PTV Clearance/Pushrod Length Question
PTV Clearance/Pushrod Length Question So this weekend I want to assemble my engine. I have a fresh 370 short block back from my builder with wiseco K398X3 pistons. These are flat tops with valve reliefs. My heads are ported 706 castings with 2.02 intake 1.60 exhaust valves milled .020''. Ill be running LS3 head gaskets with a compressed thickness of .051 and my pistons are .010 out of the block... Now I need to do 2 things 1. measure my pushrod length and 2. check PTV clearance. Now, I have some comp 7.400 pushrods of my buddies to use for checking the ptv and I have a comp pushrod length checker. I was planning to modify 2 old lifters into solid units for checking ptv. My big issue is that I'm pretty sure I'm going to need shorter pushrods, will it be ok to check the ptv clearance with the 7.4 ones? I'm assuming that if everything clears with the slightly larger pushrods I would be a ok with the correct length ones? Any thoughts, inputs, or suggestions?
TECH Fanatic
Joined: Jul 2007
Posts: 1,802
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From: Wilmington, De
^^Yep.
When checking PTV clearance, you are using "checker springs" anyways, which are only there to hold up the valve. With those springs, the adjustable tool won't have any pressure to overcome when opening the valve.
When checking PTV clearance, you are using "checker springs" anyways, which are only there to hold up the valve. With those springs, the adjustable tool won't have any pressure to overcome when opening the valve.
Run the 11/32 pushrods if the 3/8 won't fit. Check springs are simply light springs. You can probably get something that will work at a local hardware store for a couple of bucks.
I got ya, yeah i guess ill go that route. Id prefer the thicker pushrods for sure to keep deflection down. I just read that there was clearance issues on the 3/8... I keep seeing people talk about some manton pushrods that are 11/32 ill have to look into those. Any other suggestions on the pushrods supplier or make?
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Verdad Gallardo ok, got some check springs this weekend and got everything measured. I plenty of PTV clearance thanks to the this valve reliefs on the pistons, I figured id be fine but there is nothing wrong with checking.
Now I do have a question about the pushrod length though. I was using modified "solid" roller lifters for the PTV checking and the pushrod length measurement. I got a 10.5 turns on the rod checker so my math is coming out to be 7.325" pushrods.... but what about lifter preload? since this measurement is with the lifter completely locked out at what amounts to be completey pumped up should I order 7.350 pushrods instead? The lifters are LS7 units.
Now I do have a question about the pushrod length though. I was using modified "solid" roller lifters for the PTV checking and the pushrod length measurement. I got a 10.5 turns on the rod checker so my math is coming out to be 7.325" pushrods.... but what about lifter preload? since this measurement is with the lifter completely locked out at what amounts to be completey pumped up should I order 7.350 pushrods instead? The lifters are LS7 units.
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Joined: Aug 2005
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From: Monroe,NY
If your pushrod measurement with zero preload then just add the preload to that. I think LS7 lifters preload is .080 give or take. So going by that your final measurement would be 7.405 so 7.4 would work. I would do like Darth said and by a 8' caliper and measure your checker. Just remember when you measure with caliper that is the overall measurement and most pushrods are made by gauge length. My btr 7.350 pushrods had an overall measurement of 7.368 for a .018 difference. Harbor Freight has the 8 in caliper at a fair price.
If your pushrod measurement with zero preload then just add the preload to that. I think LS7 lifters preload is .080 give or take. So going by that your final measurement would be 7.405 so 7.4 would work. I would do like Darth said and by a 8' caliper and measure your checker. Just remember when you measure with caliper that is the overall measurement and most pushrods are made by gauge length. My btr 7.350 pushrods had an overall measurement of 7.368 for a .018 difference. Harbor Freight has the 8 in caliper at a fair price.
alright, measured again with the current lifters got 11 turns on the comp length checker to 0 lash with my roller rockers. then turned the rod one more turn to 12 to account for preload, giving me a stock 7.4 length rocker. checked by snugging the bolt then it took a little over 1 complete turn to hit 22 ft lbs of torque. I then grabbed some of my buddies comp 7.4 rods and dropped them in, marked the valve tips with a dry erase marker and installed the rockers to check the wipe. after rotating the engine a couple times I removed the rockers to find the mark to be dead center on the valves. I'm thinking stock length 7.4 rods are what I need. I talked to Manton today about ordering some 11/32'' thick rods and they said that using the comp checker was fine for measuring....any thoughts? sound like with the wipe and the torque hitting in spec everything should be good?