Gen 6 big block.

[Dinkster]

I'm building an engine for my 95 k2500 and I have a couple questions. I'm looking to build a 496 out of a 99 Gen 6 block. I found a stock rebuild kit for a 04-07 8.1l with stock cr pistons and an Eagle cast crank 104564250 and rods SIR6135P. Will these work properly in the the block and with the stock Gen 6 99cc heads? I don't believe there's any real difference in the blocks between the 99 and the 04, the displacement comes mainly from the larger stroke. Correct?

 

[454cid]

There are a couple of head bolts that are in different spots, I beleive. The GenVII blocks are metric. Cooling is also different although that may be more in the heads. Firing order has a couple of cylinders swapped. I have no idea on pistons.

 

[Dinkster]

Never mind, I just answered my own question. The 8.1 are 4.37 stroke vs the 4.25 on the eagle crank so it looks like the kit won't work.

 

[b454rat]

454 n 496 blocks are different. The 496 is a tall deck block.

 

[454cid]

The 496 is a tall deck block.

I was thinking that maybe the case, but I couldn't remember for sure.... the difference between Gen VII and Gen VI is a lot more than the differences between the MK4, GenV, and Gen VI.

 

[b454rat]

The 496 doesn’t share much at all with their little brother lol

 

[L29Sub]

I used a Scat crank kit to convert a '97 454 Vortec to a 489. There's a lot of nuances to this, but the outcome was excellent. Great running engine for 5 years. Towed well, no knock or heat problems.
For S&Gs, here are some part numbers.

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[1991blazer]

I’ve built a few of the GEN 6 blocks. The best block for a performance build on a budget. They have primary oiling of the mains and rods so oil starvation like the other blocks. Only downside is there is no room for a double roller timing chain if you keep the front crankshaft position sensor and the cams are different. I had a special turbo cam ground by Comp and they sent me the old bolt pattern and no fit. Also the head gasket is different for the vortec heads.

 

[Dinkster]

Thank you for all the information. I've decided to order a 489 rotating assembly, i was just hoping to find a much cheaper route to go. I had seen a complete overhaul kit for an 8.1 for around $600 plus add the crank for another $300 and I would have been golden but obviuosly that won't work with the 8.1 being a tall deck with longer rods. @L29Sub, did that cam work well with the FI? And, what kind of mileage did you see after the build, was there any improvement over the stock 7.4?

 

[Piratehunter]

Looking at the same mods for my 97 K2500 L29, depending on the cost.

@L29Sub, same questions as Dinkster on the FI and also black box upgrades needed (BlackBear?) Did you have to clearance the block for the new crank/rods? If so, how much extra work was that? What did the crank kit cost? The cam LSA is 113, do you have an auto trans and need the vacuum, any thought of a 109 or 110 LSA, did Comp Cams spec the cam for you?

@Dinkster, please share your crank kit order details and cam you're going to run.

Has anyone done basic port cleanup/polishing on those vortec heads and see any gains from that? not looking to custom flow the heads, just smooth the rough edges out while they are getting worked on.

Planning on shorty headers. Has anyone closed off the ERG, deleted the cats and seen any problems or benefits? The tune mods can delete both of the erg and behind the cat sensors, so can save a little bit of time/cost with the new exhaust setup.