Cylinder wall thickness BBM Blocks

[Fordman]

While doing some info digging I came across a post on the old forum regarding info that the BBM rep had posted regarding the upcoming heads, and block. The rep stated that cylinder wall thickness during testing/sonic mapping the blocks is that they had .330 to .450 thou at 4.250" bore. They state a 4.440 maximum bore size. If the bores maintained a minimum of .330 though out the bores at 4.440" there would still be a minimum .250 cylinder wall thickness. If we were to go with popular opinion of a .150 thou minimum would the maximum bore size not be closer to 4.600". Am I way off here or am I missing something?....Opinions welcome.....John

[Drew Pojedinec]

4.630 cylinder spacing on centers.
I think you need to divide your numbers by 2.

[jayb]

I've only built one engine with one of those blocks, but the cylinders were nowhere near that thick, more like 0.230"-0.250" at 4.250" bore according to my sonic checker.  My Pond cast iron block is thicker.

[SAcobra427]

John,   Are you talking about a BBM cast iron or aluminum block here? I just got a cast iron one and I was planning on having it sonic checked to see what it has.

[Fordman]

Iron block. I am interested to hear your results.  Please post them when you have it done. Thank you

[mike7570]

While doing some info digging I came across a post on the old forum regarding info that the BBM rep had posted regarding the upcoming heads, and block. The rep stated that cylinder wall thickness during testing/sonic mapping the blocks is that they had .330 to .450 thou at 4.250" bore. They state a 4.440 maximum bore size. If the bores maintained a minimum of .330 though out the bores at 4.440" there would still be a minimum .250 cylinder wall thickness. If we were to go with popular opinion of a .150 thou minimum would the maximum bore size not be closer to 4.600". Am I way off here or am I missing something?....Opinions welcome.....John

I picked up an iron 428 BBM from Doug and I think he gave me the same thickness but I thought he was talking about the standard 4.13 bore not 4.25.

[Fordman]

Thanks Doug. That would make more sense to the cylinder wall spec....John

[TomP]

I think head gaskets could be a bit of an issue at 4.60" bore.

[jayb]

TomP, Mr. Understatement 

[427HR]

My BBM iron block sonic test:

[Joe-JDC]

Is this sonic test with the bores at 4.345"?  If so, then they look really strong.  Joe-JDC