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Tractor Pulling Discussion Forum

cam duration debate

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Mopower

09-19-2003 14:33:39




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It has come to my attention in the art of antique motor building that there are two schools of thought regarding cams. Each one can be attributed to a different style of pulling. One method (commonly used in cars and trucks) uses a duration that allows one valve to be closing as the other one opens. This can produce more power but RPMs must be kept above a certain level to maintain the "lug". The other preferance is to have good lift and duration but no "overlap" allowing a large motor to be pulled down in RPMs, but continue to lug strong until it is stopped. I am an MM low-RPM guy myself, but other motors could use a little reving I think. I can see where depending on what class you are in, it might make a big difference. What do other pullers have to say about this?

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piston

09-21-2003 19:24:14




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 Re: cam duration debate in reply to Mopower, 09-19-2003 14:33:39  
bullet cams horn lake miss. one of the best.



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TimC

09-19-2003 20:32:56




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 Re: cam duration debate in reply to Mopower, 09-19-2003 14:33:39  
LW seems to be right on the money. I feel like a person could have a grind cut that leans toward the bleading edge and if it doesn't work out then add some more lash, especially to the exhaust valve but nothing replaces an actual dyno test.



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LW

09-19-2003 17:07:46




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 Re: cam duration debate in reply to Mopower, 09-19-2003 14:33:39  
Overlap also helps an engine scavenge, duration has nothing to do with overlap, Overlap happens do to lobe seperation you can seperate int. and exh. lobes to a point there is no overlap and have increased duration at the same time this looks good on similated dyno runs or on paper because thier is no loss of cylinder fill but these antique engines with poor head structure will make more power with an amount of overlap, 50 years ago engineers thought overlap was a bad thing there has been alot of changes in 50 years, the design of a lobe, the ramp angle , the amount of area under the curve, on two given lobes you could show the same amount of duration and one could have the valve open much longer at a given lift, there are alot of things to be conidered but I have a Moline that lugs very well at stock rpm's after a cam change and it was a 16hp gain on .030 over 403.

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Jason

09-21-2003 17:09:53




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 Re: Re: cam duration debate in reply to LW, 09-19-2003 17:07:46  
Whre would you send a cam to be ground for a G Moline 550 cubes?



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Hillbilly Hooker

09-21-2003 19:57:11




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 Re: Re: Re: cam duration debate in reply to Jason, 09-21-2003 17:09:53  
I agree with piston. Bullett Racing cams does good work. I dont have his # handy but he should answer to Confederate on this site. H.H.



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Mopower

09-22-2003 10:11:28




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 Re: Re: Re: Re: cam duration debate in reply to Hillbilly Hooker, 09-21-2003 19:57:11  
I hear Berry Cam (no relation) mentioned now and then in the pulling world. Anyone else care to weigh in on them?

-Ethan Berry



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