Cam shafts
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,465
Likes: 48
Cam shafts
I have question about cams. I am looking at cams offered in the 1984 thru 86 and the 1988 specs.
I thought the 1988 had a roller cam and that meant a steaper cam lobe and therefore a shorter duration. But the 1988 cam spec has more lift 0.410/0.419 than the 84/86 cam 0.403/0.405. But it has a longer duration 211/219 vs 202/206. So what am I misunderstanding?
What I would like is a roller cam that will pull nice from 1000 to about 5000. rpm
The LSA on the 88 is greater than the 84. Does that give it a rougher idle?
thanks
I thought the 1988 had a roller cam and that meant a steaper cam lobe and therefore a shorter duration. But the 1988 cam spec has more lift 0.410/0.419 than the 84/86 cam 0.403/0.405. But it has a longer duration 211/219 vs 202/206. So what am I misunderstanding?
What I would like is a roller cam that will pull nice from 1000 to about 5000. rpm
The LSA on the 88 is greater than the 84. Does that give it a rougher idle?
thanks
Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
A steeper lobe would give greater duration.
Typically, the larger the LSA number, the smoother the cam will idle.
You didn't say what year your car was, I assume 88, but before recommending a cam it'd be nice to know.
I have a the stock cam from my 91 L98 Corvette kicking around if you are interested.
Typically, the larger the LSA number, the smoother the cam will idle.
You didn't say what year your car was, I assume 88, but before recommending a cam it'd be nice to know.
I have a the stock cam from my 91 L98 Corvette kicking around if you are interested.
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
How aggressive the lobe profile is can be half *** judged by comparing the advertised duration to the duration@.050.
Just looking at the @.050 duration tells you nothing because you have no context to compare it to.
At least with 2 duration points per camshaft you have something to compare to.... A cam that is 300 advertised and 219@.050 is a less aggressive lobe than a cam that is 285 advertised and 219@.050... also provided the lobes are the same lift.
The more info about the cam you have the better you can judge the lobe profile. Sometimes you can get the incremental duration numbers from advertised (@ whatever lift they use), .050 and .200 tappet lifts.
I want to stress that all your comparing at this point is the lobe profile...
Once you talk centerlines in releation to advertised duration - you are now (in a back woods way) talking valve opening and closing events... Which are really the most important thing for an educated engine builder.
Will
Just looking at the @.050 duration tells you nothing because you have no context to compare it to.
At least with 2 duration points per camshaft you have something to compare to.... A cam that is 300 advertised and 219@.050 is a less aggressive lobe than a cam that is 285 advertised and 219@.050... also provided the lobes are the same lift.
The more info about the cam you have the better you can judge the lobe profile. Sometimes you can get the incremental duration numbers from advertised (@ whatever lift they use), .050 and .200 tappet lifts.
I want to stress that all your comparing at this point is the lobe profile...
Once you talk centerlines in releation to advertised duration - you are now (in a back woods way) talking valve opening and closing events... Which are really the most important thing for an educated engine builder.
Will
Thread Starter
Drifting
Joined: Feb 2013
Posts: 1,465
Likes: 48
How aggressive the lobe profile is can be half *** judged by comparing the advertised duration to the duration@.050.
Just looking at the @.050 duration tells you nothing because you have no context to compare it to.
At least with 2 duration points per camshaft you have something to compare to.... A cam that is 300 advertised and 219@.050 is a less aggressive lobe than a cam that is 285 advertised and 219@.050... also provided the lobes are the same lift.
The more info about the cam you have the better you can judge the lobe profile. Sometimes you can get the incremental duration numbers from advertised (@ whatever lift they use), .050 and .200 tappet lifts.
I want to stress that all your comparing at this point is the lobe profile...
Once you talk centerlines in releation to advertised duration - you are now (in a back woods way) talking valve opening and closing events... Which are really the most important thing for an educated engine builder.
Will
Just looking at the @.050 duration tells you nothing because you have no context to compare it to.
At least with 2 duration points per camshaft you have something to compare to.... A cam that is 300 advertised and 219@.050 is a less aggressive lobe than a cam that is 285 advertised and 219@.050... also provided the lobes are the same lift.
The more info about the cam you have the better you can judge the lobe profile. Sometimes you can get the incremental duration numbers from advertised (@ whatever lift they use), .050 and .200 tappet lifts.
I want to stress that all your comparing at this point is the lobe profile...
Once you talk centerlines in releation to advertised duration - you are now (in a back woods way) talking valve opening and closing events... Which are really the most important thing for an educated engine builder.
Will
thank you
Advanced
Joined: Aug 2007
Posts: 62
Likes: 0
Sorry for misleading you. my car is an 1984 4 spd manual. I thought of the 88 cam because it was a roller cam. I would like to roller the whole valve train, someday. I am going to port the crossfire intake and staring me in the face is lifters. I was thinking of changing them to roller lifters. Can I run rollers on a non roller cam. If I can do I use the retro typeor the ones with the instalation kit?
thank you
thank you
For the 1984 block, you will need the retro type roller lifters. The retro type roller lifters are the lifters where the intake and exhaust lifters are attached to each other, so that they do not rotate in the lifter guide. The roller lifter blocks have guides built into them, so that the lifter cannot rotate, and the lifters are not attached to each other. They are individual lifters.
Safety Car
Joined: Apr 2005
Posts: 3,624
Likes: 431
From: Dale City VA
You can run roller lifters on a non-roller cam, but you do not want to put roller lifters on a used cam.
You absolutley can NOT use roller lifters on a flat tappet camshaft.
First. A street intended flat tappet cam is a plain old cast iron core and not heat treated hard enough. The steel wheel on a roller lifter will eat it alive.
Second. Flat tappet lobes have a taper ground into them (this when mated to the crown on the bottom of flat tappet lifter is what promotes lifter rotation).... A roller lifter wheel would not run true across the entire face of the lobe - eating it up.
To run roller lifters you must use a billet steel roller cam or a SADI (Selectively Austempered Ductile Iron) roller cam core which is specially heat treated.... I caution you against running a SADI roller cam core with certain aggressive lobe profiles as many of them have failed.
Will
