I am getting ready to buy a 306 or a 402 to swap in.

The thing is they are only 2 bolt mains.
Is it pheasable and reliable to drill new bolt holes to transform to 4 bolt mains?

 

306?? Are you talking a 301 Poncho bored .030" over?

And do you mean the 402 Olds engine? Or the Chevy "396" from the good old days?

Is this for a 3rd gen?

What's you goal as far as 1/4mile ET, MPH, HP, Torque? The more info you can give, the more we can help.

 

sorry that was a 396 missed the number.. and a 402.

I was hoping to have motor rebuilt and ready to install by summer, if I get it soon. It will go through 2 stages.
The first rebuild was going to keep it carbed(for easy install to 3rd gen, nothing truely special untill I get done with school and have some real money.

The second stage was going to be rebuilding with real parts(hiPO) and swaping to EFI(TPI) and eventually see an ATI with turbo style front mount intercooler.

 

Most later SBC case castings are well suited to conversion to four-bolt caps down the middle three positions. Some older cases don't have a lot of web material if the core shifts were excessive, and might not be suitable for even TWO good holes. This is a common conversion on SBC engines. I'm not sure what engines you're asking about, however. A 305 or 400 bored +0.005" would yield those numbers.

 

396BB and a 74 402 chev BB

 

403 A.K.A. 6.6 litre

 

well would it be advisable to add 1/8"-3/16" TIG welded titanium plates to both sides, given they will clear without interferring with the connecting rods?

 

People do 4-bolt conversions all the time. It's the preferred method of improving that part of an engine, better than factory 4-bolt caps.

Milodon, Callies, maybe Oliver, maybe others, make caps that you install onto a 2-bolt block. They have the 2 outer bolts "splayed" for added strength, rather than being parallel to the 2 center ones like factory 4-bolt caps.

I would not weld on the caps, it isn't the weak part, the hardware is.

 

Was it a 403? My bad

 

so the BBC could take a drilling, and not fall apart? and the machine shop could use the 4 bolt caps to line & drill the extra holes then of course tap them.

 

Part # 11200 Milodon.

IIRC they supply the dimensions for the holes - angle, distance, etc.; I don't think you'd want them just using the cap as a drill bushing, wouldn't be precise enough since the hole in the block for tapping would be smaller than the clearance hole in the cap. But I could be wrong, there might be some ways around that issue.

 

cool, looks like I will be spend that 175 for the engine then.

 

You'd bolt the cap in place then put a drill bushing into the open hole in the cap, starting small and working your way up to the size needed for the tap.

 

Personally, I wouldn't bother trying to four-bolt a two-bolt block UNLESS you are planning on a constant 550 or 600 horses or more.

The big-block two-bolt main caps are much larger than a small-block two-bolt cap.

Not worth the money, in my opinion, by the time you count the new caps and the machine work (drilling the block and line boring/honing).

Besides, it's not that much more to go ahead and get an original four-bolt block.

I've run two-bolt and four-bolt bb Chevys many years.

The main web area is not the weak point in a big-block.

My two-cents worth.

jms

 

I sware the moderators here on some of the boards are real dicks...


but back to the subject at hand.

I do not really have all that many choices for engines locally. Like I said, I can get a 4 bolt 350, and stroke, but I just think that that has been overdone. I want something different.

So I have a 396, or a 402. I really do not want a 454, but a 427 would be sweet....

 

An all Alumnium 427....drooooooool.