Settheraytome

I've got myself an 87 vette and almost everything is stock, I'm looking to slap some new heads on to make some more HP. Summit had a few options, the best I see is Edlebrock Performer Heads http://store.summitracing.com for $616 each. Any Idea how much horsepower these will give? Anyone else got ideas for heads? Thanks Guys

tpivette

what are your plans for the motor?

if youre not going crazy and will keep the car close to stock (meaning the cam), i would look at Trickflow's new(er) 175cc heads. they flow 240cfm at 0.500" and have a similar sized chambers (56ccs) as your stock heads. Most edelbrock heads have 64cc chambers, so youll drop your compression with them. FWIW, your stock heads only flow around 200cfm... these should be a substantial improvement over stock, and would work great with TPI

theyre priced at just a hair over $1000 for the pair, fully assembled

http://store.summitracing.com/partde...5&autoview=sku

Settheraytome

Thanks, thats the way comments should be. I hate those guys who would have said something like "you should get longtube headers" or "a supercharger will get you the most HP gain." Everyone take note of tpivette and answer the question instead of throwing other opinions in.
Anyone else wanna throw in your 2 cents about the heads?

JAKE

I installed Edelbrock Performer RPM heads on my 86. Cost was right at $1,000, fully assembled and ready to bolt on. I bought them from SummitRacing and I opted for the upgrade springs to allow me to run a cam with more valve lift (no cost).

Those heads were well manufactured with high quality finishing. I never had a single problem with them. Edelbrock's quality control is outstanding.

However, compared to what's now available from AFR, etc., the Edelbrocks don't flow comparably. Had I to do it today, I'd definitely go with AFR Eliminators with 180cc intake ports. A recent article of dyno results on a 350 LT1 showed that AFR's 195s were marginally too big for those cubes, so 180s would be perfect.

Also, as another poster mentioned, watch out for any compression loss by going with heads having larger combustion chambers.

For each 1 point in compression change, power changes by 3-4 percent.

Hope this helps.

Jake

West Point ROCKS!

JAKE

Oh, and one more point.

With a intake port volume of 180cc, I'd be looking for 240cfm @ .400 valve lift.

That would tell me that the flow is outstanding, while, at the same time, the intake volume would be on the low side, meaning velocity will be high/great. High velocity will provide crisp throttle response.

Hope this helps.

Jake

West Point ROCKS!

"swamp rat"

pm me

ross.rosseland

Even with these heads you won't be much over 200 RWHP if everything else is stock...

JAKE

I'll try to find the dyno results of a stock 87, L98 350 with a pair of aftermarket heads so he can see, realistically, what to expect.

Jake

West Point ROCKS!

87stocker

I have a set of the trick flow 175's and they are great.

Settheraytome

There's another point that I've heard thrown around. Every bit of literature I've read says an 87 vette has 250 hp and 350 lb ft. Then, I was at a full on Corvette only repair shop and a guy told me that my car only has 175hp. Now, Ross up here is being specific and says rear wheel hp, but that's w/high flow heads. Do you guys think thats accurate?
Btw, I'm eagerly awaiting Jakes dyno results...

tpivette

any L98 Vette should dyno around 200rwhp bone stock. Even though GM rated them anywhere from 230 - 250 hp (depending on year and gear ratio) they were really about the same in output. the difference is minimal

JAKE

Okay, here's what I found so far. These are head flow numbers, the company that flowed them and the potential HP they'd make.

The link below is for LT1/LT4 versions but you may be able to back-track on that site and find L98 results.

http://www.malcams.com/legacy/misc/headflow.htm

I just found another site with L98 dyno results, but I could only post one link at a time here. I'll post that link in a few.

I'm still trying to find a listing of the results of JUST HEADS on an otherwise stock engine. I'll keep you posted.

Jake

West Point ROCKS!

JAKE

Here's another one, but still not exactly what I'm looking for.

http://www.geocities.com/MotorCity/7610/dyno.htm

Jake

West Point ROCKS!

JAKE

I just spent a while searching, but I didn't find any dyno results with JUST a swap in heads on a L98 engine.

Realistically, and primarily because of the small cam and restrictive intake setup your engine has, you shouldn't expect a huge jump in power by just changing heads.

I, and others, recommend taking a big picture, total approach. The way it works is to use the old air-pump comparison method.

An engine is like an air-pump, basically the more air you can get into it and the more exhaust you get out of it, the more power it makes.

Swapping one part(s) may increase that part's ability to flow more air, but doing so just reveals another cork in the system. Once that one is corrected to be a better air passer, another cork is revealed.

So, while aftermarket heads will flow more than the stockers, the cam will not allow the engine to take full advantage of them. It's duration is too short and valve lift too low. Once the cam is replaced, the intake and/or exhaust systems will become the bottle-neck.

Since you indicated you want to keep the engine mostly stock, (I take that to mean you don't want to dive into the engine internals) my advice is to go with after market heads - like AFR 180ccs - and high ratio roller rocker arms.

I recommend the path to increased power is to concentrate on the four 'C's:

Cubic Inch Displacement
Cylinder Heads
Camshaft and
Compression.

But since you're only willing to attack one of those - Cylinder Heads - I recommend you add high ratio rocker arms to the mix.

With 1.7 roller rockers, while still keeping the stock cam, you'd increase valve lift by about .060" while, at the same time, you'd add 5 or so more degrees of effective camshaft duration.

Of course, you'd need the valve train parts capable of handling all that - springs, retainers, locks and pushrods. Also, you'd need to verify the needed piston to valve clearance.

http://www.boosperformance.com/c4l98_head_cam.html

If I come across anything else I think might interest you, I'll post it.

Jake

West Point ROCKS!

JAKE

I just saw this but, for some reason, I couldn't pm you. So I sent you an email instead.

Jake

West Point ROCKS!

vader86

As stated, any L98 should dyno around 200rwhp stock on a dynojet. Stock flywheel HP would be 230-250. If its down to 175rwhp on a dynojet-type dyno, you have a problem somewhere and we'd need to see the actual dyno curve to help diagnose the problem.

If you are just planning to do heads, I would not expect much difference in what the peak value is. Where it occurs in the RPM band would likely change somewhat. The '128 heads are fine and can make more power than they do, its just that the rest of the package needs some work to get more air to the head and out of it. I think you would actually be best off just changing to 1.6RR on the stock heads instead of changing the head itself.

And you could always do some portwork on the intake, without changing the outer appearance.

B69mach1

hey, I have an 87 also. I replaced the heads with the trickflow ones a few years back. I gained no additional power when I did. I was running 14.0's in the 1/4 before and the same afterwards. I was very dissapointed, however I did notice the the motor would then rev over 5400rpm where it wouldn't before. Apparently the valves were floating, but I would have swore it was some sort of rev limiter. After that I decided to put a rather large cam in since I had heads that could support it. Next trip to the track yeilded my first 12. 12.94. And the motor pulled hard all the way to 6200rpm instead of falling on it's face at 4800. Just my experiance.

AKS Racing

was that with the factory intake untouched?

tpivette

believe it or not, its a theory that the heads/intake combo are what really choke the TPI cars and not the intake manifold. its been documented that an intake swap on an otherwise stock L98 doesnt do much to the rpm characteristics of the motor, and nets only a 0.1 sec improvement at best at the dragstrip

unfortunately, no one does heads/cam swap on a stock L98 to back this up. they always go for the intake due to all the recycled info on most websites that its the limiting factor on a TPI motor

i would like to see a L98 modified in this untraditional way to verifiy this one way or another

B69mach1

I think I had gasket matched the lower intake and ground off the wall behind the tb. I was still using the stock tb with the airfoil thing on it. Now I'm using a HSR, which is much better