Rotator flexplate problem

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dcm5899
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Rotator flexplate problem

Post by dcm5899 » Tue May 07, 2019 8:24 pm

Anybody bought a new Rotator with soft drive for a BBC and had 3 bolts between soft drive and flexplate not line up? My soft drive has two different bolt pattern diameters for some damn reason, 3 one location - 3 another. What'd you do to fix it?

Hotdog
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Re: Rotator flexplate problem

Post by Hotdog » Tue May 07, 2019 10:25 pm

Should have 3 inner holes and 3 outer holes they should all Lin’s up. Keep turning it. That’s how my rotator is

dcm5899
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Re: Rotator flexplate problem

Post by dcm5899 » Tue May 07, 2019 10:39 pm

Measured all the holes on flexplate and there all the same distance from center.

raven6947
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Re: Rotator flexplate problem

Post by raven6947 » Wed May 08, 2019 8:13 am

I had to drill and file 3 new holes in my engine flexplate. To do that I laid the engine flexplate on the workbench then laid the new flex drive over it. I used the 3 holes that lined up to locate and drill the other 3 holes.

dcm5899
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Re: Rotator flexplate problem

Post by dcm5899 » Wed May 08, 2019 8:44 pm

Guess I'm drilling mine also. kind of pissed off spending $3k and having to modify engine parts that have been made the same since the early '90s to fit an oddball pattern on the gearbox

SWAMPHUNTER45
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Re: Rotator flexplate problem

Post by SWAMPHUNTER45 » Wed May 08, 2019 8:51 pm

Same thing with any SFI flex plate for a Cadillac. If you use a titanium coated step drill it takes about 5 minutes to open it up enough for the bolts on the three holes. Some guys also encounter issues with the washers not laying flat due to the plates design. I have ground edges off washers making a "D" shape before or you can get a smaller washer that is the exact size of the bolts head.

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Slidin Gator
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Re: Rotator flexplate problem

Post by Slidin Gator » Wed May 08, 2019 9:50 pm

SWAMPHUNTER45 wrote:Same thing with any SFI flex plate for a Cadillac. If you use a titanium coated step drill it takes about 5 minutes to open it up enough for the bolts on the three holes. Some guys also encounter issues with the washers not laying flat due to the plates design. I have ground edges off washers making a "D" shape before or you can get a smaller washer that is the exact size of the bolts head.
Did it really used to require match drilling just to mate these old iron piles to a torque converter back in the day? Starting to re-think my push to get the wife to trade in her latest Hyundai for a Caddy! At least them Korean folks seem to be able to machine bolt hole patterns to line up.

Guess "Ole Rosy The Riveter" was really "Rosy The Match Driller".
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

SWAMPHUNTER45
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Re: Rotator flexplate problem

Post by SWAMPHUNTER45 » Wed May 08, 2019 11:11 pm

The plates are made to adapt a Caddy to the Rotator or other modern GM (Chevy) pattern.

If you run the old Caddy factory plate OX BOX drives can make a direct fit FYI

Some guys back in the day would drill the factory plate but you risk a break doing that.

There is a billet flywheel Mr. Branch has had in the shop that's a direct fit no mods but very costly. He runs one of them in his truck because the tranny hits so hard it bas fractured the SFI plates. The SFI runs around $100 and is really a very simple mod to work and is good for a boat application.. With the SFI mod your only opening up the hole about an additional 1/8 of an inch if that.

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