OLDS Olds 425 trans?

CleanCutty86

CleanCutty86

Not-quite-so-new-guy
Mar 15, 2020
15
13
What transmission would be good 4 and olds 425?
 
CleanCutty86

CleanCutty86

Not-quite-so-new-guy
Mar 15, 2020
15
13
No verdrive needed. Planned on a sbc but leaning towards rebuilding a 425. Already have a new th350 but guessing thats not going to hold up to it? Plans are to port and polish the original C heads and do a cam job and rods. Still running my 200r4 now. Possibly rebuild it. New to all this so kinda in the dark. Hoping to achieve plus or minus 400hp
 
olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
6,002
113
Melville,Saskatchewan
What was done to the TH350? You can get 400 HP pretty easy. Cutlassefi brought a nice 10cc dish Mahle forged piston with a 1mm ring pack. Along better rods and the right cam, it will haul *ss. The 2004R will probably need a billet forward drum.
 
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CleanCutty86

CleanCutty86

Not-quite-so-new-guy
Mar 15, 2020
15
13
What was done to the TH350? You can get 400 HP pretty easy. Cutlassefi brought a nice 10cc dish Mahle forged piston with a 1mm ring pack. Along better rods and the right cam, it will haul *ss. The 2004R will probably need a billet forward drum.
Nothing was done to the th350 it is a TCI Street rodder New in the box
 
olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
6,002
113
Melville,Saskatchewan
As fleming442 said, it is the most desirable factory crank that exists in any number. Get the aftermarket 7" rods along with the new Mahle piston and go to town. Make sure you run the right bearing clearance. The large 2.5" and 3" journals need more clearance than a SB. There is an argument between Olds experts where that number should be. You can definitely run tighter clearance with aftermarket rods than factory ones. I assume mostly street driven? Also make sure you have a good radiator, a large 2 core is a good idea along with either a 6 or 7 blade clutch fan or high output electric ones.
 
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