on center / off center

[87-TURBO-T]

is there an advantage to running one of these blocks over the other? thanks

 

[Onalky87]

I can see this being a very interesting thread bc i'd like to know this answer as well...subscribed

 

[Blazer406]

You'll get some different opinions on this..... but......

IMHO,

Oncenters are "generally accepted" as being able to support the most HP potential.....due to the fact that the piston is centered directly above the rod journal hence the term "on-center".

I believe up to somewhere over 1000 HP...... either will be just fine...... but at some (HP) point...... the people spending the $$.... just don't use a off-center block.

The "advantage" of using off-center blocks..... is you can re-use most of your stuff off your 109 motor..... like intake.... possibly headers....accessory brackets.... etc. On-center stuff is a different animal. Most max effort off-center motors use 4-bolt mains.... and have provisions for 14 bolt heads..... as opposed to the 109 with 2 bolt mains.... and 8 bolt heads....

HTH

 

[turbobuick]

You'll get some different opinions on this..... but......

IMHO,

Oncenters are "generally accepted" as being able to support the most HP potential.....due to the fact that the piston is centered directly above the rod journal hence the term "on-center".

I believe up to somewhere over 1000 HP...... either will be just fine...... but at some (HP) point...... the people spending the $$.... just don't use a off-center block.

The "advantage" of using off-center blocks..... is you can re-use most of your stuff off your 109 motor..... like intake.... possibly headers....accessory brackets.... etc. On-center stuff is a different animal. Most max effort off-center motors use 4-bolt mains.... and have provisions for 14 bolt heads..... as opposed to the 109 with 2 bolt mains.... and 8 bolt heads....

HTH

There only a few relatively minor issues to an on center when dealing with accessories and using it with all the factory components. Everything will bolt up fine, headers included. Champion will sell their intake for on or off center which used to be the biggest hurdle when using an on center motor. You have to spend some attention to cam gear alignment by milling the back of the front cover or using one of DLS's cam spacers and milling it to fit. I run two oil slingers on the crank to space out the balancer and grind down the back of the crank sensor bracket so it doesn't hit the reluctor, everything else pretty much bolts up.

Almost all on center blocks are dry sump blocks. You will need a duttwieller style oil pump or a belt drive pump which will also require a fab alum pan. I usually weld up the pick up holes in the cover, especially if you are going to mill the back of it anyway, (about 1/8" watch for the pump cover bolt). You will want to run a solid roller cam.

On center blocks are definitely stronger and they made WAY more of them so they are easier to find especially if you want a nice one. If I were building a good motor I wouldn't hesitate to use one even in a street type GN. I cant for the life of me figure out why more people dont use them and put endless stupid $$ into fragile 109 blocks to make 700+HP when it really wouldnt cost much more to build it right to begin with.

 

[S2V6RACER]

The later on-center castings are superior in strength in compared to off-center stuff. The off-center castings date back to 1985 and the latest on-centers were cast in 1999.

The off center stuff can and has made way more than 1000hp. Depending on your goals I would sway toward on-center blocks as the castings are just plain better.