NHRA. Never had any problems. However, If you trigger the unit without the coil and sparkplug wires hooked up, it will fry the unit. I've seen some guys pull the coil wire then crank the engine without it firing to adjust the valves, etc. In a conventional ignition system this works fine, but not with an MSD system. You just have to be careful not to trigger the unit with power on it and no coil/spark plug wires connected.

[mike223]

I've used them for many years when I drag raced in NHRA. Never had any problems. However, If you trigger the unit without the coil and sparkplug wires hooked up, it will fry the unit. I've seen some guys pull the coil wire the crank the engine without it firing to adjust the valves, etc. In a conventional ignition system this works fine, but not with an MSD system. You just have to be careful not to trigger the unit with power on it and no coil/spark plug wires connected.

You may be on to something there.

I've run an MSD box for years - the only problem I've ever had was a coil that went bad - the fix for that is the high vibration (urethane filled - not oil filled) coil.

But the only reason I put in the MSD box in the first place was it was the easiest way to get it rev limited that I was aware of at the time.

I have long suspected that people unknowingly induce their own problems with the MSD boxes (like maybe welding on the chassis with the box hooked up / strange ignition wiring / etc).

[glastron351]

That's a very interesting and does make a lot of sense regarding the MSD boxes. As a side note I have a MSD 6AL in my 68 mustang hooked up to an Accel distributor for over 20 years without a problem....the car is very basic electrically which probably enhances the reliability...

GoDadGo now you've done it....I sure like that dual quad system...I hope I don't have to go buy one

[glastron351]

Update-Was in contact with the For Performance Tech support and happened to get information from a tech there has built several FF Roadsters. He has had reasonably good luck with Pertronix products. After doing a bit of research I'm leaning towards something like this one;

https://www.summitracing.com/int/par...view/make/ford

It's plug and play and has a setable rev limit. Any body have any experience with these? Also does anyone ever use Vacuum advance? Looks like you can option most of these with Vacuum Advance yet I never really seem to see them hooked up

Thanks again

[mike223]

Also does anyone ever use Vacuum advance? Looks like you can option most of these with Vacuum Advance yet I never really seem to see them hooked up

It depends on what you want out of it.

Vacuum advance improves your mileage running around at low/no load - lots of people use it.


It's an additional complication in your advance curve - if you get too carried away with any combination of the advance, you risk (or induce) detonation - and that is easy to do on a performance car, especially transitioning from low throttle to heavy throttle with manual transmission + vacuum advance. Real dangerous if you can't hear it (detonation) in a loud car = burned / ventilated piston(s).

All that can also vary fairly widely with individual operator shift / throttle habits.

So some performance purists just want the absolute repeat-ability of the mechanical advance alone (without the additional complication of vacuum advance working in conjunction with the mechanical).


The vacuum advance also softens the reaction of the engine to throttle drops - some people like that - some people don't notice it - some people hate it.


It's a mixed bag - no vacuum advance for me.

[glastron351]

Thanks for the information, greatly appreciated! Driving a Cobra is not about fuel mileage so that is not really a concern for me and yes knowing my driving style I'm sure there will be repeated low heavy throttle to heavy throttle burst .

Due to the performance nature of these cars it looks like mechanical advance is the way to go. Thanks

Interesting comment about the throttle drop....I have an aluminum flywheel in my 68 mustang (351w based motor as well). Lots of people said not a good idea for the street. I actually really like it, revs up very quick so does take a bit of getting used to but sure can be fun when you adapt to its characteristics.

[mike223]

Interesting comment about the throttle drop....I have an aluminum flywheel in my 68 mustang (351w based motor as well). Lots of people said not a good idea for the street. I actually really like it, revs up very quick so does take a bit of getting used to but sure can be fun when you adapt to its characteristics.

It's a very similar effect on drops (aluminum flywheel / delete vacuum advance) - Some people love it - some people don't really notice - some hate it...

Throttle drops in these cars are something that the operator can never be oblivious to - short wheelbase / rear weight biased.


Get the car a little crossed up and step off the throttle sloppy - you're now simply "passenger" - and you're not going to like it...

[Avalanche325]

Here are my thoughts and recommendations.

Be fully and completely aware that you will need to tune the carb. If that carb was tuned by the previous owner more than just basic jetting, I would put it back to factory settings and start from there. You need to shift to wide band O2 for that.

Fuel pump capacity, and carb size for that matter, have virtually nothing to do with engine size. Let that sink in for a minute........ Fuel pump capacity and carb size have everything to do with how much HP they need to support.
Typical fuel pump sizing is 2.64HP per Lph on a basic level.(I just looked it up yesterday and I get to use it already!) Voltage, pressure, temp, etc are variables, but that is the basic number. So if your 408 has 400 HP a 192Lph pump will be fine. If it has 500HP, you need a 255Lph. The 192 tops out just over 500, but you don't want something maxxed out. You will need a low pressure regulator. You can do bypass since you have the plumbing. With all that said, you could go to a mechanical pump and a basic regulator. You may not the eccentric for the pump which would be a bit of a pain.

Have a look at Pertronix distributors. You can get a billet distributor that has multispark across the entire range (MSD doesn't), and a rev limiter all under the cap. Guys have had MSDs with no issues for years, true. Guys that buy them now better have AAA. I would bet that If you could get a NOS 10 year old one it would last. But I wouldn't buy a new one. I agree with Mike223 100% on vacuum advance. I don't have it either. I have a pretty high strung engine and sometimes have to blip the throttle when it drops back to idle. These types of "inconveniences" are part of the fun of driving a Cobra for me. It might bug someone else. If you are worried about mileage, you probably wouldn't be putting a carb on......or driving a Cobra for that matter. If I want push button convenience, I drive my Infiniti. Nasty, snotty, rough and raw.....It's Cobra time baby!

A car this light can use a single plane intake. The old "dual plane for the street / single plane is for racing" was out of date a long time ago. A single plane will move your torque up the RPM range a little, which is a good thing for these cars. Strokers like single plane. Here is an interesting article: https://www.enginelabs.com/engine-te...or-dual-plane/

I am not familiar with that particular carb. Let us know how it goes.

[GoDadGo]

GoDadGo now you've done it....I sure like that dual quad system...I hope I don't have to go buy one

While I doubt if I could tune it, it is a cool looking piece.

[JRD56]

I think it was mentioned in passing above, but if you have a roller cam it is likely a billet steel cam. An if it is you'll need a steel or bronze gear on the distributor. A cast iron gear will not work. I'd recommend a steel gear because a bronze gear will wear out if you put a lot street miles on it. It is difficult and/or expensive to replace a cast gear with a steel gear so its best to get a distributor with a steel gear from the get go.

[GoDadGo]

I think it was mentioning in passing above, but if you have a roller cam it is likely a billet steel cam. An if it is you'll need a steel or bronze gear on the distributor. A cast iron gear will not work. I'd recommend a steel gear because a bronze gear will wear out if you put a lot street miles on it. It is difficult and/or expensive to replace a cast gear with a steel gear so its best to get a distributor with a steel gear from the get go.

Excellent Point!

I had to change my distributor gear when I changed the block and also upgraded to a roller.
The folks at Davis Unified/Performance Distributor were great to deal with.
Wish I would have remember this when I suggested an HEI.

Again, Excellent Point!

[Avalanche325]

While I doubt if I could tune it, it is a cool looking piece.

If your going to get crazy, put Webers on it. Let the tuning begin!

[cv2065]

Update-Was in contact with the For Performance Tech support and happened to get information from a tech there has built several FF Roadsters. He has had reasonably good luck with Pertronix products. After doing a bit of research I'm leaning towards something like this one;

https://www.summitracing.com/int/par...view/make/ford

It's plug and play and has a setable rev limit. Any body have any experience with these?

Pertronix makes great stuff. Had a Flamethrower II and Master Blaster coil on my 67 Camaro for 5 years...no issues. High quality billet piece with small cap so that you have plenty of clearance against the firewall.

[glastron351]

Thanks again for the great information guys. Going to try out the Pertronix Distributer. It has a built in (adjustable) rev limiter and also comes with a steel gear. Great point about the gear, have heard some are easy to change others not so much.

On the 'should have checked this out first' catagory...picked up an Edelbrock mechanical fuel pump locally. When I went to install it, looke closer at my block and it has no access port on the timing chain case cover for a mechanical pump. Pulled the cover off to see if I could just change the cover..nope, no lobe even available. Looks like I'm going Electric Fuel Pump.

Avalanche325 thanks for the great info on Flow requirments to feed Horsepower. My 408 dyno's at just over 500hp previously so according to your info a pump that meets at lease 255lph flow rates is recommended. Was thinking of this Carter P4600 fuel pump. No regulator required and can support 397lph. If any one has any thoughts or other recommendations I'm always open to input. Thanks again.

https://www.summitracing.com/int/par...00hp/overview/

[jrcuz]

I saw recently that E3 the spark plug outfit also has distributors. I know nothing about them. Maybe worth looking into.
JR