Helicoils in heads

I was just given a set of iron "double hump" big valve 64cc SBC heads. They have been sitting for a while but they were been ported and had a valve job done on them before they were stored. The only potential problem is that there is a helicoil in one of the sparkplug holes. I have used helicoils on lots of things over the years but never for a sparkplug hole. Has anybody had any experience with this (good or bad?)

 

They work just fine.

 

If installed correctly it's fine, helicoils can be stronger than the original thread.

 

Have used helicoils several times, no problems.

 

The only minor issue I have had with helicoils on sparkplug holes is that occasionally, one will unscrew and come out with the sparkplug due to carbon buildup on the end of the plug. It was more a problem back in the leaded gas days when you could get a lot of buildup but it can also happen if the engine is an oil burner.

Since the hole is already threaded, all you do is screw another helicoil on the new sparkplug and put it back in. If it is a true HeliCoil brand, you break the drive tang used to install it off before you screw it on the plug.

 

They are used on aircraft engines but there are certain guide lines that must be followed to insure that there will not be a failure.Read the info on the link below
http://www.casa.gov.au/scripts/nc.dll?WCMS:STANDARD::pc=PC_90797

 

The 'old school' method is to plug the original sparkplug holes and drill new at an angle to locate the sparkplug on the piston. That was how we did it, the old 461X head. That was how the 'angle plug' head came into being.
'Back in the day it took a couple buddies and 2 sixpacks - they didn't have 12packs back then - and a good friday night, you'd be racin on saturday night, if your headers would bolt up.

 

Thanks all for the comeback.
Sounds like a go.
Just got to calculate the change in CR on a low compression 350 to make sure it is "pump gas friendly" when I get done.

 

I've got a helicoiled spark plug hole. It's in an aluminium head though. I've done about 8000 miles on it now with no problems. It was recommended I use anti seize on the plug. Before the repair was done, I was told a timesert would be a better repair, but here in little old NZ, I couldn't find anyone with the right installation kit for a Buell sized spark plug.

http://www.timesert.com/

 

HeliCoils work very well in sparkplug holes and exhaust manifold holes as well which is a bigger test of their durability than plug holes. I thought in the old days we used a locltite product specialy developed for hot location apps (I think it was green)but it's been a while so the memory may have faded or be faulty(lol).

 

I have used HeliCoils in heads for years with no problems at all.

Jimbo

 

Back in the 60s I had a 1954 Jag roadster I blew out one spark plug -- put in a helicoil (I still have the drill bit, 24/32 inch) and worked fine.

FWIW I stuffed an oily rag in the hole before drilling, drilled, screwed in the coil, sucked out the chips with a vacuum cleaner.... ran fine....

 

Mid to late '70's I used a KD kit from the local parts store to repair a stripped plug hole in an aluminum head. Came with a special tap and assortment of bushing inserts [similar to, if not the same as, Timeserts] for various plug thread sizes and depths. I used it with the head on the motor, greased the tap and blew out the hole after. Ran the motor with no problems for three years or so with no problems until I parked it for other reasons.

Ed

 

Our work fleet of vehicles were Ford 1 ton vans with V10 engines. They were noted for blowing the spark plugs right out of the heads. Ford's fix was to put helicoils in the heads, and they worked better than the original holes!

 

they may not be helicoil. There are other thread repair products out there that use a standard thread on the OD that do not require you to purchase their drill and tap.

 

And remember, all spark plus should have a small dab of anti seize on the threads and especially where a thread repair has been used. And I have installed a lot of these with no problems. Good luck.

 

I've done lots of later model aluminum heads with heli's or inserts. 2.2 OHV Chevy's are famous for stripped holes as are the previously mention modular V-8 V10 Fords.

 

No worries at all using the heli-coil. I have used them in blocks for head bolts and never had a single problem. Many guys have used them on the spark plug holes with no problems too.