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Author Topic:   Cam help
JAW
Dirt Full Roller

Total posts: 48
posted November 09, 2004 03:00 PM  
Looking for a good Hyd. cam for 3/8 dirt
Med,slow corners, low banking.
For 355 Chev.
S/R heads 76cc, 2101 edlebrock intake,4412 carb with 1"spacer.
Turning 6500rpm now.
Car weighs 2800lbs
Need something better off corner.
500 lift
246 dur at .050
102/110 center
6.83 final gear

102/110 center

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted November 09, 2004 03:28 PM  
The cam sounds pretty decent, maybe go a little smaller upper 230's-240 or so. Also I'd think about trying a dual pattern cam, keep the intake around 235-240 but run the exhaust 8 degrees longer.

More gear will always help as will more compression if your rules allow it. Might be able to keep the current cam and change gears....

waltonjr1
Dirt Forum Champ
Total posts: 516
posted November 09, 2004 03:49 PM  
That cam has a 4 degree advance ground in it the lobe seperation is 106. The intake and exhaust duration should be different since the lobe centers aren't the same. I agree that thats alot of duration, shoot for around 240.


thirty2rocksu
Dirt Roller

Total posts: 18
posted November 09, 2004 09:28 PM  
quote:
Originally posted by waltonjr1:
That cam has a 4 degree advance ground in it the lobe seperation is 106. The intake and exhaust duration should be different since the lobe centers aren't the same. I agree that thats alot of duration, shoot for around 240.



thirty2rocksu
Dirt Roller

Total posts: 18
posted November 09, 2004 09:29 PM  
quote:
Originally posted by waltonjr1:
That cam has a 4 degree advance ground in it the lobe seperation is 106. The intake and exhaust duration should be different since the lobe centers aren't the same. I agree that thats alot of duration, shoot for around 240.



put more gear in it, get a little closer to 7000rpm

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted November 10, 2004 04:06 PM  
just because the lobe centers arent the same doesnt mean it has to have different intake and exhaust durations. It could have the exact same lobe used as an intake and exhaust. The lobe centers have nothing to do with duration. That cam has 106 lobe centerline or seperation, but a 102 intake centerline. Thats where the 4 degrees advance comes from.

waltonjr1
Dirt Forum Champ
Total posts: 516
posted November 10, 2004 09:05 PM  
Seperation is the intake and exhaust centerline added together divided by two. Whatever the difference in degrees between the intake and exhaust centerline is divided in half is how many degrees advance is ground into the cam. You are right about the duration being different even if the centerlines are the same, I was not sure on that. Comp's website goes into detail how everything works, thats were I got my info from b/c I was curious as to how exactly they come up with the numbers.


streetstock82
Dirt Forum Racer

Total posts: 81
posted November 10, 2004 10:44 PM  
if the rules allow it, you might try switching to 1.6 rocker too for a little more lift. it may not help you in you position, but it usually yields more torque. If it's not in your powerband though, it won't do much.

iowatoolman
Dirt Freak

Total posts: 369
posted November 12, 2004 06:26 PM  
switching to 1.6 rockers moves the torque band up by about 500 rpm
which in the right motor acts like a late nitrious boost

drive hard or drive home

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted November 12, 2004 07:31 PM  
everyone tends to blame the engine when their car won't come off the corners hard. it could be in the chassis. a good chassis set up could make a world of difference. just think if you could pick up the throttle 50 feet sooner while you were going 5-10 mph faster.

something to think about...

Raz_900
Dirt Forum Champ
Total posts: 635
posted November 12, 2004 10:58 PM  
What kind of pistons are you running? I ran that same cam this past season in a 355, except I had SR heads cut down to 62cc with flat tops. I also can use a 3310 carb with the same intake and spacer. When I ran on 3/8s, I used a 5.67 gear, 85" tires, turned 6100-6200 and pulled many cars spinning alot more rpm than me.

I will say the motor I used in '03 with a 240/240 .490" lift and 110 sep seemed to work a little better. Although several other things changed, so it could be something other than the cam. But if you're using flat tops and those big chamber heads, 9:1 CR is going to make it pretty dang weak off the corners with that cam.

I'd back the cam off to 240 or 238, change to domed pistons or cut the heads down as much as possible. Decking the block and a small bore, thin Ferrea head gasket will help bump CR too.

[This message has been edited by Raz_900 (edited November 12, 2004).]

maniac motors
Dirt Maniac

Total posts: 128
posted December 10, 2004 05:53 PM  
try a sealed power kc1168r might not need to turn as hard with that light of car but have won races with this in cars quite a bit heavier than yours turning les than 6000

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