Heads

Looks like the difference is the 2 bolt vs 4 bolt... Plus the 2 bolt has vortec heads?...
If u call summit they will tell you im sure
Dc

 

Looks like the difference is the 2 bolt vs 4 bolt... Plus the 2 bolt has vortec heads?...
If u call summit they will tell you im sure
Dc

The L31-R engine has 4 bolt mains and Vortec heads as well

 

There is no functional difference between the 906 head and the 062 head, with one exception. Some of the 906 heads used in heavy duty trucks had a difference in the exhaust valve seat area which reduced flow.

I have no idea whether this has continued to replacement parts or not.

There is lots of internet chatter (and some errors) about this if you'd care to google it.

Here's a short description which I think is pretty accurate:

"Two Vortec castings were used from 1996-99 on GM CK trucks ('00 in vans) and SUV's utilizing the Vortec 5700 350 engine. The #906 and #062. The #906 casting head was available in two versions. One has an Inconel exhaust seat with a single angle grind, and the other has the conventional 3-angle grind on the exhausts as per the #062. The #906 with Inconel seat does not intrude into the exhaust port. It was used primarily on the HD and 1-ton truck applications where sustained towing of heavy loads & weight up inclines could cause eventual damage to a standard induction-hardened exhaust seat from excessive heat."

 

Well what i can find on the web is that in there stock form there is not enough difference to notice if any, people have used 1 of each casting # on an engine and have notice a thing.So it really doesn't matter the engine will be used in it's stock form in my 56 which is used for a cruiser.thanks again.

 

Not sure what yoou plan on dropping that engine in, but if you are going for any kind of performance, I'd look at getting a 4-bolt main short block and add edelbrock etec aluminum heads. They have come way down in price, flow better than the stock GM Vortec casting, and you can run 1 point more of compression because they are aluminum. You'd probably be pretty close to the same price.

 

Dropping it in my 56 which i don't race or drag just my cruisin machine.
Thanks for your comments.
Jim

 

Timing Covers are different... :anim_25:

 

Another question,i'm going to be using a hei distributor, and these engines have roller cams, i'm going to need to replace the gear on my distributor, is this correct?

 

You might have some fitment issues with a full-size HEI.. I recommend you consider a smaller diameter distributor (MSD has some nice stuff).. especially if you use the stock wiper motor.

 

Yes and the OEM ones have a different diameter driveshaft hole.

 

You will also have to use an electric fuel pump with either of these engines.

 

Good plan on the distributor gear.

 

What does Internal/External balancing mean? I'm not familiar with "both" on the same engine. Or do you have a choice?

Don

 

Not sure where you saw that or the context, but here's what I can say.

400 small blocks and 454 big blocks are "externally balanced" from the factory. To do this there is a counterweight on the harmonic damper at the front of the engine, and there is a counterweight on the flywheel.

On the other hand, 350 and smaller "old style" small blocks and 427 and smaller "old style" big blocks don't have weights on the damper or flywheel, and they are called "internally balanced".

On "old style" (85 and older) small block 305, 307, 327, and 350 engines, there is a small counterweight on the crankshaft flange for the flywheel. These engines are still "internally balanced".

When they went to the one piece rear main seal on the 86 up 305s and 350s, the crank design didn't provide for the counterweight on the flywheel flange. So they put a counterweight on the flywheel. The damper didn't have a counterweight. So some people still call these "internally balanced", but others call them "externally balanced". It's all a matter of point of reference, and terms and word defnitions. Or you could call it "both".

I hope this makes some sense.

 

I saw it here in this Summit link posted in the first post. In the details at the bottom. I never saw them "both" stated before. http://www.summitracing.com/parts/nal-12530283/ov

I guess they are calling it both internal and external. To me if counter weight is added outside either end of the crank, it is external period. More word definitions to confuse people. We live in a culture where saying it makes it so.

Don

 

Very good explanation Rick

An 86 up engine will take a flexplate that looks like this:

 

Is this correct flexplate.
http://www.summitracing.com/parts/sca-fp-350l-sfi/applications/

 

From the description it is (Image is a representation of this item. Actual item may vary.)

Don't forget the bolts

 

Jim, just wondering what happened to BBC project you were building?