Cracked Fenton Head

I just ***embled my 1948 Mercury Flathead. It is now 286 cubic inches. Three 97's, H-C dual point/dual coil distributor, H-C #FR 6014 cam, adjustable lifters & Fenton Heads. I have it on an engine stand and everything appears to be Great except one thing.

When cold, there is a slight amount of moisture coming from a hairline crack located below #2 plug. When it warms up, the crack closes and the moisture goes away. It doesn't appear to be cracked into the combustion chamber, only to the outside.

Where do I go from here? Run it until it gets worse, repair or replace? The water p***ages are in good shape & I don't see any other cause for concern. I milled the heads 0.010 before installation. It's the only leak I can find at this time.

This engine was last raced in August of 1961 and won it's D/Altered cl***. All the above parts were on it at that time & I would like to keep it all together as a piece of history if possible.

Regards

 

I would say fix the crack before it gets worse. Find someone that knows what they are doing and have it done right. The last time I had a crack in aluminum fixed it involved drilling a small hole at both ends of the crack, beveling along the crack and TIG'ng it up. Then grinding it down so you couldn't tell it was there. There should be some other replies coming shortly and maybe someone near you can point you to someone that can help.

 

Pay the money to have it welded properly.

 

When welding aluminum, do you need to pre-heat and temper after welding. Does TIG cause much distortion?

 

Preheat depends on how thick the part is,and the size of the welder.

Distortion is a big variable,no simple answer.

 

Jeep - What Z and Ian said.

When you're dealing with a crack, the point of the crack is where stresses are concentrated; thermal cycling will cause the crack to continue to migrate. Fix it now - a good welder wont' charge you much to fix that. Make sure you drill out the point of the crack first so as to distribute the stress after the repair - otherwise she may start cracking again.

this is the prob with old aluminum; it cyclically hardens and becomes brittle over time. heat stress is concentrated at the plug on a head - another reason to fix it now while it's still a bitty crack.

 

Thanks for the quick response. I'll locate the points where the crack terminate and drill to relieve stress. "V" the crack and find someone to Tig the area and then mill the weld to restore the contour. Sounds real easy if you say it fast enough.

Again, thanks for all the interest and help.