6 tab flexplate?

[superhondaz50]

So I just got my 12" ACC th400 6 tab torque converter, I also received my flexplate from rock auto. The flexplate only mates up with 3 tabs, can I enlarge the other three holes on the flexplate to fit TC?

Thanks

[Steeveedee]

Does it really need to have all 6 holes bolted up? There shouldn't be any issues opening the other holes up, but I'd recommend making sure that they are smooth so cracks don't have a place to initiate from.

[superhondaz50]

I'd like to have all 6 if possible. Anyone have the part number for a flexplate with 6 correct holes for a 350 engine to th400?

[truckster]

Are you sure it's not a dual bolt pattern? Early flexplates were SAE pattern and later ones are metric.

[superhondaz50]

Originally Posted by truckster

Are you sure it's not a dual bolt pattern? Early flexplates were SAE pattern and later ones are metric.

Ya, it's a dual pattern flexplate, 3 @ 11.5, 3 @ 10.75, need 6 @ 11.5

[Steeveedee]

Originally Posted by superhondaz50

Ya, it's a dual pattern flexplate, 3 @ 11.5, 3 @ 10.75, need 6 @ 11.5

How much torque does your engine put out? A 454 truck still only uses 3 bolts from the converter to the flex plate. I think you are chasing your tail with using 6 bolts.

[truckster]

Originally Posted by superhondaz50

Ya, it's a dual pattern flexplate, 3 @ 11.5, 3 @ 10.75, need 6 @ 11.5

You only need three of those bolts. That's all they're designed for. The dual pattern is so you can use the converter with either flexplate.

I would be concerned about damaging the flexplate if you redrill or enlarge the other holes.

[superhondaz50]

Originally Posted by Steeveedee

How much torque does your engine put out? A 454 truck still only uses 3 bolts from the converter to the flex plate. I think you are chasing your tail with using 6 bolts.

250hp 350ftlb, it's really low. So it should be ok leaving three tabs with no bolts? Still need to find some 3/8-16 Bolta for it too.

[truckster]

Three bolts. That's all it needs.

[superhondaz50]

Sweet, thanks!

[superhondaz50]

BTW, do you use lock washers or lock Tite?

[Bigdav160]

Either works.

BTW, one tone trucks with 350/th400 combinations used 6 bolts on the torque converter.

[superhondaz50]

Good to know the 1 ton thing. Mines 1/2 ton.

[ZEKE68]

Some later trucks used six bolts. I found a Pioneer FRA-145 flex plate on ebay which had six 11.5 holes for a 454. It was an old leftover and they don't list it any more. Now they list a FRA-141 for the 454 which is a dual pattern with 3 @ 11.5 and 3 @ 10 3/4" and the hole are very large in it.

[superhondaz50]

Originally Posted by ZEKE68

Some later trucks used six bolts. I found a Pioneer FRA-145 flex plate on ebay which had six 11.5 holes for a 454. It was an old leftover and they don't list it any more. Now they list a FRA-141 for the 454 which is a dual pattern with 3 @ 11.5 and 3 @ 10 3/4" and the hole are very large in it.

Cool, I'm gonna keep an eye out for that, if I can't find it I'll just use three bolts for the time being

[truckster]

Originally Posted by superhondaz50

Cool, I'm gonna keep an eye out for that...

I wouldn't do that. The 454 is balanced externally and SBCs are balanced internally (except the 400). The 454 flexplate has a balance weight on it, and you're going to have a heck of a vibration you just can't get rid of.

Just use the three bolts. It's how it was designed to run.

[superhondaz50]

Originally Posted by truckster

I wouldn't do that. The 454 is balanced externally and SBCs are balanced internally. The 454 flexplate has a balance weight on it, and you're going to have a heck of a vibration you just can't get rid of.

Just use the three bolts. It's how it was designed to run.

Three bolts it is. Just gotta find the course threaded ones. I ordered the ARP ones and they're fine thread and won't go into to torque converter threads.