So, is my externally balanced ZZ383 pushing 500hp going to come apart the first time I touch 6000 rpm? The guy who assembled the top end for me didn't think so, for my aggressive street driving. We talked about it...I don't abuse my car and we decided it probably wasn't worth the added expense, since the motor was already assembled from GM.. If I had started with a rotating assembly that was in pieces, it would have been a no-brainer to balance everything..

I guess we'll see...

http://forums.corvetteforum.com/c3-t...-pictures.html

 

No, It probably won't come apart but internally balanced for a 500 HP small block is by far the best option especially if building from scratch. Long term durability will be affected if pushed hard on a regular basis.
Nice motor.

 

No, of course not Never said it would

You chose a crate foundation for your engine and accepted the balance; for a new engine I would offer that the relatively small cost (in proportion) of internally balancing the engine is a very good investment. I personally wouldn't run 500 HP/6,000 RPM on an externally-balanced stroker...but everyone sets their own risk levels.

Where balance issues show up is durability - specifically the front and rear main bearings. If you're going to push it to 6K on a regular basis, IMHO I'd be doing oil analysis at every oil change.

 

Thanks for the explanation billla. That makes sense to me. I remember in the 80's people talking about "bluprinted and balanced" engines. I figured the engine had to balanced to some degree or it would fly apart but that this "balance" must some how be more precise.
If I get a new crank that will probably be the trigger to get a whole new assembly. If that's the case then I'll not risk using Chinese made components. Chinese stuff is only for parts I don't have to rely on.
As for the 383 engine, I don't really want to modify this engine to that degree. First it's a two piece rear seal 70's block. Second it's the original engine for this car and third when I build a 383 it will be built from the block up with all quality components, roller rockers, 2.02 valves with quality heds, forged pistons, 10:1 CR etc. to develop somewhere in the neiborhood of 450 hp.
I would be happy to do that now but I still have to keep my better half happy and spending $5k on a built 383 at this time is not going to do that. So in order to make me happy and keep her from grumbling too much until the financial picture gets better I figure to build up this 350 a bit. If I go super cheap I'll use all the original bottom end components with new pistons, intake, cam and original stamped rockers and live with that until the 383 can be built.
Any suggestions for a reasonably priced balanced assemby that will still provide good reliability? Since I don't have the engine apart yet I do not know how far it will need to be bored to clean up. It could be as litttle as .010. Can you get an assembly with those pistons or would I be left to combine components my self?
I don't have a builder and I'll use a shop to get the things I need done, but that's bout it. Not sure whether I should deck this block or just get a .015 gasket to get into that .040 squish range. I guess it'll depend on how square the block is and how flat the head mating surface is.

 

I knew that!!

We sure talked about it, but decided the teardown, etc probably wasnt worth it.....in my case.

 

OP, I think you might be basing your assumptions on a few things that need a bit of clarification.

By the time you do the machine work on a stock crank you've probably spent about the same money you'd spend on a quality new cast 383 crank. You can still reuse your stock rods, but the same applies - by the time you get them resized you've spent about what a new set of SCAT rods cost. Foreign manufacture vs. skilled labor - regardless of your politics, that's the deal. In the end the only real additional cost for a 383 over a 355 will be for the clearancing...which most shops charge around $200 for.

$200 for 28 CID, more low-end torque, etc....what a steal

Lots more things to talk about - but what you might want to consider is taking a deep breath and a step back...and then putting a hard budget down and seeing what folks think you can get for that amount of money

 

Yeah, tough call for sure. If you were going to be racing it, it'd be a different call.

Plus...there's no shortage of folks making big power with externally balanced engines year after year with no issues...so the best anyone can do are some "rules of thumb" and then see where the chips fall.

You've got a sweet engine there for sure

 

Thanks guys.. Now if I can just find the time to get it installed!!!

 

What I was thinking for a budget is about $2500. I figure for that I will do the following;
3 angle grind on valve seats,
New valves. Springs to suit the cam chosen and keepers.
New performer intake. Under hood space is a restriction here so airgap not possible.
Higher compression flat top 5 cc pistons forged, or hypereutectic would do also if needed to reduce cost but prefer forged for detonation durability.
block bored to .30 over (if needed) cleaned boiled and new cam bearings installed.
new cam (k1103 maybe)
.015 head gasket to get squish right. (or block decked if this option will not put me over budget)

Currently I have Hooker headers with side pipes. Recurved ignition all in by 2800 rpm. 3.55 rear end. A modified intake to allow more air for this air starved engine. Rebuilt and excellent functioning q-jet carb.

So the decision on the rotating assembly is a big one as this seems to have the most potential for an increase in the total cost of the rebuild.
I see I can get an eagle rotating assembly for as little as $450 or I could get a midrange scat assembly for $1500. Quite a range for a rotating assembly.
Deciding what I need here will dictate how much I can spend on other items.
I agree that reconditioning stock components is not very cost effective
and new components would be the route I would prefer.
According to the compression calculator on Summit a .040 squish with 5cc pistons and the 76cc heads that are on it will give me 9.02 CR. this is right where I would like to be to run 87 octane on this motor.
I'm not looking to skimp on the rotating assembly, but also don't need one capable of 700hp.
With how many people rebuild their engines I figure this is the place to get some good opinions on components that I'm not sure about.
The Cam is another area that I'm still trying to figure out what to go with. That's a whole new can of worms though.

 

IIRC, Jim Moore's 540 was initially externally balanced...look up his thread where he tore it down after a lot of hard miles on a 540...bearings looked new.
LS6 and LS7 big blocks are also externally balanced. 350's are basically externally balanced on the back end, the weird flange shape is that way for balance reasons.
Unless you plan on a lot of high rpm runs, external balance is fine. Don't overthink it.