[1950Mercury]

I have my eye on a 68 400 motor cast 9790071. I have heard that sometime during the 68 year they started drilling these blocks for 4 bolt mains. Does any one know if this is true and if so when did they start. I heard it was they didn't have to have 2 casting numbers. This block date is March 26 68

[OG68]

You're thinking of the RA II engine which had a different casting number. Both the RA I and RA II have casting number 9792506

I have a late March cast '071 and it has 2 bolt mains.

[1950Mercury]

Yes.. I heard at one time some time in 68 they decided instead of having 2 different blocks they started drilling and tapping the 071 blocks instead of having different castings. Maybe it was done later in 68 for the 69 engines. The motor I'm referring to is also a late March casting. The price seemed right at $450.00. It has the crappy 15 heads though.

[tooski]

I have two of those 0071 blocks. Both are drilled and tapped for 4 bolt mains.

[1950Mercury]

Do you happen to recall the date on those 0071 blocks?

[54nomore]

I have a March and a June (15th) block, and neither of those are drilled for 4 bolt.

[1950Mercury]

Thank you. I did pick up this March 26 block and it's not drilled either. They must have started drilling late in the 68 year.

[grandam1979]

I sold a D268 a couple years back not drilled.

[tooski]

Originally Posted by 1950Mercury

Do you happen to recall the date on those 0071 blocks?

The two blocks are in cars in separate residences. The accessible one is B279. The one that is too far away I purchased from a guy who took it out of his 69 GTO RA III 4 speed. After both engines were assembled with two bolt caps and running in cars is when I learned that if a four bolt main block has two bolt caps on them they are weaker if the extra bolt holes remain open; I said oh, crap. I have a third one wrapped up in a corner. That one is a two bolt main J038.

[1950Mercury]

I've heard the same about the drilled 4 bolt blocks with 2 bolt caps. Nothing wrong with a 2 bolt block. In mid 70's I had a 66 GTO with a built 400 2 bolt block 12.5 compression. I know it had to be close to the 450 h.p. range. It was a runner. Only problem I had was I spun a rod bearing. Too much compression. 220-225 lbs.