Do I have a flat tappet cam or a roller cam?
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Car: 1986 IROC-Z
Do I have a flat tappet cam or a roller cam?
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?
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Car: '92 RS, '84 Z28
Engine: 383, L69
Transmission: T56, 700R4
Axle/Gears: 3.42, 3.42
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
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Car: 4
Engine: 6
Transmission: 5
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.
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.
Last edited by RB83L69; 02-04-2003 at 09:44 AM.
#6
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.
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.
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Car: 1986 IROC-Z
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?
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?
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Car: 4
Engine: 6
Transmission: 5
my '86 IROC is a little different
I know for sure that it's a 350
I wasn't able to get the casting number
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.
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Car: 1986 IROC-Z
Originally posted by RB83L69
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.
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.
I have my plenum and distributor cap off right now. Maybe I can make out the block's number a little better.
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