Piston/Valve Clearance
02-28-2009, 12:04 AM
#1
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Piston/Valve Clearance Guys I bought a set of Patriot stage 2 heads. Here are the specs on the heads.
There 243 casting heads
Combustion Chamber: 64cc
Intake Runner: 227cc
Exhaust Runner: 70cc
Intake Valve: 2.02"
Exhaust Valve: 1.57"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.090"
Retainer Material: Titanium
Valve Seal Material: Viton
Valve Guide Material: Manganese Bronze
Valve Job: 5-angle
My cam specs are
231-234 .646 .598 on a 111 LSA..
Am I going to have and piston to valve clearance issues? Any help would be much appreacaited..
There 243 casting heads
Combustion Chamber: 64cc
Intake Runner: 227cc
Exhaust Runner: 70cc
Intake Valve: 2.02"
Exhaust Valve: 1.57"
Max. Valve Spring Lift: 0.650"
Spring Pressure Closed: 135 lbs. @ 1.800"
Spring Pressure Open: 375 lbs. @ 1.090"
Retainer Material: Titanium
Valve Seal Material: Viton
Valve Guide Material: Manganese Bronze
Valve Job: 5-angle
My cam specs are
231-234 .646 .598 on a 111 LSA..
Am I going to have and piston to valve clearance issues? Any help would be much appreacaited..
02-28-2009, 12:34 PM
#2
I don't know what the limits are on stock bottom end, but I went away from that much lift on my stock bottom end, to .596/.595 as I have 1.85 Jesel Shaft mounted rockers (lift reflects total lift, not cam spec).
If no one knows what stock limits are, the best way to check according to Comp is to use putty on your piston and rotate the engine with the cam installed...then remove head and measure the putty thickness with a caliper...should be at least .080"...once again, according to Comp cams instructions.
If no one knows what stock limits are, the best way to check according to Comp is to use putty on your piston and rotate the engine with the cam installed...then remove head and measure the putty thickness with a caliper...should be at least .080"...once again, according to Comp cams instructions.
03-01-2009, 01:58 AM
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Is that a Thunder Racing Trak cam? Looks almost exactly like the spec's with a 111 LSA. You'll be fine with the PTV clearance with the 64cc chamber. Only crappy thing will be replacing the springs every 8-10k miles.
03-01-2009, 09:16 AM
#6
I wouldn't run that big of a cam without notching the pistons, you're just asking for trouble. Even if it clears, a little valve float and the engine is history. I notched my pistons with a Comp XER 228/230 .581.592. A friend of mine tried a Trex which is like .610/.612 and he had P/V contact. The valves only kissed the pistons so fortunately the engine didn't blow.
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03-02-2009, 06:51 AM
#8
To the original poster, I would most certainly check for piston clearance especially since I didn't see anywhere about how much was shaved off the heads, I'm assuming a few thousandths for cleanup, but not sure if it is more. Only way to know is to check it, or run it and see let the valves notch the pistons for you. (just kidding, not a good idea).
03-02-2009, 05:49 PM
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[quote=The Alchemist;11158769]What does cam lift have to do with stock bottom end? The issue with a stock bottom end is high rpms and rod bolt stretch. Cam lift is hard on valvetrain components, but has absolutely nothing to do with the bottom end.[quote]
By stock bottom end he is referring to stock pistons that are not flycut, a block that has not been decked, rods that are stock length, and a stock stroke crank. All factors of PTV clearence, he was not reffering to wear on the bottom end. Although the bottom end does have an issue with valve on piston crimes.
By stock bottom end he is referring to stock pistons that are not flycut, a block that has not been decked, rods that are stock length, and a stock stroke crank. All factors of PTV clearence, he was not reffering to wear on the bottom end. Although the bottom end does have an issue with valve on piston crimes.
03-02-2009, 06:51 PM
#10
But again, lift has NOTHING to do with piston to valve clearance, it's cam duration, valve size, and how deep into the combustion chamber that determines piston to valve clearance. Granted, how far out of the bore the pistons stick must also be taken into account, but not nearly to the degree that cam duration does.
03-02-2009, 09:43 PM
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Sorry for trying to clarify what the gentleman was reffering to when he stated "stock bottom end", that he was not saying the stock bottom end having reliablility issues with that much lift.
Your last post makes perfect sense but it does not reinforce any point you made in your previous post even if that were your thoughts. Just understand you have more knowledge than most of us but nobody truly understands a persons thought process through type.
Also don't forget about head gasket thickness!
Your last post makes perfect sense but it does not reinforce any point you made in your previous post even if that were your thoughts. Just understand you have more knowledge than most of us but nobody truly understands a persons thought process through type.
Also don't forget about head gasket thickness!
03-03-2009, 06:50 AM
#12
My point was that if a cam that is 231/234 with 600 lift won't fit because of piston to valve clearance, then a 231/234 with 560 lift won't fit either.
I've just heard people claiming that valve lift has a role in piston to valve clearance when it really doesn't. And yes, everything else you have mentioned will impact how much clearance you have, but ultimately, it's a case of when the valve starts to open with relation to the piston location that ultimately determines how much clearance you have.
I've just heard people claiming that valve lift has a role in piston to valve clearance when it really doesn't. And yes, everything else you have mentioned will impact how much clearance you have, but ultimately, it's a case of when the valve starts to open with relation to the piston location that ultimately determines how much clearance you have.
03-03-2009, 10:45 AM
#14
Agreed, with all said above, but you have to start with the basics. I was mentioning stock bottom end for the purpose of piston reasons, etc. No, I do not know as much as everyone here, just trying to ask some "too simple" questions I guess. So yes Mr Alchemist, you are right, but I always check to make sure 
03-03-2009, 01:17 PM
#16
Duration and lift both are in fact a component in potential P/V contact, to say otherwise is very misleading. 8*-10* before and after TDC, exhaust and intake are the most critical areas when degreeing a cam. The OP says he checked things out and there ar no P/V issues, I hope that means he degreed the cam.
03-03-2009, 04:46 PM
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My point was that if a cam that is 231/234 with 600 lift won't fit because of piston to valve clearance, then a 231/234 with 560 lift won't fit either.
I've just heard people claiming that valve lift has a role in piston to valve clearance when it really doesn't. And yes, everything else you have mentioned will impact how much clearance you have, but ultimately, it's a case of when the valve starts to open with relation to the piston location that ultimately determines how much clearance you have.
I've just heard people claiming that valve lift has a role in piston to valve clearance when it really doesn't. And yes, everything else you have mentioned will impact how much clearance you have, but ultimately, it's a case of when the valve starts to open with relation to the piston location that ultimately determines how much clearance you have.
10/4 good buddy
