Piston to Valve (PTV) with new cams
08-06-2010, 02:05 AM
#1
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Join Date: Aug 2009
Location: Oregon
Posts: 81
Piston to Valve (PTV) with new cams
ok so I need help with some of my math.
I have read that some people have measured as little as 0.005-0.015 of PTV with comp cams xe270ah. I have also read that one needs "0.020" to be safe"-www.modularheadshop.com I have been told to have at lest 0.080 but that 0.100 is perfered.
so if I had the low side when I put the heads on my car of 0.005 PTV I need .015 more to be safe...?
If I get aftermarket valves I gain about 0.040 more PTV.
so if I stick with having 0.005 PTV then replace my valves and gain about 0.040 I would have about 0.045in PTV and could have 0.010 taken off the heads and still have about 0.035 and have a good chance of not needing to notch my pistons.
Im almost sure I'll have more then 0.035 PTV but if thats all i have is that really safe?
" 0.034" of piston to valve clearance. While that is tight it usually is a safe spec for the modular below 6500RPM or so"-www.modularheadshop.com
I got lots of info off of www.modularheadshop.com
I have read that some people have measured as little as 0.005-0.015 of PTV with comp cams xe270ah. I have also read that one needs "0.020" to be safe"-www.modularheadshop.com I have been told to have at lest 0.080 but that 0.100 is perfered.
so if I had the low side when I put the heads on my car of 0.005 PTV I need .015 more to be safe...?
If I get aftermarket valves I gain about 0.040 more PTV.
so if I stick with having 0.005 PTV then replace my valves and gain about 0.040 I would have about 0.045in PTV and could have 0.010 taken off the heads and still have about 0.035 and have a good chance of not needing to notch my pistons.
Im almost sure I'll have more then 0.035 PTV but if thats all i have is that really safe?
" 0.034" of piston to valve clearance. While that is tight it usually is a safe spec for the modular below 6500RPM or so"-www.modularheadshop.com
I got lots of info off of www.modularheadshop.com
Last edited by erikka.paige; 08-06-2010 at 02:07 AM.
08-06-2010, 06:43 AM
#2
Underboss
Join Date: Jan 2006
Location: Helaware
Posts: 20,273
08-06-2010, 10:02 AM
#4
Go Texas!!!
Join Date: Jul 2009
Location: Lincoln, NE
Posts: 4,613
If you haven't bought those Comp cams I would definitely think about buying MHS Stage 2 or CMS Stage 1 cams.
If you plan on doing headwork (machining the valves, piston notching) I would look at MHS Stage 3 cams. Those would be awesome cams to have.
Nick says with his stage 2 cams you will have ~.035" of clearance which IMO is the minimum amount of clearance I would want. Most stage 2 cams will clear with only .005". We're talking about the thickness of a hair clearance.
But if I remember correctly your doing aftermarket heads which then your probably not going to have any PTV issues.
If you plan on doing headwork (machining the valves, piston notching) I would look at MHS Stage 3 cams. Those would be awesome cams to have.
Nick says with his stage 2 cams you will have ~.035" of clearance which IMO is the minimum amount of clearance I would want. Most stage 2 cams will clear with only .005". We're talking about the thickness of a hair clearance.
But if I remember correctly your doing aftermarket heads which then your probably not going to have any PTV issues.
08-06-2010, 11:59 AM
#5
1st Gear Member
Thread Starter
Join Date: Aug 2009
Location: Oregon
Posts: 81
If you haven't bought those Comp cams I would definitely think about buying MHS Stage 2 or CMS Stage 1 cams.
If you plan on doing headwork (machining the valves, piston notching) I would look at MHS Stage 3 cams. Those would be awesome cams to have.
Nick says with his stage 2 cams you will have ~.035" of clearance which IMO is the minimum amount of clearance I would want. Most stage 2 cams will clear with only .005". We're talking about the thickness of a hair clearance.
But if I remember correctly your doing aftermarket heads which then your probably not going to have any PTV issues.
If you plan on doing headwork (machining the valves, piston notching) I would look at MHS Stage 3 cams. Those would be awesome cams to have.
Nick says with his stage 2 cams you will have ~.035" of clearance which IMO is the minimum amount of clearance I would want. Most stage 2 cams will clear with only .005". We're talking about the thickness of a hair clearance.
But if I remember correctly your doing aftermarket heads which then your probably not going to have any PTV issues.
and my math am I doing it right
Last edited by erikka.paige; 08-06-2010 at 12:02 PM.
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