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Old 04-11-2012, 07:47 PM   #1
bobj49f2
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Default Cleaning threaded block holes

This subject was raised on the FTE site. Is it a bad thing to do clean out the threaded head bolts holes in a flathead block with a regular tap?

I hope not, that is what I just did with the block I am trying to clean up.
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Old 04-11-2012, 07:54 PM   #2
4tford
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Default Re: Cleaning threaded block holes

Do not use a tap. They re-cut the thread and take out more material making the bolt/stud loose. Blow the hole out with air and use a used bolt.
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Old 04-11-2012, 07:54 PM   #3
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Default Re: Cleaning threaded block holes

Technically, it's better to use a thread chasing tap as it does not remove any metal.
However, if you did use a 7-14UNC tap you will be ok. i have done the same in the past when I didn't know any better. Just use plenty of thread sealer when reassembling. Here's the chasing tap.
http://www.google.com/products/catal...ed=0CHMQ8wIwAw#
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Old 04-11-2012, 07:57 PM   #4
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Default Re: Cleaning threaded block holes

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Originally Posted by 4tford View Post
Do not use a tap. They re-cut the thread and take out more material making the bolt/stud loose. Blow the hole out with air and use a used bolt.
Too late, I already ran the tap through. I only had one hole that gave me a lot of trouble and that's one I broke the bolt in. I had to drill and retap that hole. The rest the tape ran through without a problem.
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Old 04-11-2012, 08:01 PM   #5
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Default Re: Cleaning threaded block holes

You can make your own thread chaser by cutting 3 or 4 slots lengthwise on an old grade 8 bolt; wire brush it often.
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Old 04-11-2012, 08:27 PM   #6
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Default Re: Cleaning threaded block holes

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You can make your own thread chaser by cutting 3 or 4 slots lengthwise on an old grade 8 bolt; wire brush it often.
Did that to an old 3X spark plug once and cleaned up an old Model A cylinder head. Work really well
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Old 04-11-2012, 09:22 PM   #7
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Default Re: Cleaning threaded block holes

I learn something new everytime I log on.
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Old 04-12-2012, 11:11 AM   #8
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Default Re: Cleaning threaded block holes

The stud holes were very elaborate production...they were about 2 classes tighter than a general pupose tap and also had a little recess to seat the bottom of the stud firmly. They were too tight for hand assembly of stud, were pretty much leakproof, and held the studs straight so the heads would go on without a fight.
Many have of course been tapped out (some by me before I learned this), and if tapped with ordinary tap (modern class 2 I think, and every tap you can get easily is that) you will have to use the sealer that Ford did not need and go through a little ritual to set the studs straight while the goo dries, as they will no longer reliably seat at 90 degrees.
I would tap only ones with actual damage and clean the others with gun brushes and carb cleaner. Tell your machinest that you will put his head in his own hydraulic press if he taps them...machinests don't feel fulfilled unless they have run a tap through everything they can see!
You may of course have a block that was tapped out 30 years ago or that has corrosion and damage, in which case sealer time and extra work so the set straight.
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Old 04-12-2012, 09:32 PM   #9
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Default Re: Cleaning threaded block holes

Fortunately, the engine I have has bolts so have to worrying having them to set up straight.

All I really want to do with this engine is prove that it runs. I want to sell it so I would assume anyone who is interested will want to pull the heads to inspect the block so I won't worry about getting a good seal.
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Old 04-13-2012, 07:41 AM   #10
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Default Re: Cleaning threaded block holes

Let's see, the buyer walks into the shop and here is how it should go.
The engine had a broken head stud, which I drilled out and replaced, and buy the way I also tapped all the stud holes with a class 2 tap, i only wanted to make the engine run.
Helo my name is Bob
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Old 04-13-2012, 08:46 AM   #11
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Default Re: Cleaning threaded block holes

A person can still get about any size wire brush from outfits like Grainger & McMaster Carr. Chuck one in a drill and add a squirt of your favorite bore cleaner (I always like the smell of Hoppe's) and go to town. It's a lot faster than running a tap in 48 plus holes for sure.
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Old 04-13-2012, 09:58 AM   #12
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Default Re: Cleaning threaded block holes

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Originally Posted by rotorwrench View Post
A person can still get about any size wire brush from outfits like Grainger & McMaster Carr. Chuck one in a drill and add a squirt of your favorite bore cleaner (I always like the smell of Hoppe's) and go to town. It's a lot faster than running a tap in 48 plus holes for sure.
That's a good tip!
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Old 04-13-2012, 10:38 AM   #13
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Default Re: Cleaning threaded block holes

I recently had a fellow bring me a motor he bought as rebuilt. It had two leaking studs. He pulled the heads, tapped all the holes and reinstalled the heads. 26 were now leaking. It took a lot of work and time to clean all the holes and use permatex 2, tighten and straighten all the studs to stop the leaks. We put the permatex in the stud holes as well as on the stud threads and let them sit overnight before installing. He is now a happy camper.
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Old 04-13-2012, 10:38 AM   #14
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Default Re: Cleaning threaded block holes

Gun brushes are good too...easy to find about .17 up to .50 calibers, larger for shotguns...bristle and bronze, well made, clean any hole you encounter in an engine.
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Old 04-13-2012, 11:07 AM   #15
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Default Re: Cleaning threaded block holes

Quote:
Originally Posted by desotoguy View Post
Let's see, the buyer walks into the shop and here is how it should go.
The engine had a broken head stud, which I drilled out and replaced, and buy the way I also tapped all the stud holes with a class 2 tap, i only wanted to make the engine run.
Helo my name is Bob
OK, what are you talking about? I also didn't have a broken head "stud", my engine had a broken "bolt". I didn't tap stud holes, I taped bolt holes. From reading the above posts I can see there is a difference. If I had studs I'd have to be more concerned with making sure the studs were straight, I don't think there should be as much concern about this with bolts, which I bought new grade #5 bolts to replace the old rusty ones. I do realize I might have caused a leakage problem but that seems to be a rather simple thing to fix with the correct sealant.

I would not have tapped the holes if I had known this wasn't the correct thing to do. Whenever I have a hard to remove bolt I always clean the threads with an appropriate tap after removing the bolt. I did not know the block holes were tapped with a special thread. I am not a professional engine rebuilder or machinist, I'm just a hobbiest. If I had the slightest idea that what I did wasn't correct I would have checked in here first. I didn't even know this was a concern until I saw a post on the FTE side a week or so after I tapped the holes. Until then I thought a threaded hole was a threaded hole. Like I stated, when I tapped the holes the tap went in and out without noticable resistance. If they had offered some resistance I would have stopped and at the very least talked to my neighbor down the road who is a machinist and has been working on old cars for many more years than I have.

Also, when selling something I am always as completely honest as I can be. I don't want to have a buyer come back to me complaining that I cheated them. I don't like to be cheated and I don't like cheating people. When I do finally get to the point of selling this engine I will reveal everything about it. If a potential buyer doesn't like something I have for sale I do not force them to buy the item, it is totally up to them. I am sure I will have people lined up to buy it. I feel I should be able to get more for an engine that can be shown to run without any strange noises than a engine that is in pieces. I also know a major concern with flatties is the block cracks and I want to be able to pull the heads to show the condition of the block. I am fairly certain anyone who is looking for a flattie will want to pull the heads. I wouldn't pay top dollar for an engine I couldn't hear run.

I do sell parts but I am not a high end wheeler dealer, I sell parts from parts trucks and cars I buy to help finance my projects. If I didn't I would never be able to afford to play with this vehicles.

Last edited by bobj49f2; 04-13-2012 at 11:52 AM.
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Old 04-13-2012, 11:25 AM   #16
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Default Re: Cleaning threaded block holes

Most of the engines we mess with like Flatheads, Model B's, and SBC's have decks that are thinner and hence stud/bolt holes shorter than would be ideal for rigidity. A goal here, if the deck holes have not already been tapped out to class 2 by an earlier rebuild, is to maintain as much contact/grip area as you can in there. Leaks can be dealt with with sealer, and simple assembly tricks will get loose studs to set straight, but these tricks do not restore the strength of the connection.
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Old 04-13-2012, 11:35 AM   #17
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Default Re: Cleaning threaded block holes

I just ran the new bolts through a couple of the holes and there is very little noticeable wiggle in the bolts so I'm hoping with a little sealer the bolts will seal up. This engine is going to be sold to help finance my projects so I'm not going to seal the bolts myself. I want to be able to pull the heads allow a prospective buyer to inspect the block. I also, because the one head has a crack on the outside and I don't have a radiator for this engine, I'm not going to fill it with water. I'll only run the engine a few seconds, enough to let the buyer know it runs without any strange noises. I'll let the buyer decide if the retapped holes are a deal killer or not. I'm sure I'll find a buyer, I've sold stuck engines for a decent buck in the past without a sweat.
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Old 04-13-2012, 11:38 AM   #18
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Default Re: Cleaning threaded block holes

so Bruce, are the taps with a flat bottom, the ones to use for cleaning out the threaded holes in a block? my brother just got his block back from the machine shop, it was bored and balanced now he wants to clean the block threaded holes. before assembly. JAN.
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Old 04-13-2012, 11:49 AM   #19
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Default Re: Cleaning threaded block holes

Nice to see an honest seller.
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Old 04-13-2012, 11:51 AM   #20
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Default Re: Cleaning threaded block holes

Retapped holes are in no way a killer, as most blocks have already been rendered to class 2 threads there by someone who thought he was doing a good thing. Sealing and stud alignment can be fixed, the strength lost cannot be but what remains is adequate.
No, you do not want the flat bottom taps either...and they wouldn't change anything since the holes go right through.
The original holes were tapped with taps of different thread class, meaning deeper/taller thread than normal type two, much firmer engagement. Tight classed theads cannot be fully assembled by hand...if you can spin them in by hand, they have been cut back to class 2. Most things in cars and in general hardware are class 2, the higher classes are for applications like this where maximum grip and /or sealing are required. Do not tap them unless threads are actually damaged. Clean with metal gun brushes and spray carb cleaner, or something like a '49 headbolt prepared for the job: Notch it like a tap so it cuts away crud within threads, before using run it into a die and heavily wire brush it to make sure your notching did not leave any raised shards that would cut away metal in block.
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