Tapped Steam Hole Plug Size Model B block

[G_Don]

I recently purchased a 30 phaeton that came with a model B block. I took off the head and cleaned off the old copper gasket adhesive. I now have a clean block and head, however I read that you are supposed to fill the steam holes on the B block in order to avoid issues down the road.

I have searched on here and even purchased some model A manuals but can't seem to find a definitive answer as to what size hole I need to tap the steam holes to. I bought some 5/16" x 1/4" - 24 set screws and plan on drilling, tapping and screwing those in there (as long as this size is correct), then filling in whatever is left of the hole with JB weld and sanding it smooth. I plan on doing this in all 4 steam holes.

Am I on the right track? Any advice for drilling into the block to get the straightest hole possible (minus pulling the engine apart and putting it into a mill or drill press)? I obviously want to get this done right the first time around to avoid ruining something and figured I'd ask on here to get a more knowledgeable answer, or see if there is anything I may have missed?

Any advice or links to good articles on the matter would be greatly appreciated!!

Thanks in advance,
Gordy

[Jim Brierley]

You are on the right track, a 1/4" set screw may be OK. Only tap part way in so the set screws will jam securely in place, or locktite them. The plugs must be flush on the deck as their purpose is to support the gasket. JB weld works fine and is easy to file flat although sand paper wrapped around a block of wood is better than a file as it won't flex.

[Charlie Stephens]

The issue down the road you are trying to avoid is that if you run a stock Model A head on a Model B block the holes will be too close to the edge of the gasket due to the shape of the combustion chamber and will probably leak. If you run a Model a Police head, a Model B head, or one of the aftermarket high compression heads that I have seen there is no problem and you can forget about closing the holes. I don't think I would ever build an engine and use a stock Model A head.

Charlie Stephens

[nick c]

Your right, the holes are 1/4" in dia. the set screw is 5/16" x 24 tpi x 1/4" long, my chart says for 5/16 x 24, you can use a .272, .275, or 9/32 = .281 drill bit. I would use 9/32" because they are common. I don't think you will need a drill press unless you have one, a hand drill will work just fine. I would countersink them a little below surface incase it should ever need to be milled, these set screws are heat treated.
carry on nick c

[hardtimes]

Originally Posted by G_Don

I recently purchased a 30 phaeton that came with a model B block. I took off the head and cleaned off the old copper gasket adhesive. I now have a clean block and head, however I read that you are supposed to fill the steam holes on the B block in order to avoid issues down the road.

I have searched on here and even purchased some model A manuals but can't seem to find a definitive answer as to what size hole I need to tap the steam holes to. I bought some 5/16" x 1/4" - 24 set screws and plan on drilling, tapping and screwing those in there (as long as this size is correct), then filling in whatever is left of the hole with JB weld and sanding it smooth. I plan on doing this in all 4 steam holes.

Am I on the right track? Any advice for drilling into the block to get the straightest hole possible (minus pulling the engine apart and putting it into a mill or drill press)? I obviously want to get this done right the first time around to avoid ruining something and figured I'd ask on here to get a more knowledgeable answer, or see if there is anything I may have missed?

Any advice or links to good articles on the matter would be greatly appreciated!!

Thanks in advance,
Gordy

Hey Gordy,
As far as drilling 'to get the straightest' hole, I just changed heads...to keep busy, and drilled/plugged/filled as you indicate that you are into.
My 'paws' are pretty messed up and shaky and I did the job with engine in and ready to run with different head. Simple job.
IF you are lucky, you might have a whole quarter inch +/- of cast iron to drill thru. Even I could keep the bit approximatey vertical for a 1/4" or so.

I ran the screws down just below surface and put JB smear with putty knife.

The one 'tip' that I would give / do and did do...is to place a magnet around the drilled area. That way, I picked up ALL of the cut cast iron..easily. I was fortunate enough to have a DONUT shaped powerful magnet and it worked perfect. But, any magnet will do. My plugs were the 'pipe plug' shape/thread and tightened well the further screwed in. I used blue locktite also, but probably not needed. Good luck

BTW...sometimes I'm overly cautious. I also taped over the cyl holes with masking tape..your choice.

[G_Don]

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Originally Posted by Charlie Stephens

The issue down the road you are trying to avoid is that if you run a stock Model A head on a Model B block the holes will be too close to the edge of the gasket due to the shape of the combustion chamber and will probably leak. If you run a Model a Police head, a Model B head, or one of the aftermarket high compression heads that I have seen there is no problem and you can forget about closing the holes. I don't think I would ever build an engine and use a stock Model A head.

Charlie Stephens

So, if I were to run an aftermarket aluminum head (which I planned on doing) I could eliminate tapping and filling in the wholes altogether? Why is this? I don't really understand how this would eliminate the problem, but I'd love to know!!

I planned to run the original model A head at first, make sure it was running, and then switch an aftermarket head and some more banger speed equipment goodies after I could drive it down the road. If this will eliminate me tapping into the block, I'd prefer to just buy the head right off the bat (to save myself some work). I have a "Best Model B Gasket" I bought from Snyder's, if that helps.

The engine does appear to be a fresh rebuild, as the original owner who abandoned the project had claimed, but I'm not sure why the head gasket leaked (I assume he never re-torqued the head, OR he never plugged the steam holes w/ his copper model A head gasket). The pistons have "0.080" etched on them, so I'm assuming theyre bored out, and the engine was indeed recently rebuilt.

Originally Posted by hardtimes

The one 'tip' that I would give / do and did do...is to place a magnet around the drilled area. That way, I picked up ALL of the cut cast iron..easily. I was fortunate enough to have a DONUT shaped powerful magnet and it worked perfect. But, any magnet will do. My plugs were the 'pipe plug' shape/thread and tightened well the further screwed in. I used blue locktite also, but probably not needed. Good luck

BTW...sometimes I'm overly cautious. I also taped over the cyl holes with masking tape..your choice.

All the toolmakers at my work swear by the old magnet trick! I've seen tons of donut shaped magnets kicking around that guys use for drilling holes on machines. I'll definitely borrow one on Monday I'll probably also mask off the block as well cause I'm also overly cautious, unless I can get away with not tapping the steam holes with an aftermarket head.

Thanks so much for everyones help!!

Really appreciate it!
Gordy

[Charlie Stephens]

Originally Posted by G_Don

So, if I were to run an aftermarket aluminum head (which I planned on doing) I could eliminate tapping and filling in the wholes altogether? Why is this? I don't really understand how this would eliminate the problem, but I'd love to know!!

I planned to run the original model A head at first, make sure it was running, and then switch an aftermarket head and some more banger speed equipment goodies after I could drive it down the road. If this will eliminate me tapping into the block, I'd prefer to just buy the head right off the bat (to save myself some work). I have a "Best Model B Gasket" I bought from Snyder's, if that helps.

The engine does appear to be a fresh rebuild, as the original owner who abandoned the project had claimed, but I'm not sure why the head gasket leaked (I assume he never re-torqued the head, OR he never plugged the steam holes w/ his copper model A head gasket). The pistons have "0.080" etched on them, so I'm assuming theyre bored out, and the engine was indeed recently rebuilt.



All the toolmakers at my work swear by the old magnet trick! I've seen tons of donut shaped magnets kicking around that guys use for drilling holes on machines. I'll definitely borrow one on Monday I'll probably also mask off the block as well cause I'm also overly cautious, unless I can get away with not tapping the steam holes with an aftermarket head.

Thanks so much for everyones help!!

Really appreciate it!
Gordy

Ask the "what gasket to use" and "do I need to plug the holes in the Model B block" questions to the company that made the head. By the way, whose head are you going to buy? To see what I am talking about put the Model A gasket on the Model B block and you will see that the two holes are too close to the edge of the gasket. That is where the leak occurs. Another thing to watch for on some of the aftermarket high compression heads is the piston to head clearance if you pistons come up over the top of the block (usually from milling the block too many times).

Charlie Stephens

[G_Don]

Originally Posted by Charlie Stephens

Ask the "what gasket to use" and "do I need to plug the holes in the Model B block" questions to the company that made the head. By the way, whose head are you going to buy? To see what I am talking about put the Model A gasket on the Model B block and you will see that the two holes are too close to the edge of the gasket. That is where the leak occurs. Another thing to watch for on some of the aftermarket high compression heads is the piston to head clearance if you pistons come up over the top of the block (usually from milling the block too many times).

Charlie Stephens

I was thinking of buying a Lion 4 plug head head. I heard good things about them and the fact that they place the spark plugs directly over the pistons.

Any other recommendations?

I'll check the top of the pistons in relation to the top of the block.

Thanks

[Jim Brierley]

Most, if not all, aftermarket, performance, heads are made for the Model A gasket, for better flow between the valves and cyl., thus the need to plug the B block.