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Old 03-08-2019, 08:52 PM   #1
flathead47
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Default Engine block thread clean up

Getting ready to inspect and cleanup my spare flatheads ..... I understand the head bolt / stud threads are to be cleaned using a thread chaser or modified bolt due to a friction fit.
What about the cleaning the other bolt threads in the block , thread chaser or normal tap.
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Old 03-08-2019, 09:38 PM   #2
flatjack9
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Default Re: Engine block thread clean up

Normal tap.
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Old 03-08-2019, 09:42 PM   #3
Tim Ayers
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Default Re: Engine block thread clean up

If you have them, why not use a thread chaser vs. risking cutting any thread unnecessarily?
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Old 03-08-2019, 09:45 PM   #4
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Default Re: Engine block thread clean up

Being these are just storage blocks. Why chase them?

I believe you want a rolled edge chase on headbolts. The rest are okay to my limited knowledge.







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Old 03-08-2019, 11:28 PM   #5
flathead47
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Default Re: Engine block thread clean up

I only have normal taps , was going to get only the chase taps I needed.
Are there different types of chase taps?
Tinker , I have complete motors , partial blocks & want to determine which are useable , thought I would clean all the threads on the good blocks.
First flathead disassembly for me , hope the head bolts come out with no problems.
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Old 03-08-2019, 11:37 PM   #6
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Default Re: Engine block thread clean up

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Quote:
Originally Posted by flathead47 View Post
I only have normal taps , was going to get only the chase taps I needed.
Are there different types of chase taps?
Tinker , I have complete motors , partial blocks & want to determine which are useable , thought I would clean all the threads on the good blocks.
First flathead disassembly for me , hope the head bolts come out with no problems.
Bolts or studs? Do not rush either for broken ones can spell a lot more work down the road.

Heat, penetrating oil, and patience make all the difference in the world. Spent 15 hours getting the studs out of a 99A block. Sucks, but got them after trying multiple approaches.
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Old 03-08-2019, 11:45 PM   #7
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Default Re: Engine block thread clean up

heat, penetration fluid, repeat.


https://www.jalopyjournal.com/forum/...d-help.943753/

https://www.fordbarn.com/forum/showt...8111&showall=1
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Old 03-09-2019, 12:00 AM   #8
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Default Re: Engine block thread clean up

Studs & bolts , 1 motor has 2 broken bolts , that's how I got it , already have penetrating oil on the bolt heads .... hoping the rest will come out with out breaking.
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Old 03-09-2019, 12:54 PM   #9
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Default Re: Engine block thread clean up

You may wish to check for cracks & magnaflux first if you haven't already done so. Save yourself a lot of work.
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Old 03-09-2019, 01:00 PM   #10
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Default Re: Engine block thread clean up

For the rest of the threads first screw the pertinent bolt into the threaded hole. If it goes in easily,don't mess with it. I don't think it's a good idea to mess with the main bearing cap holes.
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Old 03-09-2019, 01:18 PM   #11
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Default Re: Engine block thread clean up

I personally don’t use a tap unless I have to. I have been using this set of chasers and they are cheap and work well, just keep the vertical groves in them clean

https://www.amazon.com/Lang-Tools-25...gateway&sr=8-5
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Old 03-09-2019, 04:15 PM   #12
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Default Re: Engine block thread clean up

Using a threading tap instead of a chasing tap, can result in damage or loss of the threads in the block. The cast iron is usually very soft from the annealing effect of years of heat/cool cycles, and easy to strip.
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Old 03-09-2019, 06:09 PM   #13
V12Bill
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Default Re: Engine block thread clean up

I recall reading that the threads were not tapped to the bottom of the hole. There was a slight lip left somewhat like a pipe thread to help make a water seal on those studs that went into the water jacket. The differential center section was the same way to help make an oil seal at the bottom of the bolt.
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Old 03-10-2019, 07:07 AM   #14
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Default Re: Engine block thread clean up

Pickup up a Craftsmen set in both inch and metric reasonable.
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Old 03-10-2019, 08:51 AM   #15
51 MERC-CT
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Default Re: Engine block thread clean up

Been using this set of taps from Summit Racing---

https://www.summitracing.com/parts/sum-900200/overview/
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Old 03-10-2019, 10:46 AM   #16
The Master Cylinder
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Default Re: Engine block thread clean up

I use the same thread chaser set as 35fordtn. It has both fine and course threads
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Old 03-10-2019, 11:43 AM   #17
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Default Re: Engine block thread clean up

Quote:
Originally Posted by The Master Cylinder View Post
I use the same thread chaser set as 35fordtn. It has both fine and course threads
I checked this out on Amazon, and it looks good. I was absolutely flabbergasted at the number of bad reviews that came from people who tried to use them to actually tap new holes and cut new threads. P.T. Barnum was right!
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Old 03-10-2019, 10:28 PM   #18
B-O-B
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Default Re: Engine block thread clean up

I made mine from a head bolt. Took a 4" angle grinder & cut 3 slots in the threads. Works for me. Just don't go ape & force it, but work it back & forth a little at a time.
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Old 03-11-2019, 05:18 AM   #19
Tim Ayers
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Default Re: Engine block thread clean up

Quote:
Originally Posted by corvette8n View Post
Pickup up a Craftsmen set in both inch and metric reasonable.
I have the same. If you can find it, itís the same kit Snap On dealers sell, just rebranded.
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Old 03-11-2019, 12:03 PM   #20
flathead47
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Default Re: Engine block thread clean up

Thanks for everyone's input & advice.
Tinkers links to some other threads were very helpful as well.
My takeaway from the three threads are , test the thread first with a good used bolt or stud to see how tight the thread is ,
if required clean the threads first using gun barrel brushes & cleaner ,
only chase the threads if they have been damaged by using a chase tap or a modified head bolt with 3 or 4 slots cut into it.
If the threads have been tapped using a normal tap it is not ideal, but thread sealers will prevent leakage & help with stud alignment.
The end result is to keep the threads as close to Ford spec as possible, so take your time & do not rush it.
Ian
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