Hi guys,

I'm getting fed up with TPI tuning and having issues. The car is hardly used, strictly a nice weather car that sits in the garage and is not the worth the hassle. I'm going carb.

A little background: It's an 89 350 TPI, new GM heads probably about 2500 miles ago, Hooker super comp LT's, mufflex ORY, Magnaflow, 3.42 rear, and I converted it to a T56. I had the tail housing converted to use my stock speedometer, nothing is computer dependent.

I'm unsure of which intake, carb, and distributor to use. I've read a little bit but I'm still not sure which direction to head, this is all new to me.

Thanks!

 

Distributor you will need a gm style vac advance HEI distributor.
Carb is what you are most comfortable with. Holley 650 or GM quadrajet or edelbrock. Get 650-700 cfm. Make sure the bolt pattern matches the intake.
For the intake get a low profile intake not something like the edelbrock air gap as it is taller and your air filter probably will not clear the stock hood. Also for your 89 it should have the canted bolts in the center so you may need to oval your bolt holes on the intake or plan on getting an intake designed for this.

 

I second the vacuum advance HEI distributor. Make sure to recurve it, I've found the stock curves in them to really, really suck.

I'd recommend an edelbrock performer rpm. Air gap is better but hood clearance might be an issue. If you don't like that one, just make sure it's a dual plane intake.

As for the carb edelbrocks are known for being great "right out of the box." If you'd like minimal tuning that's probably your best bet. Holleys are fantastic and it's what I run on my car, but be prepared to spend a little time with them. Once it's dialed in you'll love it. I'd recommend an electric choke.

650-700 cfm with vacuum secondaries for better gas mileage. Having a stick car you can go mech secondaries without any real loss in driveability if you'd like but the gas mileage will be directly dependent on your right foot.

I can't overstress how important it is to dial in the timing advance and tuning on your carburetor! Enjoy it though, I find it quite fun actually

 

Get the GM perfromance HEI. It comes with the correct distributor for your roller cam, it has a good curve with limited mechanical advance so you can bump up your base timing and the vacuum can actually works. I'd go with a performer RPM (or similar) and a 650 Double pumper.

You will also need to address the fuel pressure issue (regulator with return) and a good air cleaner setup that draws in cold air (not just a filer on top of the carb).

 

I am not an EFI genius by any means.. Am going to EFI 101 and advance course in Akron, OH the 22nd through 25th of next month. I have learned how to use RT Tunerpro and principal of EFI though. It really isn't that much more complex than a carb. After I started to play with force induction and go way in over my head, my friend introduced me to a few crash courses over night which taught me how easy it was to tune EFI. His principal reason was the only reason someone goes to CARB is they don't understand how the components work Don't get fustrated with it. But ultimately it is your choice.

http://efi101.com/

 

Gas mileage is dependent on your right foot whether it's vacuum or mechanical secondaries. There is no fuel economy advantage to a vacuum secondary carb if you don't open the secondaries.

Of course, if fuel economy and driveability are concerns, you'll stick with EFI...

 

I swapped my vac sec Holley for a dp on my auto dd, saw no appreciable difference in mileage. It's bad with either

 

I am not 100% sure if a well tuned carb would ever get the same efficiency as any fuel injection.

 

I get better MPG's with my 750 Mighty Demon as compared to the Miniram (not much, but measurable and repeatable). The car is also slightly faster (almost 2/10th's quicker in the quarter). I think it all comes down to low speed torque with my setup. The carb/airgap combo just has more.

Most people that complain about MPG's with a carb have very poor timing curves and no vacuum advance.

 

You don't have the adjustability with carb and dizzy that you do with EFI..

 

A carb works off of the constantaly changing depression that occurs across the venturi of the carb bores. It "senses" demand from the engine...just like EFI. Where a carb comes up short is weather changes (which are fairly minor in the grand scheme of things). EFI can also turn off fuel during deceleration which can be pretty useful. The distributor is good (if adjusted correctly), but not as nice as computer controlled. With a computer, you can relate the spark advance to throttle position and not just RPM. However, a vacuum can needs to be present on the distributor for any chance of good gas mileage. In the end, a properly set up carb can do quite well. And, as in my case, hang with EFI. Remember, the combustion chamber doesn't care how the air fuel arrives...just that it arrives in the proper mix.

 

I just got done building an engine for my 91' TA that had the TPI but im going back with a 750 holley DP. Any of y'all out there done this have any suggestions on using the factory supply and return fuel lines. From what summit says its 12mmX1.25 nuts on the lines and would like to find away to not cut up the fuel line and hook it up to my bypass fuel pressure regulator. Can't seem to find anything that goes from metric to 3/8th NPT.

 

i just got done doing this today and just put the 3/8 hose and 5/16 over the supply and return lines and clamped them and had no issues, but beware about TPI to carb ive had so many issues so far with my swap it makes me wish i woulda left my 305 in it

 

i have a 1992 camaro can i use the wiring to wire up a 1972 motor?