Need help identifying a big block

[Mike Harrington]

Howdy, new guy here and I need a little help. I've got a 1989 K3500 with a 454 and manual 4 speed Muncie tranny. The original engine spun a main bearing so I went a bought another big block engine they was used. The guy said it was a 454 and I pulled it out of an 1994 Chevy K2500. I don't think the engine is the original so I looked up the block number and this is where it got interesting....the numbers are 12561359 only that block number doesn't exist in any Chevy database I've looked up. There is a 12561357, and a 12561358 but none with a 59. And it's a very clear casting so it can't be mistaken for an 8. Can anyone give me any info on this engine and what it is? I think it's a mark VI block because the 6 bolt timing chain cover that is aluminum but its also got provisions for a mechanical fuel pump and I thought that none of the Mark VI blocks had that except for one certain casting number. And the casting numbers on the heads are 12562932 which when you look up it says they went to a Mark V crate engine. Any input or info greatly appreciated

 

[Vbb199]

Any idea of bore size?

12561358 is a 502 ci.
12561357 is 454.

454= 4.2500 bore
502 = 4.466 bore

 

[Vbb199]

, roller cam, and plastic timing cover would be characteristics of a gen VI, as well as 4 bolt main.


It's probably a 454, some of the last years of production of a 454 may have yielded.... Weird numbers.

I have heard of this mysterious casting number before

I might be wrong about the plastic cover part. The others I am sure of.

 

[Mike Harrington]

No idea on bore size as I don't want to tear into motor for just that. The timing cover is actually plastic I believe after looking again and it a six bolt cover as well. Pulled valve cover off and it's not a roller engine...or at least the rocker arms are not roller.
My main concern is I need to know if I can use my clutch flywheel off the 89 Mark IV on this engine or not and if the prom from 89 will work for this engine. Also will the TBI setup and electric fuel pump work on this new engine or does it require higher pressure than the Mark IV.

 

[Vbb199]

No idea on bore size as I don't want to tear into motor for just that. The timing cover is actually plastic I believe after looking again and it a six bolt cover as well. Pulled valve cover off and it's not a roller engine...or at least the rocker arms are not roller.
My main concern is I need to know if I can use my clutch flywheel off the 89 Mark IV on this engine or not and if the prom from 89 will work for this engine. Also will the TBI setup and electric fuel pump work on this new engine or does it require higher pressure than the Mark IV.

Are there provisions for roller stuff?
Like pushrod guides?
On my gen VI 502 ci, it's a roller motor, but uses stamped rockers, but provisions are there to make the top end full roller.

Presumably what you have is a vortec 454.
Uses much higher fuel pressure than a tbi 454.
Not sure on tbi 454 psi, but I know a small block is 9-12. It's low in comparison to a vortec 454 which might be 30-40 psi. I don't know exact numbers.


Don't know about clutch setup.
Logic says, if it came off a VI, it'll go on another VI.
However, cranks are setup for manual or automatic transmissions, or "thrust" if you're getting to the nitty gritty. But no one pays attention to that hardly ever. Lol

Seems like you definitely have a VI based off the mysterious number, and characteristics of the engine.

Do you have a pic? Or is it just heads and a block?

 

[Catbox]

I have a VI out in front of the garage.
Perhaps at lunch I can go out there and see what numbers it has on it.
That might be of help...

 

[Bextreme04]

With everything you have said so far, I think you have a goodwrench crate motor Gen V. If your engine came from a 1994, it should be a Gen V. Gen VI didn't start until early 1996 and a replacement engine would have also been a Gen V, even if it was a crate motor. Is the replacement a TBI motor, or is it a MPFI? The intake manifold and throttle bodies look nothing alike, so it should be very easy to tell the difference. If its a TBI, it is 100% a Gen V unless someone swapped to a Gen VI, which doesn't really have any benefit. A factory or crate Gen VI would have hydraulic roller cam and lifters with a zero lash, non-roller valvetrain. Very early 1996 Factory Gen VI blocks may have had non-roller cams and the mechanical fuel pump boss. By late 1996 all factory 454's were Gen VI blocks with roller Cams. My 1997 Gen VI donor motor block is casting number 10237297. It has "7.4" cast into both sides of the block near the freeze plugs and Gen VI on the front of the block under the timing cover, which is aluminum and has 6 bolts. It has no fuel pump boss on the block and the timing cover has a hole at the bottom for the crank position sensor to mount to.

For an answer to your specific question... A Mark IV flywheel will not work for a Gen V OR Gen VI engine, so which one you have is kind of a moot point. The key point is that between Mark IV and Gen V, GM went to a one-piece rear main seal that changed the required external balance weight amount. The Mark IV requires a 33 ounce-inch external weight while the Gen V and Gen VI requires 42.5 ounce-inches(its located at a different spot around the crank also).

Now, you might say "that's not that bad", but 1 ounce-inch of imbalance in the motor will create 31.9 lbs of force imbalance at 6,000 RPM... so an almost 10 ounce-inch imbalance would be a pretty big hammer blow on the engine, and would most likely result in premature engine failure.

 

[bucket]

Plastic timing cover is Gen6. Roller motors still used standard rocker arms.

Like was said, the amount of balance needed on the flywheel is different between markIV and the later engines. Looks like the same location to me, just a different amount of weight.

You must be registered for see images attach

 

[Mike Harrington]

Yes it's a TBI setup on the intake manifold not a vortec. The rocker arms are non adjustable unlike my Mark IV engine. The freeze plugs are 1-5/8 on the new engine unlike the Mark IV block. I read somewhere that the Mark V and VI TBI engines required a higher fuel pressure than the Mark IV engines but I can't find where I read that at.
Ok so if I have to get a different clutch flywheel for the new engine has anyone seen or used the balancer they make for these engines that goes between the block and new clutch flywheel? Supposed you can use a 350 clutch flywheel with this balancer and it allows for quicker rpm's. Also the new one for this 454 is a bit pricey!! Thanks everyone for the input.

 

[Mike Harrington]

Bucket....so it could be a roller engine but have regular rocker arms? I thought a roller engine had roller rocker arms as well as the cam? Or are you just implying that the block could be a roller block with provisions to make it a roller but could still have a hydraulic cam and lifter set up. This is the reason I wish I could find the block numbers somewhere so this kind of info would be easier to find

 

[Bextreme04]

Yes it's a TBI setup on the intake manifold not a vortec. The rocker arms are non adjustable unlike my Mark IV engine. The freeze plugs are 1-5/8 on the new engine unlike the Mark IV block. I read somewhere that the Mark V and VI TBI engines required a higher fuel pressure than the Mark IV engines but I can't find where I read that at.
Ok so if I have to get a different clutch flywheel for the new engine has anyone seen or used the balancer they make for these engines that goes between the block and new clutch flywheel? Supposed you can use a 350 clutch flywheel with this balancer and it allows for quicker rpm's. Also the new one for this 454 is a bit pricey!! Thanks everyone for the input.

The fuel pressure required is not related at all to the block. TBI requires much higher pressure than the carbureted engines did. They never made a TBI using a Gen VI block. TBI was available on Mark IV 454's from 1987-1990 and Gen V 454's from 1991-1995. 1996 switched to MPFI and the Gen VI 454 at the same time. All Gen V TBI engines had Hydraulic flat tappet cams and lifters and non-adjustable valve train. Most Gen VI blocks have hydraulic roller cams and lifters with non-roller rockers and non-adjustable valvetrain. They are not at all "provisioned" for roller rockers. You have to install a whole new valvetrain and pushrod guides to support roller rockers on either a Gen V or Gen VI block. A "Roller Engine" usually refers to the cam and lifter provisions as they are more extensive and require specific parts and work to the block. You need some way to keep the lifters from rotating in their bore, a thrust washer setup on the front of the cam, and a different gear on the distributor among other things to support a hydraulic roller cam.

I have never seen an additional "balancer" that would go between the block and a flywheel. I would not think a 350 flywheel(internally balanced) would work at all on a 454 crank(externally balanced).

Plastic timing cover is Gen6. Roller motors still used standard rocker arms.

Like was said, the amount of balance needed on the flywheel is different between markIV and the later engines. Looks like the same location to me, just a different amount of weight.

You must be registered for see images attach

While they are mostly mounted in the same place, the slightly different shape and cutout size should result in the center of gravity of the weight being shifted slightly more clockwise than the smaller weight.

Also, it's a small thing but they are not a "Mark V" or "Mark VI". Everything after Mark IV switched to "Generation" designations. The big blocks after Mark IV are Gen V- Gen VII when they finally stopped production of the big block.

 

[Mike Harrington]

Bextreme04....https://www.ebay.com/itm/133374136755
This is the balancer I was talking about

 

[Mike Harrington]

Well this engine has a plastic timing cover with 6 bolts, 1-5/8 freeze plugs, which all point to a generation VI block but it has a TBI intake. The valve train under the covers are non adjustable. The casting numbers in the heads are 12562932 which when I looked up state they came on a mark V crate engine. It came out of a 1994 2500 4x4 truck with auto tranny.....but im pretty sure it's not the original engine. The odometer said 252,000 miles and this engine is way to clean for that.... besides if the block is indeed a generation VI then it would have to be a crate engine. This is getting more and more confusing now!!!!

 

[Bextreme04]

Well, any Gen V or Gen VI with a fuel pump boss is a crate engine. The 6 bolt timing cover, regardless of material is a Gen VI. If you have the valve cover off, you can look down the pushrod hole and see if it has roller lifters. You can't see the rollers, but you can see if it has the blocks to keep the lifters from rotating.

This is what the stock chevrolet roller camshaft kit looks like. https://www.summitracing.com/parts/...zbLla9GIAY1lcXkwYfsT4fNtshZwj3NBoCFvEQAvD_BwE

It will have the rectangular plates over each lifter set with the metal spider piece bolted in the middle of the valley and each tang over the middle of a single rectangular piece to hold it down.

It sounds like the original motor in that 1994 went out and the owner just got a Gen VI short block from somewhere and swapped all the original Gen V top end onto it. The Gen V stuff will fit right onto a Gen VI block(mostly) with no real issues. He might have done that just to get the hydraulic roller cam provisions, but he might have just found a great deal on it also.

Bextreme04....https://www.ebay.com/itm/133374136755
This is the balancer I was talking about

That's pretty cool! The link doesn't say whether that is weighted to balance Gen V/VI or Mark IV blocks, if you go that route just make sure to verify which part number matches your engine. That plate basically just makes it so any internally balanced flywheel will work now, that means 396/427 BBC flywheels would also work. I would be careful going to a lighter flywheel that allows it to spin up faster in a BBC truck application. What that really means is you have less inertia to keep everything moving every time you engage the clutch to get moving from a stop. If you are'nt towing or lugging it while off-roading it probably isn't an issue.

 

[bucket]

The fuel pressure required is not related at all to the block. TBI requires much higher pressure than the carbureted engines did. They never made a TBI using a Gen VI block. TBI was available on Mark IV 454's from 1987-1990 and Gen V 454's from 1991-1995. 1996 switched to MPFI and the Gen VI 454 at the same time. All Gen V TBI engines had Hydraulic flat tappet cams and lifters and non-adjustable valve train. Most Gen VI blocks have hydraulic roller cams and lifters with non-roller rockers and non-adjustable valvetrain. They are not at all "provisioned" for roller rockers. You have to install a whole new valvetrain and pushrod guides to support roller rockers on either a Gen V or Gen VI block. A "Roller Engine" usually refers to the cam and lifter provisions as they are more extensive and require specific parts and work to the block. You need some way to keep the lifters from rotating in their bore, a thrust washer setup on the front of the cam, and a different gear on the distributor among other things to support a hydraulic roller cam.

I have never seen an additional "balancer" that would go between the block and a flywheel. I would not think a 350 flywheel(internally balanced) would work at all on a 454 crank(externally balanced).



While they are mostly mounted in the same place, the slightly different shape and cutout size should result in the center of gravity of the weight being shifted slightly more clockwise than the smaller weight.

Also, it's a small thing but they are not a "Mark V" or "Mark VI". Everything after Mark IV switched to "Generation" designations. The big blocks after Mark IV are Gen V- Gen VII when they finally stopped production of the big block.

Yeah, what this ^^^ guy said.

Although my gen V engine has a 6-bolt timing cover, or at least I think it does. I'd have to count them. But it for sure has less mounting bolts than a mark IV engine.