65CC heads and .600 lift cam clearance?
12-27-2017, 11:56 AM
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65CC heads and .600 lift cam clearance? Anyone have any issues? I know 65CC is a lot and I never knew the heads I purchased were shaved until I took them to the machine shop to have them ported. Now I'm praying my Piston to valve issue is from my timing being off when I was 99% positive that I had it perfect.
12-27-2017, 12:54 PM
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Lift does not affect PTV. Duration and centerlines do. Honestly, it's your valve overlap (when both are open at the same time) that really affects it.
So, what are the cam specs?
So, what are the cam specs?
12-27-2017, 01:01 PM
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12-27-2017, 01:23 PM
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The duration numbers will typically be something like 228/232. They'll almost always be in the 220-240 range on a LS. They're missing from your list. BUT if they are below 232 at a 112 LSA, you should be fine on PTV
12-27-2017, 01:28 PM
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12-27-2017, 01:48 PM
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12-27-2017, 01:56 PM
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I hope so. I'm having issues currently but I'm praying they're from timing, in which I was 99% sure I got it right. But if not I can have them flycut
12-27-2017, 01:58 PM
#9
Unless something else is going on you should be plenty fine with that cam. However being a 65cc with the heads being shaved could mean a few things. That is some LS1 heads with a little taken off, or some 317 heads with quite a bit taken off. If it's the 317's then the amount of shaving was quite a bit and that may be the issue. If that's it and you want to fix it up on a budget go with some ol 706 or 243/799 heads, stock deck, bump the compression and have plenty of room for the cam.
12-28-2017, 11:09 AM
#10
I would check it regardless, I have a 223/231 cam with .610/.617 112 LSA and I had to retard the cam 4 degrees to get my PTV in a comfortable range. I have 5.3 heads shaved to 61 cc.
12-28-2017, 11:28 AM
#12
Who started the idea that the lift on the cam effects ptv OR even shows how "big" the cam is. Its been such a farse for forever. What is it going to take fo people to get that? Its not OPs fault because he prob heard it from someone else or saw it somewhere else, but is Super Chevy going to have to run an article sponsored by Amsoil to tell people that lift doesnt determine what a cam is?
Rant over.
12-28-2017, 11:40 AM
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Hypothetical cam 220/220-118 with 800 lift will NOT hit the pistons
Hypothetical cam 250/250-110 with 500 lift WILL hit the pistons without flycutting.
Edit - no intention here of derailing the thread. Just making that clear...
12-30-2017, 08:33 AM
#16
LOLZ!!! No, it's a serious post. you reach peak lift 100+ degrees away from TDC. You can have 800 lift, but if the ICL is 108, you're at 800 lift 108 degrees after TDC. its the duration - and more specifically the overlap, and ok, to a degree ramp rates -- that determines where your valves are at near TDC when they actually stand a chance of hitting a piston
Hypothetical cam 220/220-118 with 800 lift will NOT hit the pistons
Hypothetical cam 250/250-110 with 500 lift WILL hit the pistons without flycutting.
Edit - no intention here of derailing the thread. Just making that clear...
Hypothetical cam 220/220-118 with 800 lift will NOT hit the pistons
Hypothetical cam 250/250-110 with 500 lift WILL hit the pistons without flycutting.
Edit - no intention here of derailing the thread. Just making that clear...
P/V is a direct function of lift.
12-30-2017, 09:46 AM
#18
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PTV contact is a function of both IMO. You can hold a valve open 360* if your lift is only .100
But your common ~.600 lift is no way to judge alone if the valve will hit the piston. It has a lot more to do with when the lift occurs
After all the banter you just gotta check your PTV anyway
But your common ~.600 lift is no way to judge alone if the valve will hit the piston. It has a lot more to do with when the lift occurs
After all the banter you just gotta check your PTV anyway
12-30-2017, 10:36 AM
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PTV contact is a function of both IMO. You can hold a valve open 360* if your lift is only .100
But your common ~.600 lift is no way to judge alone if the valve will hit the piston. It has a lot more to do with when the lift occurs
After all the banter you just gotta check your PTV anyway
But your common ~.600 lift is no way to judge alone if the valve will hit the piston. It has a lot more to do with when the lift occurs
After all the banter you just gotta check your PTV anyway
Last edited by Duntov1967; 12-30-2017 at 11:58 AM.
12-30-2017, 11:42 AM
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Hammer has a gift for saying things clearly and briefly that I envy.