need help picking a can.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,029
Likes: 94
From: meraux LA
need help picking a cam.
O.K this is what I have. 350 2 bolt main, with flat top 4 valve relief pistons, alum ZZ4 heads with 58cc. Headers, performer intake, Holly 650vac sec. , 4 speed with 3.08 gears. I think my compression will be around 10.0 . I was thinking of using the Compcam XE 268H which has .470/.480lift 224/230 dur 110 LSA . What do you think? I just want good performance. It is only a cruiser no drag racing for me. Sorry for the typo I need help with a CAM
Last edited by crf311; May 17, 2007 at 04:31 PM.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Funny the comp cams website dyno charts show the 262 making a touch more torq and hp; 415/348 for the 262 and 413/342 for the 268. Same thing for the 250 and the 256; somehow does not seem right to me. 
http://compcams.com/Technical/DynoSheets/.
http://compcams.com/Technical/DynoSheets/.
Racer
Joined: Oct 2004
Posts: 439
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From: Mukilteo Washington
O.K this is what I have. 350 2 bolt main, with flat top 4 valve relief pistons, alum ZZ4 heads with 58cc. Headers, performer intake, Holly 650vac sec. , 4 speed with 3.08 gears. I think my compression will be around 10.0 . I was thinking of using the Compcam XE 268H which has .470/.480lift 224/230 dur 110 LSA . What do you think? I just want good performance. It is only a cruiser no drag racing for me. Sorry for the typo I need help with a CAM
, sorry I couldn't resist.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Given your combo, if your CR is 10:1, I think CompCams XE 268H looks like a fine choice. With a stick, you could likely run the next step up, but unless your compression proves to be higher, I'd suggest staying with the 268 to maintain better bottom end with that tall gear you have. The roller version would be even better, but it's your money. 
You owe it to yourself to have that CR verified before committing...
You owe it to yourself to have that CR verified before committing...
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Given your combo, if your CR is 10:1, I think CompCams XE 268H looks like a fine choice. With a stick, you could likely run the next step up, but unless your compression proves to be higher, I'd suggest staying with the 268 to maintain better bottom end with that tall gear you have. The roller version would be even better, but it's your money.
You owe it to yourself to have that CR verified before committing...
You owe it to yourself to have that CR verified before committing...
Great advice. Check your DCR before you buy. It sounds like you might be right on the verge of having to go bigger on the cam.
Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
O.K this is what I have. 350 2 bolt main, with flat top 4 valve relief pistons, alum ZZ4 heads with 58cc. Headers, performer intake, Holly 650vac sec. , 4 speed with 3.08 gears. I think my compression will be around 10.0 . I was thinking of using the Compcam XE 268H which has .470/.480lift 224/230 dur 110 LSA . What do you think? I just want good performance. It is only a cruiser no drag racing for me. Sorry for the typo I need help with a CAM
I am only speculating here but I believe the 268 prefers a little more compression than the 262. I believe comp just changed the cam and used the same low compression engine to compare.
If I had the extra money I would have bought better heads. These heads really fit the bill for me though; cheap, Al and better than nothing.
Last edited by kevinator80; May 17, 2007 at 11:01 PM.
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
Just ran an example 350 with that cam at 106 ICL and an SCR of 10:1, and DCR was over 8.25:1.
In other words, yes, this one's close enough to requiring the 274 that the CR really needs to be checked.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,029
Likes: 94
From: meraux LA
Thanks guys, I'm going to check my CR and get back. I would love to go with a Roller cam but my $$ situation right now will not allow it. We are still rebuilding our house from hurricane katrina. I'm just messing with the vette for stress relief. I still have a long way to go on it. I have it all taken apart, blasting and painting the frame , suspension. etc. hoping to put a little more time in it by middle summer. Thanks again. Robert
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Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
I have 1.6 rockers which yields corrected numbers of 239/245 on the xe268, just above the specs on the 274. Where does that puts us?
Le Mans Master
Joined: Apr 2007
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From: Graceland in a Not Correctly Restored Stingray
The resultant change for two degrees additional duration leaves the DCR at just above 8.2. Using three degrees, DCR would be just below 8.2. Either way, this looks to be just about in the sweet spot for aluminum heads on a well tuned engine. Still, the SCR should be verified, since 10.25:1 will push DCR near 8.4 where things start getting very critical.
Last edited by TheSkunkWorks; May 18, 2007 at 03:05 PM.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,029
Likes: 94
From: meraux LA
OK I checked my CR. Here is what I have:
bore 4.035 : Stroke 3.5 : head gasket dia 4.0 : head cc 58 ; dome cc 0 ; piston to deck clearance .065. with a gasket comp thk. of .028 CR = 10.47 ; with a gasket comp thk. of .051 CR = 9.93.
I used 0 cc for the piston but they are the flat tops with 4 valve reliefs cut in. should I use a - cc to account for the reliefs?
What do you guys think?
bore 4.035 : Stroke 3.5 : head gasket dia 4.0 : head cc 58 ; dome cc 0 ; piston to deck clearance .065. with a gasket comp thk. of .028 CR = 10.47 ; with a gasket comp thk. of .051 CR = 9.93.
I used 0 cc for the piston but they are the flat tops with 4 valve reliefs cut in. should I use a - cc to account for the reliefs?
What do you guys think?
Le Mans Master
Joined: Apr 2005
Posts: 6,355
Likes: 425
From: Seattle Area WA
Yes, you need to subtract out the CCs for the 4VRs, typically between 5 and 7CCs (what's the pistons P/N?) and that deck height seems way too high. A typical 350 has a factory deck height of .025"-.030"
Le Mans Master
Joined: Apr 2007
Posts: 7,353
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From: Graceland in a Not Correctly Restored Stingray
Those reliefs will make a considerable difference here.
Your deck height needs to be reduced to no more than 0.020" to achieve good quench with an 0.028" gasket, which is a very important item when you start pushing DCR.
Also, you must run a larger bore head gasket than your cylinder bore.
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Drifting
Joined: Apr 2002
Posts: 1,716
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From: New Baden Illinois
OK I checked my CR. Here is what I have:
bore 4.035 : Stroke 3.5 : head gasket dia 4.0 : head cc 58 ; dome cc 0 ; piston to deck clearance .065. with a gasket comp thk. of .028 CR = 10.47 ; with a gasket comp thk. of .051 CR = 9.93.
I used 0 cc for the piston but they are the flat tops with 4 valve reliefs cut in. should I use a - cc to account for the reliefs?
What do you guys think?
bore 4.035 : Stroke 3.5 : head gasket dia 4.0 : head cc 58 ; dome cc 0 ; piston to deck clearance .065. with a gasket comp thk. of .028 CR = 10.47 ; with a gasket comp thk. of .051 CR = 9.93.
I used 0 cc for the piston but they are the flat tops with 4 valve reliefs cut in. should I use a - cc to account for the reliefs?
What do you guys think?
A typical stock 350 has a deck clearance of about .045 with the stock dished pistons.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,029
Likes: 94
From: meraux LA
Ok tell me if I checked my deck high correctly? Fist I put the # 1 piston at TDC by using a dial indicator until it reached the highest point. Then I laid a strait edge across and measure with a feeler gauge. I know it looks high. I'm going out of town, but I will post some pics monday. History of the motor is it's a GM goodwrench remunfactured. with about 7-10K miles.
Race Director
Joined: Mar 2001
Posts: 11,322
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From: Living in the Hartland
Don't forget you have a 3.08 gear, you need your torq low in the rpm range our it will be a dog off the line. If you plan on swapping out the 3.08 or going to a richmond 5 speed (low first and 1:1 final drive) then a bigger cam might be in order.