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I have a cam...what should I expect?
EF put in a Xtreme Energy Comp Cam.
222/232 Duration @ .050 .510/.534 Lift. What does all that mean? I plugged the numbers into desktop dyno with the little knowledge I have. Hope I got the numbers right for Vic Jr 60cc heads. PROBE forged ished pistons 8.75 to 1 compression.(Had them build the motor for boost at a later date.) HP came to 420hp at 5500. 490tq at 3500. With large headers and mufflers. Sound about right? sid:confused: |
What kind of engine? How many cubes? Single/dual plane intake? What size carb?
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Oh, and if you're asking what the numbers mean:
The 222/232 is how many degrees the intake/exhaust valves are open. The .510/.534 is how much lift (how far the valves open) on the intake/exhaust valves. Upon using the ratio rocker arms that came with the cam card, the intake valve will open .510" and the exhausts will open .534". If you have the lobe separation there, it's the amount of degrees between opening of the intake valve versus opening the exhaust valve. A cam with a lobe separation of say 114 degrees or 116 degrees would probably completely close the intake valve before it opens the exhaust valve. This gives a smooth idle. A cam with a lobe separation of say 108 or 110 would allow (for example) the exhaust valve to start opening when the intake valve was not all the way closed. This is part of the cause for really lopey radical idle engines. |
"If you have the lobe separation there, it's the amount of degrees between opening of the intake valve versus opening the exhaust valve.
A cam with a lobe separation of say 114 degrees or 116 degrees would probably completely close the intake valve before it opens the exhaust valve. This gives a smooth idle. A cam with a lobe separation of say 108 or 110 would allow (for example) the exhaust valve to start opening when the intake valve was not all the way closed. This is part of the cause for really lopey radical idle engines." How do I find out the above? They did not give me a part no for the cam. I tried going to Comp Cam site to check it out but could not find it. I think I'll just call EF next week. 351W Bored .030 Stroke 3.85 750 Street Demon Carb RPM AIR GAP intake sid |
I'll see if I can find the cam on the website.....My guess is that it's around 110 lobe separation.
Let's see a 3.85" stroke is a 392, right? 420 hp sounds right to me with low compression.....The torque is in the ballpark....maybe a touch high.....but with a dual plane intake and a matched cam, it could be right on. I'll check the website and see if I can get the cam specs for you. You can probably download the cam card from the website too.... |
Hmm.....I can't find it either. You sure about the cam specs?
Is it a hydraulic flat tappet cam or a roller cam? I have a Comp Cams cam in my engine....it's 230 degree duration with a .544" lift. 110 degree lobe separation. You're pretty close to my specs....you'll be pleased with the sound of it. :) |
blykins, in reality the Intake valve would start opening before the exhaust was closed not the reverse. An engine would never run if the exhaust opened right after the intake.
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Sorry. I didn't mean for it to be analyzed so thoroughly....just trying to relay the concept of how the valves overlap. Didn't take much time to think about how I labeled the valves.
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I want that "really lopey" sound! I'll double check the info on the cam. It is a roller cam.
Sid |
In layman's terms...
They grind the split duration to make the numbers attractive then put a big center line on it like 112 or 114 to take away all the cylinder pressure....it's a scheme dreamed up by the marketing departments so they can sell you a cam that's too big for your combination and it'll still run decent. True power is built from square cams like 530/530 lift at 242/242 duration at .050 and to increase scavenge balance between the intake and exhaust you use a combo rocker arm system like a 1.72 intake ratio and a 1.6 exhaust. Here's a good tech article that reallly explains the truth about cams and why they make power...Compliments of the now retired Harvey Crane: http://www.4secondsflat.com/Cam_Design.html After reading this you'll realize that all the glossy pages and fancy catalogs are really just a bunch of hocus pocus, real cams are selected and ground by small obscure cam companies like Racer Brown and have been for over 50 years. |
I pulled the number right off the spec sheet they mailed me. I found some cam files at http://www.smokemup.com/utils/cams.php
Couldn't find the extact one though. Sid |
Call a Cam Engineer like Jim at Racer Brown 410-866-7660 and ask him what he would grind for your combination and compare it to the cam you have.
Jim is a Good Ole Boy and is a kick to talk to, he only answers the phone after 2PM EST, from 6AM until 2 he's out in the shop personally grinding every cam he sells. |
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