Questions about difference between 970 and 1071

[Twincam]

Have a block with AEG151 casting identification. It had studs to hold down main caps. From what I'm reading, if it was a 1071 it should have used bolts. The former owner was told it was from a 970. The main caps have a counterbore, of ever so slightly larger diameter, at the end of the holes adjacent to the block. This would seem to indicate the caps are for studs with an enlarged diameter alignment feature close to the block, like what the stud systems uses. That points to a 970 configuration. I'm not familiar with the 1071 bolt design, but I'm guessing it has a similar alignment feature incorporated in the bolt directly under the head (educated guess). The main caps are stamped with 1P 7901. No other marking can be found. It is an FJ style casting.

So, does this all make sense that someone in forum could callout what this is?

Do all 1071 caps have the enlarged counterbores to work with studs even though they use bolts?

Do the studs and bolts use the same thread so it'd be possible, with alignment work, to go from one to the other?

[AndyPen]

Not sure if this helps, but this is my 1071, and that has studs.

[cmiller]

Get ahold of me (Chris Miller) in SAMOA. I went thorough all of this recently. too much info to relate over the forum. We are in the same city you know.

Chris Miller

[scott6058]

viewtopic.php?f=3&t=22413

[Simon776]

The main caps are stamped with 1P 7901. No other marking can be found. It is an FJ style casting

I would say that the main bearing caps are about four years newer than the block.

[Vegard]

The main caps are stamped with 1P 7901. No other marking can be found. It is an FJ style casting

I would say that the main bearing caps are about four years newer than the block.

This is first class Anoraking

[Twincam]

I haven’t been able to find a photo of a 1071 main bolt. At this point it’s just a matter of interest because I’ll be going with studs but if someone has a photo, please post.

Some follow on questions for this anorak.

Where does the “locating” feature of a 1071 bolt engage?
- Only near the head of the bolt?
- Most of the way through the cap?
- Through the cap and into a c’bore in the block? (That is if a c’bore even exists in the bolt style block, which I don’t know either)

[Gareth Brandt]

My april 64 1071 has bolts, (read screws). To my knowledge the block in the thread is not a FJ casting. There should be a flat surface below the oil pressure relief nut. See pic

[Twincam]

My april 64 1071 has bolts, (read screws). To my knowledge the block in the thread is not a FJ casting. There should be a flat surface below the oil pressure relief nut. See pic

There is, as well as a boss between the dipstick and filter mount areas. - Gregg

Edit: I’m now primarily interested in the bolt/stud situation with this block. I originally added the mention of “fj style” in an effort to help identify whether it was a 970 or 1071. I’m pretty convinced it’s a 1071 but would like to see photos of the main caps bolt system used in early blocks to understand if what I have is original or a modification. Photo of my block is below.

Edit2: I re-read the link in Scott6058’s post and it seems to give the best explanation. I’ll use that guidance. Thanks all.

DEDE66D6-7C91-4B0F-9C27-568B9717FFB8.jpeg

[1071bob]

If as Simon points out, your bearing caps are for a stud location the counterbore size should be .470" diameter and the stud shoulder will be 15/32" or .468" diameter. The 'bolt type' blocks are smaller.
There was a 1071 'bolt' block on e-bay today showing the bolts, not the best picture but shows the slighty bigger diameter to locate the caps, although it had five bolts and one stud!

[Twincam]

Thanks for posting that photo. Took some measurements and it’s does seem, as Simon pointed out, I have an bolt block, with stud caps. Not the best combination and will probably require an align-bore and a stepped stud set or a thin wall sleeves in the main cap to lock in the cap position. Hmmm.

.....or enlarge the counterbores in the block in alignment with the caps....