Piston to Valve Clearence Question
Piston to Valve Clearence Question Guys I'm going to measure either way to make sure I'm safe. But I want everyone opinions on if I would have clearance issues. I have Prc Ls6 2.5 heads that were milled 0.030, and a VRX4 Camshaft 228/230 .588/.592 112 LSA. I was told my countless members here that I wont have any issues. I also talked to a well known vendor where I bought the heads from and he told me I would not have any problems. The vendor also told me that my valves were setup to give me clearance when I bought the heads, what does that mean? I'm also running a Gm mls gasket. Any thoughts?
I was in the same boat as you.. everyone said id be good including a handful of professionals.. turns out I wasn't.. there is really no point in asking if you already plan to measure anyways lol. FWIW my heads were 62cc with stock sized valves cam in sig and I didn't have enough clearance on either intake or exhaust
TSP will cut the valve seats deeper into the heads to help increase PTV clearance. The only way to know for sure if you are good is to check. Anything else is purely a guess.
We do sink the valves a little bit for more clearance but like other people have said its definitely best to measure your clearance on a setup with that many variables. You just never know if something is a little different.
Guys I measured clay impressions after my piston to valve check. I have above .200 clearence with both exhaust and intake. I checked with my regular springs and checking springs with an adjustable pushrod to zero lash and got pretty much the same results. Now, does lifter preload have to be accounted for in the final numbers? Or is an adjustable pushrod dialed into zero lash the maximum amount a valve will travel?
If you used a solid lifter and clay, then it will be OK. If you used a hydraulic lifter, then the measurement will show more clearance then you actually have.
Last edited by vettenuts; Jan 30, 2011 at 07:52 PM.
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you dont need a solid lifter with checking springs.Take a spring from a toilet paper holder if you think you have stiff checking springs.Some checking springs are a little stiff
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Verdad Gallardo You'd be surprised how little of distance .100 really is.. id make the hydraulic lifter into a solid lifter and measure again with the checking springs to be safe.. $3000 mistake on my end...
If you are compressing clay, yes. Use the dial indicator method if the hydraulic lifters are in but be sure to use a zero lash pushrod length. Depending on the lifter, this still may not work. My Morels when new compressed very easily. Solids are what are really needed.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Checking P to V with bled down compressible hydraulic lifters is not telling you anything. If you can, run the checker longer and fully collapse the lifter, it is about like a solid at that point but you have to do that or your measurements are junk at best.
Well my lifters were very hard to compress. They were all new, and I couldn't get that to compress when they were out of the car with a pushrod.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
They'll keep collapsing so I would not trust any measurement until you know they are all the way bled down and then take up all that slack if you can't use a solid lifter. Sometimes they are stiff initially but you don't want to think you have P to V when you don't.
This was my 383 LT4 Vette build
Put a dial indicator on the valve retainer to make sure you are getting full lift at the spring and you should be fine. It may be hard to do with the motor in the car.
Put a dial indicator on the valve retainer to make sure you are getting full lift at the spring and you should be fine. It may be hard to do with the motor in the car.
