Finally back into the flathead
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Lead Driver
Joined: Oct 1999
Posts: 6,774
Likes: 552
From: Kalispell, MT
Finally back into the flathead
After too many years and other projects, I finally pulled the 51 merc flatty out of storage and started disassembly for a complete rebuild.
I ran this in my 48 F1 for 10 years as a daily driver.
Pullled pistons and found rod bearings are worn, one close to having no babbitt left. Crank looks ok. Might clean up at .010 under
Pistons - all 8 had broken top compression rings. Most of the pistons had damage as well. Explained the excessive blow-by I had when I quit using it.
They were standard so an over-bore is coming. Cylinder walls actually look smoothe with consistent wear, no gouges from broken rings at least.
One cylinder wall has some pitting half-way down the wall that must have been casting deformity. I'm hoping it will clean up with .040 over
Valve train looks good, oil pump came out without effort. It's the high volume pump I put in there 20 yrs ago.
That's about it for now. Looking for a machine shop that speaks flathead!
I ran this in my 48 F1 for 10 years as a daily driver.
Pullled pistons and found rod bearings are worn, one close to having no babbitt left. Crank looks ok. Might clean up at .010 under
Pistons - all 8 had broken top compression rings. Most of the pistons had damage as well. Explained the excessive blow-by I had when I quit using it.
They were standard so an over-bore is coming. Cylinder walls actually look smoothe with consistent wear, no gouges from broken rings at least.
One cylinder wall has some pitting half-way down the wall that must have been casting deformity. I'm hoping it will clean up with .040 over
Valve train looks good, oil pump came out without effort. It's the high volume pump I put in there 20 yrs ago.
That's about it for now. Looking for a machine shop that speaks flathead!
Parts Nerd Extraordinaire
Joined: Sep 2010
Posts: 4,353
Likes: 1,775
From: Western NY
I believe .030 is the next traditional size up on the Flatheads, so I would aim for that instead of .040 if able to.
Not being from MT, I can't recommend any shops local to you.
Not being from MT, I can't recommend any shops local to you.
Fleet Owner
Joined: Jul 2004
Posts: 27,290
Likes: 1,055
From: NM
Were the pistons hitting the heads? (causing the top rings to break) That can happen when the heads are milled too much and the combustion chamber isn't re-contoured.
Depending if the block passes a sonic check, my machinist always recommends going to +.060" on the bores. Gives a nice boost to compression (helps at our higher elevations).
Check with the local EFV8 Club chapter, they'll know who does good flathead work up there. Plenty of shops down here that can do it if you can't find one.
Depending if the block passes a sonic check, my machinist always recommends going to +.060" on the bores. Gives a nice boost to compression (helps at our higher elevations).
Check with the local EFV8 Club chapter, they'll know who does good flathead work up there. Plenty of shops down here that can do it if you can't find one.
Thread Starter
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Lead Driver
Joined: Oct 1999
Posts: 6,774
Likes: 552
From: Kalispell, MT
No sign of contact with heads, but I do run what I think are EAB heads on this Merc engine with standard domed pistons. No sign of having been milled, but the EAB has been ground off the face of the heads. I cc'd them before using and they measured right on for EABs.
It could be the 75K +/- miles I put on them with bumped up compression that did them in.
We do have a machinist in the valley who does flatheads. I just haven't met him yet.
It could be the 75K +/- miles I put on them with bumped up compression that did them in.
We do have a machinist in the valley who does flatheads. I just haven't met him yet.
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