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Always a good idea to Magnaflux the block.......

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The 3.8 na block is different when it comes to strength. lifter valley is not as strong as well.
I was told by other members on here that it was exactly the same, even has the boss for the turbo drain in the front of the block that just needs to be drilled and tapped..
 
Buicks leak oil,an break things alot, but it'll still get you home ...(useualy)... 8^)
 
gnfanatic,
I don't know were you got your information but the n/a 109 block is NOT any different than the 109 turbo blocks. Only thing is you have to drill and tap the front for the turbo oil return line.
 
gnfanatic,
I don't know were you got your information but the n/a 109 block is NOT any different than the 109 turbo blocks. Only thing is you have to drill and tap the front for the turbo oil return line.
Ok. so is this a definitive answer to this question?? This is another one of those 10 guys say this, 10 guys say that..... I'm looking for something so I can go rip one of the 3 people who've fucked me so far a new asshole...I know it probably won't get me any money back, but I'll be able to embarass them and call bullshit on bullshit and get it off my mind.
 
The 3.8 na block is different when it comes to strength. lifter valley is not as strong as well.
Wrong. The block doesn't have any specification before it was used in either application. I have cracked blocks and mains 4 times in the last 15 years. Everytime it was with a stock crank. Once it was girdled. The longest lasting one I have was an NA 109 that has seen at least 20 135+ passes and hundreds upon hundreds of hits on the street including N2O on top of an 800+hp tune. When in search of a good block I just pull the center caps and look for metal transfer beteeen the surfaces. If I see transfer I know the block has seen very high hp and or a lot of detonation and I make my decision very quickly.
 
Sorry guys, I misunderstood. I thought you meant all 3.8l blocks were the same. I misunderstood the 109 part.
 
When in search of a good block I just pull the center caps and look for metal transfer beteeen the surfaces. If I see transfer I know the block has seen very high hp and or a lot of detonation and I make my decision very quickly.

Please elaborate, I'm not a builder but have heard the terminology before and am interested...
 
You'll see evidence of fretting between the main registers and the caps themselves. This is due to the caps moving around. There will be metal transfer from the caps to the block and vice versa.

Neal
 
Thanks.....I understand now. I hazard to guess how many block have been sold or rebuilt in a garage and not had this done.
 
I've seen plenty of fretting on higher power motors that still did not have any cracks. The fretting indicates the caps are moving which is going to happen with high power even if it's clean, or it could happen at lower power levels with detonation.
 
I've seen plenty of fretting on higher power motors that still did not have any cracks. The fretting indicates the caps are moving which is going to happen with high power even if it's clean, or it could happen at lower power levels with detonation.
Yup
 
there must be some early 109 blocks that had less cast around the mains. The block i have now is this way ???
 
there must be some early 109 blocks that had less cast around the mains. The block i have now is this way ???
If you look at any of the blocks back to about 1982 the mains all look the same. If you have a production block it looks that way.
 
Does using studs help or make this problem more pronounced?
I just picked up a a low mileage NA motor and TH350 motor was running with about 80,oo0 miles on it.
I was planning on billiet center caps thats why i aske.
 
Does using studs help or make this problem more pronounced?
I just picked up a a low mileage NA motor and TH350 motor was running with about 80,oo0 miles on it.
I was planning on billiet center caps thats why i aske.

Using studs should help but won't eliminate the problem in a high H.P. application. Studs give greater clamping force than bolts which will reduce main cap movement. Billet caps will remove the possibility of breaking a main cap but they will walk also. Running an internally balanaced steel crankshaft helps a lot.

Neal
 
FYI,

Studs engage more of the threaded hole in the block than a bolt. A bolt, by design can never go all the way to the bottom of the threaded hole. If it does, there would be no clamp load at all. Proper stud installation includes taking a bottoming tap and cutting/finishing threads all the way to the bottom of the threaded hole. The stud is then threaded in as far as it will go.

My Thoughts: A stud may provide some additional protection against this type of damage because it pulls on more material in the block. I have a friend who is a fastener engineer. I'll ask him for his opinion.

I think Neal is right on target with his comments: Steel crankshafts will flex much less and therefore the crankshaft will not load the 2 center caps.

Dave
 
How do you think rotating assembly balance (bob weight) affects cap walk? I'm not 100% on what the different balance percentages do, but doesn't one limit affect horizontal vibration and the other vertical?
 
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