'55 GB Cylinder Boring

[MolineGB1997]

Hey all and good evening. I recently picked up a GB gas as a restoration project. It's in generally good shape, but needs motorwork as it sat outside for the last few months.

The front two cylinders are in good shape. The rear two not so much. The pistons seem ok but the cylinder block is fairly crusty on the inside.

This engine has been bored to 4.75 and appears to not have many hours on that overhaul. Pistons look like new. If I need to, how much more can I bore out these blocks safely? I've read that they can be sleeved, would save my good pistons but I'm not sure what that would cost and if it's worth it. I'm not looking to get crazy power, I just want to get it running as it should.

Bonus question: will UB exhaust and intake manifolds work on a 403? The exhaust manifold on this tractor is fubar and they seem to be hard to find.

Thanks in advance!

 

[Duey C]

Not an expert by any means. The 1940's 403 blocks were at their limit at 4.75 best I had found.
Given the low production numbers, it's worth it to fix. And a 70 horse max 425 cube four cylinder.
Surprised you haven't gotten answers yet but the guys are likely busy. I'd be just tickled if my 20's-30's 403 (413) pre G (21-32) gets close to 50 horse!

The guys here taught me the U style manifold has smaller carb mounts and air passages so it won't breathe like it should so less power. There may be other manifolds but I don't recall. Hopefully, I'll get straightened out on that.

 

[MolineGB1997]

Not an expert by any means. The 1940's 403 blocks were at their limit at 4.75 best I had found.
Given the low production numbers, it's worth it to fix. And a 70 horse max 425 cube four cylinder.
Surprised you haven't gotten answers yet but the guys are likely busy. I'd be just tickled if my 20's-30's 403 (413) pre G (21-32) gets close to 50 horse!

The guys here taught me the U style manifold has smaller carb mounts and air passages so it won't breathe like it should so less power. There may be other manifolds but I don't recall. Hopefully, I'll get straightened out on that.

Thanks for the reply. Information sometimes seems sparse on these tractors. Hopefully, I can salvage the cylinder blocks I have... Would be a shame not to use the like new pistons I have.

Not sure what to do about an exhaust manifold yet. I'm hoping a manifold from another model will fit. I thought it was strange you can get new manifolds for other moline models, but not the GB. I've struck out with all the salvage yards within a reasonable distance from me.

 

[Duey C]

Yep, a fella has to dig and study for months sometimes to gather info. I fiddle with 19 and 26 year older models and will again but there's little info. The MM's are best covered right here nowadays.
I hear you on the manifold and the fresh pistons! Just bite the bullet and sleeve it??
Years ago, some manifolds were re-cast for the 403's. Once they were used up, wasn't done again... $$
Oh! Welcome to YT!

 

[MolineGB1997]

Yep, a fella has to dig and study for months sometimes to gather info. I fiddle with 19 and 26 year older models and will again but there's little info. The MM's are best covered right here nowadays.
I hear you on the manifold and the fresh pistons! Just bite the bullet and sleeve it??
Years ago, some manifolds were re-cast for the 403's. Once they were used up, wasn't done again... $$
Oh! Welcome to YT!

Glad to be here. Best place for info is from the folks who've done it. It's my first restoration so I'm learning a lot.

 

[molinegb]

Had to get one hole sleeved on a GTB. Just make sure machinist pins sleeve properly. U manifold will fit with bit of trimming. Better off going to a newer 336 manifold off a M5,M602 or 670. Steiner has new.

 

[MolineGB1997]

Had to get one hole sleeved on a GTB. Just make sure machinist pins sleeve properly. U manifold will fit with bit of trimming. Better off going to a newer 336 manifold off a M5,M602 or 670. Steiner has new.

I see. Thanks for the help. I'm assuming they don't make new manifolds because there are others that work.

 

[MolineGB1997]

Had to get one hole sleeved on a GTB. Just make sure machinist pins sleeve properly. U manifold will fit with bit of trimming. Better off going to a newer 336 manifold off a M5,M602 or 670. Steiner has new.

Interesting that the one piece manifolds will work. Do they require a heat riser as well?

 

[molinegb]

Interesting that the one piece manifolds will work. Do they require a heat riser as well?

Heat riser application was for the burning of distillate back in the old dual fuel days. No reason for heat riser on gas.

 

[MolineGB1997]

Heat riser application was for the burning of distillate back in the old dual fuel days. No reason for heat riser on gas.

You mentioned the manifold off a 336 would work. Will that work with the original carb I have on my gb? And I've heard of the ub manifolds were restrictive on airflow. Is that the case with the newer type manifolds as well?
Sorry for all the questions.

 

[molinegb]

You mentioned the manifold off a 336 would work. Will that work with the original carb I have on my gb? And I've heard of the ub manifolds were restrictive on airflow. Is that the case with the newer type manifolds as well?
Sorry for all the questions.

UB carb or manifold. is too small. 336 is closer. You want to use the original tsx 68 carb as jetted to 403. Bolts right on. You may have to adjust or bend governor rod.

 

[MolineGB1997]

UB carb or manifold. is too small. 336 is closer. You want to use the original tsx 68 carb as jetted to 403. Bolts right on. You may have to adjust or bend governor rod.

That's good to hear. Thanks for the advice!

 

[T.R.K.]

Nobody mentioned that in order to use either the UB or the M5 manifold the governor link will have to be about 2 inches longer. (Not a big deal, but better to tell you now rather than being surprised later.) As far as sleeving your block, it has been done (To my 403) But it probably wasn't already at 4.75 bore. Take your block(s) and talk to your machinist. He could tell you for certain. I am thinking if you can get the right thick wall repair sleeve it can still be made to work.

I also think your 403 carburetor will work-(bolt onto)- on the UB or M5 manifold. You really need to use it if you can, the venturi is noticeably larger than the venturi in a regular U carburetor.

 

[MolineGB1997]

Nobody mentioned that in order to use either the UB or the M5 manifold the governor link will have to be about 2 inches longer. (Not a big deal, but better to tell you now rather than being surprised later.) As far as sleeving your block, it has been done (To my 403) But it probably wasn't already at 4.75 bore. Take your block(s) and talk to your machinist. He could tell you for certain. I am thinking if you can get the right thick wall repair sleeve it can still be made to work.

I also think your 403 carburetor will work-(bolt onto)- on the UB or M5 manifold. You really need to use it if you can, the venturi is noticeably larger than the venturi

Yeah I'm hoping there's enough material left to sleeve. I'm going to take the blocks and heads to Larsons machine in Fargo ND. I'm told they do good work.

 

[Duey C]

Oh yes, good choice with Larson's and they'll know how to help you the best.

 

[ChrisQ]

Hey all and good evening. I recently picked up a GB gas as a restoration project. It's in generally good shape, but needs motorwork as it sat outside for the last few months.

The front two cylinders are in good shape. The rear two not so much. The pistons seem ok but the cylinder block is fairly crusty on the inside.

This engine has been bored to 4.75 and appears to not have many hours on that overhaul. Pistons look like new. If I need to, how much more can I bore out these blocks safely? I've read that they can be sleeved, would save my good pistons but I'm not sure what that would cost and if it's worth it. I'm not looking to get crazy power, I just want to get it running as it should.

Bonus question: will UB exhaust and intake manifolds work on a 403? The exhaust manifold on this tractor is fubar and they seem to be hard to find.

Thanks in advance!

I would be inclined to find a good jug to bore to 4.75 and reuse your pistons. Probably will be a cheaper option than sleeving and I would be getting nervous with a sleeve at that bore size. I might have a jug laying around that would bore. If originality is not a concern, M5 style or later M670 super or LP style intake exhaust is better.

 

[MolineGB1997]

Yeah I was wondering what it would cost to buy a jug and bore it vs sleeve the one I have. Is there a difference between the m5 or m670 intake/exhaust? I would like something compatible with the factory carb.

 

[MolineGB1997]

I would be inclined to find a good jug to bore to 4.75 and reuse your pistons. Probably will be a cheaper option than sleeving and I would be getting nervous with a sleeve at that bore size. I might have a jug laying around that would bore. If originality is not a concern, M5 style or later M670 super or LP style intake exhaust is better.

Yeah I was wondering what it would cost to buy a jug and bore it vs sleeve the one I have. Is there a difference between the m5 or m670 intake/exhaust? I would like something compatible with the factory carb.

 

[molinegb]

Yeah I was wondering what it would cost to buy a jug and bore it vs sleeve the one I have. Is there a difference between the m5 or m670 intake/exhaust? I would like something compatible with the factory carb.

M5 602 670 all use same manifold. You could also use a lp one. Carb will bolt right on. No parts G's here is why I sleeved as wanted original block numbers.