mennonitemike Posted August 27, 2008 Share Posted August 27, 2008 So I blew a head gasket a month ago and two weeks after I got it all back together I break my rocker arm assembly. It seems my chain tensioner slipped a couple notches and created some seriour tension on my rocker shaft brackets via the cam and pulled the bolts right out of the head on the last three brackets. Turned my truck into a two cylinder as it's a Z24. I don't wanna take the head off again so I was wondering if I could get around that by either drill and tapping the holes and using thread inserts or just using different bolts and foregoing the inserts altogether. Any input? Link to comment Share on other sites More sharing options...
GrimGreg Posted August 27, 2008 Share Posted August 27, 2008 If you are serious about keeping the old stripped out block, take it to a machine shop and have them weld fill the bolt holes then have them re drilled and tapped. You can overdrill and insert the thred-serts, but I don't know if I trust them in such a critical torque spec application. Same with over-sizing the head bolts, it will probably cause more issues unless you drill out all of them and retap at a larger size. Link to comment Share on other sites More sharing options...
PDCCD Posted August 27, 2008 Share Posted August 27, 2008 I love Helicoils. They were actually invented for manufacturing to increase productivity and strength in aluminum. I can't remember where i read it, but it's claimed that if their installed properly they're stronger than the original threads. Something about being stainless, and dispersing the stress along the entire hole. I haven't used them for a head, but i would, that's my .02. Link to comment Share on other sites More sharing options...
jj big shoe Posted August 28, 2008 Share Posted August 28, 2008 Dunno the insides of a Z24 at all, but is there enough room between water jackets and cylinder walls and such if you decide to drill to a larger size? Link to comment Share on other sites More sharing options...
nunya Posted August 28, 2008 Share Posted August 28, 2008 If you only had a ka instead of a z, and were a little closer, I could have given you a complete head, I really just don't want to go through trying to ship one though, I AM kind of lazy. As for the helicoil idea- they hold spark plugs in heads on Ford Triton v-10's, thats what alot of dealers have been doeing when they blow the plugs out of the motor. Link to comment Share on other sites More sharing options...
sw Posted August 28, 2008 Share Posted August 28, 2008 (edited) I love Helicoils. They were actually invented for manufacturing to increase productivity and strength in aluminum. I can't remember where i read it, but it's claimed that if their installed properly they're stronger than the original threads. Something about being stainless, and dispersing the stress along the entire hole. I haven't used them for a head, but i would, that's my .02. this is the conclusion i came to aswell when i redid the treads for the front top arms. they feel way more solid then before the insert Edited August 28, 2008 by sw Link to comment Share on other sites More sharing options...
91PathSE Posted August 28, 2008 Share Posted August 28, 2008 If you are serious about keeping the old stripped out block, take it to a machine shop and have them weld fill the bolt holes then have them re drilled and tapped. You can overdrill and insert the thred-serts, but I don't know if I trust them in such a critical torque spec application. Same with over-sizing the head bolts, it will probably cause more issues unless you drill out all of them and retap at a larger size. I'm going with grim on thsi one...I've had experience with Thred-serts and I'll never do it again...Did it an old beater dune buggy...The head blew rigth weher the serts were. They cant hold a high levels of stress/torque. Link to comment Share on other sites More sharing options...
PDCCD Posted August 28, 2008 Share Posted August 28, 2008 I'm going with grim on thsi one...I've had experience with Thred-serts and I'll never do it again...Did it an old beater dune buggy...The head blew rigth weher the serts were. They cant hold a high levels of stress/torque. I'm sorry, i may be confused. Are we talking about thread inserts or heli-coils? I've used threadcerts in aluminum and steel and agree. They're nice for some applications, but i wouldn't trust them for something critical. But heli coils i still think would work well. Have you tried a google search on helicoils, you may find more specific details. Pete Link to comment Share on other sites More sharing options...
unccpathfinder Posted August 29, 2008 Share Posted August 29, 2008 Helicoils are as strong as the material they are in...if you drill out a hole and retap it for the heli and there isnt enough ED (edge distance) it will just crack over time... The helicoil is stronger than the alumunum but the tension is net b/c the strength of aluminum is the same and it is the limiting factor... i'd say call up your local mechanic and/or machine shop and talk to those guys about it to see what they reccomend...but you are going to have to pull the head...I wouldnt do any drilling/tapping on the engine without running the head through a parts clean cycle b/c the chips will prpobably not be healthy Link to comment Share on other sites More sharing options...
87pathy Posted August 29, 2008 Share Posted August 29, 2008 (edited) FACT Heli coils are stonger that threaded holes. I would not hesitate to fix nearly any stripped hole with a heli coil. BUT, make sure that the wall around the whole isn't too thin. Normall i think, about 25% of the diameter. Edited August 29, 2008 by 87pathy Link to comment Share on other sites More sharing options...
GrimGreg Posted August 30, 2008 Share Posted August 30, 2008 FACT Heli coils are stonger that threaded holes. That could be the problem, just like our exhaust manifold bolt issue, if the helicoiled bolt expands and contracts at a different rate than the others it could cause a hot spot or cold spot and blow gaskets or even warp the head. Link to comment Share on other sites More sharing options...
mennonitemike Posted September 1, 2008 Author Share Posted September 1, 2008 (edited) thanks for all the feedback! I didn't even know about the Heli-coils. I was originally going to use those solid piece inserts with the lock pins you have to hammer in. Now to head down to NAPA, PartSource or Autovalue and try to find them. p.s. just to clarify, I'm not heli-coiling my headbolt, just the rockershaft bracket bolts on the six holes closest to the rear of the motor. Edited September 1, 2008 by mennonitemike Link to comment Share on other sites More sharing options...
Precise1 Posted September 3, 2008 Share Posted September 3, 2008 First, I agree with GG, the best way is to weld fill and redrill and tap. That said, I have made MIL SPEC parts for years as a machinist, and the standard procedure is to insert helicoils in all smaller diameter tapped holes in aluminum parts. Period. Before they ever see a bolt. I've never used them in this application (what torque are the bolts?) but I'd bet they would work just fine. B Link to comment Share on other sites More sharing options...
GrimGreg Posted September 4, 2008 Share Posted September 4, 2008 Yeah, if it is just the rocker arm keeper, you are probably fine as long as there is enough material to drill/tap/heli-coil. Link to comment Share on other sites More sharing options...
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