Its a broken Main cap... The ones that hold the crank in place, they say they cant get away with just honing so its getting bored out and its getting JE forged pistons and rods. He is cranking the compression up to 11.1 by using different pistons. Also he is polishing the crank. So will my car still be driveable with the old tune? Or will i need to get it tuned right away? Any imput appreciated. Thanks.


Chris

 

If that is all he is doing, you will not need a re-tune. Your only up-ing compression half a point and adding 5 cubic inches. If the tune changes, it will be very minimal. After a while, you could have it checked for sh*ts and giggles.

 

Must have missed the original post, but how in gods name did you break a main cap? And if it broke, how didnt it trash the crank too?

 

I have no clue how it happened. I lost oil pressure on the dyno, it dropped to 25 at WOT at 6K, but he wasnt even revving it past 6K. The car is a 95 with only 83K on it..... So now it will have a new engine basically. The shop is very reputable and said the crank was fine. They are just going to polish it up. I also thought it was weird.... But I guess we will see how she runs after I get her back and broken in correctly....


Chris

 

Samething happened to mine. I think its common with LT1 6spds. When i bought my car it thought the oil pressure was low it idled at about 20lbs. I only drove about 20k before pulling the engine for a rebuild, because of stripped spark plug hole.I sold my motor to a buddy and when he was pulling it apart all the bearing were worn pretty bad, and when he took one of the main caps off it fell in two piece. I can't believe the car ran like that and it even saw some 5500k revs. I have a theory that its because my car was daily driven by a woman and i think she lugged the motor to much and beat the bearings out and broke the main cap. Now i never cruise with my RPMs less than 2k.

 

Hmm interesting. Ive seen ton of spun mains, but cant say i have ever seen a cap broken.

 

I guess i wouldn't say its common but i've seen it a few times on the board. Everytime it was a 6spd car.

 

Hm..... That is an interesting theory, i have always heard that it is bad for the crank to lug on it.... Guess I will try not to do it this time around!


Chris

 

It also beats the bearings out of a motor too. I would much rather spend a little more at the pump, and keep my motor at about 2k rpms when i'm cruising rather than beat the bearings out.

 

2 things:

1. I'm sure that there are many on here who have dealt with "so-called" reputable shops. Just bear in mind that auto shops are just like restaurants i.e., one person's opinion of the food may be that it is just wonderful but another's might be "it sucks". Just a reminder that you need to deal with most mechancis in person on location and not just take what they say oveer the phone as gospel.

2. Unless you witness the dyno and have the readouts to prove it, I wouln't necessarily take the dyno man's word that he/she didn't really over rev the sucker on the dyno. If your rev limiter is set really high on a high milage, heavily used motor, I believe that it is possible to do damage to the internals by overreving. Only had mine dynoed once, but I was doing the driving and made certain that I didn't rev it to 7 grand. JMHO