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Hey guys ,

I need some technical information .
My 403 Olds engine is having a rebuild/clean up at the shop today here in Belgium and the Keith Black pistons will be used with an .024 overbore
They are gonna give me 9.5 compression with my stock heads .
I think with some other parts ( cam , intake , headers , ... ) around 400 hp
I have read that when you use a halo support girdle , you don't necessary need a forged steel crankshaft to hold up with the extra Hp .
Is this true ? Because , ok , it's an extra investment of a 1000 $ when the crankshaft is here in Belgium ,
but I don't want to crack my stock iron crankshaft either !

Please advice ,
Thanks
Tommy
 

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At 400 hp you dont need the forged crank. If you were looking for 500hp and constant rpm in the 6000+ range, you should consider it, but under that its not neccesary. Olds nodular iron cranks are quite strong. run the girdle, you wont have any issues.
 

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Old(s) Fart
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FYI, all Olds small block gasoline engines from 1964 to 1990 use the same stroke and bearing sizes. The forged crank from a 1964-1967 Olds 330 motor drops right in to a 403. Of course, you'll need to rebalance and the crank flange has a different bolt pattern so you need to use a 64-67 flywheel, but these cranks are available on e-bay for about $100 or so.
 

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TommyV_11 said:
I have read that when you use a halo support girdle , you don't necessary need a forged steel crankshaft to hold up with the extra Hp .
Is this true ? Because , ok , it's an extra investment of a 1000 $ when the crankshaft is here in Belgium ,
but I don't want to crack my stock iron crankshaft either !
The main girdle or halo is to keep the bearing caps from "walking" and causing bearing distortion and main bearing bulkhead movement. But I suppose it's a matter of wording- the crank could be said to have been protected by using a halo, by default.

If you're only at the 400 HP level, I'd use studs and Dick Miller #5946 main cap straps. The girdle (at least Miller's) needs pan work and other machining to fit it properly- he (Dick Miller) has a set-up that's strong (see example below, prob. a 455 w/4-bolt mains) but it's $1500.00.

Thing is, this is what's required for one to actually tie everything together and not just look like it's doing something- all the surfaces have to be flat and square to one another, or else strength is lost. This is overkill at the 400 HP level.

On the other hand, if the reciprocating assembly is balanced, and the main bearing caps are machined flat on top and held down w/ARP studs and the 1/2" steel straps, there's less machining that has to be done, and while it's not as strong as a full halo, it's plenty strong enough for 400 HP, IMHO.
 

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