Main cap stuck???

M

Mac29

Member
I am new to flatheads and tearing down my first one (59A). I got it most of the way tore down with out problem. Got the rear and front main caps off but the center one will not budge. Any tricks?

Got another newbie question. The rod ends seem too big to pass through the cylinder. Do they need to come out through bottom with crank out?

Thanks,
Mac
 
If there's a ridge at the top, you need to use a ridge cutter to remove it. The pistons normally come out the top. Once the crank is out, you can remove them thru the bottom, but on assembly, they go in from the top.
If you have the bolts out of the center cap, use a block of wood and a hammer to move it back and forth to remove it. Brass hammer will work also. Don't use steel on steel. Disaster in the making! Take your time, soak the area where it sits to the block with a good penetrating oil. Be patient, it will come off.
 
Barry-ct said:
If there's a ridge at the top, you need to use a ridge cutter to remove it. The pistons normally come out the top. Once the crank is out, you can remove them thru the bottom, but on assembly, they go in from the top.
If you have the bolts out of the center cap, use a block of wood and a hammer to move it back and forth to remove it. Brass hammer will work also. Don't use steel on steel. Disaster in the making! Take your time, soak the area where it sits to the block with a good penetrating oil. Be patient, it will come off.
Click to expand...

Would like a tutorial on getting all the pistons out from the bottom.

R
 
I've never run into this BUT, if this 59 block happens to be one of those early ones with 3-1/16 bore chances are the 59 rods won't come out the top. Only half the 3-3/16 pistons will come out the bottom. Walt
 
Hey Walt,
If they are 59 rods and a 3 1/16 bore, how would they ever have installed them?? Just curious
John
 
Probably measuring the rod cap ??
The rod cap is bigger then the bore but if you measure the rod it will be just a tiny bit less wide and fit into the cylinder.
 
There are some 3 1/16 engines that have been fitted over the years with 8BA crank and rods.Usually for cheap bearings or if floaters have been unavailable.Assembly is very tricky, especially with 4 ring pistons.The piston has to be pushed through the bore enough to fit the gudgeon and bottom ring and the crankshaft lowered on to the rods.Cheers.
 
Thanks all for the input. Got the Pistons knocked out today. I did not realize that there is a 4th ring on the piston skirt. Once I got it past the ridge in fell right out.
As far as that center main cap.... It is stubborn as a mule. I can't get it to lift off the studs. I am just gonna let the my machine man get it.
 
Smart man . . . if you have drama, don't screw it up . . . give it to the machine shop and they'll get it sorted out. Better safe than sorry!
 
Mac29 said:
Thanks all for the input. Got the Pistons knocked out today. I did not realize that there is a 4th ring on the piston skirt. Once I got it past the ridge in fell right out.
As far as that center main cap.... It is stubborn as a mule. I can't get it to lift off the studs. I am just gonna let the my machine man get it.
Click to expand...

The studs on mine were slightly splayed apart, and there is a ridge on the cap that sticks in the groove on the block. Together they made it harder than normal to disassemble and assemble, it tends to stick. Whoever takes it apart should exercise care so as not to damage the bearings.
 
Guys; The 41a --221 parts replacement engine in a "59" marked block-- had the
221 crankshaft with 2" rod journals , not the 59 crank with 2.139" journals.
All 39-48 221 & 239 had the same mains.
Going to Stray Cats this weelkend at Dewey, OKlahoma.
Love these flatheads, huh Mac29?

Luck & fun! Gene Tulsa
 
Walt Dupont--Me. said:
I've never run into this BUT, if this 59 block happens to be one of those early ones with 3-1/16 bore chances are the 59 rods won't come out the top. Only half the 3-3/16 pistons will come out the bottom. Walt
Click to expand...

oldford2 said:
Hey Walt,
If they are 59 rods and a 3 1/16 bore, how would they ever have installed them?? Just curious
John
Click to expand...

Guys; The 221 in "59" marked block had 2" rod journals --221 crank
(81 block 39-42 *), Not a 59 crank 2.139" rod journals
Trying to multi post -- still learning.
Gene Tulsa
 
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The rods are a tight fit in the block with a standard bore. Well, not tight as such, but not much clearance.
 
1. There is a good chance of extracting the studs with cap still there if you can get hold of a threaded collett type stud extractor. Maybe someone near you has a set.
2. Knocking loose motion of the cap should be rotational, obviously by a very small amount with crank in place. See if you can rotate it a thousandth or two by trying to rotate it with punch and hammer.
 
An article from a localMVCC news letter

"Big crank into small block"
" Regarding the inter-changing of parts.The small block (81)will accept the large big end crank but the con rods will not fit through the bore.This can be overcome by inserting the pistons first and then fitting the con rods from the bottom of the block.This must be done before the crank is fitted.The crank is then lowered down and the rods fitted.On 4 ring pistons the bottom ring must be fitted after the con rod is fitted to the piston from the bottom of the block, The above procedure is achievable but not recommended as it is a difficult job."
The last piece of advise is probably very pertinent.Cheers
 
I've bored alot of 39-42 blocks to 3-3/16 and installed 8BA crank and rods. You can bye the aluminum rear seal retainer for the block and rear main cap. Walt
 
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