Another cam recommendation. Hyd roller - Chevelle Tech
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post #1 of 39 (permalink) Old Sep 17th, 19, 10:52 AM Thread Starter
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Ron
 
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Another cam recommendation. Hyd roller

I currently have the Clay Smith "Old School" Hyd roller cam in my 496,( https://www.claysmithcams.com/hr-880...x-of-5700-rpm/ ).When I had the 4 speed trans the engine would surge at lower rpms and was pretty annoying, I tried to tune the surge out of it but never could, I eventually changed the trans to a 700r4 and the surge was absorbed by the converter, I can still hear the surge but cant feel it in the car. I am changing back to a 4 speed and don't want the same issue. So, I want a different hyd roller cam that will cruise smoothly at lower speeds.

70 Chevelle, total street car.
496 10.3 compression
iron 049 heads with bigger valves and a little porting work.
3.73 rear gear with 275/60/15 tires (28" tall)

70 Chevelle SS396 (496) Straub roller, 700r4
69 Malibu convertible (sold)
95 Z28 Convertible T56 6 speed
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post #2 of 39 (permalink) Old Sep 17th, 19, 2:45 PM
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Re: Another cam recommendation. Hyd roller

Not completely sure, but surging to me sounds like a carb tuning issue.
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post #3 of 39 (permalink) Old Sep 17th, 19, 2:53 PM
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Re: Another cam recommendation. Hyd roller

Ron,FWIW I run a 248/[email protected] 110 LSA and I have no surge. What does the timing curve look like?


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post #4 of 39 (permalink) Old Sep 17th, 19, 3:14 PM Thread Starter
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Re: Another cam recommendation. Hyd roller

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Originally Posted by mr 4 speed View Post
Ron,FWIW I run a 248/[email protected] 110 LSA and I have no surge. What does the timing curve look like?
Timing is at 18 initial ,gives me 36 around 2800 rpm. Vacuum can hooked to manifold vacuum. I have tried the initial up to 24 and down to 12 no difference except I get a lot of detonation at the higher setting.
I have tried to tune the carb every which way but ran out of ideas.
Actually I think the cam is a little small for a 496, on the dyno it made peak power just shy of 600hp, at 5300 and began falling off fast after that.
I know some people want it to have that rumpity sound at idle, I don't care about how the idle sounds, I just want it to run good and not surge, I want the drivability. The car runs great with a lot of power, this cam makes great power until I get to a little over 5000.
Thanks guys, any specific cam to recommend?

70 Chevelle SS396 (496) Straub roller, 700r4
69 Malibu convertible (sold)
95 Z28 Convertible T56 6 speed
TC #54 Gold



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post #5 of 39 (permalink) Old Sep 17th, 19, 3:26 PM
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Re: Another cam recommendation. Hyd roller

I would try running without the vacuum advance and see if the surge goes away. If it does,then the amount of vacuum advance needs to be limited.
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post #6 of 39 (permalink) Old Sep 17th, 19, 3:59 PM
 
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Re: Another cam recommendation. Hyd roller

In that CID Ron, I haven't had anyone with a surge issue. Have you borrowed a carb from someone and tried something else? I have a ton of C3 customers with factory 4 speeds and they all love that cam in 454 to 468 CID. A 496 should swallow it and with the power dropping the way it does after 5300 it does swallow it.

The 229's little brother is .221/235 on a 109 LSA. I have a ton of guys with C-10's that love this thing as it will haul the heavy's down the road.
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post #7 of 39 (permalink) Old Sep 17th, 19, 5:56 PM Thread Starter
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Re: Another cam recommendation. Hyd roller

Quote:
Originally Posted by cstraub View Post
In that CID Ron, I haven't had anyone with a surge issue. Have you borrowed a carb from someone and tried something else? I have a ton of C3 customers with factory 4 speeds and they all love that cam in 454 to 468 CID. A 496 should swallow it and with the power dropping the way it does after 5300 it does swallow it.

The 229's little brother is .221/235 on a 109 LSA. I have a ton of guys with C-10's that love this thing as it will haul the heavy's down the road.
Thanks Chris, yes I have tried 2 other carbs, Now I have a Quick Fuel 750 Vac secondary carb, I have also tried a Holley 750 vacuum sec carb and an AED 850 double pumper, all act the same. I haven't tried disconnecting the vacuum advance, I'll try it tomorrow.

70 Chevelle SS396 (496) Straub roller, 700r4
69 Malibu convertible (sold)
95 Z28 Convertible T56 6 speed
TC #54 Gold



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post #8 of 39 (permalink) Old Sep 17th, 19, 6:02 PM
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Re: Another cam recommendation. Hyd roller

With that iddy biddy cam I would think it would be smooth.
I have a much larger cam and only had surge if I did it with the pedal!

I also don't surge in OD unless it is at less than 1800 rpm which is when the cam clears up
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post #9 of 39 (permalink) Old Sep 17th, 19, 6:03 PM
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Re: Another cam recommendation. Hyd roller

TRy your vacuum advance on ported...see if that helps. Or try without it.

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post #10 of 39 (permalink) Old Sep 17th, 19, 6:34 PM
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Re: Another cam recommendation. Hyd roller

what gear/rpm was it surging at?

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post #11 of 39 (permalink) Old Sep 17th, 19, 6:36 PM
 
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Re: Another cam recommendation. Hyd roller

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Originally Posted by tacomatrd View Post
With that iddy biddy cam I would think it would be smooth.
I have a much larger cam and only had surge if I did it with the pedal!

I also don't surge in OD unless it is at less than 1800 rpm which is when the cam clears up
Your cam is a solid flat tappet. When comparing a flat tappet lobe to a roller lobe for area you need to subtract 18 degree if your comparing the lobes for area. 18 is not set in stone but a good starting point. So your Flat tappet that is 250/256 in roller area would be 232/238 @ .050"
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post #12 of 39 (permalink) Old Sep 17th, 19, 7:15 PM Thread Starter
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Re: Another cam recommendation. Hyd roller

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Originally Posted by cuisinartvette View Post
what gear/rpm was it surging at?
It surges anywhere from 2200 to 2800 rpm in 4th gear (od) at steady speeds

70 Chevelle SS396 (496) Straub roller, 700r4
69 Malibu convertible (sold)
95 Z28 Convertible T56 6 speed
TC #54 Gold



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post #13 of 39 (permalink) Old Sep 17th, 19, 8:56 PM
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Quote:
Originally Posted by cstraub View Post
Quote:
Originally Posted by tacomatrd View Post
With that iddy biddy cam I would think it would be smooth.
I have a much larger cam and only had surge if I did it with the pedal!

I also don't surge in OD unless it is at less than 1800 rpm which is when the cam clears up
Your cam is a solid flat tappet. When comparing a flat tappet lobe to a roller lobe for area you need to subtract 18 degree if your comparing the lobes for area. 18 is not set in stone but a good starting point. So your Flat tappet that is 250/256 in roller area would be 232/238 @ .050"
Is it really 18 degrees??
I thought it was around 6 or so. That's pretty crazy. I am going to switch to a roller cam in the next year or so, expect a call when I'm ready!
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post #14 of 39 (permalink) Old Sep 17th, 19, 9:19 PM
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Re: Another cam recommendation. Hyd roller

Chris, what about HFT to HR? Have a friend with a 454 thats getting a set of 290s and a Edelbrock street ram
Had a bottom of the page HFT trying to get him into a roller. Not sure he knows what hes missing.

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post #15 of 39 (permalink) Old Sep 17th, 19, 9:51 PM
 
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Re: Another cam recommendation. Hyd roller

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Originally Posted by cuisinartvette View Post
Chris, what about HFT to HR? Have a friend with a 454 thats getting a set of 290s and a Edelbrock street ram
Had a bottom of the page HFT trying to get him into a roller. Not sure he knows what hes missing.
A flat is physically limited to lift rate. Modern day heads flow air quick. You want to open a valve and shut it as quick as possible to make the biggest bang in the shortest amount of time. Delphi shut down the flat tappet lifter production line. Flat tappet lifters today are coming from China.
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