LQ9/243 push rod length HELP
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Teching In
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LQ9/243 push rod length HELP Im trying to verify proper push rod length of my build. Using a LQ9 block. 243 casting heads that have had a 0.003" clean up job done. Felpro head gaskets. TSP stage 2 high lift truck cam 212/218 600"/600" with 112 LSA. Using LS7 style lifters. And stock rocker arms with trunion upgrade. Measuring the intakes using the comp cams length checker i find that the rocker is loose when i have it set to 7.3125 and tight when set to 7.325 (numbers arnt exact as im just turning the tool 1/4 turn at a time). The tight reading at 7.325 + 0.070(preload) would give me a length just under 7.400 which is good as those are the push rods texas speed sent me. But when i measure exhaust valves im finding the exhaust valve to have no play when the tool is set to 7.3125. Is it common to have different lengths for intake and exhaust or am i doing something wrong. Ive checked a couple different cylinder and this seems to be what im getting.
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Yes that is somewhat common.
"Ideal" preload is within quite a wide range; .060" - .100" or so. It is not common for there to be so much variation between int & exh in a mostly stock motor that one length won't work on both.
Texa Speed sells push rods in .025" increments, no doubt others do as well. Find a length that puts both I & E in that range if possible, otherwise see if they'll sell half sets or at worst buy 2 sets.
"Ideal" preload is within quite a wide range; .060" - .100" or so. It is not common for there to be so much variation between int & exh in a mostly stock motor that one length won't work on both.
Texa Speed sells push rods in .025" increments, no doubt others do as well. Find a length that puts both I & E in that range if possible, otherwise see if they'll sell half sets or at worst buy 2 sets.
Did anyone do valve work on the heads? Usually they are pretty close to each other in length, although you admit your numbers aren't exact.
One thing to verify is that the piston is at TDC on the firing stroke. Be careful using the timing chain for this, as when the dots line up #1 and #6 pistons are at the top but one is on the firing stroke and the other top of exhaust. Can't remember which was which with the timing chain (cam dot at top or bottom) for cylinder #1 so its best to rotate until you see the #1 intake close (use a pushrod to follow the motion making sure you keep some downward force on it to overcome the friction of the lifter tray that will likely keep the pushrod up) then bring piston #1 to the top. Then verify your measurements.
One recommendation, get larger OD pushrods like the 11/32" OD Mantons. You can also get them in separate lengths.
One thing to verify is that the piston is at TDC on the firing stroke. Be careful using the timing chain for this, as when the dots line up #1 and #6 pistons are at the top but one is on the firing stroke and the other top of exhaust. Can't remember which was which with the timing chain (cam dot at top or bottom) for cylinder #1 so its best to rotate until you see the #1 intake close (use a pushrod to follow the motion making sure you keep some downward force on it to overcome the friction of the lifter tray that will likely keep the pushrod up) then bring piston #1 to the top. Then verify your measurements.
One recommendation, get larger OD pushrods like the 11/32" OD Mantons. You can also get them in separate lengths.
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Teching In
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Thanks for the reply guys. The only valve work is a lapping I did by hand. The exhaust definitely took more time to clean up. But if the ideal preload is 0.050-0.100 then the 7.400 I have would work just fine.
