Hi, are the D-port Vette heads really worth it? I like the fact that they have the smaller chamber than the iron TPI heads I have. If a guy could get a set of these heads for a good price, can they be made to flow good with a little porting at home, or is it wise to just get a set of aftermarket ones? I have a pretty aggressive combo in my motor now and I think the stock heads are holding me back alot. If anyone needs more info, or has some input please post it! Thanks

 

In a word YES!!!!
How does 317 rwhp 418 rwtq sound?

Done with TPIS big mouth,LT 4 hot cam, 1 3/4
SLP's, 3:45's and a 52mm TB. AS&M runners.

This was done on another car w/350.

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Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

[This message has been edited by Dyno Don (edited August 24, 2001).]

 

I have a pair of 89 aluminum vette heads for sale if your interested. Asking $450 for the pair. Email me for a phone number.

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1991 Z28 305 5spd 1LE, TES headers, dual cats, 3 Chamber flowmaster, Comp cams .488/.495 212/218, 187 head castings with bigger valves, self-burned eproms.
All work done by myself, and proud of it!
SOON TO COME 327 Miniram (3/2002) PARTS NEEDED:Titanium valvetrain parts, stud girdles, fluidampnr, miniram, bulletproof bellhousing, MONEY(im in college).
Find a .bin on the internet and want it burned? I'll do it for you!

 

I just got my aluminum L98 heads today, and would like to know specifically what needs to be done to them to make serious power! I'd be REALLY happy if I got over 300 HP out of my 350! I'm planning on keeping the stock TPI (ported of course) on my motor, and have SLP 1 3/4 headers and exhaust. I'm having my 700R4 rebuilt but am probably going to use a stock-replacement converter. Is 300 HP realistic?

 

I should have read your mods better.. You're getting 317 RWHP with a 305? Damn, that's awesome. I shouldn't have much of a problem getting close to that with a 350 then, should I?

 

These heads can make some good power. I got mine used and did some self-porting. I pocket ported the heads, intake and exhaust, and polished the exhaust runners and port matched them to my intake. This took about a day and I would recommend some porting to these heads. They are great, but the combustion chamber design is somewhat outdated, not a biggie though.
My results with a stock base & runners, and ported plenum are in the sig. This is with a mild comp cam and the 356.
300 hp would be easy cheesy.

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'88 RS (originally 2.8)
-350, .040 over, vette alum. L98s, stock tpi.
-305 injectors & chip
-TES headers & edelbrock cat back
-3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
on a 2.050 60 ft.
(Damn the 2.8!)

 

350, not 305... trust me.

Pay lots of attention to the bowls and short side radius, and clean up the port entry some and they are good to go. The exhaust is pretty good as is, just make the port larger.

 

I'll try to answer your question, but you'll have to forgive my hazy memory as it's been 9 years since I've done any hotrodding... and I've slept since then.

L98 Vette heads can be modified to perform pretty well but aren't that hot right out of the box, at least compared to most aftermaket heads. You should be able to modify them for less than a set of new aftermarket heads and probably save a lot if you can find a set of used ones cheap (it doesn't matter if they need rebuilding, you are going to be reworking them anyway).

Vette heads really suffer on the exhaust side and the valves are small. I assume you are going to use them in a street car, rather than a race only car, so I would do a decent street porting job, which would include:

1. Replace valves with larger stainless steel, high-flow, swirl-polished valves. If I remember correctly, 2.02 valves won't fit without replacing the seats, but something like 2.00 will fit.

2. Do a competition 3-angle valve job... preferably done on a Serdi machine, rather than by hand.

3. The major work needs to be done on the exhaust side; the short turn radius can use a lot of help.

4. Open up the bowls on both intake and exhaust sides.

5. In the chambers, the valves need to be unshrouded.

6. Port match the heads to the intake, blending the ports in about an inch or so. (this is something that you can probably do yourself with a Dremel tool). You don't want to polish the intake ports (... or chambers) on a street motor.

There are other concerns with these heads that must be considered. If memory serves, the springs are only good to about .480 lift and aren't strong enough for hotter cams, so a new set of srings may be in order if you are using a fairly hot cam. There are some high performance GM springs (maybe from a 302??) that will take lifts up to about .520 and fit without machining the spring seats. If you need more lift, you will probably have to get springs that will require spring seat machining in order to fit. With stouter springs, you may want to get titanium retainers and keepers.

These heads come with self-centering (or whatever it's called) rocker arms, and the guide plates aren't true guide plates. The slotted tips of the rockers keep the rockers and push rods from moving around. The (so called) guide plates are just there if things get too out of hand. If you are going to chunk the stock rockers in favor of roller or roller-tipped rockers, you will have to replace the rockers, guide plates, and (I think) push rods (I seem to remember that these use bigger diameter push rods that won't fit with regular guide plates), and possibly the screw-in studs may be different size. I recently saw somebody that sells slimmed down roller rockers that will fit under stock valve covers, but regular roller rockers won't. Roller-tipped rockers will fit under stamped steel covers, but Vette aluminum covers have some webbing inside that interferes and will have to be removed (breaking it off will do) in order for them to fit.

Another consideration is that these heads have no provision for EGR. If you are in a strict smog state, they may not be viable. I think Vettes draw gas for EGR from the headers. I think there is a pipe that connects from the headers to the EGR valve. Fabricating something along those lines (or using Vette headers) would be required for proper EGR operation. Besides the smog aspect, EGR reduces cylinder temp (due to decreased back pressure) and thus reduces pre-ignition. Aluminum heads naturally run cooler than iron heads, so the heat from the lack of EGR should not be a problem.

Surfacing the heads will reduce chamber volume on these already small chambered heads (58cc ??), but unshrouding the valves will remove some material and return the chambers to about stock volume. Different thickness/type head gaskets can be obtained to increase or decrease cylinder volume and thus a corresponding change in compression ratio.

It wouldn't hurt to put bronel valve guides (a bronze alloy for street use, rather than plain bronze). And lastly, you might as well install some positive retaining valve seals.

As you can see, these heads take some work but you should be well rewarded in performance and should still come out cheaper than aftermarket.

Good luck