Need help picking a cam.
Thread Starter
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
I can see that the block has not been milled,however I can't say the same for the heads. I feel they were probably decked before I bought it, but I don't know how to tell. With the numbers I submitted, can anyone double check my est. on my C.R.??? 
Later
Sly
Later
Sly
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
That's the problem. U need to measure c.r. for urself.
Originally Posted by sly vette
I can see that the block has not been milled,however I can't say the same for the heads. I feel they were probably decked before I bought it, but I don't know how to tell. With the numbers I submitted, can anyone double check my est. on my C.R.???
Later
Sly
Later
Sly
Buy a cheap calibrated tube/vile and a plexaglass cover plate - i know Comp Cams sells'm cause i got 1. Measure each chamber in the heads (then average or choose largest or smaller to soot ur estimates), install the rotating assembly and measure piston volume at TDC while the engine is out of car - u cannot measure this with block in car, i have tried. 
1ml = 1cc then convert to c.i. calculate c.r.. Plenty of on-line c.r. cruchers for u (search most hot-rod forums) - just plug in the numbers.BTW i'm losing faith in ur machinist if he doesn't zero deck the block and can't accuratly calculate c.r..
Larry, sorry to bust ur bubble but boring increases c.r. with same head chambers. And a roller cam while making more hp would reduce the overlap area (due to ramp design) and increase sly's dynamic c.r. - moving the wrong way on c.r. also. 1 more item is how much more pwr that roller gonn'a make. My guess closer to 10hp than 20hp. Thats 'bout $100 per hp and will still be losey off the line/out of the hole. $800 better spent on new rear gear set to match eng combo.
And that's my 2 cents.
cardo0
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by sly vette
can anyone double check my est. on my C.R.???
Later
Sly
Later
Sly
But if I make some assumptions:
Bore of 4.06
Stroke of 3.48
Combustion chamber volume: 64cc
Head gasket thickness .038
Deck height .020: (it's probably more if the block has not been decked)
Piston valve pockets: 5cc
Your actual compression ratio: 10.08:1
If your deck height is .030" (more common) and if your valve reliefs are more like 7cc, your comp ratio drops to 9.64:1.
You sure as heck don't have anything in the 11:1 range.
LarsBTW.... I'm running a 357 ci with 49cc heads...
Last edited by lars; Mar 12, 2006 at 10:43 PM.
Advanced
Joined: Jan 2006
Posts: 58
Likes: 2
I agree with lars. I have built alot of engines in my time. No way close to 11-1. I would surprised if you are at 10-1, I think more like 9.8 in my opinion from what you have said.
Remember this too, people have brought to your attention your rear gears. Well, with 3.08 gears and the stock type tires that came with your vette, I would suggest something like a Comp Cams xe262 cam. It is alot more than stock, but with those gears, anything bigger and you will be sorry. It will be like tring to pull out on a ten speed bike in 7th gear if you go with the 285 duration cam you mentioned. The ex268 cam it the biggest cam with stock converter. Don't get me wrong, you can use the ex268 cam, and it will "sound cool" but I put money on it that if you compared apples to apples, and another vette was next to you at the light, and you had the ex268 cam and he had the ex252 or xe262 cam, you would see his tail lights.
If you want the car to move, invest in gears in the back, then from there figure out the rest. I say 3.55 or topps 3.70 gear, then you can use the ex268 cam, anything else, go with the smaller cam. Might not sound as cool, but who cares, it will run better.
Remember this too, people have brought to your attention your rear gears. Well, with 3.08 gears and the stock type tires that came with your vette, I would suggest something like a Comp Cams xe262 cam. It is alot more than stock, but with those gears, anything bigger and you will be sorry. It will be like tring to pull out on a ten speed bike in 7th gear if you go with the 285 duration cam you mentioned. The ex268 cam it the biggest cam with stock converter. Don't get me wrong, you can use the ex268 cam, and it will "sound cool" but I put money on it that if you compared apples to apples, and another vette was next to you at the light, and you had the ex268 cam and he had the ex252 or xe262 cam, you would see his tail lights.
If you want the car to move, invest in gears in the back, then from there figure out the rest. I say 3.55 or topps 3.70 gear, then you can use the ex268 cam, anything else, go with the smaller cam. Might not sound as cool, but who cares, it will run better.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
This just reiforces that u need to nail the c.r. before chosing a cam.
Originally Posted by Jchrisd
I agree with lars. I have built alot of engines in my time. No way close to 11-1. I would surprised if you are at 10-1, I think more like 9.8 in my opinion from what you have said.
Remember this too, people have brought to your attention your rear gears. Well, with 3.08 gears and the stock type tires that came with your vette, I would suggest something like a Comp Cams xe262 cam. It is alot more than stock, but with those gears, anything bigger and you will be sorry. It will be like tring to pull out on a ten speed bike in 7th gear if you go with the 285 duration cam you mentioned. The ex268 cam it the biggest cam with stock converter. Don't get me wrong, you can use the ex268 cam, and it will "sound cool" but I put money on it that if you compared apples to apples, and another vette was next to you at the light, and you had the ex268 cam and he had the ex252 or xe262 cam, you would see his tail lights.
If you want the car to move, invest in gears in the back, then from there figure out the rest. I say 3.55 or topps 3.70 gear, then you can use the ex268 cam, anything else, go with the smaller cam. Might not sound as cool, but who cares, it will run better.
Remember this too, people have brought to your attention your rear gears. Well, with 3.08 gears and the stock type tires that came with your vette, I would suggest something like a Comp Cams xe262 cam. It is alot more than stock, but with those gears, anything bigger and you will be sorry. It will be like tring to pull out on a ten speed bike in 7th gear if you go with the 285 duration cam you mentioned. The ex268 cam it the biggest cam with stock converter. Don't get me wrong, you can use the ex268 cam, and it will "sound cool" but I put money on it that if you compared apples to apples, and another vette was next to you at the light, and you had the ex268 cam and he had the ex252 or xe262 cam, you would see his tail lights.
If you want the car to move, invest in gears in the back, then from there figure out the rest. I say 3.55 or topps 3.70 gear, then you can use the ex268 cam, anything else, go with the smaller cam. Might not sound as cool, but who cares, it will run better.
Well i agree with lars too. But only the owner that verifies the c.r. really can tell what the c.r. is and choose what cam will make it work. If the c.r. really was 11.2 or greater that eng would have a very short life with a 262* cam let alone a 252*. The long duration 280*-285* duration cam is only to keep the engine from detonating on pump gas - reducing the dynamic c.r.. It might s_ck to drive with 3.08 gearing - but it would live with a 280* cam.
This should reinforce the need to measure actual c.r..
Enough said. cardo0
Thread Starter
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
Thanks again for all the help guys. I had the ring and pinion changed when I bought the car,due to the fact that I needed something more "highway friendly" and the old gear set was a 3.9:1 and trashed. I never expected to build a street racer,my holeshot days are long gone. All I wanted to do was rebuild the eng. and drive it. but when I took the eng apart,I found that I had 2 spun rod bearings,two broken piston skirts and the cyls.were at .030 over already. After checking the cyls. I found that I had to have another .030 taken of to make them right. I think I will look for 5 speed but I just can't afford that kind of cash right now. Or I guess I could throw good money after bad and change the gear set,I don't know. I'm getting input overload,and maybe alittle burnt out after working on this car almost nonstop since late Oct. Might be time to take a step back and take a deep breath and review what I have going on here now. I guess I'm getting alittle discouraged also,it seems that this car is taking me places I never intended to go,although It's been one hell of a ride.
Later,
Sly
Later,
Sly
Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
You are experiencing what all of us go thru at some point. You get frustrated and want to quit, thats ok, just take a break and recharge. I had a goal this weekend; come Sunday at 4:00 I made a mistake and knew I was going to be next weekend and several trips to my friends shop to use his press. I was so frustrated sitting there looking at the pos that I wanted to bash something!! Instead, I sprayed the trailing arm bolts again and went in to watch some of the race on tv. When i came back I took out the remaining tension on the stuck bolt and got it out with my bfh 
. Now I can make one trip to use the press and next weekend I should have the entire rear suspension back under my car!! If you don't want a break, move on to some other small job that will give you some success.
. Now I can make one trip to use the press and next weekend I should have the entire rear suspension back under my car!! If you don't want a break, move on to some other small job that will give you some success.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
That "pro2k" cam your machinist recommends is small ... aka "RV Cam". It's either P/N CS1014R or CS1151R.
The cam I suggested is "pro3K" CS1062R.
In between those is another decent "pro3K" choice: CS1013R 443"/.465" 214*/224*.
If you have typical +60 forged 4VR flattops (i.e. SP P/N L2256F forged 4VR flattop minus -6.1cc DV, 1.563" CD) & stock deck & 64cc chambers & 0.015" steel shim gasket CR very close to 10.47:1 ... very close to 9.89:1 w/ 0.039" composition gasket.
If you have 9.5:1 - 10.7:1 CR, I still suggest CS1062R ... so does SP.
The cam I suggested is "pro3K" CS1062R.
In between those is another decent "pro3K" choice: CS1013R 443"/.465" 214*/224*.
If you have typical +60 forged 4VR flattops (i.e. SP P/N L2256F forged 4VR flattop minus -6.1cc DV, 1.563" CD) & stock deck & 64cc chambers & 0.015" steel shim gasket CR very close to 10.47:1 ... very close to 9.89:1 w/ 0.039" composition gasket.
If you have 9.5:1 - 10.7:1 CR, I still suggest CS1062R ... so does SP.
Originally Posted by sly vette
I'm making progress,I think...Heres some more #s
Cyl. Dia 4.060
Stroke 3.48
Flat top pistons
Gasket thickness.038 and I come up with 360c.i.d. and 11.2331:1 C.R.
The guy that is doing the machining for me,although very proficient at what he does,really dose'nt have much knowledge when it comes to building a perf. motor,and he admits it. He has a cam that will work in my eng,however I think the comp. is too high for it. these are the specs on the cam he has.... Sealded Power/Speet pro 2000 series.
Cam lift Int .280
Ex .295
Valve lift Int .420
Ex. .443
@.050 Dur.
Int .204
Ex .214
Personally I dont think this enough. What do you guys think?
Later,
Sly
Cyl. Dia 4.060
Stroke 3.48
Flat top pistons
Gasket thickness.038 and I come up with 360c.i.d. and 11.2331:1 C.R.
The guy that is doing the machining for me,although very proficient at what he does,really dose'nt have much knowledge when it comes to building a perf. motor,and he admits it. He has a cam that will work in my eng,however I think the comp. is too high for it. these are the specs on the cam he has.... Sealded Power/Speet pro 2000 series.
Cam lift Int .280
Ex .295
Valve lift Int .420
Ex. .443
@.050 Dur.
Int .204
Ex .214
Personally I dont think this enough. What do you guys think?
Later,
Sly
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
If the 64cc camelhump heads were flat milled simply to straighten/level (not cut to gain lotsa CR) ... only to straighten/level ... typical cuts for straighten/level reduce chamber volume about 1-3cc ... 64cc shrinks to about 63, 62 or 61.
-edit-For CS1062R cam, SP suggest valvespring P/N VS739R (single w/ damper, 1.264" OD, 110# on seat ... aka "Z28 spring") ... whatever, make sure your heads have decent springs ... ensure rockers, springs, retainers & seals are clearanced for .480" lift at valve with room to prevent coil bind when hot.
Originally Posted by sly vette
Thanks again Jackson. I will be giong with your suggestion, and using the Pro3K cam#1062. Thanks to you and all the others that have helped me out recently.
Later,Sly
Later,Sly
Last edited by jackson; Mar 14, 2006 at 09:50 AM.
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by cardo0
Increases overlap a few degrees but adds 'bout .3" lift to vlv - a good thing.
cardo0
cardo0
The famous 327/350 camshaft had 222 degrees duration at .050" lift and .447" lift at the valve. This engine had 1.5 ratio rocker arms, so, the lobe lift was .447/1.5 = .298". A 1.6 ratio rocker arm would move the valve .4768". So, 1.6 ratio rocker arms WILL NOT "add 'bout .3" lift to vlv".
BigBlockk
Later.....
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by sly vette
What I really don't understand is,stock,this motor would put out approx.8.2:1 C.R. and now with the cylinders @ 4.060 and no other significant mods. that would impact the C.R. I'm way up to 11.2:1C.R. Am I missing something here???
Later,
Sly
Later,
Sly
Me thinks you need to check the compression ratio and stop guessing. The health of your engine depends on it.
With your gearing the camshaft should be kept short. Compression ratios in the 8's should be something less that 212@.050" lift. This will help build low speed torque. 9's = 222, 10's = 232 and 11's = 240.
BigBlockk
Later.....
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
OOoopps!
Originally Posted by BigBlockk
This is not correct. Overlap is a function of the opening and closing events (duration) of the camshaft lobes, not rocker arm ratio. Rocker arm ratio amplifies the linear motion of the valve lifter. It does not open the valves earlier or close them later.
The famous 327/350 camshaft had 222 degrees duration at .050" lift and .447" lift at the valve. This engine had 1.5 ratio rocker arms, so, the lobe lift was .447/1.5 = .298". A 1.6 ratio rocker arm would move the valve .4768". So, 1.6 ratio rocker arms WILL NOT "add 'bout .3" lift to vlv".
BigBlockk
Later.....
The famous 327/350 camshaft had 222 degrees duration at .050" lift and .447" lift at the valve. This engine had 1.5 ratio rocker arms, so, the lobe lift was .447/1.5 = .298". A 1.6 ratio rocker arm would move the valve .4768". So, 1.6 ratio rocker arms WILL NOT "add 'bout .3" lift to vlv".
BigBlockk
Later.....
Also 1.6 ratio rockers while they increase the "through area" and effectivly increase overlap a few percent - ur right they do not increase duration (of vlv events). But the eng will see a higher amount of the total vlv lift "flow area" in overlap (more crossing area on both ramps) is what i should have said. And i feel its something to consider when increasing rocker ratios.
:o Pardon me must'a been too tired to proof read that day.
But i also agree that sly needs to measure that c.r. for himself rather than use opinions and guesses of his c.r. from no-names off the internet. Only that machinist knows what pistons went into that block and may not want to disclose the vital info - or may have lost it already.
cardo0
Thread Starter
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
After a more exact comp. check, I;ve come up wiyh 9.7:1 CR. and i've chosen a Sealed Power/Speed Pro cam #1013. Thanks for all your help. By the way,I'm now looking for a used spread bore.750 c.f.m. carb. if anyone has one ,P.M. me. Thanks
Later,
Sly
Later,
Sly
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by sly vette
After a more exact comp. check, I;ve come up wiyh 9.7:1 CR. and i've chosen a Sealed Power/Speed Pro cam #1013. Thanks for all your help. By the way,I'm now looking for a used spread bore.750 c.f.m. carb. if anyone has one ,P.M. me. Thanks
Later,
Sly
Later,
Sly
http://motors.search.ebay.com/search...&fsop=1&fsoo=1
BigBlockk
Later.....
Safety Car
Joined: Dec 2004
Posts: 4,071
Likes: 0
From: San Diego CA
Originally Posted by sly vette
After a more exact comp. check, I;ve come up wiyh 9.7:1 CR. and i've chosen a Sealed Power/Speed Pro cam #1013. Thanks for all your help. By the way,I'm now looking for a used spread bore.750 c.f.m. carb. if anyone has one ,P.M. me. Thanks
Later,
Sly
Later,
Sly
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Originally Posted by desi
then call someone who knows what they are talking about and double check what their 'expert' recommended... Crower and Isky cams would be a good start.
