Pushrod Length & P/V Clearance
04-21-2008, 05:27 AM
#1
Pushrod Length & P/V Clearance HI Guys, I am building 6.0 LS1 engine that has been bored over .030 ,that is forged on the pistons and rods. The pistons have valve reliefs which I believe are 6cc's. I was running a Comps Cam 231/237 595-598 114+4 with some LS1 heads that were milled .055, the valves barely hit the pistons and left a little mark.
Now I have an MTI C1 Cam 222/222 .566/.566 114 with some LS1 Heads that are milled .065 . Do you guys think that with this new setup the valves will hit the pistons? This MTI cam has a smaller lift of about .029 than the comp cams one!
What compression ratio will I have? If I am not mistaken, with the heads milled .065 of an inch, wouldn't that put me at around 11:6:1 compreesion ratio?
However, I am using the 6.0/6.2 GM MLS gasket which I believe has a compressed thickness of .060, so would this put the head milling to around .058 takin the extra .007 gasket thickness into consideration , as opposed to using the other GM gasket that has a compressed thickness of .053 . With the valve reliefs at 6cc's would that bring my compression ratio to around 10:8:1 or 10:9:1?
What length of pushrods will I need, the 7.350 or 7.250?
I used the search button and I was able to come to this conclusions, however I can be wrong, and this is where your expertise is needed!!!!
Any help would be greatly appreciated!!!
Now I have an MTI C1 Cam 222/222 .566/.566 114 with some LS1 Heads that are milled .065 . Do you guys think that with this new setup the valves will hit the pistons? This MTI cam has a smaller lift of about .029 than the comp cams one!
What compression ratio will I have? If I am not mistaken, with the heads milled .065 of an inch, wouldn't that put me at around 11:6:1 compreesion ratio?
However, I am using the 6.0/6.2 GM MLS gasket which I believe has a compressed thickness of .060, so would this put the head milling to around .058 takin the extra .007 gasket thickness into consideration , as opposed to using the other GM gasket that has a compressed thickness of .053 . With the valve reliefs at 6cc's would that bring my compression ratio to around 10:8:1 or 10:9:1?
What length of pushrods will I need, the 7.350 or 7.250?
I used the search button and I was able to come to this conclusions, however I can be wrong, and this is where your expertise is needed!!!!
Any help would be greatly appreciated!!!
04-21-2008, 09:23 AM
#2
A couple of things going on here...
1) duration affects PTV clearance more than the lift. Since you dropped 9 degrees intake duration and 15 degrees exhaust duration, you should be in good shape for clearance.
2) once you take more than .040" off your heads, they start flowing less and less. At .065", you may start losing power, especially since you made a major downsize in cam at the same time. The less that the heads flow, the more duration is required to make the same power.
3) pushrod length is probably best determined with an adjustable pushrod, once you've determined that no shims are required to get the valvetrain geometry correct.
I used these values to calculate your compression:
Chamber Volume 66.67 - 10.83 (every .006 removed = 1cc) = 55.84cc
Dish/Relief volume = 6cc
Cylinder Bore = 4.000
Stroke = 3.622
Positive Deck Clearance = .007
Gasket Volume = 4.065 x .060
Nominal Compression = 11.196:1
I don't have access to a DCR calculator right now, but you may be marginal with that much compression and that smaller cam, depending on the ICL you install it on.
1) duration affects PTV clearance more than the lift. Since you dropped 9 degrees intake duration and 15 degrees exhaust duration, you should be in good shape for clearance.
2) once you take more than .040" off your heads, they start flowing less and less. At .065", you may start losing power, especially since you made a major downsize in cam at the same time. The less that the heads flow, the more duration is required to make the same power.
3) pushrod length is probably best determined with an adjustable pushrod, once you've determined that no shims are required to get the valvetrain geometry correct.
I used these values to calculate your compression:
Chamber Volume 66.67 - 10.83 (every .006 removed = 1cc) = 55.84cc
Dish/Relief volume = 6cc
Cylinder Bore = 4.000
Stroke = 3.622
Positive Deck Clearance = .007
Gasket Volume = 4.065 x .060
Nominal Compression = 11.196:1
I don't have access to a DCR calculator right now, but you may be marginal with that much compression and that smaller cam, depending on the ICL you install it on.
04-23-2008, 10:37 PM
#5
I used these values to calculate your compression:
Chamber Volume 66.67 - 10.83 (every .006 removed = 1cc) = 55.84cc
Dish/Relief volume = 6cc
Cylinder Bore = 4.000
Stroke = 3.622
Positive Deck Clearance = .007
Gasket Volume = 4.065 x .060
Nominal Compression = 11.196:1
I don't have access to a DCR calculator right now, but you may be marginal with that much compression and that smaller cam, depending on the ICL you install it on.
Chamber Volume 66.67 - 10.83 (every .006 removed = 1cc) = 55.84cc
Dish/Relief volume = 6cc
Cylinder Bore = 4.000
Stroke = 3.622
Positive Deck Clearance = .007
Gasket Volume = 4.065 x .060
Nominal Compression = 11.196:1
I don't have access to a DCR calculator right now, but you may be marginal with that much compression and that smaller cam, depending on the ICL you install it on.
Chamber Volume 66.67 - 10.83 (every .006 removed = 1cc) = 55.84cc
Dish/Relief volume = 6cc
Cylinder Bore = 4.030
Stroke = 3.622
Positive Deck Clearance = .007
Gasket Volume = 4.065 x .060
Nominal Compression = 11.352:1
Also, I plugged these values into the PianoProdigy DCR Calculator, and came up with an SCR of 11.38:1 and a DCR of 8.55:1 when installed on a 114* ICL. Depending on your available octane, that's about the max you can run on 91 octane, expecially with your larger quench of .053".
