Correct bolts/nuts used on SHP converters

[Steve Antonucci]

Hi all !

I am trying to find the correct bolt & nut combinations that would have been
used at the factory to attach the 6-lug converter to the flex-plate. I am
primarily interested in 1969 era SHP big blocks. Can anyone post an image of
one of these bolts & nuts? Honestly, I have no idea what they look like. Are
they coarse or fine thread? Any lock washer used from the factory? Lastly, any idea where I can find 6 of these? Are they repro'd by anyone?

Thanks,
Steve

[Joe L.]

Re: Correct bolts/nuts used on SHP converters

Steve-----

There was nothing special, at all, about the converter-to-flexplate bolts used for 1969 and 1971 SHP and HD big block applications with THM-400. They were the same as those used for all other THM-400 applications except that 6 bolts were used rather than 3. For 1969, the bolts used in PRODUCTION were GM #1362977. These were a PRODUCTION-only piece that was never available in SERVICE. However, they did have SERVICE equivalents. These were GM #1484645 which also later became the PRODUCTION bolt, too.

The GM #1484645 was a 3/8"-16 hex bolt of 0.50" length and of FLANGED head design. It was of GM 280-M material grade (SAE grade 5, 3 line) and it was of plain finish.

Later, the GM #1484645 was replaced for PRODUCTION and SERVICE by GM #3987930. The latter is identical in description to the above except that it is of 0.59" length. It will SERVICE all applications originally using the previously described bolts. It remains available from GM for a current list price of $2.40/each.

The Corvette THM-400 torque converter bolts usually use no nuts. Instead, the bolts thread into weld nuts on the converter. Some SERVICE converters may use nuts, but I believe that most, if not all, originals did not.

To anticipate another question regarding what manufacturer's headmarks were used on original bolts: I have no idea.

[Verle R.]

Re: Correct bolts/nuts used on SHP converters

Joe,

I have not tried to get a converter for a turbo-400 with six bolts for a long time but my experience on rebuilt standard converters now is they all come with metric threads. I expect that unless extraordinary measures are taken it may be difficult to get a rebuilt real "superturbine" torque converter with SAE threads.

Do you know the specifications for that torque converter, stall speed, etc?

Thank you,

Verle

[Joe L.]

Re: Correct bolts/nuts used on SHP converters

Verle-----

I don't have the specs for the SHP/HD torque converter.

The 6 bolt converter is no longer available from GM; it was available until fairly recently, though.

For Corvettes, the use of metric fastener converters began for the 1979 model year. I was not aware that converters for pre-79 converters were now metric, though.

[Verle R.]

Re: Correct bolts/nuts used on SHP converters

Joe,

It appears that at least the rebuilder for our area (Oklahoma) has switched everything to metric threads. When we rebuild an automatic and get a converter from the specialized transmission shop they are metric. If it is an older car we must find metric bolts.

Verle