Hey guys, I'm a new guy just looking for some opinions. I have read through all the old tech articles I could find easily and didn't find a direct answer to my question, background first. I am a former ASE certified mech and I know my way around the older cars fairly well. I drove a C4 today I am thinking about purchasing. It has QA1 adjustable coil overs with single reservoirs. The cars suspension felt great, real tight and very responsive, but to me it didn't feel much stronger than my 87 IROC I used to have (no disrespect intended). My question; can I make the tune port L98 engine stronger without changing the injection style and keep the tune port style injection in place. I have seen Edelbrocks runner and base plate configuration but it looks really pricey to buy both and from past experience I don't think it will create that much of a hp gain. I know the heads are a small port 58cc variety, which means high compression is easy to attain. But it also looks like the runner volume is small, thus limiting flow characteristics. I would like to keep as many stock parts as possible, ( except for injectors and a larger throttle body). Can the heads be ported, or would I be better off building another short block and going with Vortec style heads then bolting the tune port system back on? I would like to keep the tune port system for nostalgia, and I am looking for a respectable 275-300 ponies at the wheels. Thanks in advance, great to be here. If there are old posts like this please just direct me to them, I am not trying to hog post space.

 

Suggest a 92 or newer.

With the LT1 engine, you already have the 300 ponies - stock.

The attached spreadsheet breaks down the hi-lights of the C4 lineage - year by year.

 

Thanks, is that the same engine platform that was in the 94 Z28? I had one of those cars, although I was pleased with the performance, I had alot of issues with the ignition system on that car.

 

If looking at an L98 C4 I suggest '88-'91 as these had the #113 "D"-port heads that bring maybe 10chp more than the prior heads.

Such an L98 can be built to put 300 hp to the rear wheels:
-port & work the #113 heads
-go with a nice cam, TPIS has a good one
-do FL headers with true dual exhaust
-add LT runners (to keep that TPI low end torque)
-improve the ignition to fire well to 6,000rpm
-install a 160 deg T-stat and program the fan on/off around that temp
-bump fuel pressure to match added air flow

If you get an A4, try a 2,000rpm lock-up 12" TC and a Trans Go shift kit.

For such a build up I like the '88 & '89 years.

I had my prior '88 Vette up to 300chp with stock heads & cam & headers. The above mods would easily have pushed it to 360chp.

FYI, when making 300chp my '88 ran low 13 in the 1/4 mile and would pull a bone stock LT1 because the TPI makes more low end torque.