Thread: I can't decide what engine to build....need advice

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Originally Posted by 35chevy

Can you help me understand the difference between the recommended 282 solid and the 282 roller? Duration is pretty close, the solid is 236/236 and the roller is 230/236. the intake valve closing point on the solid is 44 degrees and the roller is 41 degrees. wouldn't that make the roller have a higher dynamic compression since the intake valve closes earlier? What an I missing here?

Because of the lifter having a roller on the cam end vs. a flat surface, more aggresive rates can be used on the cam lift.... then there's the friction thing, a roller offers much less friction and wear on the cam lobe then does a flat tappet.... Richard can give you all the specifics on the difference in cam specs, I'm one of the "lightweights" on cam selection, and always defer to the experts at selection time!!!!!

Originally Posted by 35chevy

Can you help me understand the difference between the recommended 282 solid and the 282 roller? Duration is pretty close, the solid is 236/236 and the roller is 230/236. the intake valve closing point on the solid is 44 degrees and the roller is 41 degrees. wouldn't that make the roller have a higher dynamic compression since the intake valve closes earlier? What an I missing here?

Yeah, I must have used closing numbers from a different grind. Sorry. I went back to the post and changed it so that subsequent readers will be able to make sense of it, then added a dyno of the 12-432-8.

Because of the lifter having a roller on the cam end vs. a flat surface, more aggresive rates can be used on the cam lift.... then there's the friction thing, a roller offers much less friction and wear on the cam lobe then does a flat tappet.... Richard can give you all the specifics on the difference in cam specs, I'm one of the "lightweights" on cam selection, and always defer to the experts at selection time!!!!!

I understand the difference between flat tappet and roller....I'm trying to understand the difference in dynamic compression between the two. These two cams look real similar. I used the dynamic compression calculator on Keith black's website and I came up with 8.095 with the xr282hr roller and 7.941 with the solid lift 282s. Techinspector1, are you getting the dynamic compression numbers from the DynoSim software? I'm not sure how accurate the calc. that I'm using is. I like the xr276hr too though....

Personally, I wouldn't trade 14 ft/lbs @ 2000 for 12 hp @ 5000. The motor will be seeing 2000 way more often than it will 5000.

That's the same page I was on, Later.............

Just for kicks I emailed comp cams for a camshaft recommendation. They recommended the xr288hr-10. I tried the camquest software and this cam is one of the ones recommended. I'm pretty settled on a smaller cam. I'm just wondering how they come up with thier recommendation? What software do they use?

Tech are you sure that picture is appropriate for this site?
Oh those are cams, sorry about that.
Reminded me of something else.
HE! HE! HE! Kurt