I got a deal on a CAT 4340 steel crank with a 4.125" stroke. So I am going to try it in my bowtie block. The bore will be 4.165 with the 4.125 stroke makes 449.6ci or 450ci rounded off .With a 5.875 rod, I can stay with my 1.062 compression height, so the JE pistons are off the shelf. Our local machine shop has done that much stroke before. I will use Lunati Pro mod rods, and a .850 base circle cam. The rods will still need to be clearanced slighty. I know the 1.4 rod ratio isn't the best, but I am going to give it a shot. I will have Lloyd Elliot work my heads(AFR220 competition package) some more and cam it up to probably the 264/270 range. I will keep my miniram. And it will still see some nitrous. This isn't a 100,000 mile motor, but at just over 6000 rpm and the little bit I drive my car, it will last a while, It should pick up some torque!

 

Jim,
This is very close to the combo that we had discussed prior in my track car. I was running a 4.125" crank in a 4.155" bore in an aftermarket block with GM 18° heads and 18° intake converted to FI. This was the package that was being fed by the D2R blower and required the 4" Toledo Pro hood. The engine was fine, but unfortunately, the chassis did not work well on this car. Currently that car is in pieces, with me trying to figure out what I want to do with the parts.

My JE pistons were custom, as I had to run the deep dish to get down to 9.0:1, but the billet rods were off the shelf. The crank (other than the massive balance job required; it will require lots of Mallory metal) was basically off the shelf. I did use the Comp Cams solid roller small base circle camshaft.

This package can be done. However, mine was only 447 cid. You will be 3" larger due to the larger bore.
Aaron

 

that's frickin crazy man...good luck!

oh, a little off topic yet on...what is the largest cubes possible on stock 4 bolt main block...like the one in my GM Goodwrench 350 crate sitting on my stand? it's a regular production 4blt main and nothing special that i know of. I'm thinking of building a small block in the background while the BBC nears completion as more of a learning experience than anything. i have aspirations to straight mount it in my 93 Talon TSI and make it RWD...otherwise, it MAY go into my 77 vette upon interior restoration or into my brother's firebird...we dunno yet...but i've been pondering a big stroker just to see how nasty i could go on stock block...

i REALLY would like to sell the complete "LM1" in longblock form (pan, manifolds included...you need intake and ignition) for about 500 bones...if no one bites, i'll build it up...

 

i hope it runs okay the rod stroke ratio is beyoynd bad its horrible its going to wear out the side of the block and pistons prematurely
and i hope you can get a good ring seal on it

 

I agree that is going to be really stretching the limits of the ratio to the max. Might be ok or a pure drag setup, but running it on the street will wear it out quicker than heck.

For the few extra CI/power you will gain, I think that its not worth it if you ask me.

You could put your compression higher on the current setup and gain just as much, and only compromise fuel costs; money to redo the engine when its worn out will be much more since your going pretty large on the bore now. At the end of it all, you might have a throw away block.

Stick with the 421, that is a good motor and capable with the right stuff to run some AWESOME numbers. Wish I had your solid rear setup - I would show you.

 

I know this isn't a motor that goes 100,000 miles or maybe even 50,000. Say if it lasts 10,000 miles which I'm sure it would with maybe 20-40 passes a year, it would last me 20 years at that rate, since I drive my car 500 miles a year. Hell, I'll probably get bored with it in a few years and pull it out, and build something else.

I just really want to try something different.

 

...

 

Not a daily driver, huh? And I take it that you have a fat wallet.

 

Congrats on pushing the envelope. Even if it isn't the baddest smallblock around, it's got to be damn close to the biggest! Here's to innovation - and prove to us how that rod length won't really wear things all that much.

Take before/after pictures of the bore so we can compare - that would be a neat project.

 

Biggest stroke in factory block:
As an answer to FUBAR, the 408 and 421 were based upon production L-98 type blocks. It gets expensive quickly, as the rotating assy must be first rate.

r/s ratios (theory vs practice)
OK here is my take on the r/s ratio. I have run many different combos (383, 396, 408, 421, 447) throughout the years. I have not torn down the 447 (1.42 r/s), because it is still complete and I have not decided what I am going to do with the package. It has been together for ~7 years, but does not have more than 8K miles. The car made big numbers on the dyno, but would not track straight at HRP.

However, I will say that the 408 (1.47 r/s) and the 421 (1.45 r/s) are both street engines. They have run for well over 15K miles each and I have seen no appreciable increase in piston wear or block side wear on either motor. I still have the 408 in my street car.

I will say that if given the option to increase the r/s ratio, I certainly would, but unfortunately, most if not all of us can not afford to build a tall deck SBC. And for a street engine, the scr will need to be fairly low, which requires some dish (more for the FI guys) and precludes a longer rod, thus forcing the less than desireable r/s ratio.

Bottom line, if we could live in a theoretical world, most of us would choose the 6.125" rod and acheive 1.7 r/s ratios or better. Since we don't, compromises will be made.

Aaron

 

Go for it!! This is not daily driver, it is a toy / hobby so why not just do it because you want to?
I have most of the parts for a 454 small block for my next project which will be in 2 years.
Check this out
http://www.4wheeloffroad.com/brandpa...i_small_block/

Yedi