cam area vs power

[pastry_chef]

Pontiac 455
Lets say bore 4.185 , stroke 4.21.
9.2 compression ratio.
Cast iron dport heads 2.11 intake , 1.77 exhaust valves - intake 250 CFM @ .500 exhaust say 215 CFM.
Matched dual plane intake.
1.65 rockers.
Quad jet carb.

Estimate how much power difference?

Smaller hyd roller on 110 LSA

Intake
276 @ .006
224 @ .050
145 @ .200
.335 lobe

Exhaust
282 @ .006
230 @ .050
151 @ .200
.340 lobe

----------------
Larger hyd roller on 114 LSA

Intake
290 @ .006
236 @ .050
160 @ .200
.3800 lobe

Exhaust
304 @ .006
244 @ .050
161 @ .200
.3830 lobe

[panic]

The area is only one difference, there are more

[pastry_chef]

Picture

compare.png

[MELWAY]

That 114 LSA with low Comp and restricted heads will kill it

[CamKing]

The larger cam will move the power curve up about 500rpm, and make about 40 more HP.

[Nut124]

Just curious; why would the bigger cam run so much more LSA?

In my application, bigger cams almost always run less LSA and milder cams run more LSA. And overlap is what makes power.

[pastry_chef]

Thanks for the comments.
This was not my engine, cam selection or dyno. Attached dyno image of two results.
Important note: reportedly the smaller cam version detonated itself to death on the dyno. I strongly believe that engine was sick or maybe the cam was retarded.

276 VS OF.jpg

Believe it or not, some Pontiac people believe the LSA shift from 110 to 114 was the lion's share of the power increase.

Here is another similar engine using the smaller roller cam (110 LSA) and it yielded better results, just over 490 HP.
https://www.hotrod.com/articles/hppp-12 ... uska-dyno/

[novadude]

Believe it or not, some Pontiac people believe the LSA shift from 110 to 114 was the lion's share of the power increase.

It seems like Pontiac people love to repeat the "wide LSA" propaganda on the forums. There probably IS something to keeping overlap in check with pontiac 30 deg seats (as compared to a convntional 45 deg seat), so a long duration cam might prefer wider centers, IMO. However, it seems like too often Pontiac people buy into "wider is better" as a general rule.

[CGT]

If i had an engine that picked up 45ftlbs from changing between those 2 cams, I would be looking more into the dyno, equipment, or testing methods as opposed to the camshafts. Horsepower is one thing, but torque don't change like that unless its a really, really strange situation. I call bullshit, or bad testing on the whole thing without knowing more.

[Stan Weiss]

Clearly the engine with the smaller cam had some problem(s). Just look at the difference in BSFC.

Stan

Pontiac_BSFC.gif

[Orr89rocz]

What valvesprings were used on the two cams? 1000 rpm gain at peak? Was there a float issue? Something does seem way wrong with the first cam

[mt-engines]

Why did it only correct 2hp @4800 on the first sheet, then 30hp on the second?

Id say your testing wasnt apples to apples

[David Redszus]

Picture
compare.png

Clearly there is a difference in lift between the two cam lift curves. But there is also a difference in
two important areas: IVC and EVO.

At the crank angle of maximum piston air demand, which cam has more valve curtain area?
During exhaust blowdown, which cam has more area?

With a properly measured cam lift curve, the angle area can be determined which is more useful than lift
by itself.

An air mass flow sensor should provide an accurate insight to the relative value of each cam for this specific application.

[Stan Weiss]

Why did it only correct 2hp @4800 on the first sheet, then 30hp on the second?

Id say your testing wasnt apples to apples

The correction factor on each sheet look almost constant per sheet. I would say that the cam was not changed and dynoed on the same day..

Stan

[maxracesoftware]

The correction factor on each sheet look almost constant per sheet.
I would say that the cam was not changed and dynoed on the same day..
Stan

Stan , i'm not getting same results as you ??

maybe i'm looking at the wrong Dyno Sheet picture ??
this is what i calculate :

Dyno HP Weather Correction Factor = (CBHP * BSFC) / FuelLbsHour

Dyno HP Weather Correction Factor = (428.7 * 0.514) / 218.1
Dyno HP Weather Correction Factor = 1.010324622

Dyno HP Weather Correction Factor = (514.4 * 0.500) / 240.1
Dyno HP Weather Correction Factor = 1.071220325

HPCF : 1.010324622 -VS- 1.071220325