"L98 valve spacing"

[turbo camino]

What's the actual numbers for valve spacing and stud spacing, on the L98 head?

[mag2555]

I don't recall the numbers, but that's not a very beefy head to begin with if your thinking of moving the valve centers on, especially when there ported and on a motor making 430 hp or more your asking for trouble!

With all the aftermarket heads out there today at your disposal, why would you be thinking about messing around with that casting to such a level?

[pdq67]

Got to ask??

What is an L98 head?

It's a new number by me??

pdq67

[mag2555]

It's the first Corvette Aluminum head based on the standard iron heads.

[rebelyell]

small 58cc comb chamber, std "wedge" configuration, Not "fast-burn"

/wikipedia
L98 Years: 1985–1992

The new 1985 L98 350 added tuned-port fuel injection "TPI", which was standard on all 1985–1991 Corvettes. It was rated at 230 hp (172 kW) for 1985–1986, 240 hp (179 kW) for 1987-1989 (245 hp (183 kW) with 3.08:1 rear axle ratio (1988-1989 only)), and 245 hp (183 kW) in 1990-1991 (250 hp (186 kW) with 3.08:1 rear axle). Aluminum cylinder heads (Corvette only) were released part way through the 1986 model run, modified for 1987 with D-ports, and continued through the end of L98 Corvette production in 1991 (still used on ZZx 350 crate engines until 2015 when the ZZ6 received the fast burn heads).[12] The L98 V8 was optional on Jan. '87–'92 Chevrolet Camaro & Pontiac Firebird models (rated at 225 hp (168 kW)-245 hp (183 kW) and 330 lb⋅ft (447 N⋅m)-345 lb⋅ft (468 N⋅m)) The 1987 versions had 20 hp (15 kW) and 15 lb⋅ft (20 N⋅m) more and a change to hydraulic roller camshaft. Compression was up again in 1990 to 9.5:1 Camaro/Firebird and 10:1 Corvettes, but rated output stayed the same.

[turbo camino]

Not looking at moving anything, just wondering how much difference there is between these and standard, and more to the point, why this info is so hard to find. Because it bugs me.

Valve/stud locations were carried over to the LT1/LT4 unchanged, right? Are the dimensions a secret or something? I have googlesearched several times over many many years and never found anything. Found dimensions for standard, Brodix 11-whatever, Canfield somethings, nothing that references L98. I hit a wall every time I go looking. It's a small block Chevy for cripe's sake, there are drawings and blueprints and specs for every dimension for every SBC variant all over everywhere, and there's nothing on what exactly "L98 spacing" means, in real numbers??

[turbo camino]

Cast# 10088113. Also used on the ZZx crate motors.

[BOOT]

Can't help you with any numbers but I bought Jomar stud girdles for my 128 heads(should be same as 113), they say on them Bowtie/corvette part num 1108 for the ultra-lite.

So maybe someone has the bowtie's stud spacing?

[6.50camaro]

Aren't AFR eliminator series suppose to be L98 stud spacing? Dan

[F-BIRD'88]

I believe it is the same as the 305 heads.. 1.89" ??

The L98 engine also came with a cast iron cylinder head too . 1.94x1.50 valves. Casting # Ends in 083 or 217.
So these are "L98 Heads" also.

[BOOT]

Aren't AFR eliminator series suppose to be L98 stud spacing? Dan

I'm not sure but think they are L98 type because of the angle plugs as it says in a few places online like this Jegs link https://www.jegs.com/p/AFR-Airflow-Rese ... 7/10002/-1 Jegs Ad says standard valve spacing

When I tried to research my BPE heads, that were the 1st version like AFR. I found Jomar has different stud girdles for the AFR & corvette heads(L98), since I returned the heads I never got to find out what girdles works.

[turbo camino]

Well I feel, not better, but I guess less bad, about not being able to find anything in my previous searches.

[bill jones]

Here are some spacings of just the valve and stud centers of some personally checked small block heads---probably sometime in the 1990's

------------------------------------valve----------valve------------stud---------------stud
--------------------------------- int to exh----#1int/#3int------int to exh-------#1int/#3int
-------------------------------------c/c--------------c/c---------------c/c---------------c/c
Gm 10061101 aluminum-----1.909"----------2.701"----------1.803"-----------2.795"
Gm 14011049 stage 5.5------1.910"----------2.698"----------1.805"-----------2.796"
Gm Vette #14011128----------1.909"----------2.701"----------1.803"-----------2.790"

Gm swirl port castiron--------1.853"----------2.705"----------1.774"-----------2.795"
Gm #993 cast iron-------------1.855"----------2.697"----------1.782"-----------2.789"

Gm #882 cast iron-------------1.863"---------2.698"
Dart 2 Cast iron----------------1.889"---------2.693"-----------1.770"----------2.795"
Dart 2 ('98)---------------------1.888"---------2.698"
Dart 220's aluminum----------1.895"---------2.697"-----------1.775"----------2.787"
Brodix "streethead"-----------1.888"---------2.673"------------1.772"----------2.792"
Brodix Track 1-----------------1.883"--------2.668"
Brownfield/AFR---------------1.910"--------2.720"------------1.778"----------3.044"

[BOOT]

My sportsman II(bassed on dart II) use standard spacing girdles, but those gm head numbers don't make it look so standard... I mean, I knew vette heads and vortec were diff but didn't know gm moved em around that much.

[enigma57]

You might consider AFR heads. My son has a set of '91-'92 SLP Firehawk headers he is going to run in his '92 Camaro. These were made for the L98 heads and because of the odd angle of the L98 angle plugs, he ended up going for AFR head with the L98 plug angle. Really good flowing heads compared to the original L98 castings and available in several port sizes.

Happy Motoring,

Harry