Confusing desktop dyno numbers.

enkeivette

enkeivette

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Mar 30, 2008
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I was playing around with the valve lift on desktop dyno with my engine, seeing what the difference between 1.5 and 1.6 rockers would be.

My cam is 236 in 242 ex/ .520 in .540 ex/ 110LSA with the 1.5 rockers. Changing the exhaust rockers to 1.6 (increasing the valve lift to .576) I gain 6 hp at peak rpm, but when I change the intake rockers to the 1.6 (increasing valve lift to .555) the peak hp goes down 2 hp.

What's the verdict? Am I maxing out the potential of my AFR 195 heads? Or should I not trust the software? (This engine is supercharged if that matters)
 
I don't know much about the Desktop Dyno, but I have heard of some guys getting a touch more HP by swapping the rockers at the corners-- 1,7,2,8 to the 1.6 ratio.. I don't recall is they were changing both intake and exhaust or just exhaust..
 
TimAT said:
I don't know much about the Desktop Dyno, but I have heard of some guys getting a touch more HP by swapping the rockers at the corners-- 1,7,2,8 to the 1.6 ratio.. I don't recall is they were changing both intake and exhaust or just exhaust..
Click to expand...

:confused: That's strange. I don't think I'd mess around with only certain cylinders like that.
 
My uncle told me that some of the guys who run out at Hobbs NM run 1.6's on the corners on the intakes because they are so far from the carb. I'm not sure whether it does any good or bad though.
 
I saw someplace that GM had experimented with the different ratio rockers at the corners. Kind of like the 4-7 firing order swap thing. Sounds really weird, but seems to work.
 
enkeivette said:
TimAT said:
I don't know much about the Desktop Dyno, but I have heard of some guys getting a touch more HP by swapping the rockers at the corners-- 1,7,2,8 to the 1.6 ratio.. I don't recall is they were changing both intake and exhaust or just exhaust..
Click to expand...

:confused: That's strange. I don't think I'd mess around with only certain cylinders like that.
Click to expand...

It's to minimize the difference between the flow from cylinder to cylinder. I've read about this in GM's performance book, and I've heard it from several other places that some race teams do it. However, for the street it wouldn't be worth the effort. It's just for the guys trying to get every last HP out of the allowed rules.
 
I've seen similar results on EA Pro SIM's, and would conclude it's an indication that you likely need more exhaust valve timing under the curve to optimize things. Of course, however sophisticated the software may or may not be, a computer SIM isn't the real thing, so it's too bad you can't play around with lash loops to verify this (that's a hyd cam, right?).

Bottom line; while you might consider installing the 1.6's only on the exhaust, is ~6HP actually worth the trouble and expense? IMHO, a K&N filter and Z-max treatment would probably be a better investment.
 
TheSkunkWorks said:
I've seen similar results on EA Pro SIM's, and would conclude it's an indication that you likely need more exhaust valve timing under the curve to optimize things. Of course, however sophisticated the software may or may not be, a computer SIM isn't the real thing, so it's too bad you can't play around with lash loops to verify this (that's a hyd cam, right?).

Bottom line; while you might consider installing the 1.6's only on the exhaust, is ~6HP actually worth the trouble and expense? IMHO, a K&N filter and Z-max treatment would probably be a better investment.
Click to expand...

Went with the 1.65 rockers, increased my lift from .520 in, .540 ex to .576 in, .594 ex. Worth the cost? No. But my 1.5 rockers felt a bit stiff at the rollers, Glenn convinced me not to chance it. So I figured if I'm buying new rockers anyways, why not? This time I went with Harland Sharp rockers and they have a lifetime warranty.
 
enkeivette said:
TheSkunkWorks said:
I've seen similar results on EA Pro SIM's, and would conclude it's an indication that you likely need more exhaust valve timing under the curve to optimize things. Of course, however sophisticated the software may or may not be, a computer SIM isn't the real thing, so it's too bad you can't play around with lash loops to verify this (that's a hyd cam, right?).

Bottom line; while you might consider installing the 1.6's only on the exhaust, is ~6HP actually worth the trouble and expense? IMHO, a K&N filter and Z-max treatment would probably be a better investment.
Click to expand...

Went with the 1.65 rockers, increased my lift from .520 in, .540 ex to .576 in, .594 ex. Worth the cost? No. But my 1.5 rockers felt a bit stiff at the rollers, Glenn convinced me not to chance it. So I figured if I'm buying new rockers anyways, why not? This time I went with Harland Sharp rockers and they have a lifetime warranty.
Click to expand...

It's always easy to just blame Glenn. :amused:
 
glenn64vette said:
enkeivette said:
TheSkunkWorks said:
I've seen similar results on EA Pro SIM's, and would conclude it's an indication that you likely need more exhaust valve timing under the curve to optimize things. Of course, however sophisticated the software may or may not be, a computer SIM isn't the real thing, so it's too bad you can't play around with lash loops to verify this (that's a hyd cam, right?).

Bottom line; while you might consider installing the 1.6's only on the exhaust, is ~6HP actually worth the trouble and expense? IMHO, a K&N filter and Z-max treatment would probably be a better investment.
Click to expand...

Went with the 1.65 rockers, increased my lift from .520 in, .540 ex to .576 in, .594 ex. Worth the cost? No. But my 1.5 rockers felt a bit stiff at the rollers, Glenn convinced me not to chance it. So I figured if I'm buying new rockers anyways, why not? This time I went with Harland Sharp rockers and they have a lifetime warranty.
Click to expand...

It's always easy to just blame Glenn. :amused:
Click to expand...

That guy is a SOB. :friends:
 
enkeivette said:
glenn64vette said:
enkeivette said:
TheSkunkWorks said:
I've seen similar results on EA Pro SIM's, and would conclude it's an indication that you likely need more exhaust valve timing under the curve to optimize things. Of course, however sophisticated the software may or may not be, a computer SIM isn't the real thing, so it's too bad you can't play around with lash loops to verify this (that's a hyd cam, right?).

Bottom line; while you might consider installing the 1.6's only on the exhaust, is ~6HP actually worth the trouble and expense? IMHO, a K&N filter and Z-max treatment would probably be a better investment.
Click to expand...

Went with the 1.65 rockers, increased my lift from .520 in, .540 ex to .576 in, .594 ex. Worth the cost? No. But my 1.5 rockers felt a bit stiff at the rollers, Glenn convinced me not to chance it. So I figured if I'm buying new rockers anyways, why not? This time I went with Harland Sharp rockers and they have a lifetime warranty.
Click to expand...

It's always easy to just blame Glenn. :amused:
Click to expand...

That guy is a SOB. :friends:
Click to expand...


:twitch::lol::lol:
 
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