Yellow Bullet Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
5,575 Posts
Discussion Starter · #1 ·
Looking at putting some of my parts I have laying around. Assembly should be right at 800Hp mark and was wondering what you guys think would be the better block,

Gen IV or Gen VI, all thinks being equal, .030 over and hard blocked to bottom of waterpump holes.

Gen IV 361959 older block but not sure if these would be stronger. 2 bolt block as of now.

Gen VI 10237297 standard deck as well, BUT I like the priority main oiling these have. And is OEM 4 bolt main.

THOUGHTS?????? I am leaning towards the Gen VI but does these block require any special of GEN VI only stuff like the Gen V's (cranks, rods, heads, cams etc)?

Thanks John
 

·
Registered
Joined
·
295 Posts
I've been running Gen VI block for nearly 15 years now, roots boosted @ 10 lbs about 850 hp. No problems.
Besides what's already mentioned, watch what head gasket you use on it (especially if you go to an aftermarket head) - the coolant flow is a little different.
Front timing cover is different - you'll need to change it to run a double roller chain - cam uses a thrust plate to control end play.
 

·
Registered
Joined
·
3,093 Posts
I would go with the GenVI block for all of the above reasons. Maybe I would sonic test both blocks and let that be my deciding factor. Thickest cyl wall for the win.

I have been shopping for a GenVI 502 block for quite some time. They are hard to come by. I want to build a street 4.5 bore engine.
 

·
Registered
Joined
·
979 Posts
I've been running a gen VI block making around 800 on motor and 1100 on nitrous in my river boat for some time and it has been no problems to me. I'd run the VI
 

·
Registered
Joined
·
2,379 Posts
I've been Using a Mark 4 block (IV) and I am over 1000hp with it and no issues at all. Coolant passages still stock, and will work and interchange with tons of parts. Either block will work well, just depends on what extra parts you have laying around vs what you will need to build the Gen VI. Just my 2cents.
I have the high nickel block also.
 

·
Registered
Joined
·
260 Posts
Mark V1 has .300 higher lifter bores that is a plus. They both are a 1 pc. rear seal . Go with the 6
Had to put my glasses on thought you said Mark V and Mark VI
It would be nice if the Mark VI is a bow tie block.I have a Mark V Bow Tie and the cylinder walls sonic tested very thick. 4.600" bore no worries at 15 - 1 compression.I had many Mark IV 's also all were Bow Tie blocks. 400 - 1150 Hp.
 

·
Registered
Joined
·
5,575 Posts
Discussion Starter · #8 ·
YES I too am leaning towards the 6. It will only be .030 over and just a mild street motor, nothing too radical.

Thanks for your input.
 

·
Registered
Joined
·
295 Posts
Can I use my solid gen IV cam in this block?????
You can use the cam but not the lifters -- Gen VI lifter bores are .300" taller. You'll need a different front cover to run a double roller chain -- or machine the stock cover for clearance.
I believe Comp Cams makes an aftermarket cover for Gen VI.
I bought a machined out stock cover from Scott Schafiroff about 15 years ago - not sure if they still do that.
 

·
Registered
Joined
·
13,484 Posts
it is all a matter of what you can affford and the power level..
just had a gen six that cracked on the OUTSIDE of the block just below the head deck surface in between the two center cylinders..

there is no safe mannor to secure it even with pins or reverse twistspiral hook type plugs.. but just to get by, I may spray weld to get thru the end of season untill the guy saves his pennies to get a aftermarket block..

....I have seen quite a few others that seem to have thin spots here too as well as the well known issue with the rear cylinders being thin in the rear back side....
 

·
Registered
Joined
·
979 Posts
You can use the cam but not the lifters -- Gen VI lifter bores are .300" taller. You'll need a different front cover to run a double roller chain -- or machine the stock cover for clearance.
I believe Comp Cams makes an aftermarket cover for Gen VI.
I bought a machined out stock cover from Scott Schafiroff about 15 years ago - not sure if they still do that.
Or use a jesel and use any cam stepped nose or std chevy
 
1 - 12 of 12 Posts
Top