Thread: Help with cam selection 350 chevy

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I currently have a 350 sbc 60 over with forged flat top pistons and stock crank and rods. It has stock 76cc heads. Edelbrock RPM performer intake and hei distributor and MSD box. All I remember about cam is that it is 488 lift. I lost cam card as I built engine 10 years ago and moved twice. On a chasis dyno the car made 267 hp and 307 torque and ran out os steam around 5500.

I would like to do a head and cam swap and get the motor to around 425 hp. The heads I am considering are the aluminum Patriot performance 185 cc with 64 cc combustion chambers. The heads made 420 hp in the Sept 2012 Carcraft magazine. They did not specify the camshaft thet used. What will my compression be with flat the 64 cc heads? I am open to other heads but my budget is $1000. I would like a nice choppy idle.

The car this will be in is a 1968 camaro with a 12 bolt rear with 3:73 gears. Tremec tko 600 transmission with .64 overdrive. Car is set up to handle, not drag race.

I will be going the 1/4 track in late september with some buddies. The cars they have are a LS1 Trans am, 2007 Shelby, and 2012 Challenger srt8. I would like to step up my game and show what the old school engines can do. Any help would be appreciated. Thanks

CompCams XE 268 cam (.477/.480 lift; 224/230 degrees duration) is a very popular cam for a 350 performance engine. Another choice would be the Lunati Voodoo 60102 (.468/.489 lift; 219/228 degrees duration). Personally, I would lean toward the Voodoo cam as it was a later, better design by Harold Brookshire who also designed CompCams XE line. Either one should provide you with up around 400 hp at the flywheel and decent street manners. Anything over 400 hp would probably take either AFR or Profiler heads with a larger hydraulic roller cam, all of which would bust your budget.

Thanks rumrumm. The cam I have now has a .488 lift. Unknown durations. Do you think I should get 1.6 rockers to add alittle lift and leave the cam I have now? I know it is hard to tell without knowing duration. It would save me some work especially dropping the oil pan on my back in the drive way?

Just popped off my old heads. On the # 5 cylinder wall from the deck to about an inch down there was some surface rust. No pitting. The engine was built in 1998 but doesnt have more then 8000 miles. The motor didnt get started for the first time til 2003. Is this a major concern ?

A little surface rust--I would not be concerned about it. I would highly suggest changing out the cam. If you don't know the specs, you are really in the dark about your engine. It could be an old style cam where as one of the newer designs will give you a better overall power curve. Bigger is not necessarily better in most cases. As far as 1.6 rockers arms, I am not a fan so I am biased regarding their use. The power increase with 1.6 rockers is marginal, and you will have to make sure that your valve springs will support the increased lift and not put you into coil bind. More trouble than they are worth in my opinion.

oops, wrong thread!!!! Another senior moment I guess.......

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.

Thanks tech. I will be ordering parts tomorrow.

This may be some very helpful reading regarding static compression and dynamic compression.

understanding DCR (dynamic compression ) - ChevyTalk --The Social Network for Chevy Fans

Thank you very much for the link, Lynn. I particularly like the tutorial by John Erb, Chief Engineer for KB pistons. He's one of my heroes.

WOW!!!! Somebody building a wicked small block in a car that actually has a 5 speed instead of the usual 'glide!!!! More power to ya, keep bangin' them gears, don't become "shiftless"!!!!!!!

One more question before I ordered all of my parts? Would there be much of a difference in hp if I got the Patriot 225cc heads as opposed to the 185 cc heads. Will this have any effect on my cam selection? Price difference between the heads in $80.

Originally Posted by fmg camaro

One more question before I ordered all of my parts? Would there be much of a difference in hp if I got the Patriot 225cc heads as opposed to the 185 cc heads. Will this have any effect on my cam selection? Price difference between the heads in $80.

to much head for a 350 less you plan on buzzing it past 7500. and you will move up your power band so it may start at 3500+ to 7500 in a very lite car they could work. but it more the just port cc . its the how the port works .before i drop money down on that head i would used AFR . DART . BRODIX.PROFILER . i am a dealer for all of them heads. if you think you need a bigger port i have some 215 dart pro and some SHP 200 heads on there way. i sold my last set of dart SHP 180s.. i am just not sold yet on China heads that may change?? but right now i am sticking to a uSA made casting