Hello,
This is my first time here since I don't actually own a third gen. But, the time has come to start modding my TBI 305 powered 1991 Caprice wagon, and this forum seems to be all-knowing when it comes to TBI/ TPI tech.

The wagon is not my daily, though I'd like to preserve its street manners as much as possible.

So, I had a crazy idea for this car, and I'd like to know if what I've figured out is entirely reasonable.

My idea is a vortec 350 with a TPI intake, running off a 411 setup, with a small turbo.
I was thinking that 400ish ftlbs would be achievable with the vortec heads and cam, and about 7.5 psi of boost at like 8-8.5/1 compression so I can run 87 octane. The idea here being an essentially stock feeling vortec 350 under light throttle.
I should add that I'd also add headers and dual exhaust (probably 2.5") to the car.

This would be in front of a 4L80E, with 3.08 gears, and 1400ish rpm stall converter.

Is this unreasonable to ask of a 350?
Thanks.

 

I was making more than 400 ft/lbs with the tiny 300 hp marine cam and headers.

 

Thats encouraging! I'd definitely be happy with more, but 400 ft/lbs and 325 hp would just be my minimum for this much work.

 

About what I was making at the crank with the marine cam, ported marine intake, a little head work and headers. Had a 3.73 gear and 30.5" tall tires. Moved my conversion van along pretty good for a 6,200 lbs living room on wheels.

 

My bone stock 305 tpi with 7-8 psi trapped 108-109. 110 on 9. Had issues it wouldnt go faster with more. Valvesprings and ignition my guess. That’s probably close to 280-300 whp. Stock i bet it wasnt 200.

ive run the 411 pcm on my twin turbo 400” sbc. Works good, but i wish i didnt do it and just ran holley instead. I hate hp tuners lol But for 80e control holley would be alot more money

a good 350 vortec on 7 psi would be a fun car. Probably well over 400 lb ft at the tire cuz mild tpi 350’s are 330-350 wtq. Problem is dont put all that torque in too early, its gonna be tougher on stock rods and being on pump gas, chamber pressure gets up there so can be more sensitive. Just leave timing out around peak torque and ramp it in. Good boost control helps. You’ll have a long flat power curve

 

Sounds like it should be totally doable!

A few months ago I picked up an 86 Toyota Toyota 4x4 with a 5spd and a factory turbo, it's gotten me hooked on that old school turbo feel and sound! Both that and the Callaway twin turbo C4 Vettes, (which I've never driven unfortunately) were what gave me this idea.


I was thinking that I could even use the L03 in the car as a testbed. There's nothing that wouldn't swap over, and I wouldn't feel too bad if I screwed something up.
Ideally, the 350 would also have forged, dished pistons as well, just to be safe.

 

Well, I found a TPI setup for my wagon yesterday. Guy was selling two complete intakes, I managed to talk him down to $375 for both and a harness. Me and my buddy split it, so I ended getting a complete intake for about 180 when it was all said and done. The only they're missing is all the bolts holding everything together.


The seller included two intake boots and MAFs as well.

Both lowers are the pre 87' intake pattern, and I was told that all of this is corvette stuff. One intake has OEM 305 injectors, and the other has Lucas 01D104B 24 lb/hr injectors, based on the P/N.

I've done a bit more research and asking around, and I'm thinking that I may somwhat abandon the turbo idea for now. I'm just not sure it's necessary for the performance I'm looking for. I underestimated the legendary 350, NA power from a TPI Vortec should be perfect for this car. That said, a turbo is not completely off the table

 

Definately full of poop saying they are Corvette. Those are very obviously F-car fuel rails.

 

That's interesting, I didn't know that. That makes sense seeing as one has 305 injectors. I don't think it really matters either way for my application.