how many psi does that motor put in the cylinders, ours put about 180-190psi

 

130-150 I beleive but I beat the **** out of that thing. Rpm's tach out @ 8000 - 8300. Don't forget they use those things to hold airplanes together.

 

well maybe ill just tell him to try and if a plug blows out then happens. i didnt know they used helicoils on planes for their bolts.

 

Yup check out there website. I was suprised to know that too.

http://www.emhart.com/products/helicoil.asp

Heli-Coil is the approved Screw-Lock Screw Thread Insert source for Boeing Aircraft per specification BACI12AE rev B.

 

we also heili coiled my buddies Carb to his Aluminum intake..
455 Big block havnt had a problem in 3 years.

 

update, so the mechanic called, he said that he straightened out most of the threads but its still about 2 turns from bottoming out. he said it runs good but he called the machine shop anyways and no one will install and helicoil in an aluminum head because the aluminum expands and contracts too much and because the densities of steel and aluminum are differrent the hole would get bigger faster that the steel helicoil so no one would do it. he said it runs good and isnt missing so im gonna try and hit up on some new heads and pray for the best, or im going to deactivate that cylinder and injector. but until then i think ill just see how it does.... im pretty sure i want to put my truck in the car crusher and start over. get a used regular cab and put a 6.0 in it.

 

Hmmm...an Al. hole could reduce in dia when it heats up. The metal expands outward in all directions (so radially inward), thus closing the hole. The steel will expand outward radially making it stronger due to a thermal fit. I have no proof of this, just thinking out loud. It seems logical to me.

I think it's important to note the way a heli-coil works. It's not just a steel threaded insert stuck in a Al. hole. The original Al. threads will be drilled out, and the head will be tapped again, with a larger than original tap size. The heli-coil itself is then threaded into the new Al. threads. Then the spark plug will be thread into the steel heli-coil threads expanding the heli-coil into the Al. threads.

 

thats the way i was thinkin but im pretty sure a machine shop would know what the deal is. my valve seals i think are gone to hell so hopefully i will get these heads for 175 and then ill put them on. (yea i know, more problems) but i asked him how much he charged, lets just say it was alot...but he was like you could come over here some saturday and we could do it together and since we'd be closed, no charge. so il do that sometime.

 

I hear what your saying but IDK if that is true. I mean when you have bearing in an aluminum case and it needs to be removed heating the entire case in the oven to around 250 degrees will expand the aluminum to a point where the steel bearing will literally fall out. So I would say the hole would get larger. Either way the plug would be applying pressure against the coil at all times and it would not have a chance to pop out unless the hole grew almost a 1/4 in.

You are right about the install though there not just dropped in a hole they are threaded in. Which makes it very strong IMO.

 

i guess this is why i asked if anyone had actually done this exact thing, i knew the responses and the theorys and opinions i would get (mine being pretty much the same as yalls) but i wasnt to see if anyone had any physical back up for this kinda thing to explain why the machine shop would refuse to do it unless they just want 600$ to remove the head and repair it rather than a 15 minute permanant fix, im not sure which machine shop my buddy uses.