Crank and Block

T

turboman38

It costs money to go fast
Joined
Aug 1, 2001
Does anybody know what the real difference between a turbo block and crank and a normal 231 block and crank? I have heard the turbo block has an extra oil passage drilled for the turbo and a turbo crank has the "rolled filets". Are there any other differences? How much stronger is the turbo crank?

Also are the rods the same between the two engines?
 
Yes, the rods are the same. The differences between the block and crank are very well versed on gnttype.org.
 
The 109 block is identical in N/A applications except it has an oil drain back hole.

The N/A crank is a door stop

86/87 3.8 Rods are all the same front wheel drive or rear.

The 86/87 heads 8445 are all the same.

4.1 and turbo cranks are the same rolled fillets on all journals.
 
Originally posted by turbodave231
The N/A crank is a door stop
Click to expand...


Who has actually destroyed one of these? What conditions did it fail under? I understand how the rolled fillets will strengthen the crank. I just want to know where and when an N/A crank will fail.
 
So, you mean you want to be a cheapskate and use a NA crank? That's only going to last if you keep the boost way down and never, ever...ever detonate the motor, and do nothing more than drive the car on the street in a nice polite fashion.
 
Originally posted by Ellis
Who has actually destroyed one of these? What conditions did it fail under? I understand how the rolled fillets will strengthen the crank. I just want to know where and when an N/A crank will fail. [/B]
Click to expand...

Have a non-turbo crank from a 3000 mile '87 only driven on the street, some WOT, but not abused. Caused $3k damage to the motor.

Wouldn't we ALL like to know when and where our cranks will fail?

It has to be the opposite of smart to invest thousands of dollars into a car/motor, and NOT use the proper crank [or other good parts].

The GM engineers specified this crank for the turbo motors only, so they must have had good reason to spend the extra few dollars.
 
I too would like to have some sort of idea what these cranks can withstand. I know, it sounds cheap, but the turbo cranks are not easy to come by. I have 4 109 blocks sitting on the floor. One has a destroyed turbo crank. Cannot be turned. The other all have rolled fillets on the mains, but not the rods. They came from the junkyard like this. The motor in my car has a non turbo crank also. I did not know this when I bought the engine. It was out of a 1986 GN, and it had been freshened up before I bought it. I destroyed the bearings(they all just fell out when the caps were removed. I even melted a piston. A good 1/2 - 3/4 inch section, gone! But you know what, the crank is fine. Now that is 5 109 blocks, and no turbo cranks. That would be a ton of moeny, and alot of searching to find 5 cranks.
If the block is girdled, will this help the crank last longer? Just looking for alternatives.

How did I do that to the motor?? Well, I run some pretty good numbers (12.5@ 108) with 25# boost on 93 octane(alcoholic motor). I was tuning it, and pushing it to the edge, and then over the edge last year. This year the boost is lower, and I am seeing similar times with less traction. (Looking for 11's on whitewalls. I'll do it, even if it kills another motor!)

Brian
 
Originally posted by Scott231
So, you mean you want to be a cheapskate and use a NA crank?
Click to expand...

No, I am not looking to be cheap. I asked a legitimate question out of curiousity. That the GM engineers put them in the turbo motors "for some reason" doesn't answer the question. These are the same group of people who put the weeny 7.625" 10 bolt in the M6 Firebirds and Camaros with LS1s.

The only difference on an N/A crank is the lack of rolled rod fillets. The rod fillets are a copressive residual stress. What I understand is that this helps significantly with FATIGUE strength. I only know one guy personally who has destroyed a crank. It was a turbo crank in a drag only F-body, and it bent. He was revving high and boosting hard. Crank bent between the mains. The throws were not the source of failure.

So, maybe a better question is this: do the cranks tend to fail by snapping off rod throws? Or do they twist the crank apart at the mains? It seems that under detonation, the most prodigious amount of stress is placed on the mains, not the rod throw.

Not trying to upset anybody. Its just a question.:)
 
Originally posted by Scott231
So, you mean you want to be a cheapskate and use a NA crank? That's only going to last if you keep the boost way down and never, ever...ever detonate the motor, and do nothing more than drive the car on the street in a nice polite fashion.
Click to expand...
This is so un-true I about fell out of my chair! There has been more than one NA crank run into the 10's. Actually the guy Rich from Rich's Auto in NJ has been running one for about 2 years in the mid 11's and I know one other person personally going 11's and running over 20 PSI with one.
 
not being a smart a$$ INTERCOOLER, but would you use one? i have often wondered the same thing that he is asking, but i feared stuff being thrown at me..( ducking now )!!!!:D
 
Originally posted by peterkin
not being a smart a$$ INTERCOOLER, but would you use one? i have often wondered the same thing that he is asking, but i feared stuff being thrown at me..( ducking now )!!!!:D
Click to expand...
I have! My car only ran 12.8 but I beat the crap out of it and sold the motor. It isn't my first choice but at the time it was all I had access too. I have also used a .010"/.030" turbo crank into the mid 11's with no problems. I would look for a crank that will clean up at .020"/.020" and use it first as a middle of the road low buck option ($120) and if you can't afford a .010"/.010" ($300). Next would be a NA crank in the $135 range.
 
Originally posted by Intercooler
This is so un-true I about fell out of my chair! There has been more than one NA crank run into the 10's. Actually the guy Rich from Rich's Auto in NJ has been running one for about 2 years in the mid 11's and I know one other person personally going 11's and running over 20 PSI with one.
Click to expand...
And they are NOT detonating their motors. Ad Nick stated, why would you put in an inferior piece? Turbo cranks aren't that hard to come by...you just have to pay for them. There are prolly 3 or 4 always up for sale on gnttype and prolly a few here in the parts for sale section.

Just because someone is asking $400 for a crank doesn't mean they will not take less for it.:rolleyes:
 
geez, I bought one at a local machine shop already machined 010/010 for $155...went back a year later and picked up another one, 010/010 for $200...

Try your local automotive machine shops...You have to tell them to look for the ones with the pressure rolled fillets on the rod journals(most don't know there is a difference), but you'd be suprised, they are out there...Most places usually have a few extra core cranks around...The place I got mine from had to look through all of the ones the had to find one...
 
The 109 block is identical in N/A applications except it has an oil drain back hole.
Click to expand...

Not too sure about this...it seems there is much more meat in the lift valley and lifter bore area of the Turbo than N/A block.
 
Originally posted by GTEATER
Not too sure about this...it seems there is much more meat in the lift valley and lifter bore area of the Turbo than N/A block.
Click to expand...

Are you comparing the same castings? You can't compare a 84 block to a 86 block. A '109 casting is a '109 casting.


The 86/87 heads 8445 are all the same.
Click to expand...


'8445 heads started in 1983 and where used on 4.1's and some FWD motors as well. Very common peices.
 
I had a N/A crank in my gn for over 2 years w/ about 2500 miles on it. I went 10.40's a bunch of times at the track. I was not aware the shop I had the rebuild done at put in the N/A crank. I always ran C116 gas, and had speedpro engine mang. system (30 psi boost). I had the motor rebuilt when I found the N/A crank, but I never hurt that crank. If you don't detonate it the N/A crank will live.

Mike B
St. Clair Shores, MI
 
Originally posted by Intercooler
Actually the guy Rich from Rich's Auto in NJ has been running one for about 2 years in the mid 11's and I know one other person personally going 11's and running over 20 PSI with one.
Click to expand...

Who's that?

-Banning.
 
quote:
--------------------------------------------------------------------------------
Originally posted by Intercooler
Actually the guy Rich from Rich's Auto in NJ has been running
one for about 2 years in the mid 11's and I know one other
person personally going 11's and running over 20 PSI with one.
--------------------------------------------------------------------------------

Who's that?

-Banning.
Click to expand...

Uh, I think his name is Rich:rolleyes:
 
No, I'm talking about the "...one other person personally going 11's and running over 20 PSI with one."

-Banning.
 
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