I know that GM switched to roller cams in 1987, but the L98 in my '86 IROC is a little different... I have centerbolt valve covers, which came out in '87. I'm pretty sure that someone swapped in a later-model 350 in place of the stock 305. How do I tell what type of cam I have? I'd like to put the LT4 Hot Cam in my engine... that should go right in if I have a roller cam, right?

 

if you have a l98 you have a roller. there were no l98s in 86 irocs so as you suspect someone has swaped it.

 

Great. Now, I'm assuming that it's an L98... it's a 350 block with L98 heads...

 

I guess the only way to really find out, would be to pull off the intake. If you see the spyder retaining thinga ma jig, you have a roller, if not you got a flat tappet

 

Yep, no way to tell from outside; even if it's a late model block of a casting number that could be equipped for factory rollers, it might not have been (truck block) or somebody might have put a flat tappet in it; and even if it's an early block not equipped for rllers, somebody might have put the original design roller system in it.

Only way to know for sure is to take it apart and look.

And, as always, if you haven't run the block casting number, you may find it's not a L98 (or any other 350 for that matter) at all, since a 305 and a 350 look the same from the outside. Used car salesman to newbie trading in an import: "Yeah, it runs so strong it must be a 350!" Buyer, impressed by a totally unfamiliar level of torque, unable to differentiate: "The dealer said it had a 350." Buyer resells car: "It's a 350". Next buyer, who's never taken it apart: "I paid for a 350, now I'm pissed!!" We've heard it plenty of times before.

 

Actually, you might be able to get a look at the retainers and spring clamp by simply removing a rocker cover. Another easy way to tell is to remove a push rod and measure the length (on stock engines). It doesn't have to be that difficult.

BTW - My '86 was built in July/August of '86, and has a flat tappet cam (with even flatter lobes). unless you happen to have acquired one of the 70 or so factory test mules equipped with the L98, your engine was probably replaced.

 

Thanks for all the advice. I know for sure that it's a 350... while I wasn't able to get the casting number, I did manage to make out a "5.7" stamped on the back of the block (and almost squished my head in doing so).

About a year ago, I had a thread pertaining to the exact origin of my engine. Vader, I remember you saying that I might have a test mule in that thread. Just out of curiousity, would my VIN number still denote a 305? It does. Also, what would those spring clamps and retainers look like under the cover?

 

If we each had a dollar for every time that sort of thing was posted on this site, we'd all be rich.

Get the casting number. It's the only way you'll ever know. Same for the heads. If you don't have casting numbers, then you don't know what you have, period. But even that won't tell you for sure whether there's a roller cam in whatever block you've got.

If you don't have a casting number, then for all you know those heads could be swirl-port 305 TBI heads, and you might have a whole 305 TBI motor in there... after all they use centerbolt valve covers too.

 

I checked the heads a while ago... they're L98 heads (I'm at school; I don't have the casting number on my heads here). Like I said, I wasn't able to make out the casting number on the block to see exactly which 350 it is, but I know that it's at least a 350 due to the stamped "5.7" on the back.

I have my plenum and distributor cap off right now. Maybe I can make out the block's number a little better.