SM performance billet 4 bolt mains?

[daytonairoc]

I was reading a thread about cranks when somebody mentioned there are 4 bolt mains for our blocks. This was the first time I've ever seen this.

I wanted to get some more info. I'm in the process of building a 2.5T1 motor. This motors duty will be mostly autocross and lapping days with less then 20 lbs of boost depent on the event. Basically I'm using stock parts with a few extras like ARP fasteners, Shot Peened rods.

I like to find more info on these SM performance billet 4 bolt mains. Like do I need to line bore the caps if I use arp studs or mains bolts? Whats the cost? Do they use the OEM main bearing?

I haven't been able to find a website on them either.

[OmniSRT4]

Quote:

Originally Posted by daytonairoc I was reading a thread about cranks when somebody mentioned there are 4 bolt mains for our blocks. This was the first time I've ever seen this. I wanted to get some more info. I'm in the process of building a 2.5T1 motor. This motors duty will be mostly autocross and lapping days with less then 20 lbs of boost depent on the event. Basically I'm using stock parts with a few extras like ARP fasteners, Shot Peened rods. I like to find more info on these SM performance billet 4 bolt mains. Like do I need to line bore the caps if I use arp studs or mains bolts? Whats the cost? Do they use the OEM main bearing? I haven't been able to find a website on them either.

http://www.streetmachineperformance.com/

You can PM them here at the username SMPerformance.

The story is this. SM Performance (the 9 sec guys in canada) made some of these for there race car. I contacted them about them and I was told they would reproduce them for I believe 300$ a set.

As far as I know, the only people who know about these is SM performance, and anyone I have told, since these have never been advertised anywhere.

[iniviate]

you will need to have the block line bored if you're using different caps...

[contraption22]

Has anybody ever broken a main cap?

[DirectConnection]

Quote:

Originally Posted by iniviate you will need to have the block line bored if you're using different caps...

Correct. Even if you were to tear-down the shortblock... I'd reccomend line honing the mains since they will be out of round from all the years of service.
I haven't seen a main bearing failure in these cars so I wouldn't be overly concerned, especially at the power level you are going to run at. 500hp is a different concern.

[OmniSRT4]

Quote:

Originally Posted by contraption22 Has anybody ever broken a main cap?

Not that I know of, that is not what they are for. The 4 bolt billets reduce flex, just like a CB vs a Non-CB. If you broke a main cap then you are beyond help.

[OmniSRT4]

Quote:

Originally Posted by DirectConnection Correct. Even if you were to tear-down the shortblock... I'd reccomend line honing the mains since they will be out of round from all the years of service. I haven't seen a main bearing failure in these cars so I wouldn't be overly concerned, especially at the power level you are going to run at. 500hp is a different concern.

I suggested using them if he was using a non-commonblock. You dont need anywhere near 500hp to get excessive flex in some of the older blocks. (more like 300) I would recommend using them in combo with a cast crank on a 16v hybrid as well.

[DirectConnection]

Quote:

Originally Posted by Akuma I suggested using them if he was using a non-commonblock. You dont need anywhere near 500hp to get excessive flex in some of the older blocks. (more like 300) I would recommend using them in combo with a cast crank on a 16v hybrid as well.

I wouldn't doubt there's alot of flex in a 300hp common block, either.
Not sure why someone would want to go through the extra effort of installing these in the early style block, when simply going to the common block with *much beefier mains* would be much easier and cheaper.

Like I mentioned... never seen or heard of a main bearing failure, but doesn't mean it hasn't happened either. I think if the mains are more secure, then the crank may not want to flex as much, and possibly help keep rod bearings in line and square. (I have seen alot of rod bearing failures though)

Wouldn't hurt to upgrade to them though if you look at it that way.

[OmniSRT4]

Quote:

Originally Posted by DirectConnection Like I mentioned... never seen or heard of a main bearing failure, but doesn't mean it hasn't happened either. I think if the mains are more secure, then the crank may not want to flex as much, and possibly help keep rod bearings in line and square. (I have seen alot of rod bearing failures though)

Thats exactly what they are for. This is why chevy went to 4 bolt mains on its small block.