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Discussion Starter #1 (Edited)
I am looking at a complete, supposedly running gen 5 454, casting# 10114182, which is a 4 bolt block, with ,i am sure, cast internals. The engine is complete from throtle body to pan and fan to flex plate, including wireing harness and computer.
I am looking at this engine, to hopefully put in the boat, just to get back on the water for this season. The guy is wanting $480 and i am sure i can get it for $400. I was looking at the same engine, at my local junk yard, for $800+ tax.They are wanting $1000+ tax for a mark iv, at the junk yard!
I have a few questions about the difference between the mark IV and the gen5 engines.
I know the gen 5 has no fuel pump boss and i would have to run an electric fuel pump.

My main concerns are the oil pan and intake manifold/ carberator.
Would it be safe to run the stock oil pan or is it imperative to run a bigger oil pan.

Is there a difrence in intake manifold fitment, between mark iv and gen 5?
If not, how would a tunnel ram w/ two 600cfms work on a bone stock 454 truck engine? If not so good what might a good intake and carb be for a stock 454?

Are the front and rear bolt patterns the same between the mark iv and gen5? would my mark iv engine plates, fit the gen5?

Any thing else I need think about to just stick the engine in the boat and run it?
 

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I am looking at a complete, supposedly running gen 5 454.
I am looking at this engine, to hopefully put in the boat, just to get back on the water for this season. The guy is wanting $480 and i am sure i can get it for $400. I was looking at the same engine, at my local junk yard, for $800+ tax.
I have a few questions about the difference between the mark IV and the gen5 engines.
I know the gen 5 has no fuel pump boss and i would have to run an electric fuel pump.

My main concerns are the oil pan and intake manifold/ carberator.
Would it be safe to run the stock oil pan or is it imperative to run a bigger oil pan.

Is there a difrence in intake manifold fitment, between mark iv and gen 5?
If not, how would a tunnel ram w/ two 600cfms work on a bone stock 454 truck engine? If not so good what might a good intake and carb be for a stock 454?

Are the front and rear bolt patterns the same between the mark iv and gen5? would my mark iv engine plates, fit the gen5?

Any thing else I need think about to just stick the engine in the boat and run it?
Are you certain it's a Gen 5 and not a Gen 6? Gen 6 is more desirable as far as something you might possibly want to build later, in that improvements were made to make it more compatible with aftermarket and early heads.

The engine will bolt in place. I just sold a Dooley pan for a Gen 5/6, have a couple of others. You might get away with the stock pan for just mild cruising. Wouldn't be my first choice since there is not much in the way of oil control.

The intake manifold fit is the same as well. I guess it's hard to spend money on pan and intake for something that is just "temporary". My first boat years ago I put a couple of cheap engines into it after I had wounded my good 427, ran a 402 until it blew and then some cheapy 454. Looking back I guess they were better than sitting home.
 

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Discussion Starter #4
Are you certain it's a Gen 5 and not a Gen 6? Gen 6 is more desirable as far as something you might possibly want to build later, in that improvements were made to make it more compatible with aftermarket and early heads.

The engine will bolt in place. I just sold a Dooley pan for a Gen 5/6, have a couple of others. You might get away with the stock pan for just mild cruising. Wouldn't be my first choice since there is not much in the way of oil control.

The intake manifold fit is the same as well. I guess it's hard to spend money on pan and intake for something that is just "temporary". My first boat years ago I put a couple of cheap engines into it after I had wounded my good 427, ran a 402 until it blew and then some cheapy 454. Looking back I guess they were better than sitting home.
Barry, the casting numbers say it is a 4 bolt gen 5 block. I have physicly looked at the engine and there is no provision for a fuel pump.

My only thinking is that this would get me on the water , relatively inexpensivly, untill I can get my engine put back together, as long as I dont have to put alot of coin into an intake/carb and pan.
I have not come accross any gen 6 and not many mark iv's that they dont want a lot of money for.
 

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Discussion Starter #5
Front and rear bolt patterns are the same
The manifold will fit, but I think the T ram will run like shit with the stock cam. A dual plane from E bay and one of your 600s will probably work better.
The oil pan could work, but you might see a pressure drop when you de-accel.

You will need the balancer and flex plate from the Gen5
Bob, the balancer and flex plate are still on the engine.
 

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Barry, the casting numbers say it is a 4 bolt gen 5 block. I have physicly looked at the engine and there is no provision for a fuel pump.

My only thinking is that this would get me on the water , relatively inexpensivly, untill I can get my engine put back together, as long as I dont have to put alot of coin into an intake/carb and pan.
I have not come accross any gen 6 and not many mark iv's that they dont want a lot of money for.
Know what, you could try it with your tunnel ram and easy enough to swap manifold in the boat if you had to?
 

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Production Gen 6s don't have a fuel pump boss either. Only Gen 6 over the counter service replacement and crate engines have fuel pump bosses.
The easiest way to tell a production 5 from a 6 is the timing cover. 5s have 10 bolt covers and are steel, 6s are plastic, and have 6 bolts

I find it funny that the 5 gets all poo pooed because of a fuel pump boss, even from people that don't run a mechanical pump, and for the head decks, even though virtually all after market heads seal just fine. Seems like the 5s are a steal if those are the biggest reasons for trash talking them compared to a 6



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Discussion Starter #8 (Edited)
Production Gen 6s don't have a fuel pump boss either. Only Gen 6 over the counter service replacement and crate engines have fuel pump bosses.
The easiest way to tell a production 5 from a 6 is the timing cover. 5s have 10 bolt covers and are steel, 6s are plastic, and have 6 bolts

I find it funny that the 5 gets all poo pooed because of a fuel pump boss, even from people that don't run a mechanical pump, and for the head decks, even though virtually all after market heads seal just fine. Seems like the 5s are a steal if those are the biggest reasons for trash talking them compared to a 6
I did not know that part about the timing covers, i will check that tomorrow.
I also did not know the 6's did not have a provision for a fuel pump. I thought that they brought back the fuel pump boss on the gen 6.
I did look at and write down the casting # which is 10114182. That casting number identifies the block as a 4 bolt gen 5.
Depending on whose site you look on, it also identifies it as a tall deck, but i am sure it is a 9.8" deck block?
is there any reason not to trust the casting numbers. engine is also out of a Suburban.
 

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I did not know that part about the timing covers, i will check that tomorrow.
I also did not know the 6's did not have a provision for a fuel pump. I thought that they brought back the fuel pump boss on the gen 6.
I did look at and write down the casting # which is 10114182. That casting number identifies the block as a 4 bolt gen 5.
Depending on whose site you look on, it also identifies it as a tall deck, but i am sure it is a 9.8" deck block?
is there any reason not to trust the casting numbers. engine is also out of a Suburban.
They only brought the pump boss back in over the counter blocks and crate engines.
If you know it came from a Suburban, then it is not a truck engine.


You can also ID Gen 6 by the factory roller lifter setup in the valley, and slightly revised deck water ports.
This is a factory roller Gen 6 with no pump boss.
Ignore the monkey sounds:wink2:

Westech Performance 496 Chevy Big Block Build Gm Gen Vi Big Block Photo 2



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Production Gen 6s don't have a fuel pump boss either. Only Gen 6 over the counter service replacement and crate engines have fuel pump bosses.
Another exception to that is Gen 6 tall deck blocks, I put one together a few years back(and have photos). It also has the oil port on the block above the timing cover.
 

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Discussion Starter #11
Well i am thinking, if i can get it for $400 or less, i am going to go ahead and pick the thing up, if not for nothing more than a spare rebuildable core.
Rare to find a big block, of any generation, around here for that price.
Like I said the wrecking yard is wanting $800 plus tax for the same exact engine.
 

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Dual plane air gap intake for a stocker

The gen 5 & 6 use a different intake gasket which are held in place by the head gaskets and notched for the valley tray,with no exhaust port cut into it for the thermostat choke. The automotive head gaskets runs too hot and will have to be changed to marine type..use only gen 5/6 head gaskets... even if you run after market heads..The mark 5&6 share the same oil pan but won' t work on a 4. Good idea to replace the auto pan to a larger marine pan...Gen 6 heads have 7/16 hole in the front of the castings, as the 4 uses 3/8 and I think the 5 has two 7/16 and one 3/8 so you might have to drill any accessory brackets that mount to the heads.
 

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Discussion Starter #14
Aside from the camshaft and crankshaft, are there any diffrences between the internals of a mark iv, gen5 and gen6?
 

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I would not hesitate at $400 for a complete motor

I run a Gen-V using 781 heads with all Mark 4 valve train & cam components from a Mark 4 donor motor. Dooley 10qt. Gen-5 pan and the stock timing cover. Dual plane GM performance intake.

The Gen 5 rockers, guide plates, push-rods and studs are different from other generations. They are non adjustable and use a funky stud. Mark 4 cams bolt right in and I believe I used the donor timing set as well. It is important to check the water passage fitment when using stock Mark4 GM heads as some are very close to not sealing well. I had a little over 1/8th overlap and it has not leaked in 8 years now without a tear down and poor winterizing habits. I believe I used some Mercruiser head gaskets but they could be Detriot Gasket 59354HG. I have both in boxes on the shelf and don't remember any more. There are also rear seal adapter kits if you choose to run a 2 piece seal crank shaft.

One issue to pay close attention to is the oil filter adapter and the bypass system used. There is only 1 right way and a few wrong ways depending on if you use a remote filter with a cooler etc. Just be aware things are in proper order.
 

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Add to the above.
All Gens are 4 bolt. Not all oil pumps will work with Gens, but all oil pumps will work on MKIV. The inside main cap bolts are longer(the cap is taller) and the bolt head on the rear main of the Gens can interfere with some oil pumps.
All Gen 6 are roller cam, and require different rollers than IV and 5s. The lifter bores are about .300 taller than MK and 5s. Flat tappets work fine in either.
Cams from either will work in either, but you need to know what changes you need to do to make them work. 5 and MK cam interchange, 6 cams in MK blocks, and MK cams in 6 blocks require mods.



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One difference that is important is the gen 5 & 6 use a small o ring between the block and rear main cap to seal the oil galley ...but not the IV...
 

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The gen5 -6 use a 1 piece rear main, cranks are different then the mk 4's.
Ah come on Futs, keep up. The OP already mentioned that. :D
One difference that is important is the gen 5 & 6 use a small o ring between the block and rear main cap to seal the oil galley ...but not the IV...
You have some funny ideas what a Gen 6 requires. Like intake gaskets and marine head gaskets or it will run too hot. In a lake full of cold water?
This O ring? What happens if you leave it out? How did MK IV work without it? Anybody see anything odd about this picture?
gen 6 oring.jpg



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