If I had two cams with the same duration and lift all the numbers were identical what would be the difference in the two cams execpt the obvious lack of resistance in the roller set-up.

 

Ramp rates or fried flat tappet lifters and cam. You can't get a flat tappet lifter to follow as aggressive a ramp rate as a roller can follow. There is more to it, but that's the main thing at it's simplest.

 

Roller cams generally have steeper ramps than flat tappet cams, so it would be unusual to find two cams with the same advertised and .050" duration.

 

Unless of course they're factory cams; where the factory didn't bother to take advantage of the improvements that the roller system would allow. For example, the peanut 82-86 LG4 cam, and the peanut L03 cam.

If you have 2 cams that are the same, ...... they're ..... uhhhh.... the same. Regardless of the lifter foot design.

Aftermarket roller cams are, and pretty much always have been, FAR more aggressive than flat tappet cams. That's why people went to all that trouble in the first place. The factory just evidently didn't "get it" when they borrowed what the rest of us had been doing for all those years and messed it up.

 

Thank you guys for the info!

One of the main reasons I ask is because 3000 miles ago I put in springs to match comp cams CS XE262H-14. I do not remember what size the springs were so I wanted to get a roller cam that was close to those specs.

Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 224
Advertised Duration: 262 int./270 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.464 int./0.470 exh. lift
Lobe Separation (degrees): 114

This cam was pretty sweet and I do not want to buy parts that did not break during my rocker stud problem.

Let me know guys. Thanks!

 

I assumed you wanted something EFI friendly, so I looked around a bit. This Crane cam seems to fit the bill...

Hyd Roller Cam for EFI
2000-5500 rpm range
112* LSA
--
270* intake
276* exhaust
--
214* intake (at .050)
220* exhaust (at .050)
--
.452" intake
.465" exhaust

Crane grind number is 2032

 

I have a stock brand new convertor that I would like to use so if I could get a cam that has like a 1500-5500 range that would be great.

Air_Adam thanks for the work put in, I appreciate it. Is it the duration that determines the rpm range.

Let me know I like the education!

by the way this is for Tpi

 

Everything about the cam, to some extent, determines RPM range... the spec'd RPM range is where the mfg thinks the cam makes the best power.

Duration is what makes the biggest difference in performance though.

 

I found the numbers on the springs I have.

They are comp cams 981-16
1.7 installed hieght
105 seat preasure
125 open hieght
295 open preasure
Coil Bind Height (in): 1.150 in.
Outside Diameter of Outer Spring (in): 1.254 in.
Spring Rate (lbs/in): 417 lbs./in.

what size roller cam can I use

 

Did you ever decide what size cam to get?

 

yes I think I am going to go with comp cams 08-302-8

Basic Operating RPM Range: 1,200-5,200 RPM
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 220
Duration at 050 inch Lift: 210 int./220 exh.
Advertised Intake Duration: 264
Advertised Exhaust Duration: 274
Advertised Duration: 264 int./274 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.480 exh. lift
Lobe Separation (degrees): 112

this is the cam that will work with the springs that I have. the only thing that I dont like is the fact that it does not have a dual patern

after I port the heads(stock 081's) it should not make much difference

this time around I am also going with a higher compression ratio.

somewhere in the 10:1 neighborhood.

 

I notice you've got .480 lift on the intake and exhaust. Will you have valve guide boss to retainer clearance issues? I ask because I've got .487 on 081 heads with springs that give me 110# pressure at an installed height of 1.7", and from things I've been reading on this board I think it might be the cause of the problem I'm having.

 

explain a little more about what you are talking about with guide boss clearance

I know little

 

I know little too and am just learning.

The guide is what the valve goes up into and helps keep the valve going up and down straight. Now, the retainer is what sits on top of the valve spring, and the distance between the lowest point of the retainer and the top of the valve guide is the guide clearance.

From searches on 3rdgen.org it seems people are saying that factory heads can only handle at the most .480" lift or thereabouts, unless you take your heads to a shop and they shorten the guides as required. Just last night I read of a guy who increased the lift of his cam by putting 1.6 rockers on. It caused too much lift and he ended up knocking chunks of his cam and wrecked the lifters.

With the cam you've chosen, I'd do some asking around and see if your cam is going to cause you any grief or not.