Cleaning threaded block holes

[bobj49f2]

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.

[4tford]

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.

[19Fordy]

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#

[bobj49f2]

Originally Posted by 4tford

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.

[uncle max]

You can make your own thread chaser by cutting 3 or 4 slots lengthwise on an old grade 8 bolt; wire brush it often.

[tiquer]

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Originally Posted by uncle max

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

[jim1932]

I learn something new everytime I log on.

[Bruce Lancaster]

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.

[bobj49f2]

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.

[desotoguy]

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

[rotorwrench]

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.

[1952henry]

Originally Posted by rotorwrench

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!

[4tford]

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.

[Bruce Lancaster]

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.

[bobj49f2]

Originally Posted by desotoguy

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.

[Bruce Lancaster]

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.

[bobj49f2]

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.

[jan bogert]

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.

[4tford]

Nice to see an honest seller.

[Bruce Lancaster]

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.

[jkeesey]

If it is labeled as a tap its not correct. It should be a chaser or thread restorer. The edges of a tap are sharp and designed to cut anything out of its way, a chaser has more rounded edges designed for straightening existing threads. Unless the tap is very old and worn out I wouldn't use it for cleaning. A flat bottomed tap is simply for tapping closed end holes.

[Ian NZ]

I removed all the studs on my V8 engine tapped the holes out with a bottoming tap and I then placed antiseize on the threaded bolts when I fitted the aluminium heads, tightened the bolts down to the correct torque, and I have had no problems with water leaks. I am not using antifreeze.

[HCO41]

I'd like to open this subject again. Earlier in my career I worked for a large cutting tool manufacturer. One of my jobs was creating the specs. For "special taps". We manufactured Carbon, Cut thread and ground thread taps. Since 7/16-14 is the thread size this thread is addressing, I can tell you that our blocks would have been tapped with a ground thread tap. Tolerances are much closer. I don't know what class thread Ford originally used, but I suspect GH-2, possibly GH-1. The ground taps we stocked in this size were GH-3. Carbon and Cut thread taps were tooled to this dimension, but tolerances were not as stringently controlled as the ground taps. (Carbon and cut thread taps are generally roll formed). Ground thread taps are classed higher or lower than nominal size and designated by GH (above nominal), GL (below nominal). Each limit (GH-1,2,3,4etc. and GL-1,2,3,etc.) has a tolerance range measured to the 4th place (ex. .0001-.0003). The taps purchased at our local hardware store or even industrial supply store would likely open up the threaded hole more than originally intended. I took a look at the rethreading taps on the link posted above and noted that there was no class specified. I would have to trust their intended use and would definately use them before a hardware item. If I still had access to special overruns, I would be looking for a 7/16-14 GH-1 bottoming tap.
Hope this helps for the future

[TStiles]

This site is a nonstop education. Thanks all for your contributions. HCO41 shared details not commonly known to the shade tree guy. Great information!

[Ross F-1]

A question: are the specs in the Ford workshop manuals for head bolt torque on 8BA-style engines assuming dry threads, or oiled? All these sealers undoubtedly reduce friction while sealing, I would assume. Some reduction in stated torque values would be in order if the specs assume dry (which is my experience on other engines).

[Bruce Lancaster]

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Here's an old Model A forum post on the threads...
model A used same threads as V8.Marco came up with blueprint, grade 4 fit in early standard, a later print showed 5 I think. I found 1930's thread specs from Ford sources, don't really know translation to modern class 3 or whatever.


http://www.fordbarn.com/forum/showth...lass&showall=1

[rotorwrench]

I think the classes have remained unchanged from the opriginal SAE classification. This chart goes into some detail about taps.
http://www.newmantools.com/taps/tapclass.htm

This stuff hasn't changed much over the years but only a few industries worry about bolt hole and nut fit to a fastener. Aviation still uses them for the older equipment like the Radial engine cases where a lot of studs are used in aluminum castings. My Rex suply catalog has taps in every fit but they have pages & pages of taps to poor over till you find what you want. Most machine shop suppliers have these types of products.

[Marvin/TN]

There is a GM product that works very well as a thread sealer. You can get it at any GM parts dept, may have to order it at some dealers. It is pipe sealant with PTFE P/N 12346004. Good for any bolt that goes into the water jacket. It also makes the bolts and pipe thread plugs etc easy to remove. It isn't cheap but nothing good is.

[HCO41]

I looked at both links above and recognized the taps listed as "stock" items. These sizes and class limits are what is the more popular fits used in general industry. "Stock" taps (ground thread) may have been used in Engine blocks, but I doubt it because these taps, on an average, will produce 75% thread. The only thing that seems somewhat ironic about this discussion is the point brought up by rotorwrench. The quality of the bolts we might use as replacements might not be of the highest quality since so many fasteners are made off-shore now. A tap other than stock whether it be for tolerance, shank size, flute configuration, point type or flute hook is considered "special". I felt the 7/16-14 GH-1 would be a good choice for rethreading since it would have a slightly smaller major and root diameters, yet would effectively clean the stock threads. Previous attempts to rethread blows this all away since most would use the "Hardware store" tap.
Here's a couple of examples of Ford taps we supplied as "specials" and their use in production. We made a special short projection pipe tap (NPT) used to tap the intake manifolds for the heater hose fittings. Short projection was needed so that tap wouldn't bottom out in the manifold before full thread was produced. This was in the late '60s, so I can't say I ever saw special tooling for our flatheads. The other taps we supplied were those used in a set-up to tap the pan rail. Ford was having trouble with sloppy set-ups in this area, breaking taps because the taps weren't aligning with the drilled holes. Instead of paying a little more attention to setting the station up probably, Ford asked us to come up with a solution. The solution: Anneal the tap shank so they could bend a little and "find" the hole. This significantly reduced breakage, however I suspect that some of the pan bolts may have gone in a little crooked?
I still think a GH-1 tap would be a good rethread size. Do any of the above posters have a better suggestion?

[HCO41]

This is a heads up! I went to the link 19Fordy posted above. You will notice that there are 3 taps shown but 7/16-14 was the only description. The link showed several suppliers of this (these?) items. I went to Jegs sight and the same group of three taps was shown. I specifically asked (Larry) if they were offering three taps or just the 7/16-14. He assured me that a 3/8-16 and a 1/2-13 were included. I ordered the taps.
When I got my confirmation it only showed the 7/16-14. I sent Jegs an inquiry via email and got a call from them. Guess what; "Larry made a mistake". I was then offered a five piece rethreading tap set for over $100.
Watch out!!!

[jack orchard]

How about these?

http://www.summitracing.com/parts/sum-900200/overview/

[Ross F-1]

Originally Posted by jack orchard

How about these?

http://www.summitracing.com/parts/sum-900200/overview/

Not sure if those are the same ones I have, but it appears to be. Mine are made in USA, they work well. They take out lots of crud but no metal.

[V848 Ford]

Look for for a Gh1 class tap . That is a cuts tighter threads you will have to probably have to special order it from a tool supply co . Go to a parts house and they will give you dumb looks . It dosent hurt to use a thread sealer

[HCO41]

I've got a set like that shown on Summit link. I first used them to clean 5/16-18 and 3/8-16 threads in a 78 transmission case and cast iron clutch cover. Even with cleaning the tap after each hole, by the time I got to the last couple of 5/16 holes used for top cover the chaser was showing signs of wear. I finished up with a worn plug tap that I cut the end off. I don't know if the 7/16-14 will reach bottom head bolt threads.
Follow up: I received the 7/16-14 chaser from Jegs. It looks to be a highend product that I believe is made from hss (M-1?). Still seems a lot ($26) for one tap and their ad is deceiving. (See my post above)

[Tim Ayers]

Thank you all. I've used both the old head bolt with notches and gun brushes in a drill with cleaner. Both work well.