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How goes it guys...... I'm in the middle of a heads cam swap. Cam: Polutter v2 239/244 .635" .610" 112+3 lsa Heads: PRC 243's milled .030" Head Gasket: Cometic .040"
The reason for my post here is through all my searches I have not seen PtV clearance checked this way and seems like a much better way and much more accurate than dealing with clay on the pistons. Also, correct me if I'm wrong or just say, hey dim wit, that won't work because...
but seems like the same concept as clay on piston.
First I made a piece of clay that looks like a stick of gum shown below.
Then I set my push rod to the proper length, removed check spring and let valve sit on piston top, bolted down rocker and set the piece of clay on the top of the valve tip as shown below.
Turned the motor over, removed the clay, cut the clay and measured as shown in the three pictures below.
Doing it with this method I came up with clearances of
Intake .040"
Exhaust. .065"
I previously checked PtV clearance with feeler gages and check springs and with that method I came up with
Intake .045"
Exhaust .080"
Maybe it's been done this way many times but do you guys see any error in this method besides probably being off a tit, .010" due to not having the valve springs in.
Ended up cutting valve reliefs of .032" and think they turned out pretty damn nice for my first time as shown below.
Last edited by 98CayenneT/A; Jan 30, 2020 at 07:16 AM.
So as you was turning engine over, did you make sure from lifter roller to valve side of
rocker arm was all tight? pushrod seated at both ends, rocker arm pressed on both sides?
Yes, I just kept light pressure on the pushrod side of the rocker and let the piston push the valve up into the clay and let the push rod push the rocker arm tip down into the clay.
Looks pretty well thought out to me. Whats your new clearance with the reliefs?
Original was .040" on the intake
Then I cut the reliefs and set the depth at .032"
Remeasured my PtV clearance with the method explained above and came up with .073" so should get .080" and some change with the valve springs installed.
I will take it unless someone points out a blatant mistake or reason for why it won't work.
How did you determine the spot in the pistons to cut the valve reliefs without marking them? I have cut valve reliefs in several hundred of sets of pistons myself as a professional engine builder and machinist, and even factory valve notches in pistons rarely line up with the actual valve positions in the heads. Also as a reference, TDC is not the point at which either valve are closest to the piston. It looks like the piston is awful high in the cylinder in your pic, unless its just for the illustration. Just asking....
Last edited by CNC-Dude; May 12, 2017 at 07:31 PM.
Yes, I just kept light pressure on the pushrod side of the rocker and let the piston push the valve up into the clay and let the push rod push the rocker arm tip down into the clay.
Well there is always more than one way to skin a cat, nothing wrong with
using your Brain and doing something other than what everybody else does.
Did you cut pistons with a cutting tool in head and head bolted down, then
drill motor and precision tape to mark depth?
How did you determine the spot in the pistons to cut the valve reliefs without marking them? I have cut valve reliefs in several hundred of sets of pistons myself as a professional engine builder and machinist, and even factory valve notches in pistons rarely line up with the actual valve positions in the heads. Also as a reference, TDC is not the point at which either valve are closest to the piston. It looks like the piston is awful high in the cylinder in your pic, unless its just for the illustration. Just asking....
He said he turned the engine over, wouldn't that still just show the tightest
clearance no matter where the piston is?
How did you determine the spot in the pistons to cut the valve reliefs without marking them? I have cut valve reliefs in several hundred of sets of pistons myself as a professional engine builder and machinist, and even factory valve notches in pistons rarely line up with the actual valve positions in the heads. Also as a reference, TDC is not the point at which either valve are closest to the piston. It looks like the piston is awful high in the cylinder in your pic, unless its just for the illustration. Just asking....
I used the Lindy fly cutting tool where the mandrel is the same size as a stock valve stem to put threw the valve guides then the cutting wheel is about .050" larger than the stock ls1 valves.
When I cut them I put the head on with no gasket, turned the motor over until the piston pushed against the head then set my depth.
With cutting with the piston at the top and cutting with no gasket the cut should be higher and as the cylinder goes down it would move closer to the center of the piston correct?
I do realize where I have my piston positioned in that picture is not where the valve to piston is closest.
Well there is always more than one way to skin a cat, nothing wrong with
using your Brain and doing something other than what everybody else does.
Did you cut pistons with a cutting tool in head and head bolted down, then
drill motor and precision tape to mark depth?
Yes I used the Lindy fly cutter for stock size ls1 valves.
The Lindy cutting wheel is about .050" wider than the stock valve stems.
I covered the piston top and gap with transmission assembly grease then bolted the head down snug with a couple bolts. Vacuumed up the metal shavings which stick to the grease
Yes I used the Lindy fly cutter for stock size ls1 valves.
The Lindy cutting wheel is about .050" wider than the stock valve stems.
I covered the piston top and gap with transmission assembly grease then bolted the head down snug with a couple bolts. Vacuumed up the metal shavings which stick to the grease
Oh and I see you did it in the vehicle, so everything was nice and easy. lol
Oh and I see you did it in the vehicle, so everything was nice and easy. lol
Lol, my life is miserable right now....j/k
I'm doing this in my single car garage at my townhouse.
Space is tight as hell. I have a plastic picnic table set up in my living room with a bunch of new parts.
Car is up on 4 jack stands with the exhaust and transmission laying underneath due to me pulling it out to send to yank for a different set up.
Lol, I like it.
I often wonder what life would be like if I would be contempt just driving a stock vehicle.
I mean where the ONLY Mod is Tinted Windows, that kind of stock.
With cutting with the piston at the top and cutting with no gasket the cut should be higher and as the cylinder goes down it would move closer to the center of the piston correct?
The intake valve location relative to the piston moves as the piston moves further downward, so you are introducing error into it by this method. The opposite happens with the exhaust valve as it moves upward. Before you button everything up, clay the piston with the valves adjusted just to confirm the valve locations in the piston as a double check.
The intake valve location relative to the piston moves as the piston moves further downward, so you are introducing error into it by this method. The opposite happens with the exhaust valve as it moves upward. Before you button everything up, clay the piston with the valves adjusted just to confirm the valve locations in the piston as a double check.
Sounds good, I will do that. Thanks much for the advice.
I will take all the advice I can get, kinda diving into this head first
Pretty interesting way of checking PTV, but you are still stuck with measuring clay, which is very imprecise. With a cheap dial indicator, you could have been more precise. Were you not happy with 0.040" I and 0.065 E?
Pretty interesting way of checking PTV, but you are still stuck with measuring clay, which is very imprecise. With a cheap dial indicator, you could have been more precise. Were you not happy with 0.040" I and 0.065 E?
Originally I was going to run it until I read thread after thread about .080" I and .100" E and still thought about running it but decided to play it safe. I will be spinning it to 6800-6900 rpms
Also I go to power cruise once a season which is a free for all road course with a long straight away where I absolutely beat the ever loving **** out of my car in August air so I just cut them.
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Piston to Valve method 
