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Author Topic:   377??
dirtracer14
Dirt Maniac

Total posts: 128
posted August 05, 2001 03:26 PM UIN: 23443678
Are there any real tricks to a 377? We have lost the same one 3 times now. The first time the 3 inner mains broke. The second time we lost the cam (to much spring). Now the 3rd time we put about 20 laps on it and the filter is full of copper. I havnt pulled it apart yet to see i kinda wanted to see if there were things i should look for as i was taking it apart.Thanks

Racer4
Dirt Forum Racer

Total posts: 93
posted August 06, 2001 03:34 PM
Are you running the spacers for the bearings? I have heard these cause too much deflection. So a lot are going to cranks like scat offers with the 400 main sizes. Also are you running the fact 4 bolt block? If so, this is supposed to be a weak setup. Have you had the line bore checked on the block?

dirtracer14
Dirt Maniac

Total posts: 128
posted August 06, 2001 08:16 PM UIN: 23443678
This last one was a 4 bolt the first one was a 2 bolt the 2 bolt broke the 3 inner caps. I pulled the 4 bolt down last night and found that the thrust bearing was gone on the back side of the rear main but didnt apear to be bad in the block. It looked to me like the rear cap had been walking from the wear between the block and the cap. The 4 bolt block was just line honed not bored and the 2 bolt was bored. I think ill look for a new block to start with. Btw the reat of the mains looked ok.

Racer4
Dirt Forum Racer

Total posts: 93
posted August 07, 2001 02:42 PM
From what I gather on this board the only way to zing a 400 block is to use splayed caps, also I don't know all the casting #'s, but with any block there are good one's and bad one's, the 509 was a good one, I know there's another too.

dirtracer14
Dirt Maniac

Total posts: 128
posted August 08, 2001 12:06 AM UIN: 23443678
This was over 13 to 1 with light weight pistons and rods I think we will stick to the 350s

CUZZ45
Dirt Roller

Total posts: 7
posted August 10, 2001 07:10 PM
IF YOU ARE USEING H TYPE BEARINGS MAKE SURE THE TANGS FIT INTO THE SPACERS I HAD TROUBLE WITH THIS AND HAD TO FILE THEM DOWN A LITTLE IF YOUR NOT USEING THE H'S AND YOU ARE RUNNING AN AFTERMARKET CRANK THAT COULD BE THE TROUBLE

owracer
Dirt Maniac

Total posts: 103
posted August 11, 2001 07:38 AM
I built a 377 last year and also had the same problem with wearing the backside of the thrust bearing. My machine shop told me that too much pressure against the back of the crank caused the wear.
I was also told when I started building this engine to use as long of rod as possible to relieve side pressure on the cylinder walls.These engines tend to want to split the no.7 cyl wall.

dirtracer14
Dirt Maniac

Total posts: 128
posted August 11, 2001 10:27 AM UIN: 23443678
I think the the rear cap was tipped on the block, Only 1/4 inch of bearing was hitting.We got the block used and i think the caps were from another block. I think if we try to build it again we will use a block that was running befor we start or if i can find a good used bowtie block

BILLY BOB
Dirt Forum Racer

Total posts: 81
posted August 29, 2001 02:59 PM
The best way to go is to use the two bolt casting and splay the caps. The 2 bolts have more meat where the mains attach and make a better unit.

doowchuck
Dirt Full Roller

Total posts: 45
posted August 29, 2001 07:07 PM
I also run the 377 and have broken the center main caps. I went to billet caps but didn't bother to wse the splayed bolts.
Seems to be OK so far. My fingers are crossed.
John

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