jr73

I am building a 383 stroker. I bought a short block from Summit and it's been a slight pain getting components that will work on it. Anyway I think this motor is externally balanced am I right? The flex plate has a large weight on it. My dilemma is I have a stock balancer off the 350 that came with my 73 and an after market balancer which looks like it's balanced for a certain motor by the looks of all the metal machined off half of it. Which one will work?

JoeMinnesota

What crankshaft are you using? That will determine your needs.

You need a 400 flywheel/flexplate and a 400 balancer, if it is a stock 400 crank with mains turned down for the 350 block, or if it is an EXTERNALLY balanced aftermarket crank. If you have a newer flywheel or flexplate for a 350 you can obtain a balance plate to hang between that and the crank to externally balance it.

If it is an INTERNALLY balanced aftermarket crank, which some of the better ones are, you can likely use a neutral balanced flywheel/flexplate and a 350 balancer.

Research the crank and that will determine needs. Regardless, spend the money to have your rotating assembly balanced, especially on a stroker.

As for the aftermarket balancer you have there, not sure - may be a 400 balancer but I would look for p/n's on it or ask an engine shop or wherever you got it to be sure. Be aware that your 350 balancer will physically fit and bolt up, but will be wrong if it is an external balanced crank.

jr73

Joe, the flex plate came with the shortblock from Summit. Should be the right one for the motor.

jr73

Summit tech line says I need a neutral balanced one. What are they referring to?

C3 Stroker

The stock balancer from the 350 (without added weights or metal machined off) is neutrally balanced.

PainfullySlow

That would be the one on the left however I would not use it. From the picture you posted it looks like there is a substantial groove worn into the balancer where the timing cover oil seal rides. This will pretty much guarantee that it leaks oil there.

I would purchase a new balancer.

jr73

this is what they said to use but it looks heavy on one side dont you think?
https://www.summitracing.com/parts/p...ional-products

cooper9811

From your posts, it sounds to me the short block is internally balanced. The one in your picture can either be sleeved where the groove appears to be, or go to autozone and pick up a new/undamaged one for $50.

EDIT: I missed the flexplate comment - agree with derekderek.

derekderek

If flex plate they supplied has counterweight, it sounds like externally balanced engine. If so, you need 400 style balancer. You need to get summit to get you in touch with their builder and be SURE! I bought a 400 flywheel for my 400 in a boat. Turned out it was 454 fkywheel. Bow rails on boat shook back-forth 3 inches at idle. Shook like a harley. You MUST be positive you have the right components.

L88Plus

Some kits for late model engines continue with internal balance on the front and external on the rear, just like factory engines with 1-pc rear main seal. It's absolutely critical that you get the correct one.
You'll know it if you got the wrong one because the engine will shake like a bear cub crapping a pine cone.

JoeMinnesota

If they said to use this one, you can obviously use it and it's not a lot of $$.
Appears you could use a standard 350 balancer as well, but I agree with Cooper that yours must be sleeved or else spend a few $$ on a new OEM balancer. The one in this description is for internally or externally balanced applications and has a removable weight to convert to external balanced if you need that.

jim-81

Post the link to the Summit short block you got and we can take a look at it.

PainfullySlow

That balancer has a removable weight on it so that it can be used for either internally or externally balanced engines.


This is probably your best bet.



If it matters I literally just purchased this balancer for my own 383 engine build two days ago. It got very good feedback and since it is going to be a mild build I went a bit with form over function since I wanted the nodular iron look

HeadsU.P.

Actually, its my understanding that the groove in the balancer has been machined there. Its an old trick to machine a "V" groove to keep any fluid from going past it.

There is nothing in the timing cover that would grind a notch like that no matter how many miles on the engine. Just a rubber seal.

gkull

jr73, I went to the summit site. Did you buy this ATK short block?

https://www.summitracing.com/parts/hpe-sp15/overview/

What harmonic balancer do I need for this motor? Will a stock 350 balancer work?
Asked by JERRY on February 27, 2018
A:
Thank you for your question. ATK SP15 383 stroker short block requires an internal balance damper. Compatible OEM type balancers like Summit 161350 or 161358 will work, or if you require a damper with an SFI approval Summit C4265 may be a better choice.
Summit Racing Answer - February 28, 2018

PainfullySlow

Interesting, I have never heard of this. A quick search of the most expensive (so theoretically 'best' and 'no expense spared') balancers do not show any groove cut into the balancer. I would think that if any balancers would have it, it would be these.




Do you have a link to any info on this technique?

Big2Bird

Then why do they make these?

https://www.summitracing.com/parts/f...make/chevrolet

L88Plus

Groove wasn't worn by a rubber seal.
It was etched by dirt and grit on the outside of the seal.
I've never heard that it was machined there on purpose. Ever.

Big2Bird

Cranks get the same groove at the rear seal. How much is the rubber and how much is contamination, I don't know.
Given enough time, water will cut thru granite, so there ya go.

HeadsU.P.

No, I do not have a link to that procedure. If you picture an upside down "V" you can see how it would be impossible for fluid to go uphill. But evidently its old school technique and no longer works or not that well.

Back in my U.A.W. youth I made tens of thousands of those balancers. But someone else did the actual machining of drill-n-tap, keyway slot.
I believe the groove was more popular on small engines.