One thing I could do that might make sense would be to get another 264/268 cam ground but on a different LSA. Maybe tighten it up to 106 and see what happens. That way most of the variables would be controlled. Not sure it would worth the time and effort to do that test, but it would be a logical thing to do.

One thing I could do that might make sense would be to get another 264/268 cam ground but on a different LSA. Maybe tighten it up to 106 and see what happens. That way most of the variables would be controlled. Not sure it would worth the time and effort to do that test, but it would be a logical thing to do.

I suppose it makes sense to ask where you're looking to see improvements over the 264/268 on 108...

I've read that article a few times and I think it needs some editing for clarity. I don't think the author ever says how the cams were installed. Were they all installed straight up? He also doesn't talk about the big effect that LSA can have on valve to piston clearance. And I think some of his conclusions are wrong. He says the 101 LSA cam has a wider powerband but I think that is wrong. Looks to me like the 101 cam falls off faster than the others.

I remember there was a thread here about LSA (i think) and Monte Smith seemed to like a wider LSA if the heads were good.

Monte, along with some others on here, built/build serious sh!t with mega-flow heads, high CR and/or power adders, and comparatively narrow usable power ranges at high(er) RPM. When you're flying at that altitude, the "right" LSAs are in a different range than what Joe Average needs... IMO.

Junk like mine w/ moderate cubes, semi-pump gas CR, a lower RPM limit and comparatively small-port & limited-flow heads doesn't necessarily see improvements from wide(r) LSAs. This is one of those topics that I've seen David Vizard and other established engine builders having to agree to disagree on, 'cuz DV seems to lean towards as tight an LSA as possible on builds that the others just shake their heads at. "They" will say 110 or 112, and he'll say 105 or 106. He's got his methodologies, but as Andy pointed out, they're far from universally accepted.

My own tests years ago on a much milder combination than I have now didn't pan out like I'd expected. Three SFT cams dynoed on a pump-gas 440 making in the low-to-mid 500s HP:
- 251/255 on 108
- 254/254 on 108
- 255/263 on 110

For THAT COMBINATION, the 255/263 on 110 was the worst across the board. The 251/255 x 108 and 254/254 x 108 were very close with the best peak #s coming from the 254/254. However, the 251/255 revved out much farther before valve float kicked in w/ the 254/254. I went with the 254/254, but on the track when I ran shorter tires (275/60R15 drag radials vs my 29" slicks), I was getting into valve float on the big end and killing my MPH. In retrospect the smaller cam might have worked better overall in the car and not have beaten up the valve job as quickly.

None of this stuff is a "for sure" thing. And even the best educated(?) guesses of the results sometimes miss the mark by a pretty large margin vs what the real world shows.

OK, I've probably broken my soap box from standing on it so long. We now resume your regularly scheduled programming...

Brad, if you look at the opening closing points of the 255 vs the 254 cam, and were to install them both at say 108, the only event that changes is the exhaust opening discounting the ondegree difference in intake timing. Maybe your motor had great exhaust ports , which makes me wonder how your motor would have responded to something like a 252/248/107 or 106 lsa cam

Turns out I don't have a clean A to B test with the same exact parts on both engine due to the problems I had with the vacuum pump. I wasn't able to run the QRI cam with a vacuum pump since I had issues with it so all of my current testing is with breathers. The engine is making right around 750 hp with the QRI cam using breathers.

I made 775 hp with the HXL cam using a vacuum pump and Wilson Indy. I made 745 hp with the HXL cam using breathers but with the M1 Wilson intake. (std port intake) I never tested the HXL cam with breathers and the Indy Wilson intake so I don't have that as a baseline.

My guess is that the HXL cam with breathers and the Indy Wilson intake would hit 755 or 760 hp in an A to B test but I wouldn't be surprised to be wrong.

Another thing is the weather. The last few days have had cold air so the correction factor is negative. Even thought the correction factor is only a few percent different than the previous tests, that is enough difference to throw some doubt on the comparison.