69ttop502

I called Crane, Lunati, Crower and Competition cams yesterday and asked for a recommendation based on the following. 502 inch, iron heads with rectangular ports and 9.5 to 1 compression(after milling), Demon 850, 4 speed, 3.70 gears, not sure on the intake yet and I told them I wanted 550-600 horsepower and that it is a street car and I wanted a solid flat-tappet. I was most impressed with the guy at Comp, the others seemed like they were just reading out of a catalogue. He recommended a custom grind with lifts of .578 and .604, duration at .050 of 240 and 250 ground on a 112 LSA. He said it would rev to a little over 6000 and would have great street manners but might have vacuum trouble but should make 600 horsepower. The other recommendations were all slightly milder cams both in lift and durations. Any thoughts on this cam? Could someone run a desktop dyno for me? Thanks.

norvalwilhelm

You have this beautiful 502 with 3.73 gears and a FOUR SPEED. You will kill that motor on the highway. Why not a overdrive transmission?
As for the cam it certainly isn't too wild. With the 502 cubes it will tame the 240-250 duration down. Should also have a nice idle. The 112 lobe centers will help the vacuum alot but it cost mid range. The best cam I had was a Crane 256-264 @ .050 with 108 lobe centers. Not much vacuum at idle but about 3000 it really came on all the way to 7500 in my 460.

MassVette

I love all the knowledge and experience you find on the C-3 Forum, available at the click of a mouse!
:yesnod: :yesnod: :chevy :chevy :chevy :yesnod: :yesnod:

69ttop502

MassVette you are absolutely right about this forum only every question I get an answer to leads to even more questions. Norval you are right about the tranny, that may be next year's project. What are the lift specs on the cam you mentioned and what did it rev to and how much horsepower?

ML67

Norval,

I’m curious about your aversion to cams w/ wide lobe spreads, particularly for BB street engines. I’ve seen you comment similarly in previous threads. I run a 255/260 @ .050 street roller w/ 112 LSA installed 4 degrees advanced. It gives me good idle characteristics, amazing mid range and top end. Jim Moore (427Hotrod) also runs a slightly longer duration 112 lobe spread solid roller in his 540. Granted these engines are 1/4” stroke longer and 38 cubic inches larger than a 502 and will generate more toque than a similarly cammed 502.

I took the liberty of generating DesktopDyno2000 torque and HP figures using the cam specs supplied by Comp on both 112 and 108 lobe centers for a 9.5:1 502. The 112 spread was advanced 4 degrees (108 intake centerline) and the 108 lobe spread cam was installed 2 degrees advanced (106 intake centerline) both common settings for the respective lobe spreads. And yes I checked both cams at several advance/retard settings and only slight changes were evident. Here is what DD2000 gave:

112/108 108/106
RPM Torque Torque Net +/-
2000 442 430 -12
2500 477 465 -12
3000 503 490 -13
3500 539 529 -10
4000 567 556 -11
4500 583 575 -8
5000 579 571 -8
5500 553 544 -9
6000 508 505 -3
6500 453 455 2


112/108 108/106
RPM HP HP Net +/-
2000 168 164 -4
2500 227 221 -6
3000 287 280 -7
3500 359 353 -6
4000 432 423 -8
4500 500 493 -7
5000 551 544 -7
5500 579 570 -9
6000 580 577 -3
6500 561 563 2


I accept DD2000 is far from perfect, however it is reasonably accurate, and is a good tool to compare engine and valve timing variables. As you can see the wide lobe spread configuration gave better performance through 6000 rpm.

On what basis do you feel you lose mid range w/ a wide lobe spread? I previously ran a 260/271 @ .050” solid roller with a 108 lobe spread in a 468 and experienced poor idle characteristics and somewhat lazy throttle response below 2500 rpm.

By the way, I think Comp’s cam recommendations are spot on for 69ttop502’s stated configuration and desired output.

Take care,

Mark

[Modified by ML67, 9:38 PM 11/28/2001]


[Modified by ML67, 9:42 PM 11/28/2001]

Steve439

I'm really surprised Comp Cams recommended a cam with 112 LSA.
I thought 110 was their trademark...

That cam sounds about perfect. I have a 234/244 with 112 LSA solid
roller in my 502 and think I could have gone a little bigger.

I do get 16 inches of vacuum and it runs like a bear...

norvalwilhelm

I have had about 7 cams in the motor over the years and by far the best one I found was the crane F 256/3634-2S-8 with 256 and 264 @ .050 and I really like this cam with it's this is just guessing 106-108 lobe centers . I always installed the cams straight up. I read alot about lengefelter really liking this street roller R288 something which I could look up. It was 244 duration .623 lift 112 lobe seperation. Spent about $1500 converting to this setup and it really was lacking compared to my old F cam. Talked to my friend who is a well known street and strip racer and owns the speed shop, and Roger a CanCar racer for 40 years and they both said not to go roller and not to go with the 112 lobe seperation. I did what I wanted and the cam is not as strong from 3000 up as the old F cam. The old cam was still pulling hard at 7500 plus and this new roller is done by 6000. I know the old cam had more duration but in the 3000-4000 range the old F cam really pulled alot stronger then this Roller.
I don't have any facts just a feeling every time I nail it. I now run a blower so that old cam with it's 108? lobes would not work. I also spent the $1500 so I don't want to throw it away going back.
My new blown motor has alot more power then my old flat tappet nitrous 400 slicked car but it is alot slower.

69ttop502

Thanks guys for the great info. It is good to know that the cam they recommended should work for my car. I have also considered a solid roller but as a cost consideration I will stay flat tappet. Just curious though, how much shorter duration could I run in a roller at the same horsepower level. I am also thinking vacuum here.

ML67

It is interesting we have had very different experiences. I am a fan of solid roller cams -- more vacuum and less "radicalness" than a flat tappet cam of similar duration -- and a wider, more powerful rpm band to boot. You can have the best of both worlds.

In order to accurately compare the effect of flat vs. roller and wide vs. narrow lobe spread, duration should be held constant. Otherwise you are changing too many variables -- which one was it, the roller, the lobe spread or the duration?

I prefer a wide lobe angle -- 110 to 112 for the street. For me the slight (if any) mid/top range gain w/ a tight lobe spread cam is not worth the loss of idle vacuum and low speed throttle response. Again this is my preference and my experience.

Thanks for answering my question.

Take care,

Mark