retarding cam?
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retarding cam?
Has anyone ever retarded a cam and seen an improvement? If the engine does like the cam retarded does it mean that the engine wants a bigger cam?
In my experience, retarding the cam has little if any effect on the peak numbers. It just shifts the power band up the rpm range. So, if your motor is dropping off at the big end and you don’t want to put a taller gear in, retarding the cam may give you a little higher power band and show improvements at the track.
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bill jones
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-My life is at 4200 elevation and mostly SBC oval track applications and I've never yet seen an application here that wants to be retarded.
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-We do run the big chief head BBC bracket racer engines with the cam installed to where everything clears everything best and sometimes that is further retarded than I think the engine should want, but those things still run pretty decent.
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-I think that if the engine ran better with a particular cam retarded, and everything else had been worked out for best power, then it probably needs either a larger cam and/or a wider lobe spread.
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-One thing I would do is to measure the cranking compression and see what you have.
-I have seen where a straight up cam might have 150# and then advancing it 6 degrees bumped the cranking compression up to 180# and yet the car slowed down because it had way more power than could be hooked to the track with the cam advanced.
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-Your question has a vary wide range of possibilities and until the application you are interested in is know to us, and some more substance to that application is explained, it's going to be hard to generalize the answers.
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-We do run the big chief head BBC bracket racer engines with the cam installed to where everything clears everything best and sometimes that is further retarded than I think the engine should want, but those things still run pretty decent.
---------------------------------------------
-I think that if the engine ran better with a particular cam retarded, and everything else had been worked out for best power, then it probably needs either a larger cam and/or a wider lobe spread.
------------------------------------------
-One thing I would do is to measure the cranking compression and see what you have.
-I have seen where a straight up cam might have 150# and then advancing it 6 degrees bumped the cranking compression up to 180# and yet the car slowed down because it had way more power than could be hooked to the track with the cam advanced.
--------------------------------------------------
-Your question has a vary wide range of possibilities and until the application you are interested in is know to us, and some more substance to that application is explained, it's going to be hard to generalize the answers.
One thing I have noticed in the SBF and SBC with EFI and very long runners, the later you close the intake valve, the more power they make. Peak and average. Obviously the first response is to make the cam bigger. Now you have no dynamic. Then, move the LSA tighter and ove the IC tighter as well. Now you have cranking and dynamic with loads of overlap that is not needed or wanted.
I guess the theory is that the inertia behind such a long column of air is such that it still fills the cylinder after BDC on the intake stroke. I do it on EFI and it works. On short runner EFI or carburetor stuff, I am in agreement with these other folks. It usually does nothing.
If you think you need a bigger cam, add rocker ratio and tighten the lash. That will tell you a good stroy!
Good Luck!
I guess the theory is that the inertia behind such a long column of air is such that it still fills the cylinder after BDC on the intake stroke. I do it on EFI and it works. On short runner EFI or carburetor stuff, I am in agreement with these other folks. It usually does nothing.
If you think you need a bigger cam, add rocker ratio and tighten the lash. That will tell you a good stroy!
Good Luck!
Jay Allen
CAMSHAFT INNOVATIONS
www.camshaftinnovations.com
CAMSHAFT INNOVATIONS
www.camshaftinnovations.com
bc,
I'm with Jay on this one, if you have piston to valve clearance the higher ratio rocker will give you feedback to a larger (or smaller) cam. Try the intake, make a pull or pass or lap whatever you do, then add the exhaust rocker and repeat the test. I have seen this test realy surprise some people, makes a too big cam look real bad, it helps to know if the head moves air at the new lift range as well.
PFM
I'm with Jay on this one, if you have piston to valve clearance the higher ratio rocker will give you feedback to a larger (or smaller) cam. Try the intake, make a pull or pass or lap whatever you do, then add the exhaust rocker and repeat the test. I have seen this test realy surprise some people, makes a too big cam look real bad, it helps to know if the head moves air at the new lift range as well.
PFM
Re: retarding cam?
I retarded the cam in my super/stocker from 103 to 108 and made one of the best runs ever. Tried it on the dyno go and it would loose 15 hp.?