head gasket choice
08-04-2019, 03:54 PM
#1
head gasket choice The car will be NA, street driven only. Which head gaskets should I get:
SCE pro seal composite, gives .043 quench, bore size 3.970 which is almost an exact fit, $54/pair
or
Cometic MLS, gives .039 quench, bore size 4.000 which is about .003 larger than exact fit, way more $$ at about $160/pair
The bore size I need is a little hard to measure due to the bevel at the top of the bore which is not exactly the same size on all the bores, and anyway have to sort of eyeball it even using a caliper. 3.970 seems close to exact, 4.000 a little large. Which is more important, quench or exact bore size fit? Also, there's the $$ difference.
SCE pro seal composite, gives .043 quench, bore size 3.970 which is almost an exact fit, $54/pair
or
Cometic MLS, gives .039 quench, bore size 4.000 which is about .003 larger than exact fit, way more $$ at about $160/pair
The bore size I need is a little hard to measure due to the bevel at the top of the bore which is not exactly the same size on all the bores, and anyway have to sort of eyeball it even using a caliper. 3.970 seems close to exact, 4.000 a little large. Which is more important, quench or exact bore size fit? Also, there's the $$ difference.
Last edited by patSS/00; 08-04-2019 at 04:05 PM.
08-04-2019, 05:23 PM
#2
ModSquad
iTrader: (6)
You want to match the gasket to the chamber, not the bore per say. If the gasket protrudes in on the chamber edge, it will hurt flow and cause a hot spot for detonation. Call the guys at WS6Store. They will give you best pricing and stir you in the right direction regarding sizing and quench.
edit...Keep in mind that the gasket thickness will play into both your PTV and compression needs as well as your quench.
edit...Keep in mind that the gasket thickness will play into both your PTV and compression needs as well as your quench.
Last edited by Che70velle; 08-04-2019 at 05:30 PM.
08-04-2019, 05:59 PM
#3
Good point, heads are out being worked on (they're stock 241), but will check, I don't think it's possible for that 3.970 gasket bore size to protrude on the chambers. I've also read that if the gasket bore is too big, carbon can get in the space which can also cause detonation. Not having detonation is the top priority, since it was always a problem with this car before the rebuild.
08-07-2019, 03:53 PM
#4
Go for the Cometic. Just slightly larger than the bore, which is good. And a good quench number. The cost is a bit more. But (IMO) MLS is better than composite.
A year from now will you care that you spent the extra $106? No, probably not. A year from now will you care that you built a killer engine? I'm pretty sure you will.
A year from now will you care that you spent the extra $106? No, probably not. A year from now will you care that you built a killer engine? I'm pretty sure you will.
08-07-2019, 05:34 PM
#5
WS6 store has .045 thick gaskets for I believe $70. They are MLS too. But I think they are 4.070 which kinda sucks. But not horribly. I personally would prefer them to be a little tighter.
You didn't list what your piston out of the hole measurement is so can't tell you what quench willbe with those.
As for the 4.0" gasket bore....Having a 3.970 bore size with a 4.0 gasket only leaves .015 open area around the cylinder liner which is excellent. And the .39 quench is sweet too, so cometic looks like the winner here.
You didn't list what your piston out of the hole measurement is so can't tell you what quench willbe with those.
As for the 4.0" gasket bore....Having a 3.970 bore size with a 4.0 gasket only leaves .015 open area around the cylinder liner which is excellent. And the .39 quench is sweet too, so cometic looks like the winner here.
08-09-2019, 10:47 AM
#6
One problem with the .036 gasket: looks like the PTV for the exhaust valves will be around .95, which is a little less than what I've seen recommended everywhere. How much of a problem is that? If it's just an issue at high rpm, like 7K or more, than that will still work (street driven only). It's because I'm using oversize 1.60 exhaust valves, in 241 heads milled by .008.
Also to answer the question, pistons are .003 under the deck.
Also to answer the question, pistons are .003 under the deck.
08-09-2019, 11:30 AM
#7
One problem with the .036 gasket: looks like the PTV for the exhaust valves will be around .95, which is a little less than what I've seen recommended everywhere. How much of a problem is that? If it's just an issue at high rpm, like 7K or more, than that will still work (street driven only). It's because I'm using oversize 1.60 exhaust valves, in 241 heads milled by .008.
Also to answer the question, pistons are .003 under the deck.
Also to answer the question, pistons are .003 under the deck.
On the piston deck height. Did you rock the piston and get an average measurement?
Does your piston have valve reliefs? If so is the valve going to contact the edge of the relief or the piston crown?
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08-09-2019, 12:57 PM
#8
ModSquad
iTrader: (6)
General rule of thumb is .080” intake and .100” exhaust valve PTV numbers minimum. But I must say that I’ve ran .090” exhaust, on an LS engine with zero issues. Street engine that will never see 6500rpm. Runs great to this day.
Last edited by Che70velle; 08-09-2019 at 12:58 PM. Reason: Smellcheck...
08-09-2019, 02:17 PM
#10
Sounds like you can run it since you're super close on the conservative minimum clearance.
Or you can lightly fly cut.
Make sure you rock the pistons and get a min max and average out the reading to confirm your finding too. Center works if you can get true center. But from what I understand the technical proper way is to rock it and get a min max and divide by 2
Have you confirmed the .095 by measuring with clay?
Or you can lightly fly cut.
Make sure you rock the pistons and get a min max and average out the reading to confirm your finding too. Center works if you can get true center. But from what I understand the technical proper way is to rock it and get a min max and divide by 2
Have you confirmed the .095 by measuring with clay?