Camshaft Help WARNING LONG

Posted By: titan

Camshaft Help WARNING LONG - 06/10/12 03:28 PM

Hello. I Am Doing A Rustoleum Rebuild On A '72 400 with 55,000 miles on it. It Will Be A Temporary Engine Until I Build My Stroker In The Future.I Do However Plan On Stepping It Up A bit By Adding A Fresh Set Of Big Valve Mildly Ported Closed Chamber Heads I Have, A R.P.M. Intake With 750 Holley & A Cam. The Cam I Do Not Already Have, But Was Looking At The Whiplash Grind From Hughs & Have Some Questions.On A Desk Top Dyno It Appears To Make Pretty Good Power With A Fairly Choppy Idle.I Do Not Really Care About The Choppy Idle As Much As The Power Output. So, What Aspect Of The Whiplash Cam Accounts For The Choppy Idle Quality? Can I Lower That And Retain Or Better Yet Achieve even more Power?Here Are The Whiplash Specs.

Lift .518 @ 1.5 Rocker Arm
DUR @ .050 229/242
LS 107 deg
IO 12.5 BTC
EO 53 BBC
IC 36.5 ABC
EC 9 ATC

Posted By: MR_P_BODY

Re: Camshaft Help WARNING LONG - 06/10/12 03:40 PM

Quote:

Hello. I Am Doing A Rustoleum Rebuild On A '72 400 with 55,000 miles on it. It Will Be A Temporary Engine Until I Build My Stroker In The Future.I Do However Plan On Stepping It Up A bit By Adding A Fresh Set Of Big Valve Mildly Ported Closed Chamber Heads I Have, A R.P.M. Intake With 750 Holley & A Cam. The Cam I Do Not Already Have, But Was Looking At The Whiplash Grind From Hughs & Have Some Questions.On A Desk Top Dyno It Appears To Make Pretty Good Power With A Fairly Choppy Idle.I Do Not Really Care About The Choppy Idle As Much As The Power Output. So, What Aspect Of The Whiplash Cam Accounts For The Choppy Idle Quality? Can I Lower That And Retain Or Better Yet Achieve even more Power?Here Are The Whiplash Specs.

Lift .518 @ 1.5 Rocker Arm
DUR @ .050 229/242
LS 107 deg
IO 12.5 BTC
EO 53 BBC
IC 36.5 ABC
EC 9 ATC

LSA... if you go with a wider LSA it will smooth out...
it closes the intake later which gives you less cyl
pressure in low rpm

Posted By: cheapstreetdustr

Re: Camshaft Help WARNING LONG - 06/10/12 03:55 PM

the 107 number on your cam..
go to 106 for a more radical sound
110 112 for a smoother idle...
just for reference. as you look at cams..
we are not talking/adressing performance in this answer...only idle quality..

Imho if its a street car..look for lower mid range power/increases and anything that increases cyl pressure on those dished low compression pistons that 400 comes with..
(in your scenario) increasing head flow at this point isnt going to give you a gain in low rpm performance. vrs money spent.
but the right cam and intake sure will....

unless your 48k converter and 4.56 and planning on revving it all the time to find power.

fwiw

Posted By: titan

Re: Camshaft Help WARNING LONG - 06/10/12 04:46 PM

So What I Gather From What You are saying Is, To Widen Lobe Sep. I Will Loose Choppy Idle Some, But Also Loose Cylinder Pressure? I Do Not Want That, Have To Just Keep The Choppy Idle.

Posted By: 383man

Re: Camshaft Help WARNING LONG - 06/10/12 08:05 PM

Quote:

So What I Gather From What You are saying Is, To Widen Lobe Sep. I Will Loose Choppy Idle Some, But Also Loose Cylinder Pressure? I Do Not Want That, Have To Just Keep The Choppy Idle.

No he means the camshaft installed centerline. The lobe seperation angle is ground in the cam and cannot be changed.

We run a .030 over 400 (406) in my sons Dart. Its a pump gas street car that he drives to the track like me. He uses the RPM intake with a 750 DP also and it seems to work real good on it as he tried an 830 and a 800 and the 750 still ran the best. It has EDDY RPM heads that are cut a little for 10.6 comp and it runs fine on 92 pump. We use the MP .557 solid cam in it on a 105 centerline and he really likes it. It weighs just about 3600 lbs with him in the car and uses 3.91's with a Dynamic 9.5 converter. His best ever pass was 11.45 @ 117 in good air. Normally runs 11.50's to 11.70's on hotter days. But for a stock stroke 400 it works pretty good as you seem to never see anyone run a stock stroke 400 anymore as all are always stroked. I think half the people dont believe its not a stroker. Good luck with yours. Ron

Posted By: DrCharles

Re: Camshaft Help WARNING LONG - 06/11/12 12:18 AM

Quote:

Quote:

So What I Gather From What You are saying Is, To Widen Lobe Sep. I Will Loose Choppy Idle Some, But Also Loose Cylinder Pressure? I Do Not Want That, Have To Just Keep The Choppy Idle.

No he means the camshaft installed centerline. The lobe seperation angle is ground in the cam and cannot be changed.

Well, that's definitely true, but I think the post meaning is: cams with tighter LSA's tend to have rougher idles. So to get a smoother idle he would need to change to a cam with a wider LSA... right?

I suppose advancing the installed centerline would help the idle too, but that's not usually why cams are advanced...

Posted By: MR_P_BODY

Re: Camshaft Help WARNING LONG - 06/11/12 01:29 AM

Quote:

Quote:

Quote:

So What I Gather From What You are saying Is, To Widen Lobe Sep. I Will Loose Choppy Idle Some, But Also Loose Cylinder Pressure? I Do Not Want That, Have To Just Keep The Choppy Idle.

No he means the camshaft installed centerline. The lobe seperation angle is ground in the cam and cannot be changed.

Well, that's definitely true, but I think the post meaning is: cams with tighter LSA's tend to have rougher idles. So to get a smoother idle he would need to change to a cam with a wider LSA... right?

I suppose advancing the installed centerline would help the idle too, but that's not usually why cams are advanced...

The 107 LSA cam has more over lap than a 112 lsa
the over lap is the roughness/choppy idle and if
you advance the cam that only makes more cyl pressure
due to the valve closing sooner but the choppy idle
will still be there

Posted By: 383man

Re: Camshaft Help WARNING LONG - 06/11/12 04:16 AM

Quote:

Quote:

Quote:

So What I Gather From What You are saying Is, To Widen Lobe Sep. I Will Loose Choppy Idle Some, But Also Loose Cylinder Pressure? I Do Not Want That, Have To Just Keep The Choppy Idle.

No he means the camshaft installed centerline. The lobe seperation angle is ground in the cam and cannot be changed.

Well, that's definitely true, but I think the post meaning is: cams with tighter LSA's tend to have rougher idles. So to get a smoother idle he would need to change to a cam with a wider LSA... right?

I suppose advancing the installed centerline would help the idle too, but that's not usually why cams are advanced...

After I read it again I believe you are right. I think he just means different cams as I thought he was saying to advance and retard the cam in it. Ron

Posted By: dogdays

Re: Camshaft Help WARNING LONG - 06/11/12 08:32 PM

The Whiplash cam is, in my opinion, a gimmick cam. It's designed to run pretty well but its main attraction is the choppy idle. Some guys just have to have the "sound".

The most important single point about a cam is the closing of the intake valve. Advancing the cam closes the intake valve sooner. Running a tight lobe center does the same thing. But, remember that the exhaust valve opens first, followed by the intake valve. Overlap is the time when both valves are open. Increasing the overlap makes that choppy idle sound. So to get a decent idle but still close the intake valve at the right time is a balancing act.
Now on to your cam needs. I'd suggest a camshaft with no more than 220 degrees @ 50 lift for the intake and 226 @50 lift on the exhaust. I'd pick an LSA of around 110 degrees and run the cam 4 degrees advanced. I think Hughes will have a cam for you as will Lunati and Comp. I am trying not to overcam the 400 because it is basically a big 383 and is easy to overcam.

If you are choosing between two cams, pick the smaller one.

R.