Split Main VS Full Circle Main
Thread Starter
Racer
Joined: Feb 2002
Posts: 499
Likes: 19
From: Duluth MN
Split Main VS Full Circle Main
I have a couple of questions. I did a search but didn't find a real answer. My damaged 4.7 short block is a 1983. It has the wider thrust bearing and the full circle front main bearing.
I'm starting to assemble a replacement short block using a 1980 4.7 M28/11.
This block has the narrow thrust bearings and the split front main bearing.
I could drill the block and install a rolled pin for the full circle front main bearing and clearance the block for the wider thrust bearing easy enough I think...
Here's are my questions:
Can I run the 83 crank with the larger oil holes in the 80 block with the split bearings?
Is there any real advantage with the full circle bearing over the split bearing?
If I decide to try and drill the block for the rolled pin and wider thrust bearing are there any pitfalls I should try to avoid?
The mains cost alot more money for the 83 version.
I'm starting to assemble a replacement short block using a 1980 4.7 M28/11.
This block has the narrow thrust bearings and the split front main bearing.
I could drill the block and install a rolled pin for the full circle front main bearing and clearance the block for the wider thrust bearing easy enough I think...
Here's are my questions:
Can I run the 83 crank with the larger oil holes in the 80 block with the split bearings?
Is there any real advantage with the full circle bearing over the split bearing?
If I decide to try and drill the block for the rolled pin and wider thrust bearing are there any pitfalls I should try to avoid?
The mains cost alot more money for the 83 version.
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Joined: Jun 2003
Posts: 9,386
Likes: 72
From: Helsinki, Finland
I think thrust bearing change was done to make it stronger for automatics. Since yours is manual and probably will not load bearing any more than standard 928 I don't see huge benefit on late style bearing.
Single piece #1 main was made to prevent bearing from rotating and possibly make it stronger to resist load put on it by belts. Its only one out of five which was easy to change. If you just want some extra precaution against this problem you could add pins to all five bearings. If you would add SC then single piece could make sense.
I think later style crank will work fine on early block.
Single piece #1 main was made to prevent bearing from rotating and possibly make it stronger to resist load put on it by belts. Its only one out of five which was easy to change. If you just want some extra precaution against this problem you could add pins to all five bearings. If you would add SC then single piece could make sense.
I think later style crank will work fine on early block.
Race Director
Joined: Oct 2005
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From: Southern Utah
I think his reason for his madness was his very last line in the post. Not really for operational advantage.
Thread Starter
Racer
Joined: Feb 2002
Posts: 499
Likes: 19
From: Duluth MN
Thanks for the replies. I may add the late bearing on the front main just because I like the design. I'd be less inclined to drill the block side (Alusil side) for the rolled pin and more inclined to drill the aluminum girdle side though. Anyone done it this way?
And yes the question was more about the cost vs the benifit. If the bearing design change is more about the auto trans problem and less about oiling benifits I'll stay with the early style.
And yes the question was more about the cost vs the benifit. If the bearing design change is more about the auto trans problem and less about oiling benifits I'll stay with the early style.
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Joined: Feb 2003
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From: saratoga, ca
In building up several of these, i would use the bearings that came with the block type.
there is a problem with the later cranks, like an 84 with use on the 80 blocks. see my thread , but there is an issue with the block area where the counter weights will rub. a die grinder can clear this area for .030" clearance. other than that, no issues. scots is running fantastic and we used the bigger oiling hole 84 crank on the 80 euro block.
mk
there is a problem with the later cranks, like an 84 with use on the 80 blocks. see my thread , but there is an issue with the block area where the counter weights will rub. a die grinder can clear this area for .030" clearance. other than that, no issues. scots is running fantastic and we used the bigger oiling hole 84 crank on the 80 euro block.
mk
Thread Starter
Racer
Joined: Feb 2002
Posts: 499
Likes: 19
From: Duluth MN
Thanks Mark, I read about the clearance issue during my search. I'll be sure to check that. I managed to source enough parts locally to re-assemble my euro "S" short block. Thanks for posting.
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Joined: Feb 2003
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From: saratoga, ca
i showed one spot on the crank that i sanded down. (dremmeled)
there are actually to spots on that same counter weight. I dont think the other side of the thrust bearing was making contact at all.
its easier to sand down the crank than the block, and there is very little material that is removed so the balance on the crank is not effected too much.
mk
there are actually to spots on that same counter weight. I dont think the other side of the thrust bearing was making contact at all.
its easier to sand down the crank than the block, and there is very little material that is removed so the balance on the crank is not effected too much.
mk
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