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stripped hole in head
Was re-installing rocker assy's after intake change on my 427. fwd center stand stud pulled out, helicoil and all. Found some info in FE search, (all 10 yrs old posts) but wonder what the current repair procedure is.?
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Weld, machine, drill, tap.
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Use a Timesert. Larger OD, same internal thread. Drill the hole out, tap it, run the Timesert in.
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I thought it was easier to find the location with a new boss and filled, machined hole. Just wonderin'... |
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Yep, pretty common fix, doesn't really take any special tools.
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Thanks guys, and thanks Undy for the link, looks like they have a distributor right next door in Sarasota !
Now all I have to do is dig out the three threads worth of helicoil down at the bottom of the hole ! (no problem, I have DENTAL TOOLS !) I never did like the 40-45 ft-lbs torque on these studs, probably will happen to some of the others in time. A lot of tension on those studs with the higher spring pressures used with hi po cams. |
I've had the same problem. Someone had installed a helicoil at an angle, probably with a hand drill. WAY crooked. Time serts were too small. We used a 11/16 bottoming tap and installed a piece of 11/16 threaded rod, then drilled & tapped the rod. Holds 45# easily. Good luck.
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On other jobs at work. I've usually taken a piece of threaded stock. Bottomed it and locktite, even chamfered and peened the top out. Then re drilled and tapped on location. As mentioned above I think. Ralphy |
I don't think Mr. Lykins has a Bridgeport ( might be wrong - he'll correct me if I am).
But you don't really need one for this repair. You need a good drill guide. A set of rocker stands and a shaft will work nicely - and you have those already. Bolt it down with the three good ones and drill through the "bad hole". Mark you necessary depth on the drill first and instant perfect alignment... I generally use studs these days and 35 pounds torque |
Only problem is the through hole on the rocker stand may be to small or big. Depending on how bad/big the sleeve needs to be. The stand is a bit bigger than a tap drill for right size. Do you have a used stand? If you can sleeve the drill?
I've been handed more than once, just in the last year something an A&P mech tried to do by hand. Break a tap off get it all cockeyed, drills etc... Then bring it to our shop and think were going to perform miracles with an EDM. Make it like they've never been there! lol Over engineer the setup is my motto! Ralphy |
IF there was 3 heli coil threads in the bottom of the hole-----------then the STUD wasn't proper depth and most likely the cam lobes at that location were up and there was an excessive strain put on the threads as the rocker arm shaft was tightened down opening the valves-------
And if setting up in a Bridgeport milling machine you would just use the rocker boss es for the location of the hole set up and then remove the assy while drilling the head for the new threads---- If your not using a mill, then a machined drill guide tool piece would be preferred over punting the operation---------- |
http://www.drill-bushings.com/
I've made a guide on the cheap once. However it was not as critical and the hole was unmolested. I took two long bolts app. 2 inches longer from the surface being drilled. And a piece of good card board. Transfered the pattern on the card board, slide it on the bolts 2 inches away. The whole point was to give a reference to steady my hand and drill. Ralphy |
I have used Timeserts on cylinder head bolt holes in the block.......never had a problem..and that's a head bolt with a lot of torque.....
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If the original helicoil was drill and taped out of square. The bolt could have loaded the helicoil to one side heavily and started pulling the cast thread out. Then the valve train hammering the hell out of it. Just a thought!
You have a solid lifter motor also no? Ralphy |
Just to clarify:
1. I'm doing this with head on the engine, in the car. 2. The studs are the e-bock kit which are the ARP studs/nuts/washers. 3. The stud must have un-screwed when rocker assy was removed and I didn,t catch it on re-assembly. 4. This hole is the oiling hole, which is chamfered and has restrictor in oil hole. 5. The helicoil which pulled out was the original put in by E-brock, not a repair. 6. The coil pulled out cleanly taking only the alum thread matl, leaving a 1/2" hole which might just need to be tapped for a timesert. If I need to go bigger to a "bigsert", then i"ll have to drill. |
I stripped a head bolt hole in my Pond block and did it in place. I was laying horizontally across the car with my trusty DeWalt 14.4. I laid a calibrated eye-ball on it and let her rip! I then tapped it and put a 1" long heli-coil in the block. I was within a thou or two at the top of the stud after I installed it. You couldn't have done it any better with a bridgeport, I wouldn't hesitate to do it again. The rocker hole should be a piece of cake.
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Well I struck out with local Timesert dealer who said he could order it from factory in Ca. and it would only take 1-2 weeks ! HA! worthless !!
Did get a "Bigsert" kit ordered from another dlr in Fl, should have it tomorrow. |
Got the ""bigserts" kit from nearby distributor, made an alignment tool, and replaced all 4 rocker shaft stud heli-coils. As it turns out they were all starting to pull out ! With the larger threaded area of the "bigserts", they should be stronger than when new, plus I torqued them to only 35'# as per Barry R.
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drilling/tapping jig
4 Attachment(s)
some pics of alignment tool. Used a piece of oak, metal would be better as it's hard to be precise when drilling the wood.
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