140 vs 109

[HalfDozIN]

I've read that the 14 bolt hot air blocks had a taller deck height than a 109, is the same true for the 140? Are hot air pistons identical to ic? I ask this, because upon teardown of my 140 equipped hodgepodge of an 87, I've found the pistons sitting ~.085 down in the hole. They're factory pistons, but I expected them to be .060 at most. Makes for a stupendous ~7.4:1 with the 9441pt gaskets that were on it if my numbers are right.

That said, is there any difference other than the rough casting in the lifter valley? I have a 109 with surface rust in some holes, but there's taper in the 140. Machine work will be the same either way, so does it matter which one I use?

 

[THensley]

109 is a proven work horse
Deck height probably was not .085 taller , not sure what it was but the manifold would not fit correctly I would say most likely incorrect piston. I have never seen a .060 Buick piston
If I had a 109 I would use it and keep the over size as small as posable . Your pan and front cover won't of the 140 won't work
Just my Opinion

 

[HalfDozIN]

109 is a proven work horse
Deck height probably was not .085 taller , not sure what it was but the manifold would not fit correctly I would say most likely incorrect piston. I have never seen a .060 Buick piston
If I had a 109 I would use it and keep the over size as small as posable . Your pan and front cover won't of the 140 won't work
Just my Opinion

It is a 20 bolt block like the 109, so they should interchange. The strength is the question.

I wouldn't have been surprised if they were about .060 in the hole I meant, but not .085.

I Suppose they may not be factory, as they are marked "standard". Very much the factory style of dish, however.

I would say this block and the 109 both will probably have to go .020 over to clean up right, so the 109 it can be.

 

[THensley]

.	.	25528603	.	.
3.8L RWD​	1985	25524140	25518445	See 1978
.	.	25520329	.	.
Turbo Regal​	.	25520329	25518445	See 1978
Turbo Riviera​	.	25520231	25518445	See 1978

My bad first year 20 bolt The 140 is a NA block
As far as production blocks go, the 1986/87 castings are the culimination of this development. The Turbo and Normally Aspirated blocks (Casting number 25526109) appear to be identical except for the addition of the turbo oil drain back hole on the turbo version. They feature a solid cast intake area around the lifter bores, improved oiling passages (bigger to the mains), and cast "ribs" in some areas to increase rigidity as compared to the earlier blocks. Despite years of rumors that the turbo blocks had some sort of difference in metallic composition, it appears (see the section below) that this was not the case.
This is a cut and past from a old webpage