1987 Corvette L98 TPI - Going from 128 alum heads to Vortecs ???? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 10-17-2008, 06:56 AM
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1987 Corvette L98 TPI - Going from 128 alum heads to Vortecs ????

I was talkin' with a guy last night,and he has a couple of Vortec heads for sale,kinda cheap,they swapped the a V8 engine for a Diesel in his truck.-
Im currently expecting 1.5 roller tip rockers for exhaust and 1.6 for intake,and hedman headers .....i have a .30 over 1987 L98,with a ZZ4 cam and LT4 Springs.-
Well,my 128 alum heads are not the best in the world
but i don't know if its worth the swap..i already have a friend interested in my 128's.

I will retain the stock TPI.-

What can happen ? Will i add lots of torque ? or i'd better stay with the 128's and enjoy my rockers/headers with them ?

ps :i didn't imagine that the head swap would be that close,but ..it depends on your advice!
thanks
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Old 10-17-2008, 08:22 AM
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The TPI manifold won't work on the Vortec heads. Not only is the bolt pattern totally different, the vortec ports are much taller and the TPI base won't line up with them.

Someone sells a TPI base for Vortec heads, but its expensive.

The TPI is a nice setup, but its tuned for low RPM. The Vortecs with the cam you've chosen will be capable of nearly 6000 RPM, but the TPI will start wimping out at 4000.

So, I would say your choices are to use a Vortec TPI manifold and upgrade the plenum and runners for higher RPM use, OR just put an edelbrock intake on it with a Qjet carb. What you should expect is 300+ hp and a boat load more torque at a slightly higher RPM. You should expect to shred tires with great ease.

Here is a photo that shows a couple things. First, notice that this aftermarket Vortec head is drilled for both early and vortec intake patterns. Secondly, notice that the cutaway of the early manifold doesn't cover the entire vortec port. That is basically how the ports of your TPI would line up on vortec heads.

Last edited by curtis73; 10-17-2008 at 08:40 AM.
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Old 10-20-2008, 04:24 PM
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This is teh intake that you would want.
http://www.sdparts.com/product/SD381...Baseplate.aspx

Its $400 and allows you to use Vortec heads on a TPI vehicle.

I actually installed 1 on a Vortec 350 with the GMPP Hotcam kit with 1.6 rockers in a 1985 TBI 305 IROCZ and went from a stock 15.8 @88down to around 13.8 @99mphin the 1/4 mile. That was with the stock 305 chip with 32 lb/hr injectors.. it was pretty rich at idle, and woudlnt idle with the AC on. i wish teh guy spent the money and got a chipped burned. It woudl of worked much better, esp on the streets.
I also used SLP's siamesed runners, shorty headers and a single 2 3/4" exhaust.
Have had the engine to 7200 rpm, wasnt making any power, but it pulled it nicely nonetheless.
We used a 4 bolt Vortec 350 from a 1 ton Vortec truck.

peace
Hog
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Old 10-20-2008, 05:48 PM
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F I was going to switch to a vortec head I would get a GM Ram Jet (vortec) intake manifold to go with it.
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