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Help, I need clarification for pushrods and ptv with head/cam swap
In a few weeks I should be getting new heads and cam. with this i need to determine the proper pushrod length and also check the PTV clearance. My truck has (assuming) .051 head gaskets and I am going with some .041 gaskets on final assembly.
I am assuming that in order to get proper PTV measurements I need to first have the correct pushrod length. right?
a couple of things i need clarified:
-the two gaskets are only .01 (.051 vs .041) difference when compressed - this shouldn't matter and i can use the old gasket for measuring?
-to get that proper quench of .051 - i need to torque down the heads before making pushrod measurements?
-can i torque down the original TTY bolts ?
-after getting the correct pushrod length i can use the length checker to measure the PTV? since i wont have the actual pushrods until they come in the mail...
-for ptv checking, since i dont want to use the new gasket yet, i can use the old gasket and just subtract the .01 on my calculations?
-for ptv , same question as before, need to torque and ok to use old bolts?
Heads need to be torqued, and for measuring id say old bolts would be ok, or you could get studs which from my understanding arent torque to yeild so you could torque them and reuse them..... As far as using old gasket to check ptv, i would think youd be fine, but going through all that id personally buy an extra gasket idientical to the ones youre gonna end up running, so there is no question its right..... .010 ptv is a world of difference when it comes to tolerance..... If your reusing the old bolts to measure i would suggest using ft lb specs rather than degrees, just so you dont over stress the bolts.... Breaking a head bolt off in the block would ruin your day quickly
ok thanks. upon more reading I am going to check the PTV by using a dial indicator along with a degree wheel and checker springs to check the distance between the piston and the valve at crucial points in timing. for this method I can install the heads with the new gaskets so I will have an exact measurement.
the plan is to first check the PTV after installing the heads. swap out springs on cylinder 1 for checker springs. torque down the rocker arm and adjust the pushrod checker to the correct height that results in zero lash. from here i can check the PTV clearance. after confirming the clearance I can now get my pushrod final length - should be the length i previously used plus the amount of pre-load that i want (going to shoot for .04-.05). after adjusting the pushrod to this final length i can check the preload by torqueing the rockers down after zero last achieved. once preload is confirmed i can check the wipe pattern on the valve to tip to confirm everything is good to go
once everything looks good ill put an order in for the final pushrods and double check everything with the new pushrods before putting the covers back on...
check the cam degree and run it. that one should have a mile of PTV clearance.
the heads are also getting milled as well - waiting to hear back from phil as to how much they milled them. phil recommend the cam to allow for more clearance - just want to double check everything once it is bolted up. because i have never done anything to an engine before ,i am just trying to learn and make sure i have the proper procedures down before wasting a ton of time while doing the swaps. putting together a list of tools i still need and finishing up the small parts order soon. trying to do the swap the week during xmas.
from what i have seen in pictures of the lm7 dished pistons is that the valves still hit the outside diamter of the piston where the 'non-dished' portion is so the dish does not appear to help with clearance completely..
something like this
either way I am checking the clearance and made this thread to clarify how to do these checks properly and accurately.
12-04-2015, 05:16 PM
Help, I need clarification for pushrods and ptv with head/cam swap
