flathead help?

got a 50 merc flathead 2 cylinders are screwed. in one cylinder looks like a bolt was bouncing around and the piston broke and the other one looks like just the piston broke but scored the cylinder wall motor is already 30 over.my question is would it be ok to sleeve the 2 cylinders and go 60 over.and what would that cost?.thanks

 

Today, any bore over .030 is gambling. In the old days, any bore less than 1/8 was considered chicken. That block can be taken to 3 5/16 easy, 3 3/8 if you need to. The blocks have changed that much. I have a 49 block at 3 3/8 that has been running fine for years, and yes it cools just fine.

 

thanks.rest of the motor is good was a runner just was bummed when i was going to install my edelbrock heads on it at saw there was a problem

 

Mine is .040 over and it would be safe at .125 over. So .060 will be no problem. You will probably be looking at $100 a hole to sleeve it, plus sleeves.

Kevin

 

Why sleeve it? Like Don said above, you should be able to go .128 over, OR .098 farther then you are at now, safely. If that doesn't clean it up, then sleeve it.

Neal

 

well the reason i brought up sleeving it looks like one of the cylinders was smacked by a bolt at the top of the cylinder but no damage to the deck surface?

 

took the oil pan off rest of the motor is good and it for sure is a merc.

 

We go 3 5/16" all the time with no problem, 3 3/8" is a little risky but doable if you have a good block. Sonic test before boring.

 

I always thought the same-anything less than .125 over is a waste of time and what's to worry about. Well let me tell a story. Years ago I bought a short block that was 3 3/8 bore. Tore it down and cleaned it up; rering & new bearings. I didn't want to spoil the "big bore" so left the cylinders alone-I think we deglazed them. Drove it for several years and it was always noisy when cold. Quieted right down when warm. I attributed this to forged pistons. Finally,due to oiling reasons, tore it down again and found a broken ring/scored cylinder. What the hell, let's go another .030. After honing the newly bored cylinders, the machinist saw a speck in one hole-about half way down. Close inspection revealed a hole in the wall.. Checked another cyl on that side and found the same thing. What that means is that all that time I was running with about .015" of cykinder wall in those two holes ( or maybe all on that side). Several sleeves (an SEVERAL $) I now have a very nice running 291" Merc. (3.406 bore). Obviously my old 8BA block was not really happy with a 3 3/8 bore but it hung in there for quite a while with paper thin spots in at least two cylinders.

 

Dale,

have seen evidence of severe core shift in some blocks - probably was the case with yours....

 

That's what we thought too since it only showed up on the p***enger side. We'd already had to go way over on one hole on the driver's side because the scored wall would'nt clean up at +.030. He took that one out big enough to sleeve and didn't go thru.

 

Makes ya want to sonic check everything!

I've seen intake ports almost 1/4" off the gasket!

 

well upon further inspection i noticed all the cylinders had been sleeved. is it possible to remove all sleeves and run bigger pistons. also did merc rods also say 8ba or all 49-53 engines have the same casting numbers?also what looks like i have adjustable lifters.can anyone post a pic of the difference between adjustables and stock lifters.this is my first flathead engine build.

 

Some of the truck engines had .0825" thinwall steel sleeves. There was a special set of pistons made that allowed the sleeves to be removed and the cylinders honed lightly before installing those pistons. I believe the 80 overbore made a 239 engine about 252 cubic inches.
Jerry

 

If the lifter has and adjusting screw on the top, well, that's self explanitory. Stock lifters are solid and adjustments for valve clearance are done by grinding the valve stem.

 

Sleeves are available check with Joblot

 

thanks for the help i do have adjustables.