OLDS Possible olds 425 engine purchase

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Ima disagree on the restrictors. Either put it in and run it as is, or offset grind the crank to 4.25 and stick it in a 455 block with some bore. CP Bullet "496" pistons on 7.2 rods in my 468 are a magical combination. The 425 crank is steel; that's your biggest asset.
Yes, most Olds guys have moved away from the restrictors. The stock rods are soft but the light Mahle pistons will help. The aftermarket 7" rods are a very good upgrade, allow tighter clearances and way harder.
 
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My opinion on the heads.....
Don't waste your time on the B iron. Get a set of Edelbrock Aluminum at minimum. For the price you'll pay to change seats, guides, port, you'll do better getting aluminum. Regardless if you want a street or race motor.
Just saying. Can I get an amen?
 
My opinion on the heads.....
Don't waste your time on the B iron. Get a set of Edelbrock Aluminum at minimum. For the price you'll pay to change seats, guides, port, you'll do better getting aluminum. Regardless if you want a street or race motor.
Just saying. Can I get an amen?
Amen Brother! Procomp heads worked over a bit with quality components, also fit. Otherwise they flow only slightly better than big valve iron heads and have similar 83-84cc chambers. Not only do the latest Edelbrock heads flow 264 CFM on the intake side but also have a 77cc heart shape combustion chamber with a much better central angled to the exhaust side, long reach spark plug. Both heads have a raised floor, better flowing exhaust port as well. Edelbrock flat tappet valve spring heads have also dropped in price recently.
 
Ima disagree on the restrictors. Either put it in and run it as is, or offset grind the crank to 4.25 and stick it in a 455 block with some bore. CP Bullet "496" pistons on 7.2 rods in my 468 are a magical combination. The 425 crank is steel; that's your biggest asset.

What is the difference between a 425 and 455 block?
 
What is the difference between a 425 and 455 block?
Isn't the cam bank angle the main difference? The early vs late block strength is a myth and it is a block by block basis of wall thickness.
 
Lots of inaccurate info here except from a few. Let me correct the myths.
1) Don't bother with the restrictors, they don't work and waste of money
2) The only reason a 425 will "rev higher" than a 455 is because, apples to apples, with the same intake, cam, and heads, the 455 will run out of breath sooner because of the increased demand for air from the larger engine.
3) To make even 500hp from this combination you'll need very good heads, more cam, a good intake and at least headers and sizable carb. And if you're going to make any amount of power pitch the rods and pistons and buy new, modern ones.
4) The balancer AND timing tab are different. But you can use a later model timing tab and new balancer with no issues. In addition there are many offerings for universal bolt pattern flexplates as well.
5) And finally, getting cams for a 45* block isn't a problem, even a Hyd. roller. I actually prefer that bank angle as the lifter is in a more vertical position.

I'm the one that brought the Mahle piston for these to market. I offer cams and other pieces as well. I also have 428-434 c.i. stroker kits for Small Block Olds engines.

Thanks.
 
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Amen on the heads. I've got a pair of Ga heads and a couple pairs of C heads. Ratter than the cost of prepping any of them, I'll be buying ProComps for my 425. Better than stock heads in every way and really pretty reasonable for price.
olds307 and 403 , who was it that was building out the bare Procomp castings with good parts? Was it Cutlassefi?
 
If it doesn't need a ton of machine work, it's worth it. The original heads were made for leaded gas and won't like unleaded gas. You can install hardened seats or install later year heads for a 455 built for unleaded gas.
 
Just learned my machine shop closed its doors as of Jan 1st this year. I'm on the hunt for a new shop.

So the procomp heads are good or need modified to be good? Price seems reasonable if the original heads will need that much work to get right for my 500 hp goal.

What compression ratio will be needed to make the 500 hp goal?
 
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