Flexplate plate in C4 issues

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Offline Mylittlepony1966

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Flexplate plate in C4 issues
« on: August 23, 2023, 10:52:13 am »
I have rebuilt a 302 roller block to drop in my 66. I have had previous post with questions prior to the build & found good info from here.

After dropping engine in & doing up torque converter  & bell housing, the engine was bound up tight, & couldn't turn it over at all. Some facts are;

Different 302W block
New 50oz flexplate (match balancer)
Same old bellhousing
Same old Torque Converter (TC)
Sandwich plate fitted
Flexplate correct way around
All bolts/drains in TC mate & fit flexplate
TC aligned with C4 oil pump (confirmed)
Snout of TC is only just protruding through flexplate.
Flexplate appears to have a different offset compared to old 28oz flexplate.


My money is the flexplate; however, allegedly they don't make one with the correct offset.  I believe  it is the offset of the Flexplate. I'm just trying to get lived experiences for the desired outcome.

Anyone else experienced  similar, & what was the workable solution?
« Last Edit: August 24, 2023, 06:13:28 am by Mylittlepony1966 »

Online GEOFF289

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Re: Flexplate plate in C4 issues
« Reply #1 on: August 23, 2023, 12:38:14 pm »
Did it rotate by hand OK on the engine stand? If so, it really looks like its something to do with the interface between the engine and trans.

I know you say the torque converter is all the way on but this is a common problem and is worth checking again. There are three steps to the process of sliding the converter all the way in and it needs to be turned between each step. Did the bellhousing mate right up to the back of the block and sandwich plate before you started doing up bolts? The bolts shouldn't be pulling them together as they are tightened.

Offline Mylittlepony1966

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Re: Flexplate plate in C4 issues
« Reply #2 on: August 23, 2023, 12:44:19 pm »
100% 3 stages of engagement with TC. All pulled  up nicely, & yes engine  moved freely  prior. It has since been started  without gearbox.

Online GEOFF289

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Re: Flexplate plate in C4 issues
« Reply #3 on: August 23, 2023, 03:59:44 pm »
OK, well I'm out. I guess try another flex plate and see if there is something wrong there. You could put the old 28 ounce one back on and see if it turns over to either eliminate or confirm the new plate as the issue.

Offline Mylittlepony1966

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Re: Flexplate plate in C4 issues
« Reply #4 on: August 23, 2023, 04:34:05 pm »
Yeah thanks mate.

Pretty frustrating, not like this is the first time this conversion  has been done.
My money is the flexplate; however, allegedly they don't make one with the correct offset.
I believe  it is the offset of the Fkexplate. I'm just trying to get lived experiences for the desired outcome.

Offline pmb0186

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Re: Flexplate plate in C4 issues
« Reply #5 on: August 23, 2023, 10:53:06 pm »
How did you rotate the flex plate / torque converter to fit the bolts if locked up ?
There is a max and min clearance between the flex plate and torque converter, important for correct engagement of the pump and on the other end flog out pump.
does anyone remember laughter

Offline Mylittlepony1966

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Re: Flexplate plate in C4 issues
« Reply #6 on: August 24, 2023, 06:12:50 am »
I used brut force until I realised something  was going on. I baked off all bolts to see what happened & it freed up. I acknowledge  the possibility  of damage to the pump in the gear box  & it is currently  out waiting to be inspected properly.

Offline pmb0186

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Re: Flexplate plate in C4 issues
« Reply #7 on: August 24, 2023, 10:35:04 pm »
Any chance the engine came out of a manual car as the spigot bear may be still installed
does anyone remember laughter

Offline Mylittlepony1966

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Re: Flexplate plate in C4 issues
« Reply #8 on: August 25, 2023, 06:23:01 am »
Yes it was bolted up to a manual prior. The spigot was removed & crank cleaned up.

Offline Mylittlepony1966

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Re: Flexplate plate in C4 issues
« Reply #9 on: September 02, 2023, 08:56:22 pm »
To close this post, I will update what the problem  was.
The new 50oz flexplate had a different offset to the 28oz flexplate. I had to use a 28oz to get the correct profile & spacing. I had it modified to make it 50oz & rebalanced to replicate the 50oz that was used to balance the internals. Sure enough it bolted straight up without any binding.....
It was frustrating  as no one was interested in the problem .

Online GEOFF289

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Re: Flexplate plate in C4 issues
« Reply #10 on: September 03, 2023, 07:24:56 am »
Weird, never heard of that before, but glad you got it sorted.