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Old 04-05-2021, 06:09 PM   #1
31steve
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Default B block hole repair

I have a 31 roadster with a B block and transmission. I have had it for about five years and driven the car during the restoration. Since finishing the restoration I drive it frequently with no problems. Today My brother and I took it out and after five miles of driving we thought we had blown a head gasket as steam was coming out of exhaust and antifreeze was pouting from carb. Towed it home and pulled the head only to find a good head gasket but a hole in the block deck on number 3 between exhaust and intake valve. Looks like it had been repaired some how and it failed. The engines is a fairly fresh rebuild, .40 over with new valves and seats and ran good. Please look at pics and see if this is repairable. Looks like you could tap the hole and plug it but don't know if it would last? comments please.
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Old 04-05-2021, 06:31 PM   #2
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Default Re: B block hole repair

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Originally Posted by 31steve View Post
I have a 31 roadster with a B block and transmission. I have had it for about five years and driven the car during the restoration. Since finishing the restoration I drive it frequently with no problems. Today My brother and I took it out and after five miles of driving we thought we had blown a head gasket as steam was coming out of exhaust and antifreeze was pouting from carb. Towed it home and pulled the head only to find a good head gasket but a hole in the block deck on number 3 between exhaust and intake valve. Looks like it had been repaired some how and it failed. The engines is a fairly fresh rebuild, .40 over with new valves and seats and ran good. Please look at pics and see if this is repairable. Looks like you could tap the hole and plug it but don't know if it would last? comments please.
Hey Steve,
lOOKS like you will need a 'STITCH' work for repair.
That is a good repair and an experiencecd machinist/mechanic should be able to correct this problem. PROVIDING that the block is not tooo thin.

Last edited by hardtimes; 04-05-2021 at 06:36 PM. Reason: ..............
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Old 04-05-2021, 07:31 PM   #3
wwirz
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Default Re: B block hole repair

Google
metal - stitch or metal - lok. The company that does these repairs may need to see the piece to comment on whether it can be repaired by these methods.
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Old 04-05-2021, 07:32 PM   #4
Ray in La Mesa
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Default Re: B block hole repair

Been there, done that. I wouldn't waste time & money on a B block with a hole in the deck, the deck is too thin to start with then it rusts through quickly.
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Old 04-05-2021, 09:14 PM   #5
31steve
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Default Re: B block hole repair

The deck is 1/4 inch thick at the hole. Do you think a plug wouldn't hold?
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Old 04-05-2021, 09:24 PM   #6
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I would be concerned with whats below the deck.
That hole is between the ports, you have two very thin walls that you must get the plug into without causing more damage.
If the port walls are good, you might be able to use a short plug.
There should be some suspicion about why the groove was cut on the deck from seat to seat. Get this mag checked before investing too much money.

Iron Tite and Lock n stitch make the tapered iron plugs.

I hear that coating the plug with sodium silicate helps it seal better.

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Old 04-05-2021, 10:24 PM   #7
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Default Re: B block hole repair

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The deck is 1/4 inch thick at the hole. Do you think a plug wouldn't hold?
Hey Steve,
B blocks and A blocks have rusted internally. After many decades, depending on how they were(not) cared for... they are a gamble to build. One way to check condition is magnaflux. Another is to check how thin the deck is... from repeated decking. I like to visually look thru every opening for for badly pitted the block is.
And a serious cleaning inside block should give you idea, by what is taken out, how bad /thin block is.
It’s not easy to clean a block ‘thoroughly.’ while it is in service.
In your case, I’d plug it and use it. What do have to lose. Plug it put the head on and go.
You can do ‘things’ that maybe help extend block life.
Like sodium silicate... which coats areas/holes that are thin. Its a GOOD idea to follow instructions on label.
I’ve used this product for exactly this (porosity) problem. It works if used as directed.
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Old 04-05-2021, 10:48 PM   #8
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Default Re: B block hole repair

It looks to me that it may have been stitched once before and one of the stitches came out.

I would try to plug it in place, put it back together and run it and at the same time, start looking for another block.

I would suspect this block is getting pretty thin from rust in the water jackets.

My opinion,

Chris W.
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Old 04-05-2021, 11:36 PM   #9
Jack Shaft
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Default Re: B block hole repair

I'm with John,why did they groove the crack.B blocks crack and can be repaired effectively. Cracks relieve stress,properly repaired its golden.B blocks are notorious for cracking between 2 and 3 cylinder and the exhaust valve unless you have xray vision most deck and block flaws can't be detected,and an uncracked block doesn't mean it won't crack the next heat cycle.
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Old 04-06-2021, 12:35 AM   #10
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Default Re: B block hole repair

My bad, I was looking at something else!
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Old 04-06-2021, 09:10 AM   #11
Bob Bidonde
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Default Re: B block hole repair

Drill and tap the hole for an SAE fine thread size. Install a brass or bronze bolt wet with JB Weld and grind it flush with the deck. The bolt needs to have a coefficient of expansion higher than the grey iron block, so that is the reason for a brass or bronze bolt. Fill the gouges alongside of the hole flush with JB Weld.

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Old 04-06-2021, 09:44 AM   #12
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Default Re: B block hole repair

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Originally Posted by 31steve View Post
The deck is 1/4 inch thick at the hole. Do you think a plug wouldn't hold?
Steve, while it is possible that using a tapered cast iron plug would repair this, I honestly feel like there is more to this that you can't see.

My questions are as follows;
  • Why is there a ground groove across the top of the hole onto the seat?
  • Has the seat foundation cracked where the seat is soon to pop out of the counterbore?

My thoughts are you need to find someone who has a sonic tester that can scan the deck surface. If that checks out, then you need to be able to magnaflux the deck surface and correct any issues found. Then pressure test it once you have a plug peined into the hole. Hopefully you can find someone in the Asheville area that has that equipment to help you. If not, I am over the mountain from you about an hour away.

The bottom line in this is that it is likely repairable, -but the costs/risks may not be worth it to you. In other words, if this was a rare orphan car block that there was no options for a replacement, then it would need to be repaired however with that would come the need for a fist full of dollars. I'm not sure any of us can truly give accurate or further advice from our computers without knowing what I mentioned above.
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Old 04-06-2021, 11:50 AM   #13
31steve
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Default Re: B block hole repair

Good questions Brent, I don't know why the groove is cut like that but my guess was someone peened over a plug at one time and needed to remove it so they cut a slot for a screwdriver to try and get it out. They did it after the new seats were installed but before the valves were installed. The groove just nicks the top of the seats and they are tight in the block. This is the first time I have had the head off this engine so I was surprised to see this. It was a good runner and never consumed water. I can magnaflux it but don't have a sonic tester. I will check around and see if I can find a shop with one.
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Old 04-06-2021, 11:54 AM   #14
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Default Re: B block hole repair

Bob, I will probably plug this hole but was going to use ferrous plug as I was considering sealing the block with sodium silicate after tapping and plugging and I didn't think the brass or copper would work as well with the waterglass.
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Old 04-06-2021, 11:57 AM   #15
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Default Re: B block hole repair

I'm going to take a different perspective on this. Not to dis any other suggestion, but with my limited funds for this kind of thing, this is what I would do.

Use a 12NC24 tap to thread the hole, after determining which drill size to use. Cant tell from the picture what the hole size is. Use a Copper screw (preferred to brass) and heat the screw to almost red to anneal it. Clean the area meticulously of carbon, grease and anything else that does not belong there. Liberally coat the hole threads and the groove at the surface and the copper screw with "Seal-Lock Fluid Weld". Screw in the screw, cut the extra length and screw head off, leaving enough screw length to peen into the slot. The fluid weld will become rock hard as this is the perfect application for the stuff. Be liberal with it. Let dry and file the area almost flush, just barely proud of the surface. I would then reuse the copper head gasket, install the head and GO. What do you have to lose? and.....you have a very high odds of success.

Added, water glass will work with copper or brass just fine, but with the above, not necessary, unless it makes you feel better. I prefer mechanical solutions whenever possible.

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Old 04-06-2021, 12:59 PM   #16
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Default Re: B block hole repair

As Brent and others have said that groove bothers me. If you want to try a repair in the car AND the deck surface is thick enough to cut 4 or 5 threads with an irontite tapered tap. I would use an irontite tapered plug with their sealer or something equivalent and go for it. Probably mag the groove just to make sure there is not a crack. I have seen decks on B's as thin as .040-.050, not thick enough to pin! Rick.
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Old 04-06-2021, 01:31 PM   #17
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Default Re: B block hole repair

I had a valve seat come loose broke up and departed down the muffler where it still is . A chunk of the seat was still embedded in the piston top which hit the head and made a mighty racket . The previous owner had had the car for 36 years and head had never been off in living memory . I had to build a killer puller to get the head off . To my surprise I found a two plug repair in the same area as your picture not only that one plug had a semicircle cutout in way of the valve seat insert . Nothing to lose I bought another seat put it in the freezer heated the block valve area and bopped it home ( once you start bopping you must not stop !!!) The head has been on I think around 5 years now and done many miles with no failure although I must say I am still waiting for the new seat to join its buddy in the muffler .I cant understand why such a repair was done to me the block was scrap surely back then good blocks were plentiful . Or maybe what the heck lets give it a go . You have nothing to lose give it a go !!!

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Old 04-06-2021, 04:58 PM   #18
Richard in Anaheim CA
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Default Re: B block hole repair

I guess we can now call John Carlton THE BIG BOPPER.

I'm with John. You have nothing to lose so give it a try.
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Old 04-06-2021, 05:16 PM   #19
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Default Re: B block hole repair

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I guess we can now call John Carlton THE BIG BOPPER.

I'm with John. You have nothing to lose so give it a try.
I agree!

If it doesn't work, you will be no worse off than you are now.

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Old 04-07-2021, 08:16 AM   #20
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Default Re: B block hole repair

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Originally Posted by 31steve View Post
I have a 31 roadster with a B block and transmission. I have had it for about five years and driven the car during the restoration. Since finishing the restoration I drive it frequently with no problems. Today My brother and I took it out and after five miles of driving we thought we had blown a head gasket as steam was coming out of exhaust and antifreeze was pouting from carb. Towed it home and pulled the head only to find a good head gasket but a hole in the block deck on number 3 between exhaust and intake valve. Looks like it had been repaired some how and it failed. The engines is a fairly fresh rebuild, .40 over with new valves and seats and ran good. Please look at pics and see if this is repairable. Looks like you could tap the hole and plug it but don't know if it would last? comments please.
This is a typical example of where metal stitching would be useful.
it's an indispensable necessity on old engines as yours. Especially Model B engines are more prone to crack. I would recommend removing the valves and cleaning the deck to magnaflux it. Cracks may have traveled to the valve seats.
http://www.jandm-machine.com/metalStitching.html
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