Block info

[Big Turbo Scott]

Hello, I've got two questions concerning the differences between a 109 and a 291 block. The 291 has a std bore of 3.965? Are the deck heights of the two blocks the same? Thanks!

Scott

 

[turboclam]

Scott, I've got this one.

291-109= 182

PM me if you need anything else

 

[dr_frankenstein]

291 being a 4.1l
109 being 3.8l

291 is early style casting, has taller deck height, 14 bolt pan, no front turbo drain provisions.
109 is late style casting, shorter deck height, 20 bolt oil pan, front drain hole (typically on turbo motors) not all 109 have this.

 

[Big Turbo Scott]

Ok, Ive had some time to search and came up with 9.535 deck on the 291 with a 3.965 bore. What is the stock deck height of a 109?

 

[turbodave231]

The 109 block is supposed to be 9.522" . Most I have measured aren't that tall. I've machined several virgin blocks that started around 9.515"

The 109 block also has countersunk head bolt threads. All production Buick V6 blocks before 1986 had head bolt threads that came to the deck surface.

 

[charlief1]

How far down are the threads on the 109 Dave?

 

[turbodave231]

Charlie,
Just measured a block and I got .539. This one has been decked .010 so somewhere around .550 should be a good number.

 

[charlief1]

Charlie,
Just measured a block and I got .539. This one has been decked .010 so somewhere around .550 should be a good number.

Thanks Dave, that should save some agrivation on removing some of the threads on my block to help it live longer.