25500153 on center 3.8

[postal]

According to www.gnttype.org 25500153 is an on center 4.1. This block that I bought Has that casting number but a bore of 3.810". It has the cross bolted front and rear main so I take it that this is a later on center. Any body ever see one of these before?

Thanks: Jason

 

[turbodave231]

Anything is possible with Stage 2 blocks. Sounds like you have a 4.1 on-center block with lots of meat in the cylinder walls. It would be cool to sonic check the bores and find out just how thick they are. Either way, it sounds like you have a nice block.

With that small bore, it was probably intended for IMSA or Indy car use.

DR

 

[TurboDave]

I don't have all the numbers researched, but I think Dave's probably right.

But even if it is a small bore block, you can still get 4.1L out of it. Just bore it to 3.830, and use a big stroke crank and long rods.

3.625 crank
6.5" rods
3.83 bore
all adds up to 251cu (4.1L)

 

[steve hughes]

I've got a 153 that is 3.875" .

 

[750H.P.V6]

Jason,

there used to be a seperate P/N listed for 3.8 and 4.1 liter Stage II ON center blocks. The only difference between the 2 was the bore size. Both were machined from the same 25500153 casting and had cross bolted mains etc. The 3.8 liter block came with a bore size just shy of 3.800" while the 4.1 had a bore size just under 3.965" from the factory.

Neal

 

[postal]

the only difference between the 2 was the bore size.

Does this mean that it can be punched out to a 4.1 w/o making the walls too thin. Would this be a stupid thing to do? Would I be better off running thicker walls and a smaller motor. I probably dont want to get into all the hassels that come with a 9.99 or faster car. I think I would like to have a solid built low 10 second ride that if the air is right and the track is hooking maybe crack off a 9.99 just to say it can do it.

Thanks for the input: Jason

 

[750H.P.V6]

Jason,

All the 25500153 casting blocks are the same with the only real differences being casting core shift, how it was fixtured during the machining process etc. If you do a sonic check based on the 3.8XX" bore you have now you'll find the cylinders are very thick.

To answer your question: Yes you can bore the block to 3.965" which is the standard bore for a 4.1 without any real concerns. There are On center blocks still in use with bore sizes in the 4.040"- 4.060" range.

Neal

 

[opeltwinturbo]

The motor currently in the Opel is a 4.045 bore. Just went with the gapless top ring. If you are not worried about going real fast, keep the bore at 3.81 if you have the pistons. Boring, pistons, rings, gaskets all cost $$$$$. One day you may "have" to bore it. Good luck.

 

[postal]

So since this is a later style on center with cross bolted 1 & 4 mains, and extra thick cylinder walls do to the 3.810" bore then this sucker is probably the strongest version of a stage block that BMS made?

My buddy Rodger is probably going to try to make me give it back to him. Maybe we could have our old ladies mud wrestle for it. I got a few $$'s and a stage block that says my ole lady will whip his..................... She's MEAN!

Thanks for the info guys.

Jason