Sbm x block

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1975 PROSTREET DUSTER

1975 PROSTREET DUSTER

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Ok had my nos x block at machinist to have 4 bolt mains installed and line bored. Was told the line bore is way off and that bores were sonic checked and would only be good for a 4.04 bore. Never has been bored and is 3.91 rough factory bored. Which puzzled me and I'm finding this hard to believe. Was told person doing line boring was having hard time finding the centerline to machine main bore. Any comments appreciated.
 
Get a second opinion. I think somebody's fulla ****.
 
Find a machinest with 20/20 vision on the line bore. I know some of the X blocks did come 3.91 bore, back in the 80's. I agree w Al.
 
A lot of X blocks were made with the 3.91 bore and would only go to 4.04. This is not a surprise.
 
1975 PROSTREET DUSTER said:
So they cast x blocks with different patterns?
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All of the X blocks were cast at 3.91 bore. They are actually under that by a bit. My last block measured 3.840 rough bore. Second, before they sonic test it, they need to bet ALL of the rough bore out of it. Meaning, they need to get it in the boring mill and cut the bore until it's clean. Then you can get a real sonic test on it.

I've had 3 X blocks and worked on a dozen or so more. I've never seen one that wouldn't go 4.100 easy. But you can't tell that with a rough bore.


As for the main line...I have no idea how the bores can be that far off. That's ridiculous. Find a different shop if they are doing the sonic test on a rough bore.
 
yellow rose said:
All of the X blocks were cast at 3.91 bore. They are actually under that by a bit. My last block measured 3.840 rough bore. Second, before they sonic test it, they need to bet ALL of the rough bore out of it. Meaning, they need to get it in the boring mill and cut the bore until it's clean. Then you can get a real sonic test on it.

I've had 3 X blocks and worked on a dozen or so more. I've never seen one that wouldn't go 4.100 easy. But you can't tell that with a rough bore.


As for the main line...I have no idea how the bores can be that far off. That's ridiculous. Find a different shop if they are doing the sonic test on a rough bore.
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Well thats what i always understood as being the case. I thought it would be very unlikely they would use a different pattern for casting x blocks. Not sure about sonic testing without boring, i have no knowledge in this area.
 
No, they did. There thicker in some areas. Depends on the block part number.
 
All X blocks came factory with 3.91 bore. All. Every one.
Its same as factory 318 bore
They are all over the place regards how far they can go bore wise.
Have seen and heard 4.125, and as small as 4.04 as well.
Zero need to install 4 bolt caps on it. I made a true 700 horse using one with the 2 bolt caps that block came with. 13.5 compression, 4 inch stroke.
They also were made with 4 bolt caps.
 
I’m not entirely sure about that. I think some did come with bigger bores OOTB
 
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rumblefish360 said:
I’m not entirely sure about that Wyrm. I think some did come with bigger bores OOTB
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There was only one bore size, one deck height and one main bearing size for the X block. Only two part numbers, one for the 2 bolt main and one for the 4 bolt main.

It wasn't until the R series of blocks came out that there were multiple part numbers, bore sizes, deck heights and cam tunnels.
 
yellow rose said:
There was only one bore size, one deck height and one main bearing size for the X block. Only two part numbers, one for the 2 bolt main and one for the 4 bolt main.

It wasn't until the R series of blocks came out that there were multiple part numbers, bore sizes, deck heights and cam tunnels.
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Exactly correct. I have had both 2 and 4 bolt units
 
1975 PROSTREET DUSTER said:
Well thats what i always understood as being the case. I thought it would be very unlikely they would use a different pattern for casting x blocks. Not sure about sonic testing without boring, i have no knowledge in this area.
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Did you look at how rough the bore was? Rough bored means just that. And it's usually pretty crude. This weekend I'll take a picture of a rough bored R block and post it up. It's basically impossible to get an accurate sonic test on a rough finish like that.
 
Ahhhhh, thanks for the correction!

yellow rose said:
There was only one bore size, one deck height and one main bearing size for the X block. Only two part numbers, one for the 2 bolt main and one for the 4 bolt main.

It wasn't until the R series of blocks came out that there were multiple part numbers, bore sizes, deck heights and cam tunnels.
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Thank you guys for your inputs. I really appreciate it. So was there different patterns used for castings that made some thin bore and somethick bores?
 
1975 PROSTREET DUSTER said:
Thank you guys for your inputs. I really appreciate it. So was there different patterns used for castings that made some thin bore and somethick bores?
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No. It was just inconsistency in casting. Like I said, all I've seen will go at least 4.100 safely. The block I have now will go 4.135 easy.
 
I understood your comments and was only curious about rumblefish's comment that he has seen/heard of more than a couple being only able to go to 4.04. That would mean a different pattern was used. And is contrary to info i have gotten which prompted me to post this thread. I am going to take somewhere and have bore checked as well as line boring. Thanks
 
1975 PROSTREET DUSTER said:
I understood your comments and was only curious about rumblefish's comment that he has seen/heard of more than a couple being only able to go to 4.04. That would mean a different pattern was used. And is contrary to info i have gotten which prompted me to post this thread. I am going to take somewhere and have bore checked as well as line boring. Thanks
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IIRC, the book says they only go 4.000 safely. I'll have to look it up in the morning for you. The book has been wrong before though.

I'm not sure how Chrysler made it so they only went 4.000 but I know it's strange. In fact, this block I have now is a very early block. I know for sure, because the guy I bought it from bought it new in 1981 IIRC and it was still in the shipping box with the original paper work.

For the life of me I don't remember what year the other blocks were. I guess it could be that later blocks were thinner. Or the early blocks were thought to be thinner, but my block is pretty early so I'm just spit balling.
 
yellow rose is correct that the cylinders must be round and very clean to sonic test. I've sonic tested a good many and unless they are really clean and fairly round, the readings will be inaccurate. In fact, to give you an idea of how they work, I've even tested a sleeved block before and all the sonic tester will pick up (at least the one we had) was the sleeve thickness itself and not the cylinder of the block behind the sleeve.
 
I forgot to mention that the T blocks also had options for cam tunnel size and lifter bank angle, none of which was offered on the X blocks. That's why there were so many R block part numbers and only 2 Xblock part numbers.
 
Like a race block but not roller cam capable as advised by MP. An old member (Cory) found out when he tried to grind the valley area to fit roller tappets. The result, not good. It’s now a table.
 
rumblefish360 said:
Like a race block but not roller cam capable as advised by MP. An old member (Cory) found out when he tried to grind the valley area to fit roller tappets. The result, not good. It’s now a table.
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I don't remember that. Was he grinding clearance for solid rollers or hydraulics? The Resto block used the same core boxes as the R blocks and those blocks could take a 48 degree lifter bank angle. To save weight they left the cores pretty thick (making the casting thinner) up above the lifter bores.
 
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