Pushrod length ques.
Pushrod length ques. I am doing a 402 motor with afr heads milled to 66cc. I installed new lifters that I had soaking in oil for a month. When I tried the stock pushrods I marked the valve tip with marker etc. After spinning the motor I found the mark on tip of valve about 1/16 inch out towards exhaust. I don't have a length checker so I'm not sure what size to try. Also if the lifters are considered "pumped up" will there be any movement as I can push the pushrod down about 1/8 inch. Not sure if I should run motor with stock pushrods till they are pumped up or if it was good enough to soak them in oil. I would think if they weren't pumped the mark on valve tip would be in towards intake side ? Any suggestions would be appreciated.
Thanks
Ron H.
Thanks
Ron H.
Originally Posted by Shinerbock07
go with a solid lifter setup with 7.4 stock pushrods
Thanks
Ron H.
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Originally Posted by Shinerbock07
i would go with 7.6 length then and see if that takes care of it.
Thanks
Ron H.
Any comments about if it's ok to check valvetrain geometry if the hyd. lifters are new but soaked in oil and can be compressed about 1/8 of an inch ? or is that normal even if the lifter is pumped up ? or can it not be checked correctly unless there is no play/compression of the lifter.
Thanks
Ron H.
Thanks
Ron H.
You really need to get a pushrod checker. Then, figure out what lenght it takes to just touch the rocker, go .070 to .100 longer and call it good. The factory sets preload on the lifters around .120, I think this is a little excessive. The lifter will bottom out at around .160.
Originally Posted by NoMoreFWD
If your rockers are non-adjustable, your not going to be able to change the valve contact. Pushrod length will change your lifter preload only.
Now if I do put in shorter pushrods to lessen the lifter pre-load will that in turn not open the valve as much and move the contact point ?
Thanks for the help.
Ron H.
Originally Posted by Mrbowtie26
Damn, so if my valvetrain geomety is off as far as the contact line is out too far I cannot use stock rockers if I want to center the contact point and I can only do that with adjustable rockers ? If thats the case I'm not sure what to do. I wonder if it will be ok to leave the contact point of the rockers about 1/16" off of center of valve tip.
Now if I do put in shorter pushrods to lessen the lifter pre-load will that in turn not open the valve as much and move the contact point ?
Thanks for the help.
Ron H.
Now if I do put in shorter pushrods to lessen the lifter pre-load will that in turn not open the valve as much and move the contact point ?
Thanks for the help.
Ron H.
According to an article in the Aug. issue of Circle Track by Keith Dorton, rockers without roller tips can cover some error. This would be in your favor.
A couple questions.
Did you turn the motor over a couple times and are you getting a clean line on top of the valve? Maybe post a pic?
Are there any shims under the rocker pedestals? I assume there isn't, but moving the rockers down will solve your problems.
How much lift does the cam have?
As far as the lifter preload, I agree with MSURacing's post. I would lean toward .070" of preload. The dyno comparisons that I have seen make more power with less preload.
Agreed...when you have guys recommending different ratio rockers and 7.6" pushrods to fix the problem, your recieving advise from the wrong people (no offense to you guys trying to help, but you should leave it to people with knowledgeable background and not what youve read on the internet)
Get a pushrod length checker, do it right. Most likely a 7.400" pushrod is going to work perfect, if the heads are milled alot sometimes a 7.35" will be right. Only way to know is check with pushrod length checker.
Get a pushrod length checker, do it right. Most likely a 7.400" pushrod is going to work perfect, if the heads are milled alot sometimes a 7.35" will be right. Only way to know is check with pushrod length checker.
Originally Posted by stang90gt50
Agreed...when you have guys recommending different ratio rockers and 7.6" pushrods to fix the problem, your recieving advise from the wrong people (no offense to you guys trying to help, but you should leave it to people with knowledgeable background and not what youve read on the internet)
Get a pushrod length checker, do it right. Most likely a 7.400" pushrod is going to work perfect, if the heads are milled alot sometimes a 7.35" will be right. Only way to know is check with pushrod length checker.
Get a pushrod length checker, do it right. Most likely a 7.400" pushrod is going to work perfect, if the heads are milled alot sometimes a 7.35" will be right. Only way to know is check with pushrod length checker.
According to old GM thinking, you need to have the valve open 33% by the time the fulcrum to contact tip line is perpendicular to the valvestem. If you follow that, you will be at the best possible scrub radius.