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Author
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Topic: Valve size vs. Cam lift
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johnny 4-speed
Gearhead Posts: 149
From: Larkspur, Ca. USA
Registered: Oct 2004
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posted 10-29-2004 01:39 PM
   
I have a question about selecting camshafts. I run a 10.3:1 compression 289. I have World Products Windsor heads(2.02"/1.60"), they're on the big side for my small displacement motor. So my question is: Do I really need a cam with high lift(.575"+) with such big heads? It seems like a larger valve will flow more then a smaller valve at the same lift. So, at some point, I may be exceeding my 289's needs. Any thoughts?------------------
65 Fairlane
289ci
Top loader
9-inch w./ 5.13's
27"x10.5 cheaters
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capri man
Gearhead Posts: 6417
From: doerun, ga.
Registered: Nov 2000
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posted 10-29-2004 02:13 PM
good question johnny, just wish i had the answer!!  i have similar heads (candfield) and i am running .536/.544 lift.
with 230/234 dur @.050. just wondering how far i am off??------------------
mike r
racing is real
everything else is just a game.
81 capri-302-7.33 @92mph 1/8
1.54 60 ft. http://community.prestage.com/Member+Pages/789.aspx
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johnny 4-speed
Gearhead Posts: 149
From: Larkspur, Ca. USA
Registered: Oct 2004
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posted 10-29-2004 02:24 PM
I think my Crane cam is a .512"/.533", 238*/248* @ .050" JD[This message has been edited by johnny 4-speed (edited 10-29-2004).] [This message has been edited by johnny 4-speed (edited 10-29-2004).]
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 10-29-2004 05:22 PM
This is an unedjimacated guess just from limited experience, but it depends entirely on the the way the heads like to breath. If the valves are not too big for the cylinder wall and chambers and the heads are proven to flow better at high lifts, then a higher lift lobe makes more power at the same duration. The valves stay in the hungry zone of the lift cycle longer allowing the cylinder to swallow more a/f mixture and it also improves the mixture velocity in the ports. The more a/f mixture it takes in, the bigger the bang! Somewhere in the equation the amount of compression needed to burn and exhaust the extra mixture has to be figured in. ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 10-30-2004 02:36 AM
Just for reference.. The stock 405HP LS6 GM cams have a mild .050 duration of only 204/218 with a hefty valvelift of approx. .550".------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH
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Mpcoluv
Gearhead Posts: 1278
From: Charlotte NC usa
Registered: Apr 2001
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posted 10-30-2004 08:32 AM
quote:
Originally posted by bluestreek:
Just for reference.. The stock 405HP LS6 GM cams have a mild .050 duration of only 204/218 with a hefty valvelift of approx. .550".
Realize that that is a Hyd roller cam, not a flat tappet cam. Hey, a 331 stroker kit will cause those heads to be perfect.. 
I would personally pick a cam that was designed to keep the port velocity up....like a 220 @ .050 duration or so. Call you favorite cam company and ask questions.
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johnny 4-speed
Gearhead Posts: 149
From: Larkspur, Ca. USA
Registered: Oct 2004
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posted 10-30-2004 12:01 PM
Sorry, I didn't mention that my question was originally about solid camshaft profiles. But it seems that a roller camshaft can flow more that a flat tappet with less duration, due to its much more aggressive lobe profiles? In other words,the rate at which the valves arrive at full lift is much higher with the roller. Right? JD
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 10-30-2004 01:42 PM
Your right. The roller lifters can follow a more agressive profile, but don't discount solid flat cams. OEM don't like them because they're not EFI friendly and are a little noisy. They can be ground very agressive too when used with decent valvetrain. CompCams has a new XE solid line that would make a pretty decent cam for a mild strip car. They list it for GM but you can have it custom ground on a 302 or 351 stick. 289 with 10.5 compression is a good starting point for a decent solid cam in the 230-236 @ .050 range. ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH [This message has been edited by bluestreek (edited 10-31-2004).]
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mizry
Journeyman Posts: 43
From: ca
Registered: Sep 2004
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posted 10-30-2004 03:07 PM
I kinda did some experimenting on this myself. My previous cam was a .600 lift with duration of 276 at .050. my new cam has .540 lift with duartion of 266 at .050. similar duration profiles but less lift and so far it doesnt preform anything like the bigger cam. It may be in the combo of lift and duration but you wouldnt be disspointed with the bigger cam.
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JCQuinn@work
Gearhead Posts: 826
From: Lakewood, CO, USA
Registered: Jun 2001
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posted 10-31-2004 02:16 AM
A couple of thoughts on this subject.First, the airflow potential of an induction system is set by the worst flowing component in the intake path. The limit could be the valve size, the port, the manifold, or the carb/throttle body. So making a valve size change may not make any difference. Second, when the valve lift reaches the maximun flow rate it will hold that rate while the valve opens further. The effect of having a cam lobe that lifts the valve higher is to have the port flowing at its maximum rate for a longer time so the extra lift can help even if the port flow peaks at a lower value. If you have solid lifters tighten up the lash from the recommended setting. If the car picks up you could need more cam. John
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johnny 4-speed
Gearhead Posts: 149
From: Larkspur, Ca. USA
Registered: Oct 2004
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posted 10-31-2004 07:51 PM
Did a little research on the World Products Windsor heads last night. Found some flow #'s on my heads:
Intake @ .500"-228CFM, .600"-236CFM
Exhaust@ .500"-133CFM, .600"-141CFM
Now my question is, how do use these numbers to help me select the cam best suited for me? There must be some equation I could punch these figures into. As far as other limiting factors, I use a 700 double pumper, victor jr. manifold, and 1 5/8" headers. JD[This message has been edited by johnny 4-speed (edited 10-31-2004).]
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mizry
Journeyman Posts: 43
From: ca
Registered: Sep 2004
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posted 10-31-2004 09:06 PM
Do you think that the engine will have any valve to piston contact with a big lift cam? Ive used both the 31-609-5 and the 31-641-5 comp cams solid flats with the bigger cam making the most power of the comps and way stronger power band than my other crane cams. Im not too sure on the cost of a custom cam but that might be the best idea. With your heads on a 289 the cam is propably gonna be big and the power band well into 7000 rpms.
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johnny 4-speed
Gearhead Posts: 149
From: Larkspur, Ca. USA
Registered: Oct 2004
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posted 11-01-2004 01:34 PM
I recently loosened the lash on the rockers by .004, and it felt like the motor lost a little something. I'll be checking the piston to valve clearance before I purchase the next cam. How will the 106* lobe centers effect the power band. I think my current separation is 112 or 114, that's a big difference. JD
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MrWesson22
Gearhead Posts: 1280
From: Dacula, GA
Registered: Sep 2000
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posted 11-04-2004 04:29 PM
Comp cams is getting some good lift numbers for the duration on the XE solid flat tappets. I'm running a custom grind in my cleveland, and with 1.7RRs, it specs at .590/.600 lift for 282/288 adv and 244/[email protected]".
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Neal 69 Gulfstream Aqua Grande
351C/4sp
https://mustangsandmore.com/ubb/MrWesson22.html 99 GT 5 sp coupe
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