Thread: Help with cam selection 350 chevy

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In the article, they said they used a Summit 1105. That particular cam is ground on a 114 degree lobe separation angle, so expect it to be more awake on the top end than the bottom. You'll need 10.0:1 static compression ratio for the cam to make good cylinder pressure. Engineer the squish at 0.035" to 0.045" so you can run pump gas without detonation. Put initial spark lead at 16 degrees at the crank, with another 18 degrees in the weights, all in by 2800. If the motor wants to kick back against the starter upon cranking, interrupt the hot wire to the coil and insert a momentary-off switch in the line. Mount the switch so that you can enable it with your left hand while you crank the starter with your right hand. Push the momentary button and while holding it in, key the starter. While the motor is turning over, release both switches and the motor will be running. No sweat.

Hey tech a few questions for you! I calculated my compression to be 9.9 to 1.
.060 flat top trw L2256 with 6.1 cc reliefs
.020 deck
.040 head gasket
64 cc heads
Standard stroke

Am I close with the compression ratio?

When you say squish do you mean deck height and head gasket thickness added up?

I am going to use a retrofit hyd roller cam. A Lunati tech recommended their voodoo 282/290 cam. Specs are:

Advertised duration 282/290
Duration @ .050 ( int/ exh) 231/239
Gross valve lift int/ exh .535/.550
LSA/ ICL 110/106
Rpm range 2400 - 6200

This seems like a lot of cam to me. What do you think? Thanks.

Originally Posted by fmg camaro

Hey tech a few questions for you! I calculated my compression to be 9.9 to 1.
.060 flat top trw L2256 with 6.1 cc reliefs
.020 deck
.040 head gasket
64 cc heads
Standard stroke
Am I close with the compression ratio?

I don't know, let's figure it out.....
We'll figure the cylinder volume by this formula....(.7854 x bore x bore x stroke x 16.387)
.7854 x 4.060 x 4.060 x 3.480 x 16.387 = 737.9 cc's (no calc handy, did it by hand, hope it's right.) Go back over my numbers please.
Chamber volume = 65 (I always add 1 or 2, 'cause most of 'em are a little over)
Piston crown = 6.1
Piston deck height (.7854 x 4.060 x 4.060 x .02 x 16.387) = 4.2 cc's
Gasket (Victor Reinz #5746) 4.100" x 0.026" = 5.4 cc's (makes an excellent 0.046" squish with your 0.020" piston deck height)
737.9 + 65.0 + 6.1 + 4.2 + 5.4 = 818.6 cc's
65.0 + 6.1 + 4.2 + 5.4 = 80.7 cc's
Divide the larger by the smaller and find 10.14:1 SCR. This will be a good build. Increase static ignition lead at the crank to 20 degrees, with 14 degrees in the weights, all in by 2800.

Originally Posted by fmg camaro

When you say squish do you mean deck height and head gasket thickness added up?

There are 2 deck heights, so get used to saying it properly. Block deck height is the measurement from the centerline of the main bearing bore to the deck. Piston deck height is the measurement from the piston crown to the deck with the piston at TDC. Squish is the piston deck height and the gasket thickness added together.

Originally Posted by fmg camaro

I am going to use a retrofit hyd roller cam. A Lunati tech recommended their voodoo 282/290 cam. Specs are:
Advertised duration 282/290
Duration @ .050 ( int/ exh) 231/239
Gross valve lift int/ exh .535/.550
LSA/ ICL 110/106
Rpm range 2400 - 6200
This seems like a lot of cam to me. What do you think? Thanks.

That cam is right on the money for the SCR. Any less cam and you could develop too much cylinder pressure for pump gas. Install the cam straight up on the marks and use only 1.5 rockers. Check for coil bind, piston to valve clearance, retainer to seal clearance and rocker to stud clearance during your mock-up build. Shoot for 0.080" minimum clearance on the intake valve and 0.100" clearance on the exhaust valve. Use only long-tube tuned headers with 1 5/8" primaries. Use lots and lots of air cleaner area. 14" x 4" should be about right. Tighten up your butt cheeks and hang on.