# 350 block ? 1pc vs. 2pc, 2bolt vs 4



## BIGRIGZ (Oct 2, 2007)

On a SBC 350, the older blocks (pre-1985 or so) have a 2 piece rear main seal, the newer 350 blocks have a one piece rear main seal.

*Will ALL of the accesories interchange?* (such as starters, intakes, exhaust manifolds etc)

Plus, I understand that boat engines have a steel crank (needed for the higher RPM use) but, *does it matter if the block is a 2 or 4 bolt main when being used in a boat?*

Thanks for any help!


----------



## Tuna Man (Oct 2, 2007)

> *BIGRIGZ (1/4/2008)*On a SBC 350, the older blocks (pre-1985 or so) have a 2 piece rear main seal, the newer 350 blocks have a one piece rear main seal.
> 
> *Will ALL of the accesories interchange?* (such as starters, intakes, exhaust manifolds etc)
> 
> ...


2 or 4 bolt main? No it doesn't matter. People think that a 4 bolt main is stronger, well maybe in applications where RPM's exceed 8, 10,000 it might. I have seen broken cranks, but never a bottom end come apart because of it being a 2 bolt and not a 4 bolt. I have seen REGROUND (personally stay away from them/ok in automotive applications) crankshafts break, so I bought a NEW one for my 350 application. No problem with the accessories. Marine heads are different for marine applications then automotive, also the heads for the 1 and 2 piece seals are different, gasket sets are different. Marine V8 gas applications generally get about 1,000 hours of life......I say generally.

Starters are different for CW and CCW rotation, and replace a 2 long bolt starter with a 2 long bolt starter. Some have (mount with)2 long bolts and some have 1 long and 1 short bolt. My post 1986 uses a 2 long bolt starter.

Two exhaust/riser manifolds for GMC5.0/5.7 are used, a 3" and a 4"...not interchangable

Head... http://www.go2marine.com/product.do?no=82907F

Intake... http://www.go2marine.com/product.do?no=90133F

exhaust... http://www.go2marine.com/product.do?no=90151F


----------



## BIGRIGZ (Oct 2, 2007)

WOW, Tunaman! You're a wealth of SBC info!! How did you learn so much about engines? I want to learn everything I can about them. This is my first 350...

Are there any other things to consider if shopping for a block to build?

Thanks, Ken


----------



## X-Shark (Oct 3, 2007)

> WOW, Tunaman! You're a wealth of SBC info!! How did you learn so much about engines?




Because when we were "Young" we eat, sleep and drank this stuff. 



I gotta agree about the 2 bolt vs 4 bolt main's. The rods will come out of it before the mains do. 



Max Rpm I bet you ever turn with the motor is 3500 as the secondaries will be open and you will not like the fuel bill. Cruise will be right at 3000RPM.



Forget all the power adders that make power at higher RPM. If you add them it will be a Pig. You want Low and Midrange Torque.


----------



## Tuna Man (Oct 2, 2007)

> *X-Shark (1/5/2008)*
> 
> 
> > WOW, Tunaman! You're a wealth of SBC info!! How did you learn so much about engines?
> ...


Got about 9 years on you..:doh..Yea as kids we ate, slept and drink that stuff, not necessarily because we couldn't have someone else do our work (1965 working in a body shop for $5.00/hr), but we came from a different generation. We (for the most part) wanted to do those things instead of sitting in front of a TV playing games (which we didn't have). Our thing was meeting at the local gathering hole and showing off the enginewe just built.We weren't raised in a drug happy society, like this or last generation is, so we didn't have to be concerned with that peer pressure.

BIGRIGZ....Like I told you on the phone...SBC were my thing and I can just about put one together blindfolded if someone would adjust the torque wrench for me. Although many things have changed since the early 60's, the SBC's relatively remained the same. The 265/327 and the 350's were GM's backbone of V8's. Now they put all this damn electrical/electronics in vehicles it can and will drive me crazy.:banghead:banghead:banghead:banghead


----------



## fishnfool (Oct 2, 2007)

yep, the SBC is what we all grew up on(at least if you wanted to go fast....reasonably priced!) I agree about the 2 bolt vs. 4 bolt blocks as well. The factory two bolt blocks actually have more material cast into the main webs than the four bolts do. That why a lot of guys that race a two bolt block will just do splayed four bolt caps and MAKE the two bolt into a four bolt and be stronger. From a low maintenence standpoint I'd go with a late model 1 piece rear main seal though. It's just easier to do and the new blocks are OK for the most part. Not AS strong as the older heavy castings but good enough. 

I'm finally getting away from the old SBC ways and doing my first LS1(genIII) motor stuff now. My 92 Camaro is getting it's transplant right now and it'll be a carbed 98 LS1 with a good set of CNC'd heads, a BIG camshaft, 2002 rods with a load of ARP bolts and studs throughout. It pulled well over 400rwhp before it got freshened up so we're hoping for more(huh Matt?) Add a little spray to it and I hope it will be happy!! Good luck with the motor.


----------



## sniper (Oct 3, 2007)

I think the change year was 1987 

Things that wont work from one to the other:

Heads

Intake Manifold (due to differant bolt angles on 4 of the bolts)

Fly Wheel (Differant Bolt Pattern)

Oil Pan (Main Seal Size is Differant)

Other than that everything is interchangable.

Starter is the same.


----------



## Hook (Oct 2, 2007)

> *X-Shark (1/5/2008)*
> 
> 
> > WOW, Tunaman! You're a wealth of SBC info!! How did you learn so much about engines?
> ...


Unless you are going to build up the compression of the motor you will NEVER need a 4 bolt for a boat.


----------

