consensus needed... compatibility of TPI between years

[rrubel]

I've put my TPI parts on eBay and was asked by a potential bidder if they'd fit any year's TPI engine. I was pretty sure they would (he thought there might be some difference between AL and CI heads, but I was pretty sure there wasn't). Am I right? Were there any changes that would cause an early TPI to not fit a later block? This is plenum, runners, manifold.
Thanks.
[RICHR]

 

[Eagle85C4]

I bought some extra TPI parts off of ebay, thinking I could port and polish them and replace all at once. Then I found the changes...
On the plenum, it depends if the year had the ninth injector or not. My 85 has the 9th and on the plenum where the T/B bolts on, look carefully, if there is a small triangular hole below and between the twin air openings then it is an early model plenum. This triangular hole allows air to "pull" the 9th injector fuel into the intake. When the did away with the 9th then they removed the triangle opening in the plenum. The runners for the early TPI had the hole for the ninth, later ones either had the hole plugged or gone all together. I bought a set of edelbrock runners and it was plugged, easy enough to remove it.
The intakes differ as well, the biggest difference is where the EGR valve is located, in the early ones, the EGR is mounted under the plenum. later years the EGR is located on the passenger side rear of the intake.
I do have later year plenum, partially ported, and later year intake if anyone is interested in having a set to play with , as in porting and polishing. On the plenum there is a small dam across the bottom of the air inlet holes. These are to help produce the venturi effect to help bring the 9th injector gas into the plenum. But if you use a hole saw they are easily removed and the removal does produce a difference in air volume for the intake.
I also have an intake for the later year....both can be had to the first decent offer....

 

[rrubel]

Thanks, Eagle. I also found this decent web page http://www.classictrucksweb.com/tech/0402cl_tpi/
however it doesn't seem to be 100% correct. My manifold is from an early 86, but has the heat riser on the passenger rear like the later ones do.

You bring up another point I hadn't considered in my upgrade process - that 9th injector. I'm not sure if the SuperRam has provisions for it. Wonder how easy it would be to block off the fuel line to it and reprogram the ECU to fire all 8 on ignition like the later ones do.
[RICHR]

 

[Mart]

Hey Rich,

I can't find them on ebay.

Where are they

Mart

 

[Eagle85C4]

Rich...I would think Jeff would be the one to talk to about the programming. Once you mentioned it I now wonder how they handle cold stating on the later L-98's without the 9th? Does the ECM allow for more fuel upon start? And how does it acertain the outside temp to allow for the addition of fuel to start? It has to be varied somehow.
And you being from MD...it still gets cold there towards winter.... I remember the fun I used to have driving from Falls Church, Va. to Laurel, MD, The Johns Hopkins Applied Physics Lab, in a Porsche 914-6. The beltway could be pure hell on a decent day, much less then with a foot of snow on the ground...84, 85, 86 somewhere in there they had a good winter storm. I made it to work in a car 4 inches off the ground when those with the 4x4's were stuck home. Needless to say I caught hell from those guys for showing up...made them look bad.

You might want to hang on to your TPI parts, I am going to build up a near stock motor for a spare tp prepare for one of those rainy day situations. And the way GM keeps discontinuing Corvette parts...well it is getting scary. Someday those parts will be like gold. JMHO
Take care Rich

 

[Eagle85C4]

Hey Mart....just what are you looking for? I have many spares if Rich has already sold his....

 

[Mart]

I am thinking of porting the plenum, along with some custom work on the finish, and I know Rich has an early 86 like mine.

Mart

 

[rrubel]

The auction is here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=36474&item=2452011733

I agonized about selling them but I need the cash to finish my project, plus need the room in the garage (you would not BELIEVE the parts I have strewn around and in storage, extras for the Vette and both Subarus). I really don't intend to bring this motor back to stock at any time, and there are enough TPI-based motors out there that I think I will be able to find stuff for a long while.

Jeff's the guy who made my current PROM; he'll have to reburn it for the new mods but at that point I'll ask him about the injection. The newer L98's fired all 8 at startup. I get the idea they did it regardless of outside temp, though if that were an issue the IAT sensor would probably work fine.
[RICHR]

 

[Eagle85C4]

Check with Rich first, only fair, then let me know as I have a plenum and intake that will work for you. Like I said earlier, plenum is partially ported and polished. I did this before I knew there was a difference and I could not use them.

 

[rrubel]

Heh... I have no problem with Mart running the prices up on eBay (there's one other guy bidding right now), losing, and then buying yours . I need $375 for the port/polish/match work, most of which I have, but I may have a line on a J55 front brake package at a decent price and need cash for THAT as well. It never ends...
[RICHR]

 

[KANE]

I built TPI for my 78 out of salvage yard parts.

ALUMINUM HEADS-
The intake manifolds will have the 73 degree offset for the four center bolts.

IRON HEADS-
These cars use the conventional 90 degrees for all 12 bolts.


Here's where it gets tricky.....
F-body TPI cars:
86-89 cars-
Throttle body and upper plenum are matched together for the EGR passages. They don't interchange with 90-92 TPI throttle bodies and plenums. Chevy changed a few more things than just the MAF into MAP.

Corvette TPI-
Identical for 1985 when being compared to 86-89 TPI F-body cars. Both cars had iron heads and no EGR pipe.

Corvette TPI
86-89 manifolds do not swap with F-bodies directly do to EGR pipe. You can use them just be prepared to block the EGR pipe or provision.

MAF (9 injector) fuel rails will swap with MAP rails if the injector provision is blocked on the fuel rail.

The 8 injectors will swap among all vehicles with 350s.

Fuel rails from F-bodies are not direct replacements for Corvettes and vice versa. The lines enter on the drivers side for the F-body. You can get the to interchange... but be prepared to dork with the parts to get them to fit. Be warned, a 305 is set with lower PSI than the 350s... you can use 305 injectors but you will need to increase the fuel pressure if you use them on a 350.

MAP sensors will interchange between 305s and 350s. Same with MAF sensors.

The LT4 knock sensor isn't as sensitive as the LT1 or L98s. You can use the LT4 knock sensor on an L98 but you must monitor detonation closely because the sensor is less sensitive.

IAT, TPS, CTS, IAC will all interchange for 305s, 350s, and MAF / MAP Corvettes and F-bodies. However, these don't swap with LT1 / LT4 cars.

Hope that helps a little....