cam vs heads?
cam vs heads?
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Elder User
Joined: Jul 2002
Posts: 526
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From: USA
cam vs heads?
i have been contemplating putting a new cam in my truck.. the one i am looking at the most is the comp cams 268h cam. but i have heard that sometiems a cam makes no difference if the heads arent ported, so my question is, should i get the cam or should i get the heads ported then get the cam later as money permits? will it make a noticable difference if i keep the heads stockl and spring for the cam now? also if anyone has a desktop dyno, i would like to know where you bought it cause i want to run my engine combo thorugh it.
thanks.
1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
thanks.
1977 F250 460
C6 Hedman Headers
Dual 40 series
edelbrock performer
holley 4150
msd 6a and blaster coil
Elder User
Joined: Jan 2000
Posts: 966
Likes: 2
From: Crooked River Ranch, OR
cam vs heads?
The cam you mentioned is fairly mild and will work with a stock converter and 3.55 gears... It would work with stock heads but you could wring a few more ponies out of it if you'd remove the "smog bump" on the exhaust side of the head (just inside the exhaust outlet).
You can get the engine software through Summit or Jegs. Have fun, Deen
You can get the engine software through Summit or Jegs. Have fun, Deen
Senior User
Joined: Jun 2002
Posts: 423
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From: Oklahoma
cam vs heads?
I'm working with a 460 out of a '77 Mercury Marquis and installing larger exhaust valves and porting the exhausts was recommended as a "to do" before going to a hotter cam. The builder also recommended Crane's H-266-2 Dynomax cam over Comp. Cam's 268.
Postmaster
Joined: Aug 2001
Posts: 2,882
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From: Nevada
cam vs heads?
I'm not familiar with Crane but generally speaking Comp's lower end cams are a 'square' pattern with intake/exhaust duration and lift being the same.
The 385 engine with with stock heads or near stock heads has a compromised exhaust chamber. You'll realize more benefit using a cam that has dual pattern, 10 degrees more duration and lift on the exhaust side.
The 385 engine with with stock heads or near stock heads has a compromised exhaust chamber. You'll realize more benefit using a cam that has dual pattern, 10 degrees more duration and lift on the exhaust side.
Senior User
Joined: Jun 2002
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From: Oklahoma
cam vs heads?
Cam Specifications, Crane H-266-2
Degrees Duration @ .050 Int./Exh......210/218
Degrees Advertised Duration Int./Exh..266/274
Degree Lobe Separation Open/Close.......114
Lash Hot Int./Exh.......................000
Gross Lift Int./Exh..................487"/.504"
The split duration/lift is exactly why he picked the Crane over the Comp. Cams.
Degrees Duration @ .050 Int./Exh......210/218
Degrees Advertised Duration Int./Exh..266/274
Degree Lobe Separation Open/Close.......114
Lash Hot Int./Exh.......................000
Gross Lift Int./Exh..................487"/.504"
The split duration/lift is exactly why he picked the Crane over the Comp. Cams.
Senior User
Joined: Jun 2002
Posts: 423
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From: Oklahoma
cam vs heads?
My apologies. I read my previous post and saw I called the Crane cam Dynomax. It's actually the POWERMAX cam. Just contribute the typo to a lack of hand/brain coordination.
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Senior User
Joined: Aug 2002
Posts: 301
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cam vs heads?
What heads? If they're post '72, chunk them. I've run the early heads(I have 7 sets) & a cam change on them is awsome! Had a car in the 10's with stock valves & ports
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Postmaster
Joined: Aug 2001
Posts: 2,882
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From: Nevada
cam vs heads?
C8, C9, DO, DI and D3 heads all flow about 125-135cfm on the exhaust side in stock form. With the exception of chamber size and D3 valves sitting .100" higher in the chamber than early heads, there's no difference in flow, which is the name of the game. Both will support naturally aspirated engines with cams up to about .500"
With a pro porting job, not the local machine shop, and larger valves, the early heads will flow up to 200cfm and D3s 180-190cfm on the exhaust side. After 175cfm, most porters think more about the entire combination, including velocity, not just the heads. There are lots of ported D3 heads out there supporting 650hp.
With a pro porting job, not the local machine shop, and larger valves, the early heads will flow up to 200cfm and D3s 180-190cfm on the exhaust side. After 175cfm, most porters think more about the entire combination, including velocity, not just the heads. There are lots of ported D3 heads out there supporting 650hp.
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