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View Full Version : Issue's with walk main bearing caps. With blower motor.


57 Chev yellowjacket
06-25-2012, 09:39 AM
Looking for some help.

I run a Bbc superchagered 14/71 k-8 @ 43% overdrive it makes 40 lbs of boost here, Mag 44 with crank trigger at 32 degrees. I run a lenco auto.

1.) My first problem is that i'm walking the main bearing caps with this tune up. The car works great here i run a 6.88 @ 214 mph.

I heard from some other engine builders that the caps were walking on them with the timing at 32 degrees and they are have better luck at 28 degrees and then creeping up on it to 32 degrees.

Would anyone out their have some experience with this matter?

Gaz64
06-26-2012, 03:17 AM
What fuel are you using?

32 degrees seems a lot for 40 psi of boost pressure.

With a motor like that, you should have a main cap girdle.

57 Chev yellowjacket
06-26-2012, 07:03 AM
I'm running alcohol. Who would make one of these girdles? This is a Merlin 4 blot main with steel splayed main caps.

msdtech1955
06-26-2012, 10:34 AM
you cant just slap a main gridle on!

the best way , is to have the motor a[part ...( no crank in it)
torque the main bolts and gridle THEN check the bore on the crank journals

also, nothing else is damaged in the motor?

57 Chev yellowjacket
06-26-2012, 04:50 PM
Sorry maybe some miss understanding here. We run it with this tune up it works great be we had to turn it down a little.

When we were checking the bearings and removed the main caps it showed signs of metal transfer from the block to the caps.

Now talking with some other engine builders. They had this happen to them and this thoughts were it was to much timing. With his blower motor he's running them around 28 with MSD digal 7.
I'm trying to find out if there's anyone out there that run it to this to learn a little more. I know there's guy's out there that are running bbc that easily make 2500 Hp. I'm just try to find out how there doing it.

As for a gridle i haven't even seen or hread of one for a Big block Chev. Is there one?

msdtech1955
06-27-2012, 09:19 AM
what size fuel pump ?

buzzard catcher or a big and ugly?

57 Chev yellowjacket
06-27-2012, 09:30 AM
I don't have the info with me on fuel pump. I work away from home and won't be there for another 15 days. Can i get back to you on this. This fuel system has been all flowed. If that helps?
The hat is a carbon Fiber i think it would be a buzzard Catcher. I think it a Mark 5 i believe if that helps also.
Just a question. Where you going with this?

msdtech1955
06-27-2012, 10:47 AM
trying to figure out if the motor is happy on fuel...
does this have a data logger ? and what are the cylinder temps?

57 Chev yellowjacket
06-27-2012, 11:50 AM
Yes i have a v300. Cylinder temps were only 950's highest 1100 kind of in this range. We still had to clean this tune up a little. But when we found the metal transfer we backed it right off to figure some things out. But would really like to turn the over drive back up again. We did put on a fuild damper in the bottom pulley when we fix the main caps. Because when we tried to pull the blower hub off it was weld on we distoryed the puller tring to get the hub off. There was only 9 pass on the motor.

msdtech1955
06-27-2012, 04:09 PM
and did we check the zero mark on the balancer >

57 Chev yellowjacket
06-27-2012, 04:24 PM
Yes. Everything was set up correct.