I have markIV 454's one block has had some helicoils done for the head bolt threads, no big deal... well one must have been tapped at an angle and the bolt will not go in with the head on, It was a running engine until I took it apart, I have no idea how they had a bolt in it before, I am using new hads and bolts, I cannot see if thye modded anything to make it work. The threads are not the greatest to hols the helicoil, is there a wat to tap it bigger then the 1/2" and also still use a 7/16" helicoil?

I want to retap the hole but the threads for the 1/2" tap are not good, what is the next size up? I cannot imagine I have to scrap a block for one thread...

you may need to take it to a good machine shop....they should be able to care of this..Rob

there are inserts called ''timeserts'' that take a bigger hole they might work

Sounds like your bad luck is giving me more time to get ours together quicker.
Jr.

That is a l resort... I just assembled the shortblock...

I am leaving for work.. I will call you in a few...

On an old motor I had used helicoils and never had a problem gettting the bolt to start. When you screw the bolt in without the head on how far is it off compared to the other head bolts?

Problem is that the person who drilled it before I had the engine did it on an angle, so with the head on it will not start, it needs to be at 90 degrees.

First off, if it's a helicoil, it won't hold the torque you need. You need a thread insert. The difference is substantial. You can drill the block while assembled- go to a rental house and get a magnetic-base drill. Rent the jacobs chuck adapter too. McMaster-Carr will have a broad selection of different sizes of thread inserts as well as the taps and tap drills. Do not use the threadlock they apply to the insert- use Loctite stud locker. Myself, I'd use studs instead of head bolts

My buddy that owns a machine shop gave me this... worked great!

http://www.timesert.com/html/bigsert.html