I have a good 396ci 2 bolt block out of a 1968 Chevelle that has been sitting in my shed for years.
I also have a good Eagle 4.00 inch forged steel crank and a set of 6.135 rods.
Can you install a 4.00 inch crank into a 396 block and make a 427 out of it?
Looks like if I bored the 396 .030 over to net a bore of 4.125 and then used the 4.00 inch crank you would net 427ci's.
Looks like the biggest issue is the lack of pistons that are available that would support this configuration?
I was just basically seeing if I might have enough stuff laying around to piece together a motor that I could turn around and sell or if its even possible to do this.
What do you think would it be worth doing if it is possible?

 

Hi

As little as I know, the cranks for 396 and 427 are the same.
Only the bore changed.

I have a 396 CI 68 Camaro block bored to 427 in my Vette .
Nothing wrong with it ( except that it might be a touch lighter )

Rgds. Günther

 

I know that the 454 (4" crank) used the same block as the 427 (4.25" bore), except it had clearancing notches at the base of each cylinder to accomodate the wider throw of the rods. I an not sure if modern rods will allow you to put a 4.0" crank in 396 block. Others with actual experience will need to weigh in. Either way, I would think your or your machinist could clearance the block without much difficulty.

I agree that you will have difficulty finding pistons to fit your needs with that bore. However, I am told that custom piston can be had at reasonable prices. You also may be able to punch out the block to 4.25". I don't know if GM changed the casting when the went to the 427 or if they just bored bigger. Others may be able to chime in.

 

Maximum you can take a 396 block to is +125 and you better sonic check it. This limits what you can do. The New Z06 LS7 engine uses a 4.125 bore flat top piston, a 4.00 stroke and a 6.067 rod. Pin size is .925, Big block piston pin is .990 So you have to sleeve the rod end or bore the piston. Don't know if this will work but your limited to creative thinking or custom pistons. To do this you need the LS7 pistons, pins, pin locks and ring pack, Sleeves for your rod ends and a good machine shop. Deck height, compression height and valve clearance will all be issues. Just bouncing some ideas around.

 

Either build a 396 or find someone with a 68 chevelle who needs that block.

The pistons for a 4" stroke would cost more than what the engine will ever be worth.

I'm sure that there's a reason that this isn't a popular combination, though it would probably make a good truck motor.

 

It's actually a good build for todays times with the fuel prices skyrocketing.

Have 2 under way today, including 4 add'l "kits" in stock, with the same Eagle (internal-balance) 4.000" stroke cranks. Had a few sets of +.030" slugs built recently incorporating the correct C.H. (1.655" x 30 cc domes) for the combo.

It does go into the blocks with minimum effort, a small amount of grinding at the lower section. Mainly depends on the rods, more specifically, the brand/type, to help facilitate the amount of "fitting".

As of now, the only "negative" is there are no "stocking" pistons available. I doubt there will be in the future, due to the somewhat limited number of customers wanting this 4.125" x 4.000" platform.

As stated it will give you an "easy" 427" BB. We also have the 4.375" cranks going into the 454" BB's with an "internal" balance setup as well. This will yield 504" (4.280" x 4.375") without making the bores "paper-thin"!

All these combo's will be based on the 116/118 O.C. heads and run on fine "pump-gas".

Thanks, Gary in N.Y.

P.S. This combo, "small bore/long stroke", is what's needed if anyone is "chasing" ANY sort of economy while still maintaining some decent power levels. Won't get to dyno any this year, so far! Haven't made the actual "sale" just yet on the 396" platform!

 

Thanks for replys, tips, and suggestions guys!!
You know I have spoken to a number of people over the years about this motor but it just does not spark any interest. The block has never been decked and the stamp on the blocks front drivers side pad is clearly visable. I have the factory nitrided crank, rods, and pistons too but it has just sat out there for years. Thanks again.

 

KB makes a piston for this combo:

http://www.kb-silvolite.com/performa...tails&P_id=110

Good Luck

 

Here are the pistons you need. http://store.summitracing.com/partde...8&autoview=sku
$375 - No need to buy custom.

 

Before I put any money into it, I'd put the block on that auction site with casting #s and see if someone needs it. If some one does, they would rather you not have done anything to it.

I had a couple of double bump heads that were pretty much useless to me (one was damaged but repairable). Got more than I thought they were worth and the guy even arranged for shipping. I simply wrapped them in cardboard and left them on the door step.

If you end up needing to ship it, suggest uShip to the buyer. I shipped a 1000lb turbine door to door PA to TX last month for < $400.