Rebuilt 1953 mercury flathead. Used standard Felpro gasket set with "standard issue" head gaskets and now I have a head gasket leak. I am running Edelbrock aluminum heads, do I need a special head gasket? I sealed all the threads on the head studs and have a few weeping at the head nuts and also building pressure in the cooling system. I did a leak down test and really dont have any large variances from cyl to cyl. Motor runs great and does not overheat. Would like to know if aluminum heads take a specific gasket before I order. Thanks in advance for any help.
You might have a warped head. I use permatex non hardening on all my head bolts. Have you re-torqued them after a run and cool down? Usually should be done at least twice. What are the other specs on the engine. Bored, stroked,cam?
I use Fel Pro head gaskets DRY (no sealer) with my Edelbrock heads. I DO use #2 Permatex on the head bolt threads. Several re-torques (55#) after start-up--ZERO problems.
How long has it been run? These leaks usually stop by themselves after a while. For sure you need to do multiple torques on the heads. Most people advise torquing to a maximum of 45 ft/lbs for aluminum heads. I use plain grease on the head gaskets (I like Fel-Pro as well) and have had no problems. With flat surfaces and proper preparation, the heads should not requires any kind of special sealer, which only makes it more difficult to clean up next time. What kind of sealer did you use on the stud threads? Did you use hardened washers under the nuts?
I always go through 3 different heat cycles to torque the heads. What torque are you using? To check your heads for warpage, using bluing on your engine mating surfaces, both the engine and the heads. Reinstall. Slightly torque it. Take em off and view your wear surfaces.
I always spray copper coat on flathead head gaskets before installing, whether copper or composite. I believe your problem might be in the head bolts. Did you tap the block to clean the holes? They should not be tapped with a cutting tap, only a cleanup tap. The original stud/bolt holes were a tight tolerance, and when somebody "cleans" them up with a regular old tap they do more harm than good. Also, I don't know how a bolt into a wet hole can seal when a guy keeps torquing it. That's why I prefer studs. You can glue them in with a thicker sealer and never have to worry about the weeping after torquing. After you are all done torquing them, put a can of Silverseal into the radiator.
In the first post, he clearly states "studs" and "nuts". I disagree with your suggestion to use "Copper-Coat". The part about trying to preserve the threads in the block is spot on though.
I use standard gaskets with aluminum heads. The rookie mistake I made was not using hardened washers. The standard hardware store ones I used cupped badly.
I used permatex on the studs. Hardened washers and torqued to 50 lbs. It started to leak after the retorque. I have a large straight edge and heads and block were flat. I will try a 2nd retorque and see if that helps. Its bored 40 over so I dont think its too large for the standard gasket set.
I wouldn't worry about the .040" overbore. I have an 3 5/16" bore engine I ran with standard gaskets with no problem. (I carefully checked the fit first, though.)
Sorry I just read 53 and assumed bolts. I glossed over the studs and nuts. I think a standard gasket should cover your overbore okay, the big bore is meant for 3-3/8". The weeping is kinda normal with a flathead, but leaking combustion into the water is not. You are going to have to pull the heads and find the problem. You saw I suggested copper coat, but others don't.
Just curious whether the heads are the 8BA style or the earlier 59A type ....... if they're the 59A type a plug is needed in the 8BA block for this conversion.
Flatheads have the dirtiest cooling system, I have used the sealant blocks that come with a re-building set, and Silver Seal as well, run it a while and I bet it will seal up.
As said, retorque and usually it will seal up. I usually resurface the block when rebuilding, and that helps allot. Once I even resurfaced a set og new Offy heads, they where straigt, but the surface was a little rough. If your leak down test show no leak, then sealing the combustion should be ok. Once I was fooled by the pressure build-up, aslo thought there where a crack or bad head gasket, But no. Ran the engine without thermostats was a mistake. With thermostats, it calmed down. KBS
I always use Chevrolet bolt sealer wither bolts or studs, stays pliable will not leak after retorqueing part #12346004 best stuff I've ever used a little pricey though........
Update, I retorqued the heads for the 2nd time. The nuts seemed really loose which was odd as I had torqued to 50 lbs first time, any way seemed to seal up nicely. My upper rad hoses were even sucked in a bit and no bubbling or coolant on the floor. Will take out on its maiden flight this weekend. Thanks for all the help.
You're not out of the woods yet, it can take up to 5 retorques (my own personal record) before everything settles in permanently. Just keep an eye on it after the next half dozen drives or so and periodically after that.
Am I reading correctly that some of you use the standard size head gasket on the 3 5/16 bore. Is it a given or does the mating size have to be checked very carefully? As apposed to just installing the big bore set. (more $'s) Thank you, Fourdy
I did it, but only because I was in a hurry to see how my new engine ran. Like I said, I checked it carefully and there was no interference between the gasket and the piston. Some of the "fire rung" did overhang the edge of the cylinder a bit in a couple of places on a couple of cylinders. I did the initial firing and tuning with them, but installed a set of "big bore" Fel-Pro's I ordered from Speedway as soon as I got them in. I was afraid that if I ran it too long and got it up to temperature and ran for a while, the overhanging edges might have gotten overheated and caused pre-ignition. I know I shouldn't have done it, but everything else was ready to go, so...... It might have been OK long term, but I just didn't want to chance it. It was pretty close.
I myself always use copper coat, I think the tiny copper particles help the heat transfer process and the sealer aspect can't hurt coolant leak issues.
Whose head studs are you using? I only use ARP as they hold torque and don't stretch like a lot of the cheap aftermarket ones. In you have the non-ARP ones, you'll probably need to heat-cycle and torque it at least 3 times. I use ARP teflon sealer on all my head studs - and rarely have any leaking issues.
dont know stud brand. Leaking and seeping have stopped . Runs really good. Will check torque after I run it a bit more. now I have to put a pcv of some type on it, the oil fumes coming out of the fill tube stink.
First, if the center of the gasket sandwich is asbestos or similar, soak them in tub for an hour before installing....the gaskets will compress to the maximum when torqued, per George McNichol, who knows a lot about this subject...(How to build a flathead V8 Author). Second, I vote yes on Copper Coat. Nothing helps if the block or heads are not "flat". Multi retorques, yes.
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