found a set of aluminum heads but 2 of the spark plug holes have been heli-coiled. is this safe to run at high rpm's? ive never had an engine with them so im looking for some experienced advice here..... anyone?
I've done quite a few at work but not sure about high compression,high RPM use. I wouldnt think it would be an issue. The heli coil is threaded into the head just the same as the spark plug was. Anyone have some race experience????
that's what i was thinking and had the same concern about high compression and high rpm's. my engine will be around 11:1 and i plan to spin it to 7K on a daily basis
In that case Dave...dont worry about the helicoils.You will break other parts before you pop a properly done helicoil.If you are really concerned about it.Install new ones with JB weld on the helicoil.Put JB wled on the insert...screw it into position.Insert a spark plug with some bearing grease on the threads into the helicoil and let it set up over night.Now remove the old spark plug and your good to go.I have done this on High compression set ups and boosted ones too.Never had one let go.
Loctite wont surround and bond the helicoil in place like JB weld will.Realistically you could use any high heat 2 part epoxy to do the job.
Heli-coils...are not much more than a wire screwed into a threaded hole... this was my choice at the plant i worked at for 30 yrs. Keensert & Keysert Key-Locking Inserts Keensert & Keysert Key-Locking Inserts provide high strength and reliability and are designed to provide high resistance to rotation and pull-out loads. After installation into the tapped hole, the locking keys on each Keensert/Keysert are driven down through the threads of the parent material, locking the insert firmly and permanently in place. Keensert/Keysert Key Locking Insert Features - Can be used in virtually any material including aluminum, cast iron, steel, & plastics - Positive mechanical lock against rotation - High strength and flexibility provides maximum pull out strength - Easy installation and removal, can be installed using standard drills and taps. However, Keensert installation kits are also available if needed - No prewinder tool required - Impossible to cross-thread during installation - No tang break off needed Keensert/Keysert Key Locking Insert Materials & Finishes - Materials : Carbon Steel, Stainless Steel, Bronze, Nitronic 60 - Finishes : Silver Plate, Cadmium Plate, Dry Film Lubricant Keensert/Keysert Key Locking Insert Thread Types Keensert Key-Locking Inserts are available in standard & screw lock forms. - Metric - UNC - UNF
Helicoils are stronger than the original metal in most cases. I've never used them in spark plug holes myself, but have seen it done on VW heads [aluminum air cooled ]. I used them in a York style AC compressor a few years ago that had stripped the mounting bolt holes, it never came loose again in 100,000 miles. I have had them screw back out when you took out a bolt, so JB Weld or Loctite sounds like a good idea.
I wouldn't use JB weld either on a spark plug hole, but that's just my opinion. I've seen that crap become brittle and chip/flake before and I wouldnt want it falling into the motor when you change plugs, etc
The better aluminum heads are helicoiled from the factory in all the bolt holes. The steel threads are far stronger than the aluminum.,
Those heads are gonna be unsafe, man. I will do you a favor though... If you'll box 'em up and send them my way, I can exchange them for some nice strong iron heads I have. Maybe I can recover my shipping costs when I recycle the aluminum...
