Are my valves hitting the pistons?
Are my valves hitting the pistons? I just got my pushrods and gaskets and all so I'm buttoning the engine up (In my dining room) and I was just checking things over. Valve covers off torquing the rockers after several revolutions and such and i notice the engine makes a thumping sound with each valve opening and closing. Is this just the heavy springs i have (Patriot gold 650s) in conjunction with the high lift of my cam (cam card says .647)? I dont think its my pistons hitting the valves as its more of a poping sound, the plugs are out but the faster i turn it over the faster it goes. It's almost like a "lope".
Even with the plugs out? Or you saying its blowing compression back into the intake when the exhaust opens?
Cam card
Valve adjust HYD HYD
Gross Valve Lift .647 .647
Duration @
.006 Tappet Lift 285 285
Valve timing Open Close
@.050 INT: 11 BTDC / 43 ABDC
EXH 51 BBDC / 3 ATDC
These specs are for cam installed
@106.0 Intake centerline
Duration @ .050 235/235
Lobve Lift .3810/.3810
Lobe separation 110.0
Cam card
Valve adjust HYD HYD
Gross Valve Lift .647 .647
Duration @
.006 Tappet Lift 285 285
Valve timing Open Close
@.050 INT: 11 BTDC / 43 ABDC
EXH 51 BBDC / 3 ATDC
These specs are for cam installed
@106.0 Intake centerline
Duration @ .050 235/235
Lobve Lift .3810/.3810
Lobe separation 110.0
I would of checked it with clay.Your intake valve is open at 11 degrees before top dead center,which is really early.It might be hitting the intake valves,kinda sounds like clicking?
If the heads are already bolted down, you really need to check PTV. Use the method that employs checking springs and a dial indicator. There will be some audible clicking of the valves closing but with a huge cam like that you really should have verified your PTV prior to final assembly. Certainly do it before you attempt to start it.
Well the last cam i had was am HPE S cam 238/242 .608/.612 on 115+5LSA in an LS6 with slightly milled heads and 2.055 Ls6 ET heads and it cleared. intake valve opened 9 degre BTDC. I think its just the sound of the valve closing like you mentioned. If the valves bend, they bend. Heads were the next step once the motor was in an running.
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You are correct, the 238/242 .608/.612 on 115+5LSA appears to have an IVO of 9BTDC. Definitely worth checking!
Originally Posted by Shawn MacAnanny
I think its just the sound of the valve closing like you mentioned. If the valves bend, they bend. Heads were the next step once the motor was in an running.
Well i was wondering if the sound i heard was of the valves hitting. Everyone keeps telling to to check PTVC but to me honestly, its not worth the cost of head gaskets and bolts to do it. I paid $200 for this longblock so its basically a disposable template for me.
I say you're going to be flycutting the pistons as soon as you start the motor when the intake vavles start to smack the top of the piston. I could be wrong, but you are cutting it close and may be pulling the heads and motor sooner than you think, especially if you get any valve float.
if your valves are hitting pistons it will stop the engine from turning over. i'd guess the thumping you are hearing is the valve seating. speaking numbers only, that cam shouldn't cause any ptv interference. i assume those are lsk lobes?
Thats exactly what i was wondering is if it were hitting if i would feel it when turning the motor over. If it bends the valves, that fine, I'll buy my after market heads, flycut the pistons then, then install new bolts and head gaskets. Otherwise i dont see a point in spending $150 on bolt and head gaskets for a $200 engine that could possibly run on these heads long enough for me to listen to the shortblock and watch it make oil preassure.
Thud, thump, pop, click. These terms are kind of nebulous when it comes to trying to convey you message over the internet. If the plugs are out compression is non-existant so it's not a "hiss". Better to note just what is happening when you hear what is you say you are hearing and then describe the event and associated sound. Say, relate this to cy.#1. What stroke are you on? Where is the piston? Are the rockers rockin or are they static? That might be a better way of describing your problem.