thicker head gasket instead of flycutting??
10-04-2006, 04:39 AM
#1
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thicker head gasket instead of flycutting?? i have a Lunati 55008 cam (237/242 595/595 112) and when i asked Lunati on their tech line if it would clear piston to valve they say "all cars are different and your in that grey area". my question is can i just get thicker head gaskets to get myself out of that "grey area" and be on the safe side? i know if i dont it will be close but i think id rather just be safe. any thoughts?
10-04-2006, 08:08 AM
#3
TECH Addict
I'd just get the pistons flycut. Having had a bit of a look I don't think it should be that expensive. Or you can try it yourself if you get the correct gear.
There's no point in loosing SCR, you might as well just swap to a smaller cam.
There's no point in loosing SCR, you might as well just swap to a smaller cam.
10-04-2006, 08:11 AM
#4
TECH Senior Member
FYI with flycutting you loose SCR as well.
Most important is that by running a thicker gasket, you widen your quench and therefore are more prawn to detonnation.
Most important is that by running a thicker gasket, you widen your quench and therefore are more prawn to detonnation.
10-04-2006, 10:39 AM
#5
What heads are you running? Stock castings leave the valves about .200 from the deck surface according to Lou @ LGM, where AFR 205's milled to 59cc still have .220 clearance. It pays to check, as stated above.
Also, with fly cutting, you would be increasing the dish volume in the top of the piston, but that should be more than offset by the volume saved by running the thinner gaskets. Given the 3.9" effective area of the gasket volume, the half-moon shaped cuts you make at 2.0x and 1.6x inches should add much less volume than you are able to remove with adequate milling.
Gasket Volume (3.9/2)^2 x 3.1416 x .020 = 0.2389 ci
Rough Intake Relief Volume(2.08/2)^2 x 3.1416 x .020 = .0680 ci
Rough Exhaust Relief Volume(1.68/2)^2 x 3.1416 x .020 = .0443 ci
Total change in Volume = (.068 + .0443) -.2389 = - .1266 ci approximately half the volume removed by the thinner gasket. This is assuming both valves were at minimum clearance before, and required the same amount of material removed to compensate. What it doesn't take into account is the valve angle and that the deepest portion of any material removed is at the smallest effective area of the circle. I used rough estimates of the whole volume of the circle, where I suppose it should be much less.
Unless someone knows some fancy math to fugure that out, I'd say it's better to get out the burrette.
Also, with fly cutting, you would be increasing the dish volume in the top of the piston, but that should be more than offset by the volume saved by running the thinner gaskets. Given the 3.9" effective area of the gasket volume, the half-moon shaped cuts you make at 2.0x and 1.6x inches should add much less volume than you are able to remove with adequate milling.
Gasket Volume (3.9/2)^2 x 3.1416 x .020 = 0.2389 ci
Rough Intake Relief Volume(2.08/2)^2 x 3.1416 x .020 = .0680 ci
Rough Exhaust Relief Volume(1.68/2)^2 x 3.1416 x .020 = .0443 ci
Total change in Volume = (.068 + .0443) -.2389 = - .1266 ci approximately half the volume removed by the thinner gasket. This is assuming both valves were at minimum clearance before, and required the same amount of material removed to compensate. What it doesn't take into account is the valve angle and that the deepest portion of any material removed is at the smallest effective area of the circle. I used rough estimates of the whole volume of the circle, where I suppose it should be much less.
Unless someone knows some fancy math to fugure that out, I'd say it's better to get out the burrette.
10-06-2006, 12:46 AM
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Originally Posted by Z'mnypit
You could, but with a thicker head gasket your going to lose compression. Why not check the PtoV clearence when installing? I would think that cam would clear...