When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I just bought a 425 I was looking for just a 455 block but didn't pass on a deal. The guy took it apart all part and was in great condition and put back in one piece. I know the Chevy 454 vs the 427 the 427 is the best and Pontiac a 455 vs a 428 the 428 will out run a 455. Even a olds 455 vs the 425 the 425 will out run a 455 Olds. All cams and intake and carbs being the same. What are the views on a 425 Olds motor ?
Gerald
PS
My brother runs a 425 parts in a 455 block for better cam selection never blows a engine.
I just bought a 425 I was looking for just a 455 block but didn't pass on a deal. The guy took it apart all part and was in great condition and put back in one piece. I know the Chevy 454 vs the 427 the 427 is the best and Pontiac a 455 vs a 428 the 428 will out run a 455. Even a olds 455 vs the 425 the 425 will out run a 455 Olds. All cams and intake and carbs being the same. What are the views on a 425 Olds motor ?
Gerald
PS My brother runs a 425 parts in a 455 block for better cam selection never blows a engine.
1. I think the 455 block has the 39 degree lifter angle........the 425 can have 45 or 39 degree lifter angle. The 39 degree cams are much more available in any grind.
2. The 425 is a shorter stroke engine but same bore as.455. I would think the 425 will buzz up in RPM's well. The 455 longer stroke has more "swinging mass".
3 The 455 will have more torque.
......Just my two cents worth
Ralph has pretty much nailed it. All 425 cranks are forged. Nearly all 455 cranks are nodular cast. Piston compression height is different, along with rod length. 425 rods are 7.000", 455 rods are 6.700". Other than the lifter bank angle, they are pretty much the same. You can swap the reciprocating assembly from one into the other.
Ralph has pretty much nailed it. All 425 cranks are forged. Nearly all 455 cranks are nodular cast. Piston compression height is different, along with rod length. 425 rods are 7.000", 455 rods are 6.700". Other than the lifter bank angle, they are pretty much the same. You can swap the reciprocating assembly from one into the other.
Except you both omitted one thing, every 425 block I’ve ever seen had a shorter cylinder length than the 455. Not an issue unless you’re going to stroke it beyond the 455’s 4.25” stroke.
Except you both omitted one thing, every 425 block I’ve ever seen had a shorter cylinder length than the 455. Not an issue unless you’re going to stroke it beyond the 455’s 4.25” stroke.
Fair point, Mark. I was thinking of swapping OEM parts, not stroking it even further.
Heavy cars need the torque more than they need the higher RPM limit.
A longer-stroke engine can be faster/quicker than a shorter-stroke engine depending on weight, gearing, tire size, etc. The shorter-stroke engine is not automatically "better".
Location: Colorado Springs Colorado/Thousand Oaks Ca
Posts: 1,722
On my next Olds engine build I'd like to try a 425 myself.
" Heavy cars need the torque more than they need the higher RPM limit"
I think that depends on what the car is used for, and how the car is setup, An Oldsmobile is aways cylinder head limited, small bore, which demand small valves, combined with small cross sectional port area, IMO the shorter stroke could help, I'd like to find out.
Last edited by VORTECPRO; March 30th, 2021 at 06:40 AM.
IMO the shorter stroke could help, I'd like to find out.
Dude it ain’t rocket science(no pun intended), it’s simple physics. If you have limited induction capability as you mentioned, guess what, a smaller engine will spin higher because it’ll take longer to use up the available air. I’ve pointed that out on here a hundred times.
Example, 30 years ago when NASCAR started with restrictor plates, the teams immediately went from 358ci engines to 331’s in the hopes of keeping the revs up. NASCAR said no-no and made them go back to 358’s.
I my self and my Brother Ron Nickels race the 425 for years and like it better than a 455. I raced my 70 W-30 455 with a 73 Mopar 440 I out ran him till I reached the 1/4 on the street and ran out of engine then the 440 just keep passing me up after I was done in RPM's. Think out a 427 Chevy and 427 Ford and a 425 Olds don't you think they are better for racing than a 454 Chevy 460 Ford and a 455 Olds or Pontiac ? My Brother runs a .060 over bore 455 Olds block with 425 pistons rods and crank.
Gerald
Location: Colorado Springs Colorado/Thousand Oaks Ca
Posts: 1,722
Originally Posted by Gerald Nickels
I my self and my Brother Ron Nickels race the 425 for years and like it better than a 455. I raced my 70 W-30 455 with a 73 Mopar 440 I out ran him till I reached the 1/4 on the street and ran out of engine then the 440 just keep passing me up after I was done in RPM's. Think out a 427 Chevy and 427 Ford and a 425 Olds don't you think they are better for racing than a 454 Chevy 460 Ford and a 455 Olds or Pontiac ? My Brother runs a .060 over bore 455 Olds block with 425 pistons rods and crank.
Gerald
A 440 head is similar in flow to a Olds, but heres the difference, a 440 bore is bigger which allows bigger valves, advantage Mopar. A production 440 head worked over can flow around 290 CFM @ 28 inches, same with a production Olds head, but both have a small cross section. Now when you look at a BBC production head worked over now your looking @ 380 CFM, with a much bigger cross section, which will support bigger than 427 cubic inches. When I think about a 425 Olds with a production Olds head I can't see why it wouldn't run similar to a 400 SBC which would run hard with a 290 CFM head. My 71 Buick is a prefect test bed for a engine like that. Always looking for a virgin 425 core.
A 440 head is similar in flow to a Olds, but heres the difference, a 440 bore is bigger which allows bigger valves, advantage Mopar. A production 440 head worked over can flow around 290 CFM @ 28 inches, same with a production Olds head, but both have a small cross section. Now when you look at a BBC production head worked over now your looking @ 380 CFM, with a much bigger cross section, which will support bigger than 427 cubic inches. When I think about a 425 Olds with a production Olds head I can't see why it wouldn't run similar to a 400 SBC which would run hard with a 290 CFM head. My 71 Buick is a prefect test bed for a engine like that. Always looking for a virgin 425 core.
since you mention chevy head flow .what is the peanut port head referring to?and what type of flow numbers would they give .this may be off topic here and i apologize ,but i know nothing about chevy heads
Location: Colorado Springs Colorado/Thousand Oaks Ca
Posts: 1,722
Originally Posted by deadeyejedi
since you mention chevy head flow .what is the peanut port head referring to?and what type of flow numbers would they give .this may be off topic here and i apologize ,but i know nothing about chevy heads
A BBC peanut port head is a 1974-1989 small port smog head used on trucks, typically they will flow in the 230 CFM @ 28 inches bone stock, many people talk very bad about this head and say never use this head. My ported street peanut port heads flow around 306 @ .550 lift @ 28 inches after porting with a 2.190 intake valve.
Last edited by VORTECPRO; April 2nd, 2021 at 05:45 PM.
A BBC peanut port head is a 1974-1989 small port smog head used on trucks, typically they will flow in the 230 CFM @ 28 inches bone stock, many people talk very bad about this head and say never use this head. My ported street peanut port heads flow around 306 @ .550 lift @ 28 inches after porting with a 2.190 intake valve.
March 28th, 2021, 10:55 PM
