Pushrod length driving me crazy!!!!
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Pushrod length driving me crazy!!!! Ok guys I need some opinions.
I am in the process of installing an LS3 top end on my LS2 vette.
Im running the stock LS2 cam and lifters.
The heads are Texas speed LS3 heads that have been milled to achieve 66cc's which is about .025 taken off
The question is, Can I use my stock LS2 7.400 pushrods? If the heads hadnt been milled I wouldnt even be asking.
I have heard from several shops that I should be just fine and that ill just have some additional preload.
Some have said that I will definitely need shorter pushrods.
Please dont tell me to measure, I have an adjustable length checker but am in a huge time crunch to get this done at the moment and need to get it put back together.
Opinions needed!!!
I am in the process of installing an LS3 top end on my LS2 vette.
Im running the stock LS2 cam and lifters.
The heads are Texas speed LS3 heads that have been milled to achieve 66cc's which is about .025 taken off
The question is, Can I use my stock LS2 7.400 pushrods? If the heads hadnt been milled I wouldnt even be asking.
I have heard from several shops that I should be just fine and that ill just have some additional preload.
Some have said that I will definitely need shorter pushrods.
Please dont tell me to measure, I have an adjustable length checker but am in a huge time crunch to get this done at the moment and need to get it put back together.
Opinions needed!!!
I would run shorter pushrods, 7.375"
If it was an aftermarket cam with a smaller base (that you usually run 7.425" pushrods for) then I would say the 7.4s would be perfect. Or if you had aftermarket lifters that required different preload.
But if all you did was just mill the heads, then do the same to the pushrods and keep the stock preload.
If it was an aftermarket cam with a smaller base (that you usually run 7.425" pushrods for) then I would say the 7.4s would be perfect. Or if you had aftermarket lifters that required different preload.
But if all you did was just mill the heads, then do the same to the pushrods and keep the stock preload.
You try a couple of those pushrods you already have, EL marko marker on the valve stems, put your pre load and turn the motor a few times and look at the wipe pattern and go from there. If its towards the exhaust side, then its too long. Towards the intake side, too short.
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It takes 15 min to measure for push rod length. How Longs it gonna take you to replace cam/ lifters? Standard pre load is .060 you can go as much as .075 but that is pushing it
Last edited by jimmyg; Jan 6, 2016 at 09:05 PM.
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Thread Starter
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I'm still going to measure it tomorrow once I get the heads on. I was just hoping to plan ahead and pick up my push rods that I would most likely need. But now I have another question. I just picked up my ls3 heads. They already had lower retainers and seals installed that were used with a dual spring. I am installing new ls3 springs. the reason I bring this up is because the lower retainer that is on there is thicker than the stock lower retainer. Basically it will be like I'm shipping the spring. Is there any problem with that? Or should I replace it with a stock lower retainer. I do plan to install my LS 7 cam later this fall and I'm sure some added spring pressure might help with valve float? What do you guys think? Install new lower retainers and seals? Or should i be ok with the ones that are on there
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From: Some where between Orlando and Miami, FL
Do yourself a favor, measure first. Then measure again. Then measure a third time. Ordering two sets of pushrods gets expensive especially when you ordered a first set that was custom from Manton. I speak from experience. -J
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From: Wilmington, De
You're on the path to potentially big mistakes. You need to measure your pushrod length. There is no way around it. Having the internet guess what length you need is going to lead to a thread later on down the road about lifter failures.
Just as an example, in my engine with LS3 heads milled .030, .051 head gaskets, BTR SLR lifters, and a Lunati cam, I had a pushrod length of 7.325 to get .075 of preload. When I switched to another Lunati cam without changing anything else, I needed to bump up the pushrod length to 7.350. So, you can't assume or guess. You need to measure.
If you are using a replacement beehive spring, then you should get new replacement seals/seats for the beehive spring. Otherwise, you are altering the spring's installed height, which changes the ratings of the spring. You can measure the installed height with what you have, and if it is within spec, you can run it. However, you need to make sure the spring isn't being shimmed so much that it reaches coil bind during rotation.
Just as an example, in my engine with LS3 heads milled .030, .051 head gaskets, BTR SLR lifters, and a Lunati cam, I had a pushrod length of 7.325 to get .075 of preload. When I switched to another Lunati cam without changing anything else, I needed to bump up the pushrod length to 7.350. So, you can't assume or guess. You need to measure.
If you are using a replacement beehive spring, then you should get new replacement seals/seats for the beehive spring. Otherwise, you are altering the spring's installed height, which changes the ratings of the spring. You can measure the installed height with what you have, and if it is within spec, you can run it. However, you need to make sure the spring isn't being shimmed so much that it reaches coil bind during rotation.
Whenever cylinder heads are milled, I always tell my customers to measure for push rod length.
There are too many variances that can occur to guess at push rod length when heads have been milled.
There are too many variances that can occur to guess at push rod length when heads have been milled.