SBC 4 bolt vs 2 bolt

[Joker69Camaro]

Im in the middle of part collecting for my project. I was kicking around doing another motor, the camaro has a fairly fresh (>20k miles) 350 warmed over with world heads. It is the original block for the 69 camaro and has a 2 bolt main.

My question is it it really worth the hunt for a SBC 4 bolt 1 piece rear main to build a new motor? In addition, I honestly lack the room for a block in my garage. (under the bed is out too, there are lights, electrical and body panels there.)

I suppose I should add that I would like to go with a supercharged 383 in the end.



Thanks for your input.

Jeff K

[Randy67]

I would convert your block to a splayed 4-bolt main, instead of finding an existing 4-bolt block. JMHO

[Joker69Camaro]

I never even thought of that option...good call sir!

[wendell]

Seeing it's the original block, I wouldn't do anything to it. Either drive it as is (with out putting a rod through it) or make space under the bed for it. In a few years (when everyone is goofing on the out dated PT cars and you can't give them away) there'll still be a strong market for an original '69 camaro.

[sharp67]

I built a hi power 383. After all the machine work on the block and adding billet splayed 4 bolt. I was in it deep. After the fact I realised I should have bought a after market iron block that was already machined. It would have been close in total cost and the aftermarket block has several benefits over a stock gm block.

[Joker69Camaro]

Thanks for your input guys! I think Ive decided to keep this motor in the car untill the project is done, then I may do something at that point. I looked at all my documentation last night and realized the motor only has 11k miles on it, after it was built 4 years ago. Other than a leaky rear main seal, she's fairly strong.

Thanks for the input!
Jeff K

[Randy67]

Other than a leaky rear main seal, she's fairly strong.

That means it's running right. Just about every 2-pc rear main I have seen either leaks or weeps oil to some degree. If it's not leaking, check the oil.

[Joker69Camaro]

Lol this is true, when I built the motor no leaky ,this time i paid someone to build it (pins in shoulder said i couldn't turn wrenches)and it leaks. Go figure.

[senor_camaro]

2 bolts are good up to 500 hp, or so Ive heard. if your buidling a High HP engine I would go 4 bolt or aftermarket block. It all depends on your budget. Once my 2 bolt goes Im buying an LSX motor and swaping it in.

[TT302Z28]

I have beat the hell out of 2 bolts and never broke a cap....This is one of those things I believe to be just like cams..if 2 is good you must need 4.

If you are going to throw big power adders at it, be sure to stud the bottom end. This will keed the caps from walking. BTW, that is what the 4 bolt blocks were for.

One more thing, it has been noted over the years that 2 bolt blocks are stronger than 4 bolts in the main webbing area. The outer bolts and material removed for the larger caps weaken the blocks core.

Keep your good engine and build a $50 4 bolt if you really feel you need that.

[TT302Z28]

What are the most likely points of failure in a SBC? Rods, Crank, Cam, Pistons.

[JEFFTATE]

If I was gonna' build a stock GM small block ( for serious use ), I wouldn't hesitate to use a 2 bolt block.
But , I would have it machined for the splayed 4 bolt caps.
I'd use steel caps on it , with a forged crank , high quality lightweight rods , and forged pistons..
But , the cost of an aftermarket block has come down so much , I'd go that route , if my budget permitted..

The usual thing that goes on a smallblock is a rod or bearing , or the crank.

[WS6]

Another thing that was touched on sort of for anyone to consider is that the "modern" 86+ SBCs are very easy to find with a roller cam and single piece rear main seal. You also get the center bolt valve covers which tend to not leak unlike the perimeter bolt valve covers. If I was going to build a SBC, I would find an L98 (350TPI) or any number of other car motors that had a roller cam and one piece rear main. The benefits of a roller cam are tremendous. The ever so popular GMPP ZZ4 is nothing but a carbed L98.

Besides, steel caps and ARP studs on a 2 bolt engine is plenty strong enough for a hot rod that's making good but not ridiculous power. You'll save yourself a bunch of money if you're honest about the build and could care less about impressing people with your parts list.

[Joker69Camaro]

Thanks guys this is alot of the information I was looking for and confirmed alot of the things I have allways believed true.
I believe if/when I replace this motor it will most likely be with a aftermarket block.