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Cam caps bolts - stripped threads

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martinz1000r
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Cam caps bolts - stripped threads

#1 PostAuthor: martinz1000r » Wed Nov 15, 2017 8:15 am

Setting up cam timing on the Lawson. Noticed previously helicoiled holes have become loose again and a couple of other holes are close to letting go. What is the recommended fix here? I know others have solved this regular issue but couldn't find any of the posts where it was covered in detail. It's actually a Unitrak head flowed by Tim Blakemore many years ago so not going to give up on it!
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Julian_Boolean
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Re: Cam caps bolts - stripped threads

#2 PostAuthor: Julian_Boolean » Wed Nov 15, 2017 12:24 pm

Chris Tombleson fixed mine with threaded inserts, didn't charge much, I dropped the head off with him one Saturday, picked it up the next Saturday
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ADRIAN H
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Re: Cam caps bolts - stripped threads

#3 PostAuthor: ADRIAN H » Wed Nov 15, 2017 12:40 pm

Time inserts
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Re: Cam caps bolts - stripped threads

#4 PostAuthor: chrisu » Wed Nov 15, 2017 1:23 pm

ADRIAN H wrote:Time inserts



^^^ this

martinz1000r
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Re: Cam caps bolts - stripped threads

#5 PostAuthor: martinz1000r » Wed Nov 15, 2017 2:41 pm

I got a time sert kit. My concern was the dowels used to locate the caps. The flared top of the serts is larger than the diameter of the dowels so they'd flop about in the holes rendering them useless.

@Julian - it's not so much the who. I know Chris well and know he's capable but he's the other side of the country from me. I've a local machine shop that can implement the most appropriate fix. It's just a question of the best answer on the how element.

I also got a great tip off the facebook forum to help install the cams without over stressing the threads which cause them to let go in the first place. Ratchet straps around the engine and cams hold the cams down square against the spring pressure allowing the caps to be bolted down with no stress on the threads. So simple i am surprised it never crossed my mind before. Do the same when removing to!
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ADRIAN H
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Re: Cam caps bolts - stripped threads

#6 PostAuthor: ADRIAN H » Wed Nov 15, 2017 3:11 pm

Debben Performance in Ringwood, should be able to sort your head out.
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KWACKERZ1
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Re: Cam caps bolts - stripped threads

#7 PostAuthor: KWACKERZ1 » Wed Nov 15, 2017 3:26 pm

Martin, I use 7" record G clamps to take up the tension, much easier and granular than ratchet straps would be (I would imagine as I have never used ratchet straps) You can get plastic ones as well.

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Re: Cam caps bolts - stripped threads

#8 PostAuthor: ZedHead » Wed Nov 15, 2017 3:58 pm

My concern was the dowels used to locate the caps. The flared top of the serts is larger than the diameter of the dowels


I have used Helicoils before with no problems. The bolts are made of soft cheese so don't trust a torque wrench on them.

It is worth removing the tacho worm to avoid a lot of damage if this fails to engage the exhaust camshaft.

I like the G clamp tip :)

needaz1100r
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Re: Cam caps bolts - stripped threads

#9 PostAuthor: needaz1100r » Wed Nov 15, 2017 6:37 pm

[quote="martinz1000r"]I got a time sert kit. My concern was the dowels used to locate the caps. The flared top of the serts is larger than the diameter of the dowels so they'd flop about in the holes rendering them useless.

I'd be getting the threads sorted first. The timesert would have to be set into a counterbored hole as you say, and it needs the flange on the top to seat it while you wind the tool through to fix the insert lower down, so you can't just grind the flange off.

That will leave you a hole too big for the dowels, so either make dowels with the ends different, one end to fit the new hole in the head and one to fit the cap, or have the caps bored to the same as the head and have bigger dowels made to suit.

I'd go the first route personally.
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Re: Cam caps bolts - stripped threads

#10 PostAuthor: kev edwards » Wed Nov 15, 2017 7:43 pm

zcap00132.jpg
The time-serts i believe are the same thread as the helicoils if the top lip on the sert is ground to just slightly under 8 mm and then slot the top so you can use a screwdriver to put it in, you could then shorten the locating dowel a tad so it fits, if that is not possible have shouldered studs made 8mm to 6mm, two types one for the doweled holes and one for the non doweled, you will be able to tap the holes all the way to the hole bottoms and only leave a spiral line on the doweled holes, i have used this method successfully it's a bit of a wiggle to get the cams in, i have also made the 10mm insert with dowel incorperated for someone in Norway which was fine, but i would use as a last resort only.


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