Alwyn678

Is the 4 bolt main really necessary or worth the extra $ in a soley used street car application?

MrJlr

IMO....no. You'd have to be running high RPMs and a lot of HP before that became an issue.....
A 2 bolt main if fine to around 500HP....

A SBC 2 bolt is a stout little dude....no worries...

Easy Mike

No. Nice to have, but not necessary.

TheSkunkWorks

As mentioned, not really necessary for milder applications, but definintely more desirable the furhter you intend on pushing things. You can always install main studs (suggest ARP or Milodon), or convert to 4-bolt with aftermarket splayed caps, so ultimately there's nothing really wrong with a good 2-bolt block.

1955pirate

My '69 coupe has the 300 HP, 350ci engine. When I had it rebuilt I was somewhat surprised to find it is a 4 bolt main engine. I guess I assumed the 300 hp was a 2 bolt. Is there an alpha/numeric designation for the '69 300 horse engine?

Alwyn678

Ben Lurkin

Depends on the engine and what you plan on doing with it. For most applications a 2 bolt is fine. However, high hp applications, high rpms or a power adder need a 4 bolt in a sbc. I've had the main bearing caps walk on 2 bolt 400's which means you just lost the bottom end. These were street-strip engines that hit 6500 rpm with some frequency. A 350 or smaller would go more.

A BBC is almost bulletproof with a 2 bolt. Unless you really spin one of those, 7k or higher, they will be fine. Again, a power adder changes the picture.

427Hotrod

I feel better having then in my street car!

JIM

Indiancreek

Many Ford engines at the race track in two bolt as well as Chevrolet. There has been debate on this topic since the 60s, as I expect will happen again in this thread. They range from cap walk to weakened upper main saddles.
Personally I feel if you run a WELL balanced internally balanced engine with in 7,000 rpms or so either will serve you well as long as there are no other issues. I would like to know the ratio of main issues to crank rod and piston issues.
Normally when you loose a main, something else took it out. Crap through the bearings as an example.
I'd bet a dirty engines have taken out more mains than the caps. Not getting out all the junk empackted in oil journals claim more mains and rods for that matter I'd guess. Jet washers don't always get it all out.

Corey_68

For a street/DD money is best spent elsewhere IMO.

surfertom

install a stud kit on the mains , no worries

Indiancreek

If you go to studs, then align hone, you may as well pick up a set of splayed cap billet caps since you'll be paying for an align hone anyway. You can find them used on line and at swap meets for a fair price. It's easier to align hone the used ones anyway.

bmans vette

Just about to say the same thing.
Studs are great but most people think you can just swap out the main cap bolts for studs.
Same goes for swapping main caps to billet caps.
Line hone will run anywhere from $300-500.
If you are going to that expense why not go 4 bolt main?
Others may experience other mileage.
Bman