Alec Bryant

Hey guys I got alot of questions and I need accurate information before I dump my money into this engine.

First off has anybody swapped their 3.1 out of a 90 or newer firebird with an older Corvette L98 TPI? any related discussions you know of could help.

Last week I was at a swap meet and came across a Vette engine and transmission. 112k on them, the car was junked so the wires from the computer are hacked up and will need a new harness. I payed 300$ plus I picked up an aluminum drive shaft for 50 out of an LS1 camaro. The Engine is not seized, and should run if I hooked everything up. I have the starter and will be doing a compression test hopefully this weekend.

Now here is where I am having the most trouble.

I keep hearing that since my car has a speed density setup I need to convert the engine to SD from MAF. What in my car is still run off the SD when I change the computer and everything? ( I am keeping my stock 120 mph gauge set up I hate the 140 Mph one. ) I have heard of aftermarket harnesses but I hate the price tag. This build is in no rush but I am planning on putting it in the car NEXT winter the soonest.

Fuel wise, my fuel lines are brand new, What do I need to change about them to hook up to the TPI. fuel lines on the engine itself are cut up and need to be replaced. I know I need a larger fuel pump. I know I need a different oil pan for the engine so it will fit in my firebird the old one is dented anyway.

I hear the torque arm on the Transmission out of the Vette is different than the Fbody 700r4 one. Whats my best choice for getting all that to mount ?

Electronic wise I am completely confused and need advice that is proven will work. I know about the 9th injector and how the fbodys did not have them. I got a really good deal on this setup and it has alot of potential. If i go to SD will all the wires and plugs sticking out of the engine now hook up or what. I do not care about emissions My car no longer needs it in Connecticut in fact I am ripping the smog pump and cat out of my car this winter. Suspension and radiator are no big deal I know what I am upgrading for that. Is there a true painless setup that I can just change my tacometer and whatever to keep my gauges and not have an engine light on 24/7 that is painless on my wallet? I do understand it will cost alot for the swap but to dump that much just to hear it run sounds stupid. And I do not want to go to carbed, Im trying to upgrade my car for god sake.

My Goal for this engine is to have the power I lust for but get as good if not better Mpg as my 3.1 My neighbor has a 91 L98 in his GTA and gets better mpg then my 3.1 so I know it is possible. I hear a nice lower intake, throttle body and exhaust will wake up the engine. It is and will be my daily driver in the summer and spring. The car is mint and I had it since I was 12, restored it with my dad so selling it for one with the power i want is an insult.

I need help and will appreciate any thanks!

Alec Bryant

( I have pictures of the engine here )

http://s1238.photobucket.com/user/am...?sort=3&page=1

five7kid

iTrader: (14)

SD vs. MAF is engine/ECM dependent, not car dependent. What the V6 has is irrelevant to the engine going in.

It appears your engine has aluminum heads, so it must be a later '86 (first half of the '86 model year had cast iron heads). That doesn't really affect anything but the exhaust gas feed to the EGR valve. It doesn't appear you got the exhaust manifolds with the engine - they wouldn't fit a 3rd gen, anyway, but the exhaust gas feed can be adapted to 3rd gen manifolds.

3rd gens got the 9th injector through 1988. Not sure what that's coming from.

If you didn't get the ECM (you don't say that you did), you can get a '90-'92 3rd gen SD ECM and harness and install it on your engine/trans. The 9th injector and MAF will be eliminated.

I think the transmission output shaft housing can be swapped from your V6 TH700 onto the Vette TH700. Not completely sure if the output shafts are the same, though. Some weird things happen with Vettes (said by a C4 owner). Not even sure if the Vette speedo is cable or electronic.

Your V6 tach will need to be changed for a V8 tach. Not a big deal. I know the difference is a resistor on the tach circuit board, but I don't know any details beyond that.

I believe the '90 V6 used a VSS buffer box, but TPI did not. Might want to check further into that.

I don't know what you would need to change on the fuel lines. I believe all you need to do is find TPI flex lines, but I don't have personal experience in that.

The TPI base is only part of the TPI restriction. The runners are also big contributors. From what I've seen, it makes more sense to get a Holley Stealth Ram and put your injectors/TB on it - less money, better performance than aftermarket base & runners. A bigger TB won't make as much difference as headers and free-flowing exhaust will.

Your 3.1 radiator should be the same as an L98 radiator. Of course, if you want to upgrade...

Alec Bryant

Thanks for all that Its usefull. I managed to grab a harness actually about everything electrical out of a 90 trans am 5.0 tpi so i will need to burn the chip correct? I do want to make this a good gas saver i know a guy who got 27 highway with his camaro with this engine. Would you know my best size for fuel injectors? also Its weird it is out of an 86 vette but it does not have the 9th injector. All i really want to do for mods is a 58 MM throttle body and either an LT1 lower intake or edlebrock lower intake and a nice pair of headers. Also a performance chip. I should be around 300 horses with that i hope i hear it does not take much to wake up these engines. That with my aluminum driveshaft and a 342 posi rear end should challenge my neighbors Ls1?