When I originally assembled engine/tranny in car, the torque converter threads for flexplate bolts got stripped so I heli-coiled them. Everything was fine but a few hundred miles later they came loose and the flexplate got slightly buggerd up.

So I got another torque converter then reassembled everything with same flexplate and a bit of locktite. It eventually worked loose again a few hundred miles later. At that point I used LOTS of locktite. That seemed to do the trick, but now a few thousand (4 or 5 maybe) later they are loose again. I don't think these bolts are original, I believe they are hardware store grade 8 units.

So now ... I haven't taken everything apart yet. I'm not sure 100% what the issue is, but I'm guessing since the holes are slightly ovaled thats why I'm having continuing problems. Kragen lists a new flexplate for $10 and summit has one for $30ish for 5/16" bolthole (Summit one, an MP unit, isn't specifically for a slant but I thought somewhere I read the slant and smallblock bolt pattern are the same?)

Should I just try an arp or MP bolt set and leave the flexplate on there, or are the hardware store bolts sufficient? I know this is oakey but I also thought that since the tranny has recently been rebuilt I have no need to drop it again anytime soon, so why not just put a small tack on every bolt so that would keep them in place for sure? I figured next time I need to remove things I can just cut the flexplate, since its alread dammaged anyway it wouldn't matter. The only downside I could think of this is balance issues. I'm just trying to avoid labor of dropping the tranny but if I must I must.

Nobody likes to drop a trans AGAIN,,,,but once you had a new flexplate and bolts to go with the new convertor and trans,,,well its all new....and for a while. On my non slant work truck I had to go with an aftermarket flexplate to avoid the problems you speak of and more. I replaced the flexplate and the crankbolts and convertor bolts and hadn t even thought of it again till now.

Did you ever get you FI setup working?

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Sandy has the right way to do the job, but....
If you want to do another round of "glue them in", use Devcon metal filled epoxy or JB weld an see if they hold.

And for the "meatball surgery" option, remove the starter and the dust cover. Roll the engine around so you can get a 1/4" drill bit on the converter's mounting lugs as they pass the starter opening. drill them out and retap to the larger 5/16-24 flex plate bolt size. Those won't come loose.
DD

Small block and slant flexplate bolt patterns are NOT the same.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Yep, there is one crank bolt hole that is about half a bolt hole off. A little time with a rat tail file will make it work.

Pierre, I have about a bazillion stock converter bolts. If you need some let me know, I'll send you a set.

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Official Cookie and Mater Tormentor.

Pulled the bolts today... bolt holes aren't huge but they are eggshaped. One even has about 1/8" play. Threadlocker/epoxy isn't an option either because the threads in the torque converter are buggerd up. Theres no room to drill for a bigger screw because on one of the lugs the hole is at the edge of it.

Sooo... bit the bullet, orderd a flex plate torque converter and some bolts (thanks for the offer slantzilla but I figured I may as well have them send it in the same order)

The guy there (that rebuilt my transmission a few years back) said not to use hardware store bolts either. The proper bolts have a bigger head then the typical hardware store bolt.

He also said no threadlocker is needed, but he said I could try the high heat high strength stuff. The type I used before is just high strength - good to 300deg. The high temp stuff is good to 450deg. Does transmission fluid (and hence the converter) really get that hot for a normal street car (with a smidg of spirited driving every now and then) ?

I would recommend thread locker, on the flexplate and converter bolts. I have seen them come loose many times. Use the "blue" locktite, and you will be able to remove the bolts when you want to. Do not use the "red", it is for bolts that will not be removed.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The high strength is red, blue is medium. I'm not sure what color the high strength/high heat is.

At the rate the bolts are coming loose on me I may as well use cement or something

According to the bottle you can undo bolts with red locktite on it if you apply heat. And since these bolts are relatively small the loctite has less surface area to grab on

Got the flexplate/converter today.

Good thing is the new converter has 5/16-24 thread instead of my old one which had 5/16-18. Means more surface for the loctite to grab as well.

Just noticing something.... even the new flexplate, the boltholes are still lots bigger then 5/16", infact I can put a 3/8-24" bolt in the hole, and there is still some slop (less then 1/16") at the shoulder of the bolt even. Is this normal? Because if it is then the holes on my old flexplate aren't as eggshaped as I thought they were, which puts me back to where I started.....

Edit: I was just looking around and apparently there are two flexplates, one for 7/16" bolts and one for 5/16" bolts. I thought this one I have may of been for the 7/16" bolts but thats incorrect because a 7/16" drillbit will not fit in the hole, too big.

I'd appreciate it if someone with an original flexplate w/ 5/16" converter bolts would measure the hole diameter for me just so I can doublecheck if this is the right one.

I think that might be your original problem. If I remember correctly, all flexplate to crank and converter bolts were fine thread. If coarse thread bolts were used, it would mess up the threads in the converter.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Charlie my old converter was tapped 5/16-18, I didn't force a coarse thread bolt in a fine thread hole. I've been known to do silly things sometimes but I'm not that bad

I want to know the diameter of the bolthole on an original un-dammaged plate so I can get to the bottom of this mystery.

Pierre, I believe you! I must say though that I've never taken out or put back a converter bolt that wasn't fine thread. Next time, this will be a red flag for everybody. Some of the "race" flex plates have bigger converter bolt holes... You didn't end up with one of them did you? I will measure a stock flexplate bolt hole dia. later and report back, if someone else doesn't beat me to it.

D/W

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If it ain't broke, fix it!

Race? I doubt it, it was only $10 and those race flexplates sfi approved or whatnot mumbojumbo are way more then $10. If the race flexplates are 7/16" then this isn't it because a 7/16" drillbit wouldn't fit through the hole, looks like this one was made for a 3/8" screw but I've never heard of a 3/8" flexplate bolt.

WAIT! I just reread the very first thing that you said...
You did indeed introduce the coarse threads, or so it would appear.

D/W

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If it ain't broke, fix it!

I gotcha. What you need then is the correct dia. measurement, which will be forthcoming.

D/W

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If it ain't broke, fix it!