Big block guy's ...

[GuysMonteSS]

My buddy has a 94 or 95 Gen 5 454 BBC,looks to be in decent shape except for the cam bearings.Heads are oval port casting # 12562932.Apparently there is only 28,000 miles on it.The crank,rods and pistons are still in the block and from what I can see in pictures the cylinders look to be OK.
I dont know much about the Gen V,mostly just the Mark IV.
He would like 500 HP at the flywheel and he would like to keep the heads if possible,and do it on a budget I'm sure...
Any suggestions ??
Guy

 

[pagrunt]

The Gen V is just an improved/revised Mark IV. I can't recall the changes but the strenth will be there. I think most of the changes was with the heads & the deck. There is still a bit of interchange with the Mark IV, Gen V, & Gen VI. If you understand the Mark IV you shouldn't have any issues understanding the Gen V. For 500 horses, I might look at aftermarket heads for better flow for a start. If the cam bearings are shot, do a complete tear down to ensure nothing traveled thru the block. The block should be hot tanked to ensure everthing is cleaned out.

 

[565bbchevy]

Gen 5: General Motors made substantial revisions to the Mark IV engine, and the result was christened "Gen 5" when it was released for the 1991 model year as a 454. There were 502 cu. in. versions, but never installed in a production vehicle, the 502's were over-the-parts-counter only. Changes to the Gen 5 as compared to the Mk IV included, but are not limited to: rear main seal (and therefore the crankshaft and block) were changed to accept a one-piece seal, oiling passages were moved, the mechanical fuel pump provisions were removed from the block casting, the machined boss for a clutch bracket was eliminated, the cylinder heads lost the ability to adjust the valve lash, and the coolant passages at the top of the cylinder block were revised. The changes to the coolant passage openings meant that installing Mk IV cylinder heads on a Gen 5 block could result in coolant seepage into the lifter valley. Frankly, the changes (except for the one-piece rear main seal) were all easily recognized as cost-cutting measures which also removed some quality and/or utility. All told, the Gen 5 engine was not well regarded by the Chevy enthusiasts because of the changes to the coolant passages and the lack of an adjustable valve train. As always, the aftermarket has provided reasonable fixes for the problems. The Gen 5 lasted only until 1995.

This was copied from YellowBullet

 

[L67ss]

I would ditch the heads. Tiny ports

 

[Bar50]

500 HP would be easier with a known good flowing set of heads. Big oval ports heads like the -049 and -781 with big valves flow like gang busters. A 496 kit would make it much easier. Or, higher compression pistons.

I forgot about the clutch pivot....

 

[GuysMonteSS]

Thanks for all the info.
It almost sounds like the Gen 5 is a bit of a lemon.
Can the 049 or 781 heads be made to work on one of these shortblocks ??
Maybe a set of one of those heads and a cam swap would be all that is needed ???
Guy

 

[565bbchevy]

Can the 049 or 781 heads be made to work on one of these shortblocks ??

They bolt right on but you need the correct head gaskets so the water ports don't leak. I know Fel Pro makes them and probably a few others.

 

[Bar50]

If you are open to a head swap, look for some L29 Vortec 7400 98-up 454 oval ports. They are full size ovals with 98cc chambers to make the most of flat top pistons in your motor.

The casting numbers are like -243 and -279