Hey all,
I know I could spend a lot more money on a better set of heads. I'm working on a deal to get these heads really cheap. They are stock and complete. I have a 92 L98 with no major mods, only a chip, air foil, filters.

The questions:
Besides being aluminum, what is the difference between these and the cast iron L98 heads?
The chamber size? Different from the stock cast iron heads?
Springs, valves, will I run into any issues?
I plan to get SLP's 1 3/4 headers while I'm at it. Will there be any problems/differences that would cause me problems? Like spark plugs?
Do you know the casting number of these heads? I need to make sure they are post 86, right?
Last... Your comments on these heads. I know if I had $1000.00 I would a different route with some trick heads. For the price, sub $200.00, can I go wrong? Thanks for your time.

 

For under 200$ you cant go wrong.

 

As far as I know the aluminium L98 heads have a 58cc chamber which will give you a slightly larger compression ratio on a stock L98 bottom end. They should flow a little better than iron L98 heads also. So for 200 you really CANT go wrong. LOL

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

I like the reduced weight on my front end after I installed my ZZ4 with the aluminum D port vette heads. You will notice an increase in underhood temps, the aluminum disapated heat more quickly then the iron heads. $200 sounds like a great deal.
Sorry, I'm stupid when it comes to valve sizes/lift etc.

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Rob P
89RSconvtZZ4TPI
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

 

As Rob said, you can't go wrong for $200. I got my 90 L-98 heads and complete TPI off of a friends 90 Vette for $400, so that is a great price. I knew a friend and got a really really good deal on having them fully ported, 3-angle valve job, replacing exhaust valve guides, machining for teflon seals, milling/reconditioning, cc'ing all chambers to 60 cc's, and installation of 2.00" FERREA valve and 1.5" MANLEY valves for $590. They work GREAT. You will like them, and remember that LPE uses these very heads PORTED on some of their potent L-98 based 383's, to make tremendous power.

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88 Monte SS 355 TPI/LT-4 HOT CAM/AFR Hydra-rev/ T-56 6-Speed

 

2 things missing:

There is no EGR port in the heads, nor can you drill one in. Do you need to retain the EGR for emissions?
The intake bolt pattern is the pre-87 style, so you would need to modify the intake. I have done this, its not too hard.

 

The two issues you mentioned... Do they only come into play if the heads are pre 86 or 87? What if the the heads are from a 1990 'vette? Wasn't the the only difference between a 'vette's L98 and a camaro's L98 the aluminum heads? Thanks for all the input. John

 

'85-mid'86 Corvettes had iron heads. Mid '86-up were the aluminum ones, and they are all the same.

Eventhought they have the centerbolt vavle covers, they have the intake bolt pattern of a perimeter bolt head. This means you will have to drill your intake to change the angle on the two center bolts on both sides. Another alternative would be to upgrade to an aftermarket base. It would be drilled for either angle.

As mentioned earlier, the Corvette heads have no EGR provision. If you need to remain emissions legal, you won't be able to use them. If not, then they will work fine.

The aluminum Corvette heads are the same casting as the ZZ3/ZZ4 heads. The ZZ4 used better (LT4) valve springs though.

The valve size is the same as your iron heads, 1.94/1.50. The combustion chamber is smaller.

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'91 Z28 Blue/Silver ZZ4/ZF6
335.9 rwhp 374.9 rwtorque

 

The Corvette also had better exhaust manifolds.

 

You guys have been great. Thanks!

So.. the ERR provision was not on 'vette heads. Did they have a completely different EGR setup?

Another point, but I think I answered it myself... The prototype 25th camaro, the one they had plan to make, but never did. It used 'vette heads, since it was a prototype car, they would have no emission worries/hassles? That brings up another question, how would GM get around this?

Would it be too much of a hassle to have a 'vette style EGR setup? If in fact that it's different than a camaro.

As I write this, I'm leaning towards a good set of aftermarket heads. But if there's a work around with my situation, please let me know. Thanks again everybody. John

 

I've got the L98 heads on my car too. I'm going to put in the Corvette EGR setup. Right now I have no EGR hooked up, and only occaisonally get a code 32. My smog check is next month, so I'm rushing to get the SLP 1 3/4" headers modified for the EGR tube, and the TPIS intake installed to make it legal. I finally got a digital camera so I will take pics of this when I do it.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

Kevin,
Modify the SLP headers? Is that what they are talking about when they sell the headers with or without air tubes? Or is it something completely different?

Sorry for the ongoing thread of questions... You guys have been more than helpfull! Thanks. John.

 

No. The SLP headers without the AIR tubes are sold that way for race applications, or for people who dont have to pass smog checks. The ones with AIR tubes are 50 state legal for emissions purposes. I have to weld a tube to the #8 primary up over the valve cover and connect it to the EGR port on the back of the intake, like the Corvettes do. This means I'll have to relocate my coil as well, because its in the way.

 

To clarify there are 2 version of the Vette AL L98 heads. The original was used from mid 86 through 87 and had the same exhaust port as the iron heads. It's casting # is 128. From 88 onward the exhaust port was raised 0.100" and reshaped like a "D" laying on its side (flat floor and curved sides/roof) for better flow. It's casting # is 113. These are the only differences between the versions.

 

I have casting #113 with no EGR passageways on my 305. I ignored the fact that these heads have no EGR passageways and reinstalled my EGR system. We have yearly emissions checks in Arizona (visual and sniffer). Obviously I pass the visual inspection. Here are my tailpipe sniffer values:

Idle.....Readings...Maximum
HC (ppm).....14........220
CO (%).....0.00.......1.20

Loaded...Readings...Maximum
HC (ppm).....30........220
CO (%).....0.01.......1.20

Based on my results, I would not worry about the fact that these heads have no EGR passageways. Just hook up the system as though it had (like I did) and you should be okay.

------------------
Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
12.57 @ 111 mph.
12.04 @ 114 mph (50-hp nitrous).
http://www.ozemail.com/au/jca69/mods/williesz/willie.html

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

[This message has been edited by Willie (edited October 06, 2000).]

[This message has been edited by Willie (edited October 06, 2000).]

 

Willie,
Thanks for the info.

Looks like you are getting a great deal of horsepower from those heads. Did you have a lot of work done to them?

What was the chamber size for the camaro L98 iron heads in 1992? I know these 'vette heads are 58cc and will increase my compression, but how much? Rough estimate? Thanks everybody. john

 

I have a set of 86 Corvette convertible heads (aluminum) and they have the D port exhaust. They are not the #128 casting you listed.

 

2 bonus questions.....
what does the heat riser do?
does modifying the stock intake to use these heads consist of drilling holes to match the bolt holes on the head?
Thanks,
Dennis K

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88 Formula 350

 

John, they are ported and polished. Nothing special. They do not have guide plates, so you'll either have to use self-aligning rockers or have the stud surface milled to accept guide plates.

I didn't mention last time that I also have 1-3/4" SLP headers. They were absolutely bolt-on to these heads with no mods necessary. I use stock Corvette plugs (don't need shorties) and because these heads have an angled plug design, removal is relatively simple.

Willie

 

Dman, that is what you would do, is modify the intake (if its an 87 up intake) so that you can put in the center 4 intake bolts.
The heat riser is to heat the intake when its cold to aid in emissions and help warm up the engine faster, and later it was used for the EGR system.

 

John,
Sounds like a great deal! Be sure to (if you haven't already) check for stripped or galled threaded holes. Look at all the exhaust manifold bolt, spark plug and accessory holes. It would be a major bummer if you bought them and found out later. In most cases the holes can be drilled out and a heli-coil or threaded insert plug can be installed.

I busted an exhuast stud off on my 305 TPI head when installing headers. At this point I decided to remove the heads and port them. I used an easy-out to try and extract the broken stud only to break the damn easy-out off in the head! YIKES! Well I used my dremel with carbide burrs to remove the easy-out. The damn easy-out is made out of H-2 tool steel and is hard like carbide. I had a hell of a time getting it out. After about 2 hours of dremel time and 2 bits I got the easy-out and broken stud out. The hole in the head casting was elongated from using the dremel. I made a steel guide plate(have access to a machine shop...perks of being a mechanical engineer) and a endmill setup on a knee mill to fix the fubared hole. Tapped the hole, inserted the heli-coil and was good to go! Here is the funny part........turned out that the hole I repaired was used only for stock exhaust manifolds......didnt need it with the headers. Chalk it up as a learning experience! LOL!

Sorry to go off on a tangent there!

Like I said........check ALL of the threaded holes over. If there are some damaged you may be able to repair them yourself if you or a bud have the right tools. Otherwise your good deal could be eclipsed by the cost of a shop repairing them for you.

Are you buying them from someone you know or ?

Mike

 

Well guys,
The deal fell through. The guy was as helpfull as a warm bowl of spit. Never answered my emails in a timely manner, and when he finally did, the answers to my questions were very short and unclear. Then when I followed up on how I can get a hold him, he tells me that they are sold.

But thanks for everyone's input. Take care. John

 

Hey guys,
I found some guy that is willing to sell me some L98 heads and he has a 'vette intake with it. I had a couple of questions about the setup though.

Will the 'vette base gain me anything? He had said that it was port matched with the heads. So, besides the obivious gain by the matching, does the base (stock) flow better than a camaro base?

Since I would have a 'vette base, can I use the 'vette EGR setup? Will I have to modify cylinder #8 with a fitting or something? What's involed with that task?

Thanks in advance. John