straight off our # decoding section here.

http://www.nastyz28.com/sbchevy/sblock.html

400 1970-72 4.126 4 bolt
400 1973-80 4.126 2 bolt

i have a 1978 suburban with a 400. it is the original engine and a 3951509 block.

does the info above mean 4 bolt 400's were only made in 1970-1972 and the 1973-1980 400's were ALL 2 bolt mains? the guy i got it from said he changed the pan gasket and it was a 2 bolt main, but he is a bit of a redneck shadetree type and i don't exactly trust his judgement, since he said the frame on the truck was nice and its about to crumble from rot.

70-72 400s are 4 bolt, and the rest are 2 bolt, so what you have is a 2 bolt.

The 509 block is generally a 2 bolt.

Your only chance for a 4 bolt is from 70-71 1/2 400's. Mid to late 71 is when they changed over to 2 bolts.

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My 73 (http://pic10.picturetrail.com/VOL314/466168/1171704/51225071.jpg)
My 71 (http://pic10.picturetrail.com/VOL314/466168/1171704/55082053.jpg)
My 71 (http://pic18.picturetrail.com/VOL914/466168/1171704/101445569.jpg)
parts for sale (http://www.PictureTrail.com/gid3200370)
cars&trucks for sale (http://www.PictureTrail.com/gid1265057)
parts for sale (http://www.PictureTrail.com/gid581024)
parts for sale (http://www.PictureTrail.com/gid7285884)

good, don't want a 4 bolt. wanted something to put splayed 4 bolt caps on.

Three freeze plugs on each side = 4 bolt. Two on each side = 2 bolt.

<font face="Arial,Verdana" size="2">Originally posted by 70 Z UC:
Three freeze plugs on each side = 4 bolt. Two on each side = 2 bolt.</font>

Thought there was a few blocks that that didn't work on....

????

<font face="Arial,Verdana" size="2">Originally posted by 70 Z UC:
Three freeze plugs on each side = 4 bolt. Two on each side = 2 bolt.</font>

rscamaro73 is correct!

I have two 400 blocks, a 817 and a 511. Both are two bolt mains, one has two freze plugs and the other has three. So that theory is out of the window.

[This message has been edited by ChevyReb (edited August 25, 2005).]