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Pushrod issues?

This is a discussion on Pushrod issues? within the Internal Engine forums, part of the LSx Technical Help Section category; We just finished a head/cam swap, and the sewing machine noise is crazy loud. heads are 59cc patriot stage 2's, ...

  1. #1
    Unbiased Opinion 67rsss's Avatar
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    Pushrod issues?

    We just finished a head/cam swap, and the sewing machine noise is crazy loud. heads are 59cc patriot stage 2's, and the cam is VRX3. After a bit of reading, it looked like the noise could be the pushrods, so I googled a different method to measure with. Using this method (or as close as I could get, my dial indicator isn't as nice as his) I was able to determine that we have too much pre-load. I screwed up the measurement with the adjustables somehow when we put everything together. Looks like we have 115mil (0.115 inch) pre-load on intake and exhaust. We have 7.400 pushrods now with brand new LS7 lifters, so it looks like we should have gotten 7.350 pushrods. Would this cause all the sewing machine noise we have???? We have about an hour of run time on the motor.

    This is our first mod work on a Gen III. Also the first time we ever added fuel injection to a vehicle!
    Last edited by 67rsss; 04-22-2009 at 07:11 PM.

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    Veteran Hi-Po's Avatar
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    If the heads have been milled any, the geometry has changed. 7.4's might not be perfect. I didnt read the method you posted, but I assume with DI, I know what your talking about. Are these stock rocker arms? Of course, after a Cam swap, the valve train is going to be louder. Depending on the shape of the PR's after the one hour of run time, they might take them back.

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    Unbiased Opinion 67rsss's Avatar
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    Went to 7.300 length on the pushrods (which gives us 15 mil of pre-load) and it is almost as quiet as a stocker!

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    Quote Originally Posted by 67rsss View Post
    Went to 7.300 length on the pushrods (which gives us 15 mil of pre-load) and it is almost as quiet as a stocker!
    You aren't opening your valves enough though.

    The LS1/LS7 lifters like roughly 0.9-1.1 of pre-load.
    .015 preload is WAY too low for them.

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    Unbiased Opinion 67rsss's Avatar
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    Quote Originally Posted by Mr. Luos View Post
    You aren't opening your valves enough though.

    The LS1/LS7 lifters like roughly 0.9-1.1 of pre-load.
    .015 preload is WAY too low for them.
    Most people are recomending 60-80 mils of pre-load, but that has nothing to do with how much I am opening the valves. Hydraulic valves just take up the slack to keep things quiet and to allow for expansion as things heat up. Using a short lash (15 mils in this case) will not make any difference at the valve so long as I never run out of range. Got -15 in hand and about +135 to go, so should not run out of range. Every time the valve closes and the lifter is exposed to oil pressure the cup is pushed up until the pushrod moves the rocker against the valvestem. Since the oil pressure cannot open the valve, that is all the oil that is let in. When the valve opens and the lifter is no longer exposed to oil pressure (the feed hole is blocked) the oil acts like a solid lifter. Remember adjusting mechanical lifters?

    Another thought, even if we hit a point in a very cold start in which the valvetrain contracted more than the 15 mils pre-load we have, it would just act like a solid lifter with a small amount of lash. Since we have guide holes and some rather deep locator cups in the rockers, it would take a LOT of shrinking to put the valvetrain in jeopardy.

    Oh, and this engine will never be put through super high rpm, and the valvetrain should remain more than stable enough to cover for the short lash.
    Last edited by 67rsss; 04-22-2009 at 07:16 PM.

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    I agree it will be stable....

    If a lifter calls for a determined preload, you want to shoot for that...if you are over, you hang open the valves (I can prove this lol...I did the math using the OEM lifter preload and had Morels which like .020-.030 preload), if you are under, your valve lift is being lost by what you are under.

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    I don't sell out! blackSS01's Avatar
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    I am lost, someone give me a explanation on what LS7 lifters are suppose to be preloaded. And how I do it
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    Quote Originally Posted by blackSS01 View Post
    I am lost, someone give me a explanation on what LS7 lifters are suppose to be preloaded. And how I do it
    OEM preload. LS7 lifters are what you get if you go to a dealership and ask for LS1 lifters.

    OEM preload can vary. I think I was a little high on my first post in this thread. I think the pre-load is .080-.100 for the LS1/LS7 lifters.

    If you have a stock heads that are not milled, you should be running the correct pre-load with 7.400" pushrods.

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    I don't sell out! blackSS01's Avatar
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    Quote Originally Posted by Mr. Luos View Post
    OEM preload. LS7 lifters are what you get if you go to a dealership and ask for LS1 lifters.

    OEM preload can vary. I think I was a little high on my first post in this thread. I think the pre-load is .080-.100 for the LS1/LS7 lifters.

    If you have a stock heads that are not milled, you should be running the correct pre-load with 7.400" pushrods.
    Gotcha on that part, thanks Mr. Luos. But I am running milled 243's (62CC) with LS7 lifters.

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    Quote Originally Posted by blackSS01 View Post
    Gotcha on that part, thanks Mr. Luos. But I am running milled 243's (62CC) with LS7 lifters.
    How much are they milled?
    What length pushrods?
    What cam?

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    I don't sell out! blackSS01's Avatar
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    I kinda : but I need to know specifics when I do this myself. Trying to get help, but I am totally lost on this part of a H/C build. Call me a newbie but never looked into til I started my build. I know, I'm a

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    I don't sell out! blackSS01's Avatar
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    I bought a TSP Torquer V2, forgot how much they milled but the heads are now 62CC (64CC Stock for 243's) And pushrods, I thought I had to check the preload to find out what size I need

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    Well...in theory, you would want to take whatever was milled off the heads (sounds like roughly 0.020") off the pushrods.
    So you would be looking at 7.380" or so.
    Call TSP and ask about the base circle of that cam as well. A lot of aftermarket cams are actually a touch smaller. If this is the case, 7.400" would be fine for you.

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    You need to find out the base circle of that cam. Measure it yourself if you have to. I wish I did mine, I got in a hurry and just wanted the new cam in. I now want MY specs. Pushrod length checker will help greatly, it just takes extra time.... and money. ( you gotta buy it). Just another one of those things that adds up in your cam install price.

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    Quote Originally Posted by Mr. Luos View Post
    Well...in theory, you would want to take whatever was milled off the heads (sounds like roughly 0.020") off the pushrods.
    So you would be looking at 7.380" or so.
    Call TSP and ask about the base circle of that cam as well. A lot of aftermarket cams are actually a touch smaller. If this is the case, 7.400" would be fine for you.
    Thanks a million. I will call TSP and find the base circle. So preloading is just to find the size of the pushrods, it doesn't affect the lifters or anything. Sorry but like I said before......No clue

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