Visit The Dirt Forum for More Information

Author Topic:   seat pressure?
rickb33
Dirt Forum Racer

Total posts: 99
posted August 27, 2005 08:30 AM  
My springs are rated @ 130lbs seat pressure but they currently set at about 100 lbs. Should I shim it?, is there any advantage to shimming, and adding pressure? Car runs good, turns 6700 to 6800 rpms every week.

nine finger
Dirt Forum Racer

Total posts: 76
posted August 28, 2005 06:38 AM  
watch for lost rpm. when rpm starts dropping you better shim.the worst that can happen is that the valve tags the piston and breaks off at 7000. but dont worry i have never seen it destroy the air cleaner

leapinlizard
Dirt Freak

Total posts: 402
posted August 29, 2005 06:47 AM  
Your also limiting your lift. Shimming is used mainly for retainer height. 100 pounds isn't enough. Get new ones.

racerman707
Dirt Freak

Total posts: 374
posted August 29, 2005 04:19 PM  
If they're rated at 130 pounds then the installed height on your head is too high. They sell offset keepers to make up for that height without using a shim. Check the installed height on the springs against the installed height on your head.

rickb33
Dirt Forum Racer

Total posts: 99
posted August 29, 2005 07:48 PM  
I'm using .100 valves with k-motion k-750 springs. 130 seat pressure(1.265 diameter), they are rated up to .610 lift. My motor runs fine, but I'm curious what I can gain by getting it shimmed a bit more to add more seat pressure.

rickb33
Dirt Forum Racer

Total posts: 99
posted August 29, 2005 07:49 PM  
I'm using .100 valves with k-motion k-750 springs. 130 seat pressure(1.265 diameter), they are rated up to .610 lift. My motor runs fine, but I'm curious what I can gain by getting it shimmed a bit more to add more seat pressure.

racerman707
Dirt Freak

Total posts: 374
posted August 30, 2005 06:28 AM  
If the springs are too weak on the seat you can loose cylinder pressure, torque, and horsepower.

lowrider
Dirt Roller

Total posts: 12
posted September 08, 2005 02:52 AM  
What is the highest you would want to go on seat pressure with a roller cam?

leapinlizard
Dirt Freak

Total posts: 402
posted September 08, 2005 07:33 AM  
Hyd or solid lift?

nine finger
Dirt Forum Racer

Total posts: 76
posted September 09, 2005 08:10 AM  
on the drag motors we run 340 on the seat & replace when they hit 280.

Back to the Archives