Help with cam size for mild 350ci sbc
03-21-2005, 08:32 PM
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Help with cam size for mild 350ci sbc
I need advice on a cam selection for my 350ci sbc, I currently have World Products Sportman II heads 72cc, crane roller rockers ( the gold 1.5 ratio ), .060 over flat top single valve notch pistons, performer rpm intake, Gill Manifolds Running as true dry exhaust (no fakes), not sure as of yet what my old cam size was ( getting checked ), I am not looking to spend the money for a full roller cam in this motor. This is in a 26' scarab cv @ 3,200lbs. I want to take full advantage of the dry pipes and still have an easy to start and idle boat????
03-22-2005, 08:41 AM
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Re: Help with cam size for mild 350ci sbc
Try the CompCams XtemeMarine line. But since your running dry pipes I guess it does not matter if you do not have to worry about reversion. I am running the XM272HR which is a retro-fit hydrolic roller cam and was reasonable in price given what came with the kit. The cam, roller lifters, pushrods, very nice valve springs, and a new timing chain set for $830 to my door I thought was very reasonable.
You might try some automotive boards as they may be more familiar with what makes the most power given they never worry about reversion. The performance section at www.chevytalk.com always seems to have good ideas.
Just my .02
You might try some automotive boards as they may be more familiar with what makes the most power given they never worry about reversion. The performance section at www.chevytalk.com always seems to have good ideas.
Just my .02
03-22-2005, 09:32 PM
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Re: Help with cam size for mild 350ci sbc
Here is my cam doctor specs. I think I still have to figure the 1.5 ratio rockers. What do you think of this cam.
03-23-2005, 07:21 AM
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Re: Help with cam size for mild 350ci sbc
Thanks to Bob this one is easy to read. How does this look for my set-up?
Rounding to the nearest, the cam card would read:
284*/290* @ .006”
223*/234* @ .050”
131*/141* @ .200”
112* LSA
108* ICL
IVO 28* BTDC
IVC 77* ABDC
EVO 79* BBDC
EVC 31* ATDC
59* Overlap
4* Advance
.309” I lift lobe/ .323” E lift lobe
.475”/ .485” valve, with 1.5 ratio which are inverted on the chart
Base circle run-out is well within tolerance
Peak opening and closing lifter acceleration is equal suggesting a symmetrical lobe.
Peak nose acceleration is the negative value as the lifter moves over the nose. This value is important for spring rate.
Lift at TDC is the amount both valves are open @ TDC, indicating the advance/retard position. Crossover is the point where the intake and exhaust valve are open equally, in this case about 4* BTDC
The lobe area is obtained by measuring the lift at each degree of rotation and adding them all together.
Bob
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Rounding to the nearest, the cam card would read:
284*/290* @ .006”
223*/234* @ .050”
131*/141* @ .200”
112* LSA
108* ICL
IVO 28* BTDC
IVC 77* ABDC
EVO 79* BBDC
EVC 31* ATDC
59* Overlap
4* Advance
.309” I lift lobe/ .323” E lift lobe
.475”/ .485” valve, with 1.5 ratio which are inverted on the chart
Base circle run-out is well within tolerance
Peak opening and closing lifter acceleration is equal suggesting a symmetrical lobe.
Peak nose acceleration is the negative value as the lifter moves over the nose. This value is important for spring rate.
Lift at TDC is the amount both valves are open @ TDC, indicating the advance/retard position. Crossover is the point where the intake and exhaust valve are open equally, in this case about 4* BTDC
The lobe area is obtained by measuring the lift at each degree of rotation and adding them all together.
Bob
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