5.9 Magnum Machine Shop Quotes....thoughts?

[kawahonda]

I dropped block off at the lesser known place.

If I ordered a balanced scat rotating assembly, I'm assuming my stock flywheel and converter will work without any work, correct?

My builder said I should use my factory converter. It will get an automatic stall increase by the stroker kit. Machine shop was a little confused on how it would be balanced.

[gzig5]

I think you can order the stroker kit internally or externally balanced.  Or maybe that changes with forged vs cast crank.  If you want to use your existing parts, you need to know if your current motor is internally or externally balanced. 

[JonH]

Trying to follow along, and find this a bit confusing. Not that it really matters but you say you have an engine builder advising you. Yet you are taking this engine to a machine shop that will assemble your short block. What exactly will the "builder" be doing? Are you paying him as well? You seem to have a lot of chefs in the kitchen. Hope it all works out for you...

[kawahonda]

I need to know the answer regarding if I should just use my current flexplate/flywheel/converter, and does it all need to be balanced together (engine shop's assumption, but they are not entirely sure).

Is it true that my stock converter will increase its stall by a a few hundred just simply based on the increased torque output?

My engine builder is an "assembler" and has done lots of small block mopars and has several ties to machine shops in his hometown (which is too far away for me to use). He already gave an answer to A), which is "yes", but I'd like to have a more informed answer regarding B: If I buy a balanced scat cast crank, can I just slap my flywheel/converter on and call it a day?

[gzig5]

The answer to B depends on whether you get an internally or externally balanced stroker assy, and which type your current setup uses.  Scat makes them both ways apparently.
https://www.scatcrankshafts.com/rotating-assemblies/

Somewhere around 1972 or after, the 340 got a cast crank and was externally balanced.  Before then it was internally balanced.  What do you have?  Have you ordered the kit yet?

[kawahonda]

I have a mid 90s 5.9 roller block.

1970 Challenger factory 727 setup.

Have not ordered scat kit yet....

Waiting for machinist to check bores in order to determine what size to get.

[gzig5]

1970.  So you should have a forged crank internally balanced 340 and neutral balanced converter.  You would want to get the internally balanced crank assy for your 408 stroker.   You can then use your converter and the balancer you have or a new one for a 340 (internally balanced).  I strongly recommend a new one.  Also make sure you use standard flexplate or neutral aftermarket one.  The regular 360 B&M flexplate has a cutout for the external balance, you would want the 340 version from B&M or the standard four bladed one on your car now.

This is pretty much the way I'm going to go, but I'm probably going to use a LA block with solid FT cam.

[kawahonda]

Thanks for the explanation. That REALLY helps! Sounds like I should inform the machine shop of this--they should not charge me for balancing. They had a hunch that my converter/balancer has "weights", but sounds like they need to be informed that it needs to be internally balanced, and that it will accept neutral balancer/converters. If they want to check Scat's work, that's a different story!

Would you recommend a new converter and a balancer, or just a new converter?

If my stock stall is 1900 right now (when the car feels like it wants to break away when the brake pedal held), what would my stock converter do for a 408 stroker @ 400 HP? Curious how much I should anticipate the stall increasing by. It is the opinion of my "builder" to use my stock converter because I'll "automatically" gain stall, and if I want more I can add more later, but I don't think he would disagree with me getting a custom one made to match the cam. The goal is for landing int he 13s in the 1/4 in the end. Have 3.73 eaton. Don't buy what doesn't need to be bought, basically.

Another question: My 727 has "upgraded struts", TF2 shift kit, and probably about 66k miles on it. Shifts firm and good. Should I be squeemish about the 727 taking 400 HP on street tires?

Thanks for the help so far guys. I am learning!

[gzig5]

I'm not an expert but I used to stay at Holiday Inns a lot.  My 

Internally balanced motor vs external is different than the balancing a builder (Scat or your guy) has to do to match the pistons/rods to the crank weights, as far as I know.  There has to be a basic balancing done to match pistons to crank but that doesn't answer the internal/external question.  At least that's how I understand it.  I would hope your guy knows enough to answer that question.

50 year old rubber won't last forever.  New balancer for internal balance motor will not have a counter weight.  Some have a weight that can be added or removed to service both.  Converter should be fine if it's working now. You'll have a lot more torque off idle and won't need revs to get the car moving.  Leave the tranny alone if it's OK, maybe a filter and fluid change and adjust the bands if needed.  As long as you aren't running slicks or sticky tires it should hold up.  It should be no problem making 450/450 hp/tq but it depends on your heads and cam.

[Chryco Psycho]

I agree , more tq with a stroker build will cause the converter to lock up at a slightly high RPM
Line honing is only nessisary if some of the brgs show wear on one side

[RUNCHARGER]

The 727 will handle it, More torque from the stroker will push your stall a bit higher (not a lot, expect 100-200 RPM perhaps). I would want the stroker rotating assembly internally balanced. It makes it easier to change the convertor or change to a clutch later.

[bennydodge]

My 340 block had to have the mains line honed. That was the one operation I did not have performed. The center main was to tight-at least I caught it while it was on the engine stand. I can vouch for the 727's stoutness, mine has had no mods done at all and it's held together fine. I'm running a PTC 9 1/2"  custom converter which was way to loose, had it back to 'em twice before it was good for street use. I think in hindsight I would just use the stock 340 converter..

[kawahonda]

Yep, I think my builder is recommending just that!

[ec_co]

(edit) nvr mind, i'm a dummy

[kawahonda]

It's a 90s block using as much 70s (late 60s) stuff as possible, sans crankshaft and custom camshaft. Sounds like the consensus is to reuse my 1969/1970 flywheel/converter.

Already have a 1970 340 timing chain cover to go on it.

It should be a very cool stock-lookin motor by the time I'm done with it. It will look like a 340...perhaps not act like one.