faulball67

iTrader: (2)

Just trying to see what the max valve lift is on L98 heads. I don't know if there is a difference between the heads from year to year. I've got aluminum L98 heads off of an 87 corvette. Anyone know? Between my cam and my rockers my lift should be .534/.534 and I haven't had any problems, but from the few posts I've seen I should have.

Sonix

iTrader: (1)

Around .480 is the general consensus. Measure it and find out though.

I think with .050" offset locks you'd be ok.

ckeene502

i have a tpis roller cam with .510 int. and .520 ext. with l98 heads. broke every inner valve spring on ext. side on both heads.

keene

faulball67

iTrader: (2)

My valve springs aren't stock. They came in a kit along with the cam. My heads aren't stock but it seems odd that I have been able to run this setup. From what you're saying I should have smashed the valves on the pistons by now. Although the pistons have valve reliefs, I would think that it's not enough for what I'm running. The cam is a Comp Cams Magnum with 244int/244exh at .050 in lift. They say that should be .501/.501 valve lift with stock rockers. I've got 1.6 ratio roller tips. That would be .534/.534 valve lift. Why does it work for me but yours got smashed up at .510?

91Z28-350

if your heads arent stock, then you or someone else probably had the bosses cut down for more lift.

faulball67

iTrader: (2)

That must be it. I never had it done but the guy I got them from said he had some work done. I figured he just went with a basic port and polish. I put on the new springs when I got the cam kit. I bolted up the heads and checked my clearences with some clay and they were good all the way around.

ckeene502

my valves did not hit the pistons....just the valve springs got in a bind. they are the flat wire kind(inner spring). from everything i have read on the l98 alum heads they need aftermarket springs and .100 longer valves if you go over .490 lift.

keene

305sbc

iTrader: (3)

You are referring to the spring damper inside the spring.
You can also have the spring pockets and guides machined down to handle the extra lift without binding the spring. It's cheaper than replacing all the valves.

305sbc

iTrader: (3)

It's not the lift that causes piston/valve contact. It's the timing of the valves in relation to the piston. Lifts are normally very small when the piston is near TDC.

faulball67

iTrader: (2)

Forgot about that. Don't know how I did, considering basic engine operation pretty much would keep that from happening unless I had huge lift and duration, a decked block, or the timing was really screwed up.

This is why I want to start with a whole new block and build from scratch with new parts. I hate not knowing every little thing about what I've bought. That's probably the biggest downfall of buying used heads, blocks, intakes, etc. You just don't know every little thing that has been done

thunderstick

i'm running an LT4 hotcam in mine with 1.6 RR's, .525 lift. had the heads done, though, to support that. had to open up the push rod holes and spring pockets a little bit.

ckeene502

yup...the sping damper is what broke. all of them on the tops...about 1/4 to 3/4 of a coil.

Guest

I was running .517 on the exhaust without issues on L98 AL's, different springs but stock guides,valves, retainers, locks. Clearance was getting tight but I still had enough for the seal and .060 of free space.

faulball67

iTrader: (2)

I'm going to be going with a new cam, intake manifold, and a set of victor jr heads with 1.6 roller rockers. The max lift is .650 on them, and they will flow a hell of a lot better. For my cam and intake combo I was thinking of going with either an

isky mechanical roller cam with 260/260 duration at .050" lift, .602 valve lift, and 108 lobe sepration with a Victor Jr. intake manifold

or

comp cams mechanical roller cam with 255/255 duration at .050" lift, .575 valve lift, and 110 lobe seperation with a Wieand Team G intake manifold.

I think I like the second combo better because both the cam and intake have lower basic operating rpm ranges. Just trying to get some opinions on this.

shawntmartin

L98heads come on the ZZ4 and it has a .510lift cam from the factory. What is this max .480lift thats being discussed? The Hot Cam kit is a direct bolt on for the ZZ4. (.525lift) You don't have to touch the heads. Go to salleechevrolet.com and ask them. They build/modify every GM crate engine there is. They do tons of mods on the ZZ4. (L98 Heads)Everything from stock to a 440HP version. They know what they're doing. If anyone has had problems with these heads under .525 lift then the problem is somewhere else...maybe the wrong valvespring? Don't know. But I know the Hot Cam Kit (.525) works with no mods. My buddy has it in his ZZ4.

sofakingdom

iTrader: (1)

Just because the head casting # is the same, doesn't mean the heads are prepped the same. All it takes is a little different milling on the top of the valve guide.

Remember, you're talking about a "performance" crate motor, vs a fuddy-duddy production car motor. After all the L98 had TPI, wasn't alot of point in going overboard with head prep that the motor could never possibly make use of. The ZZ4 on the other hand is expecting a MUCH freer-flowing intake setup. Lots more HP and RPMs.

Guest

Yep, could even be they used different valves. Between valve jobs, different seals, locks, retainers, valves, safest to check what you have rather than break parts if you are nearing the limits.

shawntmartin

Ahhh... the race shop at Sallee never mentioned this head was "touched" when GM put them on the ZZ4. On their forum someone had said that they had found a cheap pair of L98s off of a Corvette and was looking for a cam recommendation. Sallee suggested the Hot Cam. So I assumed that Sallee would've mentioned if the .525 lift was a problem. You know what happens when you assume!!