Difference between Mark IV and Gen VI.

[Rocket-J]

I have a GM "Bow Tie" Gen VI motor.
If I replace it with a Dart "Big M" or World Casting "Merlin" (both Mark IV compatable) what parts do I have to buy that will not bolt on the Gen VI block? I know the pan and timing cover are different, how about motor mounts, bell housing, heads, distributor and water pump?
Does Dart or Merlin have a Gen VI compatable block?
Thanks. Al

[Infomaniac]

Gen VI heads will not go on a Dart or merlin
Your cam is different also. In addition to oil pan and timing cover and timing set.
Everything else will work.

[Nucking futs]

Cranks are differant too i think.

[Infomaniac]

Cranks are differant too i think.
Yep LOL I forgot to mention that one. One piece rear seal cranks in the Gen V and VI.
You can put a Gen IV crank in them with an adapter. But cannot put the 1 piece seal cranks in the Gen IV

[Oldsquirt]

Aren't the "Bow Tie" versions more Mark IV-like? I thought they used 2-piece crank seal setup, Mark IV water passages in deck, etc, unlike the "production" Gen V and Gen VI.

[Infomaniac]

I have not seen a Bowtie MK VI but my engine is a Bowtie MK V. It has all the same features as a production MK V. I would assume the Gen VI Bowtie is the same.

[Oldsquirt]

You're right, Info, GM lists the "Bow Tie" as a Gen V not a Gen VI.
Hey Al, got any casting numbers?

[Rocket-J]

Yes I do. Casting number 10237300 is part number 10237292.
Depending on what web site you are looking at. Gen V is also call Mark V. Gen VI has some changes over the V but most everthing will swap.
I want to buy a "short block" so I am not concerned about the crank, rods, pistons etc. I just want to bolt all the parts from my Gen VI Bow Tie to the new short block. Al

[Infomaniac]

HTM used a lot of Edelbrock heads. They will go on the Dart or Merlin. Do you have iron heads? If so you are stuck with the bottom end. Is it trashed?
Bowtie stuff is good stuff.
The cam and timing set is the only real diff between MK V and MK VI. MK V uses a timing cover bolt pattern of MK IV but mates to a MK VI pan.
Anyone confused yet? LOL

[SmokinLowriderSS]

I am! So is my Mk IV. :D

[Rocket-J]

Hi Info.
Yes I have Victor CNC Chapman ported aluminum heads. 2.33' intakes. The bore is 4.530", stroke is 4.375". A better combination for the 565cid motor is 4.600" bore and 4.250" stroke. GM does not recomend boreing the Gen VI beyond 4.500". Dart Big "M" can go 4.650". I need to stay with a 9.8" deck to fit under the hatch cover and line up on my exhaust outlets. Al

[cyclone]

I have a GM "Bow Tie" Gen VI motor.
If I replace it with a Dart "Big M" or World Casting "Merlin" (both Mark IV compatable) what parts do I have to buy that will not bolt on the Gen VI block? I know the pan and timing cover are different, how about motor mounts, bell housing, heads, distributor and water pump?
Does Dart or Merlin have a Gen VI compatable block?
Thanks. Al
very different. in addition to what everyone else has mentioned.. gen v and VI blocks dont have a provision for a mechanical fuel pump. So you'll have to go electric.
Dart and Merlin are gen IV based blocks.

[Infomaniac]

Hi Info.
GM does not recomend boreing the Gen VI beyond 4.500".
That does not apply to the Bowtie block. It will go as far as a Dart or Merlin.

[Squirtin Thunder]

very different. in addition to what everyone else has mentioned.. gen v and VI blocks dont have a provision for a mechanical fuel pump. So you'll have to go electric.
Dart and Merlin are gen IV based blocks.
Unless you have a Raw Water Pump mounted fuel pump

[Rocket-J]

No problem on the fuel pump. I am all electric.
Info. Did you or someone tell me that the Gen VI did not come as a "Bow Tie"? Al

[Rocket-J]

Info,
My block started out as the 502 pn 10237292. It is not the tall deck pro block. I know what block you are talking about, but that is not mine. Al

[Oldsquirt]

Al, GM Performance Parts only lists two "Bow Tie" BBC. They are the CNC ProStock 9.8 and 10.2 deck height and are described as being Gen V based. The number you have doesn't mention "Bow Tie" but is a "Gen VI".

[Rocket-J]

I found that also. I am looking now at the Sportsman Block pn 2553463 with one piece main seal. It looks like it may be the replacement that I need. Does anyone agree? Is this block totally interchangable with pn 10237292? Al

[Oldsquirt]

Al, I just found the listings for the new "sportsman" block as well over at the Scoggin-Dickey website.
You might try calling Fitzpatrick Chevy here in Concord. They are a GMPP dealer and have always been helpful to me. They have a huge warehouse of crate engines, blocks, etc.

[Infomaniac]

I've taken those Gen VI no more than 4.500 to 4.560 with no problems.

[Rocket-J]

Thanks Oldsquirt, Info and others who helped.
GM's Sportsman Block pn 25534363 is the new series Bow Tie block that interchanges with the Gen VI pn 10237292. I found it at Fitzpatrich Chev. Thanks Oldsquirt for the heads up. :D
Now I have exactly what HTM said they sold me for $25,000, not a bored out 502. Can't always assume you get what you pay for. It will bite them in the axx sooner or later. :jawdrop: Thanks again guys. Al