cam duration

[rumpity_z28]

Hi there i have a 10.1 compression 350 with 186cc heads, i am looking at comps extreme energy line of cams and am looking for opinions on which I duration would work well on the street. I have 1 5/8 headers and edelbrock eps manifold in a third gen camaro with a 5 speed 3.73 rear.

[lefty o]

225-235@.050 . somewhere in that ballpark shouldnt be overly rowdy.

[Geoff2]

Comp XE274 for the street

[bigcam406]

are you going the hydraulic flat tappet or hydraulic roller route?

[rumpity_z28]

are you going the hydraulic flat tappet or hydraulic roller route?

Hydraulic Flat tappit

[CamKing]

I would not go over an intake duration of 228@.050"

[skinny z]

Hi there i have a 10.1 compression 350 with 186cc heads, i am looking at comps extreme energy line of cams and am looking for opinions on which I duration would work well on the street. I have 1 5/8 headers and edelbrock eps manifold in a third gen camaro with a 5 speed 3.73 rear.

Very similar to the 86 Camaro 350 that I had.
Iron heads (Vortecs), 10:1, 1 5/8" headers. 670 VS carb on an Air Gap intake.
Ran very well with 224@.050". This was COMPS XR276HR so a hydraulic roller.
The XE274 mentioned above I would think would behave similarly.
Just watch for a higher cranking compression with 10:1 and a shorter duration cam but all very manageable.

[pcnsd]

Hi there i have a 10.1 compression 350 with 186cc heads, i am looking at comps extreme energy line of cams and am looking for opinions on which I duration would work well on the street. I have 1 5/8 headers and edelbrock eps manifold in a third gen camaro with a 5 speed 3.73 rear.

Hi rumpty. I have a personal camshaft estimation spreadsheet that I'm trying to refine and since Mike has been so kind as to provide a correct answer, I wonder if I could trouble you for a few more details I need for inputs to my sheet.

1. What is the target peak crankshaft HP and RPM
2. What is the target valve lift?
3. What is the intake valve size?

Thank you for any assistance provided.

[rgalajda]

Not enough information really.
Listen to CamKing
These cams with tighter LSA don’t require as much duration .
For a true street car that has to operate in a much broader rpm range it’s better to err on the short side of duration. You will like the results far better.
Early Z28 and LT-1 cams had long durations but wide LSA of 114 to 116 to obtain decent idle.
Those cams did not make power in lower rpm range even with 11:1 compression. In fact you had to shift at high rpm to make power. Those old cylinder heads were not good.
Things have come a long way since then. Street cars can make power at lower rpm’s these days if you build accordingly.
The XE268H would be a better choice. I would think you would want a 1.6 rocker ratio In./Ex.
Both the XE274H and ZE268H have a 110 LSA
I know some people say they don’t care about fuel mileage for a street car but that is just old school thinking. The XE268H will also deliver better fuel mileage.
The Lunati Voodoo 268 would also be a good choice .It has a little more valve lift.
https://www.lunatipower.com/voodoo-hydr ... 8-276.html

Don’t fall for the Stroker McGurk theory. If some is good and more is better , then too much must be just right.

[rfoll]

I agree with the XE268 or similar. I used one in a 400 with Vortec heads and it was good for 5500 rpm. It will turn more rpm in a smaller motor.

[1980RS]

Elgin 1165P hyd cam. Has a nasty idle but makes killer power in a 350 or 400 SBC.

[mt-engines]

One of the best running street 355s I built that was similar in combo had a 224/228 112. Killer torque and great hp. Ran nice below 2000rpm.

Never had it on the dyno. But similar builds made 420+hp and 430+tq

[rfoll]

Hi there i have a 10.1 compression 350 with 186cc heads, i am looking at comps extreme energy line of cams and am looking for opinions on which I duration would work well on the street. I have 1 5/8 headers and edelbrock eps manifold in a third gen camaro with a 5 speed 3.73 rear.

Did you cc the deck and heads to be sure of your actual compression ratio? Piston manufacturers assume a zero deck most of the time. Cylinder head chamber volumes can be off by many CCs. Gasket bore and thickness varies significantly. Every cc is about 1/10 of a compression point. Tolerance stacking can make your 10:1 more like 9.5 and it will affect your cam choice. CC everything, otherwise it's a guess or an assumption.

[rumpity_z28]

Hi there i have a 10.1 compression 350 with 186cc heads, i am looking at comps extreme energy line of cams and am looking for opinions on which I duration would work well on the street. I have 1 5/8 headers and edelbrock eps manifold in a third gen camaro with a 5 speed 3.73 rear.

Did you cc the deck and heads to be sure of your actual compression ratio? Piston manufacturers assume a zero deck most of the time. Cylinder head chamber volumes can be off by many CCs. Gasket bore and thickness varies significantly. Every cc is about 1/10 of a compression point. Tolerance stacking can make your 10:1 more like 9.5 and it will affect your cam choice. CC everything, otherwise it's a guess or an assumption.

Thank you the plan is to zero deck the block and use a .039 thick gasket. I believe the flat top 2 valve relief pistons are 5cc, and the compression height is 1.560 . As far as the combustion chamber goes I have not cc them and just used what the manufacturer has stated.

[F-BIRD'88]

Comp Cams Hyd Cam #CS 268AH-8 pn 12-319-4
can use 1.6 rockers to good effect.
268/276 222/226 @.050" 108 LSA 104in/112ex
.464"/.464" (1.5rr).
.495"/.495" (1.6rr)