Ford Muscle Cars Tech Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
48 Posts
Discussion Starter #1
I have the heads off of my 351C to prepare to add my new Aussie heads to the setup. The bottom end is still together and it is what it is so I need to try and work with what is there to get the proper deck clearance for the quench. My pistons are .019 - .020 down in the hole, so I am looking for a head gasket that would allow me to reach the desired deck clearance for the quench to be effective.
Most composite gaskets seem to be in the .038 to .041 area. What are my choices beyond this? Should I go copper ? Or will I be OK with a .038 gasket with a total clearance around .058 ? .040 to .045 total deck clearance seems to be the sweet spot to shoot for, correct?
The heads chambers are around 65 to 68 cc (will be finalized as I finish the heads and have them milled) and I would like to try and keep my compression around 10.5:1. If it ends up a little less, not a big deal, I can adjust components accordingly (mainly cam).
Any suggestions or advice for me here?
 

·
Banned
Joined
·
6,355 Posts
you want perfect with it is what it is, sorry NO . heres way-- you can have Cometic make the gasket , the BIG BUT -- block and heads must have the correct finish to use them . Cheaper to just deck the block and use regular gaskets . even cheaper live with what you got
 

·
Premium Member
Joined
·
443 Posts
People not familiar with Cometic MSL head gaskets should stay quiet. I have used them for years and there is no special surface prep necessary except to make sure it is flat and smooth. A few strokes with a large flat file works great. I used their .027 thick MSL head gaskets on my 351W to get the quench down to .043. They seal just fine. You can spray a little Copper Kote on them as extra insurance. I have used them on Harley engines for years and have never had one fail or leak. You can even re-use them if they on not on too long! They are expensive though!
 

·
Registered
Joined
·
1,950 Posts
I have used them for years and there is no special surface prep necessary except to make sure it is flat and smooth.
Hmmm... so Cometic is wrong about their own recommendations?
Cometic Gasket, Inc.

And yes, I have run them on multiple engines over multiple years:)
I tend to RTFM.
 

·
Registered
Joined
·
10,300 Posts
People not familiar with Cometic MSL head gaskets should stay quiet. I have used them for years and there is no special surface prep necessary except to make sure it is flat and smooth. A few strokes with a large flat file works great. ... You can spray a little Copper Kote on them as extra insurance.
Yeah, that was a bit harsh. As already stated, Cometic does indeed have surface finish specifications, and an RA gauge is required to validate this. I take it you don't have one. Also, Copper Kote is definitely not recommended, and is only a backyard band-aid if the surface spec's are not what they're supposed to be. An example is some of the turbo Honda guys are using the spray because their factory RA is close, but not good enough, and they're too lazy or cheap to resurface their decks and blocks properly. It works. Sometimes.

Back to regular programming - 351stang67, I don't know what you had on your engine before or what else you're changing. Although quench value is going away around .050-.060", if you didn't have det before, and you are also going from open chamber to closed chamber, you may be fine. Right is right, but you may want to try a standard set of composite gaskets and see where that gets you if the budget is tight right now. If you get det before reaching MTBT (Minimum Timing for Best Torque), there are cheap work-arounds like richer mixtures, cam retard, re-curved ignition timing, etc., but those can cost a bit of power. Better fixes would be different cam timing, improving quench, better fuel, etc. Your call.

David
 

·
Registered
Joined
·
48 Posts
Discussion Starter #8 (Edited)
Back to regular programming - 351stang67, I don't know what you had on your engine before or what else you're changing. Although quench value is going away around .050-.060", if you didn't have det before, and you are also going from open chamber to closed chamber, you may be fine. Right is right, but you may want to try a standard set of composite gaskets and see where that gets you if the budget is tight right now. If you get det before reaching MTBT (Minimum Timing for Best Torque), there are cheap work-arounds like richer mixtures, cam retard, re-curved ignition timing, etc., but those can cost a bit of power. Better fixes would be different cam timing, improving quench, better fuel, etc. Your call.

David
Yes, I am going from open chamber 2V heads to Aussie heads. The heads have been ported and the chambers are now around 65cc now before having them milled/surfaced. (just cc'd them last night). They have been fitted with 2.19/1.71 valves and I am very impressed with how well they have been done. The chambers are usually small on these Aussie heads, but the ports and chambers have been blended very well. That's the reason the chambers are now 65cc vs. the stock 59-62cc.
I am also changing the cam to a Lunati VooDoo 62504. I was going with either the 62503 or 62504, but my setup is more in tune with the 62504 (especially compression). This is an occasional weekender type car & project so just a little more cam with the right setup should make for a fun ride.
The main reason I am avoiding any block work is the bottom end was redone years back and has very few miles on it (maybe 250 at the most). It has TRW flat tops, and you can still see the cross hatch pattern in the cylinders. So I hate to tear into it for that reason and the fact that I do not want to pull it from the car unless absolutely necessary.
I am thinking if I could get a head gasket down in the .027 range I could have a more effective quench, and I could keep my compression around 10.5:1 which the 62504 cam needs. If I were to have compression closer to 10.2:1 and go with the 62503 cam, I am worried I may be at more risk of detonation due to the smaller cam and less effective quench.
This is the basic dilemma I am at and trying to decide my direction.
The Cometic C5871-027 could get me to my target, but I am concerned over getting a proper seal with a MLS gasket.
It looks like the thinnest composite head gasket I've seen is .038 ?

By the way, I plan on running 92 octane pump gas, and no more than the car will be driven I can add some octane booster also.
 

·
Registered
Joined
·
9,251 Posts
I'm not looking up all those Lunati numbers, so I'll just tell you my 351C at 10.5:1 closed chamber 4V with .039 quench and 238 degree intake solid cam requires 93 octane to run well and not pepper the plugs. Our open chamber engine with 9.5:1 and a 226 intake hydro cam will use 91 without an issue. Both engines run at 180 and use 38 degrees of timing. These are drag ace engines, not driven on the street.

PS - If you think adding octane booster is going to change something, you are missing the "point". That is - when the can says "raises 20 gallons one point" that means going from 92 to 92.1, not 93. So don't go building a motor thinking crap in a can is going to save it from fuel quality issues.
 

·
Premium Member
Joined
·
443 Posts
The finger pointing was at DanH who always has something negative to say, not at you FE. I enjoy your posts, although sometimes they are out there!

I'm not possative, but I believe the recommendation for using Copper Kote on the Cometic MSL gaskets came right from the instructions packaged with them. I don't have those anymore, but I didn't just pull it out of the air. And as far as special surface prep, I'll still stand by what I said. I have used these head gaskets with aluminum heads on iron cylinders, aluminum heads on aluminum cylinders, and iron heads on iron blocks. Some combinations were new, some used, some used/new. Never once did I experience a single sealing problem. So, maybe I am all F'd Up and doing something wrong.
 
1 - 10 of 10 Posts
Top