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Old 07-02-2010, 08:14 AM
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305 torque on a 350 ?

Okay , after much thought and checking I found a great running and great sounding 350 to put in my T-bucket hot rod. It has a standard trans bolted to it now . My question : Is the torque converter off of my '91 Firebird 305 going to work on the 350 ? Or is there a going to be a balance problem ?

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Old 07-02-2010, 09:05 AM
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Um, what? A torque converter goes in the transmission and has no effect on engine balance. If your referring to the flexplate/flywheel then it depends. In 1986 chevy went from a 2 piece seal crank to a 1 piece seal. The new 1 piece design made the crank flange perfectly round so weight had to be added to the flexplate/flywheel to keep it in balance while the balancer on the front of the engine stayed the same neutral balance. When chevy made this change the crank flange was changed also so you can`t bolt a older 2 piece flywheel/flexplate on a 1 piece seal crank or vice versa. Also keep in mind most 305`s used a 153 tooth 12 inch flexplate with a straight mount starter. most 350`s used a 168 tooth 14 inch flexplate with a staggard mount starter. Now that you have a 350, use a 350 starter and flexplate.
If you used the smaller flexplate and starter on a 350, it may have problems turning the engine over fast enough to start when the engine is up to temp.
If you are referring to bolting up the 350 to the transmission you`ve been using with the same torque converter it`ll work just fine. Back in the day everything from straight 6 cylinders to big blocks all shared the same bellhousing pattern.
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Old 07-02-2010, 01:55 PM
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Quote:
Originally Posted by adantessr
Okay , after much thought and checking I found a great running and great sounding 350 to put in my T-bucket hot rod. It has a standard trans bolted to it now . My question : Is the torque converter off of my '91 Firebird 305 going to work on the 350 ? Or is there a going to be a balance problem ?
In addition to DV's info, 1-piece rear main seal engines were '86-up, '85-older were 2-piece RMS.

So, if the 350 is an '86-up (w/1-pc. RMS) you are good to go using the 305 flexplate if you want.

Regardless of the year or seal type, you can use the 305 torque converter on any type of flex plate, whether it is for a 1- or 2-pc. RMS. In other words, if the 350 comes w/a flex plate, you can bolt up the 305 torque converter w/o any worries. Hopefully I didn't just confuse the issue. And thanks for the earlier message.
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Old 07-02-2010, 02:04 PM
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Quote:
Originally Posted by adantessr
Okay , after much thought and checking I found a great running and great sounding 350 to put in my T-bucket hot rod. It has a standard trans bolted to it now . My question : Is the torque converter off of my '91 Firebird 305 going to work on the 350 ? Or is there a going to be a balance problem ?
You can get into a minor problem with the 350 which goes 2 piece rear seal up thru 1986, after that the rear seal is a 1 piece affair. This change reduces the bolt pattern diameter and adds a slight external balance requirement on the flywheel end of the crank.

If the 350 is an older 2 piece seal unit, it will require a neutral balanced flexplate with the larger crank bolt circle in order to attach a 91 transmission. If the 350 is a newer 1 piece rear seal it will require the small bolt circle flexplate which will have a small amount of counterweight on it.

The bolt pattern for the torque converter is the same for both flexplates, but there are two starter teeth for each type wheel the 153 tooth wheel which is 12.85 inches in diameter and has 10.75 inch converter bolt circle. Or the 168 tooth wheel which is 14.13 inches in diameter and uses either the 10.75 or 12.03 converter bolt circle.

So these are things you need to know about your 305 Firebird tranny to get it connected to which ever crankshaft your 350 has. If your 350 is a one piece rear seal engine, it will bolt you your 91 305 F'bird tranny. If it's a 2 piece seal, you'll have to get a flexplate that matches the crankshaft, your existing ring gear tooth count, and the converter bolt circle. This can be done at any speed shop near you or on-line.

Bogie
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Old 07-03-2010, 06:27 AM
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torque converter ? I mean flexplate

Thanks guys . I was in a hurry and meant to say flexplate . Just one of those senior moments . At any rate thanks for the replies . You both answered my question perfectly . Now I know what I needed to know . Thanks again . I really hadn't worked on cars since 1985 when I went to working on heavy equipment so I am not up to date on the newer auto engines .
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Old 07-04-2010, 10:56 AM
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Quote:
Originally Posted by cobalt327
In addition to DV's info, 1-piece rear main seal engines were '86-up, '85-older were 2-piece RMS.

So, if the 350 is an '86-up (w/1-pc. RMS) you are good to go using the 305 flexplate if you want.

Regardless of the year or seal type, you can use the 305 torque converter on any type of flex plate, whether it is for a 1- or 2-pc. RMS. In other words, if the 350 comes w/a flex plate, you can bolt up the 305 torque converter w/o any worries. Hopefully I didn't just confuse the issue. And thanks for the earlier message.
'87 and up
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Old 07-04-2010, 02:19 PM
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'86 and up
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Old 07-04-2010, 06:14 PM
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La or not to LA

Hey Big Al,
It's possible you got a mild infection of some sort of Mopar Mojo along the line since 84........ It happened to me once. Got onto questions of forged vs cast crank 340 imbalances, then pulled a weighted converter from a 318 further confusing me. Found out it's possible to have a weighted converter or an imbalanced flywheel either one or both for a 360. Couple of odd things for 340s too.

But you're home now......... Back in Kansas...Toto at foot of the bed and Bow ties on the wall. All is well
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Old 07-06-2010, 04:31 PM
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Back in Kansas

Quote:
Originally Posted by Duntov
Hey Big Al,
It's possible you got a mild infection of some sort of Mopar Mojo along the line since 84........ It happened to me once. Got onto questions of forged vs cast crank 340 imbalances, then pulled a weighted converter from a 318 further confusing me. Found out it's possible to have a weighted converter or an imbalanced flywheel either one or both for a 360. Couple of odd things for 340s too.

But you're home now......... Back in Kansas...Toto at foot of the bed and Bow ties on the wall. All is well
THANKS FOR THE GOOD LAUGH . THAT WAS GREAT !
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