We dyno'd a ~640 hp NA SBC with an OEM 400 block, then a Dart Little M. It gained about 6 hp, but 30+ ft-lb torque.

Mike

 

Would a street fill benifit the main area to any significance? 2-bolt, 4-bolt straight, 4-bolt splayed?

Thanks,

 

The problem with the mains is cap-walk. No amount of filling will stop that.

 

Mike,

I'm kinda having a hard time visualizing mains walking. With 2-bolt studs I'm assuming you've got the clamp load. Splayed mains tie you into block better. What about straight 4-bolt?

Are we talking twisting in the crank?

Thanks!
Scott.

 

No, not twisting the crank. The main caps slide (on a microscopic level) around on the block. This causes fretting damage at the interface. It means the main bolts aren't doing a good job of making the main cap stay still. 4 bolts means double the clamping force, roughly. I'm not convinced that splayed mains help with this since there is already a register-fit to prevent horizontal motion, but I am seeing some fretting damage with my 4 bolt straight steel caps.

There are pictures of fretting damage on turbomustangs.com. Do a search for "grenade", a 2-bolt main stock bottom-end 700 rwhp freak.

 

Haven't checked the link yet, but thanks. So there are lateral loads (cross-car) causing the mains to walk. I can see how a 4-bolt straight main helps in this regard.....more friction.

Now 'splayed' with outer bolts angled outward...You've got the cross-car component partially taken by the tensile load of the outward angled fasteners.

Am I close?

-Scott.

 

Scott, the main cap has a register fit that prevents side-to-side motion. I've heard of pinning the mains to prevent axial motion also. I believe this would be more affective than splaying the outer bolts.

 

Mike I have heard you talking about that 700rwhp mustang before with 2 bolt mains. How many Rpm's is he turning?

 

It's a TPI 350. I don't know for sure, but with the stock TPI runners, stock cam, and stock T3 S60 turbo's, my bet is very low rpm.

 

Here's the ultimate LT1 block...

http://cgi.ebay.com/ebaymotors/GENER...1%7C240%3A1318

One of 10!

 

Damn!!! I would love to have that engine block. Thats worth more than the entire car that you would put it in.

 

I'd like to learn more about using dowel pins in the stock mains as Mike suggests. Does anyone know somebody with experience with this?

Thanks,
Scott.

 

I got that from a local engine builder, but a google search turned up that World blocks are doweled, as are LSx blocks and some old Pontiac blocks.