Ron78Z&66Vette

The plan was to get my oil pan & timing cover on tonight so I could paint my motor tomorrow

I was torquing down my oil pump, and about when I was expecting to feel the "break" of the wrench, I all of a sudden felt a decrease in resistance.....cr@p!!

Pulled the bolt, looked normal. Looked at the threads for the oil pump bolt and they looked odd......cr@p! Double checked the bolt in the rear cap pump threads of 2 other bare blocks I have to confirm I was using the correct bolt. I then got to looking at the rear cap and saw that it had a heli-coil at the oil pump bolt threads.

I chased the threads with a tap and figured "what the hell" I've got nothing to lose. I started torquing down incrementally and the heli-coil stripped out before I even hit 30ft/lbs. I pulled the bolt to be greeted with the sight of a helicoil in pieces and an area to wards the top of the hole (the actual steel of the cap) had also broken/crumbled......WTF!!!!

Any suggestions? Has anyone even seen this before? I did a search on this and the C3 forum and found nothing, so I guess this is a new one!

The way I see it I have a few options:
1 Take the cap to a machine shop and see if they can put another heli-coil in it and hope that the crumbled metal isn't too structurally important.

2 Measure another aft cap for similar dimensions and if necessary have the machine shop "match it" for me......is this even possible?

3 Take the pistons & crank out of my current block and have a machine shop start from scratch on one of my other blocks.

What do you guys think? I'm really thinking I'm screwed.

...............one more option, just JB Weld the pump to the cap!

squat12

I haven't used these, but I've heard they work well, plus they take up more space than an equivalent helicoil, which means that you could drill and tap an even bigger oversize hole to install it over the ruined helicoil-sized threads:

http://www.labsafety.com/store/Facil.../Inserts/1266/

Randy G.

Timeserts all the way. I would never use a helicoil in that application. I have a magnesium PSI screw supercharger on my TA/FC and the manufacturer installed Timeserts where the injector bolts on. It gets hit with a 250 mile per hour breeze. They are awesome.

Find a machine shop that will put one in for you or buy a kit and do it yourself. I bought a metal brief case size box full of them in all sizes because everything on our race car screws into aluminum or magnesium. Only way to go.

Matt Gruber

i always drill and tap to a larger size.
i'd consider metric if there is an in between.
isn't that a 7/16"?
1/2 should work
maybe stud it.
or if u can drill deeper same size could work.
need a "bottom" tap,
once i ground down a reg. tap.
never used a helicoil, seems bubba to me.
good luck!

427425

Both of the recommended thread inserts will repair your problem, if installed properly. I would take it to someone that has a mill so that it can be supported and drilled/tapped at the correct angle.

If you have to replace the main cap, the block should be line honed to insure straightness and correct clearance. Good luck with the threadsert.

Allcoupedup

Please tell me you are joking about mixing metric and SAE bolts on a CORVETTE ---- and at the same time suggesting that helicoils are bubba fixes....please.....

Matt Gruber

it is already bubba-ed with a failed helicoil.
THIS is going to be HARD to fix.
if a helicoil requires drilling the hole larger, why not use a larger stronger bolt instead? that is what i do. but, i admit, many people don't succeed at the things i do, or don't even try. any fix is worth a try. so trial fit the spare cap. it has a small chance of not needing align-honing