badgta

iTrader: (4)

How is this crank balanced? external or internal? can i use my stock 89 l98 balancer?

felo72

As far as I know, there aren't any aftermarket crankshafts that are actually balanced. Your best bet is to talk to a machinest and see how much it'll cost to get it externally balanced. The cost of getting it internally balanced could cost you a ton of money. And to answer your other question, no, you can't use your stock balancer unless you take that and the flexplate in to get it all balanced together.

bluegrassz

iTrader: (3)

Most all cranks are internally balanced some what. You may still be required to use the 400 balancer and flywheel. Some are made to use the 350 balancer and flywheel.

You can even have a machine shop lighten the crank up by drilling more holes in it. Of course they rebalance it.

The best bet is to ask Scat. Try there web site, or tech support.

Did you try asking at the place you bought the crank shaft? If you have not got it yet and it is still on order, It should tell in the paper work you get with it.

later

SMasterson

That crank, from Scat, is made both ways.

The external balanced crank can use either 5.7 or 6" rods. Assuming you have the newer 1 piece rear seal you will have to run the externally weighted flywheel/flewplate for the one piece seal cranks and a 400 harmonic dampner.

This is not written is stone since the weight of the pistons and rods and how much heavy metal you can afford can affect whether or not it can be internally balanced by the balancing shop. Generally, whichever crank you buy from Scat is how you should have it balanced.

If it's the internal balanced crank you will have to use 6" rods and then I'm not sure which flywheel/flewplate you will need but you should be able to run the neutral dampner.

Either way, it will need to be balanced since new they come with no balancing done what-so-ever. (The crank throws are not drilled at all) It cost me $220 to get it done last year and I couldn't believe how much he drilled out of it.

I looked a long time to find out which flywhee/flexplate to run before finding out I needed the weighted one piece seal type flexplate and the 400 externally balanced type dampner.

You will need to take the crank, rods, pistons, pins (and keepers if full floating), one set of rings, one set of rod bearings, flywheel/flexplate and harmonic dampner to the shop when you go.

badgta

iTrader: (4)

thnks for the replies so far guys..... it's been helpful...

ther is no such thing as a 400 1 peice seal flexplate i have ever seen....

at scats site they say it balances with 1 peice mallory in no 1 crank throw with external type balncer????

87 up 350's are external balance!!

so can this motor be balanced with my balancer if i want? or will i need a 400 from gm?

i'm going to use my stck 89 l98 flexplate but this is confusing me!!

i'm taking this to whites automotive performance machine in kingsport tn.. it will cost 150 for the balanceing...

goneracin

\


im pretty sure that the latemodel 350's are not externally balanced. If at all possible, i would recommend internally balancing it if you are gonna abuse it, as external balance is a little harder on the crank. If you external balance it, someone in the aftermarket is bound to make an external balance flexplate, or you could just make 1 yourself. get an old 400 flexplate, and cut off the balance plate, or just make 1 out of some steel plate. look at where the 400 counterbalance weight is, and weld the new piece on your 350 flexplate. if its not perfect, the balance shop can finalize it.

bluegrassz

iTrader: (3)

[QUOTE]Originally posted by SMasterson
[B]

Either way, it will need to be balanced since new they come with no balancing done what-so-ever. (The crank throws are not drilled at all) It cost me $220 to get it done last year and I couldn't believe how much he drilled out of it.



I wasn't sure, Im glad you cleared that up, I wouldnt want to stear anyone wrong.

Perry93TransAm

The 87 ups are externally balanced, take a look at your flywheel /flexplate sometime and notice that big weight on one end, the dampener however is neutral. You can have any crank internally balanced it just depends on how much you want to spend. As said before bring whichever dampener and flywheel/flexplate that you plan on running to the machine shop with you so that when they balance the rotaing assembly they will factor in those. I have seen factory 400 cranks internally balance , but it cost around 800$ since malory metal is so expensive. A good freind used the lightweght 4340 non-twist forged Biillet crank from cola(1100$) and Eagle 6 inch H beam rods with SRP lightweght pistons when he built his 383 and it cost him a whopping 120$ for balancing! It all depends upon your parts.
Perry

felo72

Those blocks are still considered internally balanced. The weight on the flywheel is there to compensate for the big lug missing on the two piece rear main seal crank. The balancers are also the same for pre 87 blocks. If you want to use the same flexplate for the stroker crank, you can, but as mentioned before, the machine shop has to balance it. There isn't an aftermarket flexplate made for the one piece stroker kits that I know of here at Summit.

ede

the SBCs with the one piece main seal are NOT externally balanced. what gm did when they removed the flange from the cranks to allow the one piece oil seal was to replace the mass from the crank with the bat wing weight on the flywheel/flex plate. although it wasn't truely a weight it acted as one and added mass to the very end of the crank and hada bearing on the balance of the crank. the one piece crank seal flywheels/flexpaltes looks like it's externally balanced but it isn't.

Perry93TransAm

So if its internally balanced you can have the Flex/fly neutrally balanced and it will be fine? I think not. I had mine removed when I built my 355 in my 93 and using the stock crank they had to add weight to it to get it to balance without the flexplates weght attached. If it were truly internally balanced a neutral weight fle/fly would have had no bearing on the balance of it.
Perry

felo72

Did you even read the post from ede? There is a weight on the flywheel, but just because there's a weight on it doesn't always mean it's externally balanced.

Perry93TransAm

Yes I read it and from what he says the weight is there to offset the removal of weght from the crank , no? I am calling no one a liar I just am telling what I have seen . Did you read my post?

ede

would you say the 2 piece crank seal SBCs were externally balanced because they had a weight (flywheel flange) on the crank out side of the oil pan

SMasterson

That's why I had to order mine from Jegs. Summit didn't list a 153th, externally balanced flexplate for a one piece seal 383 Scat stroker crank.

http://www.jegs.com/cgi-bin/ncommerc...47&prmenbr=361

. . . but there's one listed there now. BMM-20238

http://store.summitracing.com/defaul...rchType%3DBoth

SMasterson

NO, I wouldn't say that, but I don't think you're asking me.

Internally and externally balanced on a SBC crank is in reference to whether or not weight has to be added to the harmonic dampner or flywhee/flexplate, or both , (parts bolted to the crank that are not part of it) to get the assembly to balance. You can run what's called a pork chop on a crank with a neutral flexplate/flywheel to balance a 400 if desired.

Fact remains, the newer one piece seal cranks are externally balanced. Look it up in GM Performace parts book and they'll explain it to you. They use a weighted flexplate/flywheel with a 3" bolt pattern instead of 3.58"and a neutral dampner.

And. . . there are exceptions to all of the above depending how how a person goes about getting they assembly balanced and their choice of parts.

badgta

iTrader: (4)

this has been interesting......

so.... can it be balanced with my stock l98 balancer and flexplate or not?

if not i need to know before i go 100 miles to get it balanced....

Perry93TransAm

Sorry I just got here to answer(been away all evening) , ede I understand what you are saying ,but the point I was trying to make is that it still takes an outside force besides the crank to acheive balance with the newer 1 peice cranks (from the factory). You are correct in the fact that technicly since the weight imbalance is outside of the pan that it is not internally balanced but refer to my earlier statement in this post.
To answer your question badgta yes just make sure you bring the complete rotating assembly to the machine shop for balancing including the dampener and the fly/flex.
Perry

badgta

iTrader: (4)

i figured a new balancer was needed.... anywho thanks to all the people that replied it was very intersting and very helpful in dertermining what need to be done...

SMasterson

Ok, what crank did you buy? Scat 9000 internal or external. What length rods are you using?

Here's the scoop on mine. I bought the Scat 9-350-3750-5700L
I used 5.7 rods and SRP pistons for 5.7 rods with 3.75" stroke. I originally had TRW's and they wouldn't clear the crank throws.

I used a flexplate for a one piece rear seal crank, with a weight attacked, and a 400 externally balanced SFI approved harmonic dampner.

The Scat 9-350-3750-6000-L will internal balance so you can run a neutral dampner but you will still need the 3" bolt pattern, weighted (newer style) flexplate for a one piece seal crank.

Maybe your balancing guy can remove the weight but it's going to have one when you buy it.

http://www.scatcrankshafts.com/serie...tcranks02.html

badgta

iTrader: (4)

9-350-3750-5700L thats the same crank i ordered the other day....

i also got the scat 4340 forged i beam rods too....

the pistons are speedpro l2491f-30 forged lighweight flattops....

the skirts are very short so i don't think they will be a prob...

are they the same you had????

let me know!!!

SMasterson

badgta, that's the exact crank and pistons I originally had purchased. I bought them from www.partscavengers.com (which I need to mention he gladly refunded my money on.)

The pistons skirts are not what hit. It was the crank throw hitting the pad under the piston pin on #2, I think. I know it was one of the two front holes because the machine shop called me over to look at it. They were mocking up the block to measure all four corners for zero deck height.

It would have taken .50 or so of grinding on the crank, or underside of the piston for it to clear. We never did understand it since those pistons were made for the 3.75" stroke 5.7" combination. After several calls to Scat and taking several measurements and veryfying I had the correct crank, Scat told me they had heard of the problem and it was a problem with the TRW pistons. They said SRP's would clear fine. I ordered them, they cleared fine. Costs me $440 instead of $270 for the pistons but I'm glad now that it's done. Hope your results are different. Let me know.

Perry93TransAm

That svery interseting, I was thinking of this combo too and was wondering about the cheaper TRWs, I had used TRWs on other 350 set-ups , but never a stroker. I guess they are out of the question. By the way, I was thinking of doing something different and I had a 305 block lying around, does anyone know who sells the stroked 305 (340) kit?
Perry

badgta

iTrader: (4)

thanks for letting me know s.......

i have to mock up each cylinder to clearence the block so i'll check it to be for sure.....

these pistons are extremely short and i dont see how a problem like this could occur but i guess they can....

well just have to see...

perry.... powerhouse sells the 305 to 335 kit check it out here

www.powerhouse.com

Perry93TransAm

Thanks!