427-454 block compared to 502 block?
Thread Starter
Melting Slicks
Joined: Sep 2002
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From: Union City CA
427-454 block compared to 502 block?
Are they the same outter size specs? THE max bore for the 427/454 is 4.31 and the 502 block must be more than 4.5inches. The point is are they the same I know there not but how much of a difference is their? Is it significant? Also is thier a weight difference? And by how much? Thanks for any info :flag
Le Mans Master
Joined: Mar 2001
Posts: 6,242
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From: Watkinsville, GA and Glen Cove, NY
Re: 427-454 block compared to 502 block? (Light84vette)
The outer dimensions are the same and I would assume the weight is the same but the big difference is the 502 has siamesed bores, no water jacket between them. The max overbore on a 502 non bowtie block would be .060 over or 4.530. You also have the Mark IV to V and VI differences as far as cooling passages and one and two piece rear mainseals. I don't believe there is such a thing as a Mark IV 502 but I could be wrong there.
Burning Brakes
Joined: Jul 1999
Posts: 923
Likes: 164
From: Hudson NH
Re: 427-454 block compared to 502 block? (Light84vette)
Standard passenger Mark IV blocks (2 or 4 bolt; short or tall deck) have a nominal max bore of ~ 4.31" depending upon core shift. GM offered a siamesed cylinder version of the Mark IV called a Bow Tie block that incorporated a 4.50" bore. The Mark IV Bow Tie block is externally identical to the passenger blocks. My 540" is a Mark IV Bow Tie block. Unfortunately GM stopped production of the Bow Tie block w/ the introduction of the Gen V block (and subsequently Gen VI block). These new generation BBC engine cases are not fully interchangeable w/ Mark IV hardware. See table below for specifics.
The good news is the aftermarket has adapted to these new generation blocks and new heads, 2-piece rear main adapters, etc. allow more interchangeability than was originally available.
And both Dart and Merlin offer excellent aftermarket versions of the Mark IV Bow Tie block.
Take care,
Mark
The good news is the aftermarket has adapted to these new generation blocks and new heads, 2-piece rear main adapters, etc. allow more interchangeability than was originally available.
And both Dart and Merlin offer excellent aftermarket versions of the Mark IV Bow Tie block.
Take care,
Mark
Racer
Joined: Aug 2002
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From: Albuquerque NM
Re: 427-454 block compared to 502 block? (ML67)
Back in the heyday of Can AM racing the BBCs would routinely be running as 510 ci of course these were based on the ZL1 block ( sleeved). Keep in mind you can get 120 over BBC pistons and this isnt something new. I surely would do serious block prep before dropping those pistons in. For the gain involved in that kind of overbore it just doesn't pay in my opinion. You can make it in other ways (ie chassis prep). For cost avings I would with the Mark IV there are just so many of them out there and parts support can't be stronger. A good built 427+ BBC will make anyone smile. :cheers:
Thread Starter
Melting Slicks
Joined: Sep 2002
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From: Union City CA
Re: 427-454 block compared to 502 block? (VetteLS6)
I'm thinking 496CID, ANyway do any of the block have cooling problems? Because since the 502 block has the water jackets to the sides instead of being all around like the 427/454 block? :confused:
Racer
Joined: Aug 2002
Posts: 289
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From: Albuquerque NM
Re: 427-454 block compared to 502 block? (Light84vette)
Nothing that a good radiator and pump can't handle. One of the concerns it heat build-up under the hood though in heavy traffic it can lead to perculation. :smash:
[Modified by VetteLS6, 12:28 AM 1/3/2003]
[Modified by VetteLS6, 12:28 AM 1/3/2003]
Thread Starter
Melting Slicks
Joined: Sep 2002
Posts: 2,631
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From: Union City CA
Re: 427-454 block compared to 502 block? (VetteLS6)
So when they put in 454CID in C4's then that means that you could put in a 572CID in a C4 because the two blocks have about the same outter specs and weight. Am I right or wrong??? :confused:
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Thread Starter
Melting Slicks
Joined: Sep 2002
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From: Union City CA
Re: 427-454 block compared to 502 block? (VetteLS6)
No I'm not talking about the new engine that chevy is coming out with. Just a 502 block and you just bore it and stroke it. Maybe get some high flow heads and go with 10.1 compression and get almost 750hp. Then maybe a 200shot on top of that?? OR you could go 8.5 to 1 and run a SC at 15psi to get 1200hp. :thumbs:
Le Mans Master
Joined: Mar 2001
Posts: 6,242
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From: Watkinsville, GA and Glen Cove, NY
Re: 427-454 block compared to 502 block? (Light84vette)
A bowtie short deck block would allow you enough room to bore and stroke to get there, I am just not sure of the limits of these blocks but surely at least a 4.6 inch bore is possible.
Safety Car
Joined: Dec 1999
Posts: 4,148
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From: Roxbury NJ
Re: 427-454 block compared to 502 block? (Light84vette)
A 502 block would not be a good choice if you really want to get to 572 or bigger. With the stock 9.8" deck height, you could have to compromise either the rod length or piston compression height to make everything fit. Most people, including me, build standard deck engines as 540s because everything fits reasonably well and still leaves enough meat in the cylinders for future overbores (maintenance, repairs, etc.) You can go to the max bore and build a 555 or 565, but then one cylinder scratch will trash a $2k block.
Bill, how's the 502 coming? My 540 project has been at a standstill all year (lack of $$ :(), but I hope to get back to it this winter if the '79 sells.
Bill, how's the 502 coming? My 540 project has been at a standstill all year (lack of $$ :(), but I hope to get back to it this winter if the '79 sells.
Thread Starter
Melting Slicks
Joined: Sep 2002
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From: Union City CA
Re: 427-454 block compared to 502 block? (Flareside)
Thans Flareside I never thought of that. SOif my engine ever blows up ( HOpefully never) or something happens to it then I could still overbore it and be safe. SO with a 4.5inch bore and 4.25 stroke I could blow this thing up two times and be safe right? LIke next time go to 4.56 then maybe 4.6 if it happens again?
BUt I dont think it can happen that many times anyway. By the way do BIg BLocks have a more of a chance to emit more toxins than Small Blocks? Say for same compression for both, both fuel injected, and both have a 140CID difference-350 vs 540? :flag
BUt I dont think it can happen that many times anyway. By the way do BIg BLocks have a more of a chance to emit more toxins than Small Blocks? Say for same compression for both, both fuel injected, and both have a 140CID difference-350 vs 540? :flag
Safety Car
Joined: Dec 1999
Posts: 4,148
Likes: 5
From: Roxbury NJ
Re: 427-454 block compared to 502 block? (Light84vette)
Thans Flareside I never thought of that. SOif my engine ever blows up ( HOpefully never) or something happens to it then I could still overbore it and be safe. SO with a 4.5inch bore and 4.25 stroke I could blow this thing up two times and be safe right? LIke next time go to 4.56 then maybe 4.6 if it happens again?
BUt I dont think it can happen that many times anyway. By the way do BIg BLocks have a more of a chance to emit more toxins than Small Blocks? Say for same compression for both, both fuel injected, and both have a 140CID difference-350 vs 540? :flag
BUt I dont think it can happen that many times anyway. By the way do BIg BLocks have a more of a chance to emit more toxins than Small Blocks? Say for same compression for both, both fuel injected, and both have a 140CID difference-350 vs 540? :flag
A standard bore 502 block isn't 4.5", it's 4.47", so you have one extra overbore there. The aftermarket blocks are usually 4.5" stock.
Remember, if you buy a 4.5" block, and want to go bigger, you will have to pay for another bore job instead of just the hone, and your throwing away boring opportunities. Some people think the extra ~10 cubes are that important, other don't, it's up to you.
If I were buying a used engine, and it was at maximum bore, it wouldn't be nearly as desirable.
[Modified by Flareside, 4:01 PM 1/3/2003]
Thread Starter
Melting Slicks
Joined: Sep 2002
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From: Union City CA
Re: 427-454 block compared to 502 block? (Flareside)
Then do you think I should buy a rebuilt 427 Engine like in the PAW in SuperChevy MAg? THen I could just bore and stroke it to 496 and be safe instead of having the fear of buying a block that is already overbored?
If it does blow or I get a clyinder wall scratch I'll replace the engine block with a 502 block or a merlin.
By the way does the Merlin outweigh the 502 block or are they the same outter specs, then same cane be said for outter specs on a 427/454 block and a merling block?
If it does blow or I get a clyinder wall scratch I'll replace the engine block with a 502 block or a merlin.
By the way does the Merlin outweigh the 502 block or are they the same outter specs, then same cane be said for outter specs on a 427/454 block and a merling block?
Le Mans Master
Joined: Mar 2001
Posts: 6,242
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From: Watkinsville, GA and Glen Cove, NY
Re: 427-454 block compared to 502 block? (Flareside)
Joe, I am still in the mode of accumulating parts. I am in the south all winter and the block is sitting in the car in the garage in N.Y. I brought the heads with me and just bought a strip dominator so I will take the Brodix and at least have the heads assembled by a guy here in Atlanta. right now I am trying to figure out how deep I am going to go into Tom's differentials catalogue also. Sorry to hear you are going to sell the 79, as it looks to be a real beauty, but if it hastens the 540 build up so it must go. I will get up there at some point and get the motor out and figure out what to do with the pistons and other machining then. Seems like I will never be driving it again. Bill.
Burning Brakes
Joined: Aug 2000
Posts: 1,211
Likes: 6
Re: 427-454 block compared to 502 block? (69ttop502)
I believe that the 502 block does not come pre-equipped for the attachment of the clutch rod drilled & tapped. This would have to be done if you were using a manual tranny. The 454 Mk VI crate motors have this drilled and tapped already, according to Sallee Chevy (unless I mis-understood their explanation, which is entirely possible.
Also, I've read that the 502's do tend to run a bit hot.
Also, I've read that the 502's do tend to run a bit hot.
