1968 ( 318 ) main bearings - Input requested

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SGBARRACUDA said:
Chris the difference in SB and BB in 74 was the Width of the thrust bearings.
Main bearings for 318's changed in 1974 to a different thrust width, pre 74 used (for example) Clevite MS-540p with a max thrust diameter of 3.374 inch, then 74 on used Clevite MS-1344p with a max thrust diameter of 3.530 inch.
Click to expand...
Thanks Roy - I used the 68 block I bought from u and it cleaned up nicely # I guess I could have used the 74 model and not really had this issue but I wanted to have the oldest one in my car first , If I ever bust it then the 1970 block u sold me will go in next .

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SGBARRACUDA said:
Chris the difference in SB and BB in 74 was the Width of the thrust bearings.
Main bearings for 318's changed in 1974 to a different thrust width, pre 74 used (for example) Clevite MS-540p with a max thrust diameter of 3.374 inch, then 74 on used Clevite MS-1344p with a max thrust diameter of 3.530 inch.
Click to expand...

The change to the main bearing flange was also cut in the blocks before the 'official' change... I have seen a few blocks earlier than 74 with the wider thrust flange machining...

Check your block before ordering...

However, the early style bearings will still work with the wider cut flange...
 
krazykuda said:
The change to the main bearing flange was also cut in the blocks before the 'official' change... I have seen a few blocks earlier than 74 with the wider thrust flange machining...

Check your block before ordering...

However, the early style bearings will still work with the wider cut flange...
Click to expand...
Ten 4
Thanks for the info
 
krazykuda said:
The change to the main bearing flange was also cut in the blocks before the 'official' change... I have seen a few blocks earlier than 74 with the wider thrust flange machining...

Check your block before ordering...

However, the early style bearings will still work with the wider cut flange...
Click to expand...
I have run into that same thing. Since blocks were only cast at certain times of the year, when your dealing with a 73-75 block, you really need to see which block you have.
 
SGBARRACUDA said:
I have run into that same thing. Since blocks were only cast at certain times of the year, when your dealing with a 73-75 block, you really need to see which block you have.
Click to expand...
Ten 4
Well I have your old 68 ( 318 ) block and its going to be used first looks like I really dont have an issue
Running later model crank in an early model block so all is good .
 
SwedishViking said:
What will be the problem with later model bearing in a early block?
Click to expand...

There won't be enough metal cut away from the main bearing boss and the bearing won't be able to seat properly... The flange on the later ones got wider...
 
I was with MOPAR back then
we were loosing thrusts- warranties
always use larger dia thrust if block is machined or if line boring your can machine
always check cranks for chewed up thrusts
I drill through the thrust bearing face into the oil feed ( and drill and reamwith about a .040 then drill the bearing face with larger and chamfer
I also chamfer the parting lines toward the rear
anything you can do to get oil to the thrust face, especially with a strong clutch

the crank works but do not use later bearings in early block without machining register
 
Wyrmrider said:
I was with MOPAR back then
we were loosing thrusts- warranties
always use larger dia thrust if block is machined or if line boring your can machine
always check cranks for chewed up thrusts
I drill through the thrust bearing face into the oil feed ( and drill and reamwith about a .040 then drill the bearing face with larger and chamfer
I also chamfer the parting lines toward the rear
anything you can do to get oil to the thrust face, especially with a strong clutch

the crank works but do not use later bearings in early block without machining register
Click to expand...
Thank you
I will find the best bearing for manual trans designed for the 1968 model block and I should be ok correct?
Thanks Chris
 
SGBARRACUDA said:
Without additional machining to the early block, the later thrust bearing won't fit.
Click to expand...
Thanks Roy for info
Later model crank fits all LA
318 engines #
My crank with proper bearings for the 68 model block will function properly.
 
SGBARRACUDA said:
Without additional machining to the early block, the later thrust bearing won't fit.
Click to expand...
That makes me wonder. Because i have a 68 318 with 273 crank. And what i can see on my order history is that the mainbearings iwe used is supported for a 74-up 318.
But the crank hade been grounded .10
Iwe ran the motor for a short while, then sold the car.
Maybe i have to check over the bearings then.
 
SwedishViking said:
That makes me wonder. Because i have a 68 318 with 273 crank. And what i can see on my order history is that the mainbearings iwe used is supported for a 74-up 318.
But the crank hade been grounded .10
Iwe ran the motor for a short while, then sold the car.
Maybe i have to check over the bearings then.
Click to expand...
Could be because of the fact that the early thrust works in a later block...so its supported '74 - up usage. Really.. the only catch is you cant fit a later model thrust into an early block that is machined for the small thust bearing.
 
Just my thinking on this subject; a lot of this is just thinking out loud. A lot of the King bearings are aluminum of some sort. IIRC< the King;s for the SBM's are AL. Supposedly harder, so the bearings are more wear resistant and have looked good in my stuff when removed.

I have raced on Al bearings in my turbo rally engine; that engine (late 2.6L Mitsubishi) has a much better oiling system design than some of the SBM stuff.....(just my opinion on that). But since you are pushing higher RPM's and loads in your SEGA engine, then I'd be thinking more about crank oiling limitations, and would push towards a softer bearing surface than AL.... just to give things their best chance to live in case of a slight loss of oil for a moment.
 
SwedishViking said:
That makes me wonder. Because i have a 68 318 with 273 crank. And what i can see on my order history is that the mainbearings iwe used is supported for a 74-up 318.
But the crank hade been grounded .10
Iwe ran the motor for a short while, then sold the car.
Maybe i have to check over the bearings then.
Click to expand...
The undersize grind on the crank would not change this. The issue is the shallow relief ground in the main cap and web on both sides of the #3 main... that relief has to be wide enough to allow the flanges of the thrust bearing to fit.

This whole discussion made me go out and measure a 1968 273 block. It turns out that the machined relief for the thrust bearing flanges in that early block is plenty wide enough to accommodate the later, larger diameter thrust bearing flanges, with room to spare. So, swedish viking, your engine is probably just fine!

Now, I cannot say this was the case in all SBM blocks prior to 1974. But it may well be that this was the case forever, and they just decided to put in a wider thrust bearing flange for other reasons, like better wear or heavier transmission thrust or something. It is interesting that this change took place in the same year that they changed the 318 to the larger heavier rods.
 
nm9stheham said:
Just my thinking on this subject; a lot of this is just thinking out loud. A lot of the King bearings are aluminum of some sort. IIRC< the King;s for the SBM's are AL. Supposedly harder, so the bearings are more wear resistant and have looked good in my stuff when removed.

I have raced on Al bearings in my turbo rally engine; that engine (late 2.6L Mitsubishi) has a much better oiling system design than some of the SBM stuff.....(just my opinion on that). But since you are pushing higher RPM's and loads in your SEGA engine, then I'd be thinking more about crank oiling limitations, and would push towards a softer bearing surface than AL.... just to give things their best chance to live in case of a slight loss of oil for a moment.
Click to expand...
Thank u for the info finally gettinf this thing together , the pistons was the only tricky part of the build.
 
do drill the thrust as I pointed out above with that stick shift
looks really nice
be sure and dial in the bellhousing
early blocks were smaller on the thrust machining but I do not know when they went larger
you can do the clearance along with a line bore
but oiling is maybe more important
with the clutch depressed all the oil wants to go out the front
sitting with the clutch depressed with a heavy clutch almost never works and is not good for your throwout bearing either
 
Wyrmrider said:
do drill the thrust as I pointed out above with that stick shift
looks really nice
be sure and dial in the bellhousing
early blocks were smaller on the thrust machining but I do not know when they went larger
you can do the clearance along with a line bore
but oiling is maybe more important
with the clutch depressed all the oil wants to go out the front
sitting with the clutch depressed with a heavy clutch almost never works and is not good for your throwout bearing either
Click to expand...

Thank u Sir.
 
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