Is there any one out there that knows if the TPI system will fit under the hood of a 75 Vette? Want to change out from the carb, hopping it has the clearance? THANKS FOR YOUR HELP, RICK 360-570-9289

 

This swap is a lot of work for nice mid range power....
I hope you have the donor car available, or else you will be chasing parts, computers, wiring, sensors fuel pump, etc....forever!!!

Even the dizzy is special, a "normal" HEI wont fit

 

What is special about the dizzy? Both large and small cap HEI dizzys fit under the TPI setup as both Thirdgen F-bodies and Corvettes got the large cap, then the later Thirdgens switched over to the small cap. They just need to be computer controlled. Go to the junk yard and pull the dizzy from any TBI truck and you are good to go.

I also am not sure why you need a parts car. TPI swap harnesses aren't hard to find, the fuel pump won't do you any good as it's in tank, the ecm was used in many cars and the PROM will probably need to be custom programmed anyway.

List of sensors:
MAP or MAF
Coolant Temp
Intake Air Temp
Knock
Oxygen
Vehicle Speed (VSS) (which is probably the most complicated)

I can't think of any other sensor that TPI cares about.

 

I am in th emiddle of doing the swap into my 78. There is a lot of info out there, wiring harnesses are also plentiful The hardest part is picking a MAF or speed density. I am going with the MAF. Lots of opinions from lots of people. But get the donor engine as complete as you can get because there are lots of SMALL things that add up fast. And I don't know about your 75 but you will need a fuel return line. ANd it will fit under the hood, but getting cold air to the engine is a bit of work. Keep us up to date with your project.

 

I have had TPI on my 79 for several years now and love it. I chose to go the Speed Density route to avoid the impossible plumbing needs for the MAF sensor. My car starts right up on even the coldest mornings and has massive amounts of torque at the speed I drive, about 3000 rpm at 60 mph. Plus great gas mileage.
All of the distributors are the same for TPI but the gear is different for roller cam engines.
Do lots of homework to keep your cost down. I recommend Chevy Thunder. They have lots of great info free and they're not trying to sell you stuff.
Hope this helps.

 

TPI on my 79. Fits fine even after going to a vortec intake and heads (these are taller than regular SBC parts) the only thing the hood touches is the very end of my cone air filter, the filter seems fine with this. TPI is just simply nice to live with.

 

Is there a reason you selected the TPI setup specifically?

 

I have a 77, and TPI fits under my stock hood. I believe that 75 and 77 have the same dimensions.

Suggest that you check out Street & Performance http://www.hotrodlane.cc/
They were one of the earliest TPI hotrodders and they still have a lot of stuff PLUS a lot of info on TPI. I used one of their harnesses to fit a 'waterproof' ecm (from a late C4 - speed density) onto my inner left fender. It was a lifesaver because with my Vintage Air install left no room for it in the cabin.

If you need help or advice, don't hesitate to PM me.

 

I just purchased a complete tpi 350 and 700r4 out of a 1987 corvette. (picking it up tomorrow) I'm getting ready to install it in my 79. I've read I can install an 82 fuel sending unit and buy a later pump (year?). Did you use the existing fuel return line? Any suggestions on what to watch out for or any mistakes I can learn from. I'm getting the stock wiring harness with the package. Did you use a factory harness or purchase an aftermarket one? I hear the stock ones have a lot of wiring you don't need. The guy I'm buying it from is giving me anything I want off the 87. I'm having him include the evap canister, electric cooling fan and all sensors, etc. Did you run into many items you have to purchase other than the stock stuff to make this change over? Any advice or suggestions is greatly appreciated.
Thanks for your input.

 

I started the same way you are (used 86 motor and 700R4) make sure you get the TV cable that runs from the throttle bracket to the trans. You will also need to install an O2 sensor, I also installed extra oil and temp sensors for the ECM so I did not have to mess with the stock gauges. The ECM will need to be reprogrammed to remove the anti theft stuff or the car will not start. Whoever does this can tell you what else needs removing. I went with a new ECM and harness from Larry's Electric (they are on the web) they also reprogrammed the ECM for my needs. I did go with the in tank fuel pump setup, but it was such a pain to deal with I changed to an external pump, works fine. The stock fuel return line also works. About a year after I had everything working I found a small leak in the fuel feed line, at that time I replaced the tank went with the external pump and replaced the fuel lines with Socketless hoses and fitting from AeroQuip. Kinda pricey, but very easy to work with. Summit racing has them. The only thing I might do differently today is, the Fast EZ-EFI 2.0 retro-fit multi-port system (also at Summit) looks like a real nice setup. It cost about three times what I paid Larry's but looks worth it. I will say this about Larry's, they provide great instructions and years after buying from them they are still happy to talk me through any questions I might have. For a trans mount and anything related to the trans talk to Bowtie they really are the one place that has everything for the trans swap. Ok this is all just my experience and opinion, if anyone disagrees, feel free.

 

Thanks for the input. Bowtie is about 6 miles from me. I planned on purchasing the 700r4 crossmember from them. I have to talk to them and see if they have any suggestions too. I'll check out Larry's and the summit kit too. Thanks again. What issues did you have with the in tank fuel pump setup. It sounded easy and too good to be true....LOL.

 

Keep on mind that all C3 Corvettes are different. The sending unit on mine just barely fit through the opening in the body of my car (I have three of these units) when you add the pump and wiring it was just to big of a pain. They would mess up the cars paint or the wiring would get tangled or disconnected. The worst (most frustrating) was when the pump worked great but the gauge did not. Like I said this could be just the difference in cars, or just as likely a lack of talent on my part. For me the external pump turned out to be easier. Don't let any of this discourage you, the difference the TPI and 700R4 makes in the drive ability of the car is amazing!

 

How much can the runners flow?

 

Not much
If you go down that road spend all your time on the base and search out some ASM used runners.
Intake system is great out of the whole ie street car dont expect them to wind up rpm wise or make any hp. Tq...they do that well.

 

I originally was going with TPI, but after talking to Jim from Jim's Performance, it was decided best to use a carb with my engine specs. I liked how it looked, but ended up selling it and going with a BG Speed Demon 750.

Give Jim a call. He may be able to help you out with any questions or parts.

http://www.jimsperformance.com/tpibuy.html

 

The largest restriction is not the runners - it is the manifold base. It is VERY restrictive. Next comes the stock runners, then stock throttle body and finally the ports in the plenum.

If you want a performance tuned port, start with vortec heads or aftermarket replacements, get a Scroggins-Dickey manifold base, add a 52mm throttle body, aftermarket runners and port the plenum. With a modest roller cam, this will extend your revs to 5500-6000 rpm, give you 420+ ft/lbs torqueover a broad range, reasonable horsepower (for a street engine) along with a smooth and responsive engine that is a joy.

 

I agree completely! I'm running a vortec roller cam crate engine with a Scroggins-Dickey intake a 52mm throttle body, headers and real duel exhaust. Don't know what it's putting out but it's sure faster than my 90 C4. I live just north of Seattle, we a blessed with some of the most fun mountain passes you could want. Last summer I took my 79 over three of them in one non stop loop to see just how much gas I could burn if I really tried. 19.75 mpg. When I bought the car in LA and drove it home up the coast, the best I got was 9 mpg and I was trying to stretch that $5.00 a gallon gas as far as I could. The biggest problem I have with mileage now is the gas getting old in the tank! Turn the key the car starts and runs smooth. It doesn't care if it's a sea level or five thousand feet it just runs great. With the 700R4 and a 3:55 rear end it turns 1800 rpm at sixty. If I nail the gas and hold it on the floor it drops down two gears and up shifts at 5200 rpm. Seems to breath fine to me. I'm sure that a well tuned carb could do some things better. They just don't happen to be things that matter to me. Just saying.

 

Did you go MAF or speed / density and why? The one I purchased is a MAF. Only down side I see so far is air filter placement. What are your thoughts? I have the factory PC for the MAF but I'm going to need to get some programming to eliminate the VATS. thanks.

 

I used speed density, using the later C4 'waterproof' unit. I wanted to put everything under the hood. I used a Street & Performance wiring harness and recalibrated chip and all of the items I described in my earlier post. The combo produces LOTS of torque and isn't out of breath until 5800+ - a thousand plus RPM over the stock system.

 

speed density. Less stuff to deal with, fits under the hood better, easy air filter install.