Worn threads of cylinder head bolts

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Worn threads of cylinder head bolts

Post by Road Hog » Mon Dec 11, 2017 6:53 am

Hello,

finally I got a GPW engine. The problem is, that most of the threads for the cylinder head bolts in the engine block are worn (I presume I am surely the first one with this problem :wink: ). In two holes the bolt rests are stuck and must be removed, in several are rests of Helicoil, in others the bolt seems rather loose. I intend to let them be repaired using Wuerth Timesert. The man from Wuerth told me, these were as strong as the original threads when properly installed. I would like to know your opinion /experience by using Wuerth Timesert for repairing cylinder bolt threads in the block.

Best,

Marc


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Re: Worn threads of cylinder head bolts

Post by Wolfman » Mon Dec 11, 2017 7:07 am

The Timesert is the better of the two processes. Although more expensive.
Be sure the person installing them keeps them on center with the hole in the head.
There are war stories out here about having block threads repaired only for the new thread to not line up.
Mike Wolford
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Re: Worn threads of cylinder head bolts

Post by Joe Gopan » Mon Dec 11, 2017 9:08 am

If the holes are not drilled at precisely right angles to the deck, there is great chance of cracking the block at those locations.
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Re: Worn threads of cylinder head bolts

Post by Road Hog » Mon Dec 11, 2017 12:10 pm

First thanks for your helpful hints. Do you think that the Timeserts are strong enough to secure the cyliner bolts,especially regarding the torque even if many of the bolt holes are "timeserted" - as the Woerth guy said? Or is there any better method to renew the blocks threads you would recommend? As long as GPW blocks are regarded like massif gold :o , only the best method available should be chosen....I am still a bit unsure and confused, hope you can understand :roll: ..
Best,
Marc

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Re: Worn threads of cylinder head bolts

Post by Wolfman » Tue Dec 12, 2017 6:18 am

Timeserts and Heli-coils are two completely different types of thread repair inserts, other than they restore stripped threads.
The Heli-coil is a coiled wire, similar to a spring. The wire size, shape and pitch are correct for a thread size and pitch for the repair being made. The damaged hole is drilled over sized and tapped to accept the heli-coil insert. Before the insert is installed, common practice is to apply Red Loctite to the insert to hold it in place. Other wise, the fit of the coil insert is all that holds it in place and seals it. They do sometimes come out on fastener removal or tend to leak if not very well sealed. But they hold the original fastener quite well and at lower price.
A Timesert is a solid piece. Like the Heli-coil, the damaged hole is drilled oversized and tapped. The solid insert ( not a wire coil ) is installed in the now oversized and tapped hole. Once the insert is in place, a tool is screwed into the insert that swells the bottom of the insert out, locking it in place. It won't come back out. At least not easily. And is a lot less likely to leak.
For one time, permanent thread repair where fluid leakage is not an issue, Heli-coils are quick. Inexpensive and very good for the repair.
In the case of a head bolt, where the fastener is most likely going to be removed sometime in the future and fluid leakage is an issue, the Timesert is a better choice. But more expensive.
Both work very well when properly installed.
Mike Wolford
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Re: Worn threads of cylinder head bolts

Post by Road Hog » Mon Dec 25, 2017 5:44 am

A guy told me that the Wuerth Time Serts were only available for metric threads. Is this true? And also I was told to use only the original bolts for the cylindre head (with inch thread). New made (metric bolts for the Wuerth threads) bolts of other material could have another thermal expansion coefficient so the cylinder head will when getting warm not be tight. I am rather confused. Is the bolt material really a problem? And are there suitable Wuert Time Serts for the MB/GPW block? Any help welcome.

Best regards,

Marc

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Re: Worn threads of cylinder head bolts

Post by Wolfman » Mon Dec 25, 2017 6:22 am

News to me. I was of the opinion Time Sert and Heli-Coil was available in Metric and US Standard thread sizes.
You want to use real head bolts and/or studs. They are a special material.
Thread length is a concern. You don't want to run out of thread before a bolt tightens up in the block and you don't need too much thread when screwing a stud into the block. Also need enough thread on the nut end of a stud for the nut to tighten up before running out of thread.
There was an after market head bolt set out, a while back, that was junk. The bolt would yield before full torque was reached and some bolts would break.
Have not heard any war stories about these lately.
Mike Wolford
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Re: Worn threads of cylinder head bolts

Post by Road Hog » Mon Dec 25, 2017 6:52 am

Mike, Bantamij,

thanks a lot for your helpful and fast hints. Obviously it is nonsense that Wuerth is only metric. A silly question: what thread designation have the original studs thread and: if two of the original studs are defect, should all studs been renewed or can they be "mixed" old and replacement?

Best,
Marc

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Re: Worn threads of cylinder head bolts

Post by Wolfman » Mon Dec 25, 2017 7:11 am

What is the defect ??
Normally, a stud or bolt could be loosened and torqued several times with out issue. Over the life of a 70 year old jeep, this could have been several times.
If the threads are in good shape but the damage is to the fastener shaft, rust pits and corrosion, it needs to go.
OK to mix and match as long as the fastener is servicable and when torquing, it comes up to torque sharply. You don't want to turn the nut or bolt a half a turn to get to the last 5 lbs. of torque once it is close. That means the fastener is stretching. Bad !!
Replacing them all is your call.
7/16 course thread in the block.
Mike Wolford
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Re: Worn threads of cylinder head bolts

Post by Joe Gopan » Mon Dec 25, 2017 7:58 am

Always check used cylinder head studs and bolts on Jeep engines for stretched or deformed threads.
Look for that hourglass shape where the threads are stretched.
Last edited by Joe Gopan on Mon Dec 25, 2017 9:03 am, edited 1 time in total.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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7 MIL SPEC MAINTAINED MV'S
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Re: Worn threads of cylinder head bolts

Post by Road Hog » Mon Dec 25, 2017 8:20 am

Two of the bolts are broken and stick in the thread of the block.

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Re: Worn threads of cylinder head bolts

Post by Road Hog » Mon Jan 29, 2018 11:52 am

Still another question: several cylinder bolts/studs go in the water channels of the block. If using Timeserts: Is there a need for any additional sealing (Loctite etc.) of the Timesert outer thread and inner thread (the 7/16 bolt thread) to avoid water loss through the threads or is the cylinder gasket simply enough to avoid this? Perhaps this project is going to make me imaging things... :shock: :shock:
Best,
Marc

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Re: Worn threads of cylinder head bolts

Post by Wolfman » Tue Jan 30, 2018 7:58 am

Lock tite on the outer threads of the time sert or heli coil.
I use Teflon thread sealing paste on the inner threads. There are those that say Permatex non hardening is the sealer of choice on the stud or bolt threads.
Mike Wolford
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Re: Worn threads of cylinder head bolts

Post by YLG80 » Thu Feb 01, 2018 5:57 am

Hi Marc,
You should also consider the EZ-Lok thin wall inserts. They are cheaper that the Time-serts.
FYI.jpg
FYI.jpg (18.15 KiB) Viewed 480 times
I've used them in my engine block at some places.
You have also to pay attention that there is enough material left around the holes when using Time Serts or EZ-Lok. It's mentioned in the specs.
That position is really problematic. I could not use an EZ-Lok here. I've used a V-Coil.
IMG_4895.JPG
IMG_4895.JPG (201.5 KiB) Viewed 480 times
Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
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Re: Worn threads of cylinder head bolts

Post by Road Hog » Thu Feb 01, 2018 7:32 am

Wolfman, Yves,

thanks for your mails.

Yves: On the shown image, the stud hole seems somehow nearer to the oval opening than on other block fotos - I did not realize that on my block as a major problem. Do you really think the timeserts are too big there? I feel they have only a very small thickness compared to the shown EZ. And even for the coil systems you must enlarge the hole (I confess I dont like the coils to fasten the studs - I would rely more to the timeserts at that problematic region). Are there also other opinions?

Best,

Marc


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