AMC 327 - 443 XRV8

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Nov 17, 2017 11:26 am

Can't teach an old dog new tricks?

Whatever, I learned to do this the hard way; use cut sheets of flashing to protect the journals while making touch up welds on the crank.

Fastened on with wire ties, they won't fall off.

It doesn't hurt to use aluminum tape in less critical areas and cover the rest of the crankshaft with wet towels... they still might catch on fire so be ready (as any welder should always be ready with an assortment of fire extinguishing devices)

Anyway, this is how to protect the journals for touch up/detail welding work done on a crankshaft (use tie wire to secure wrapped on cut-to-fit steel flashing to protect the journals) neither will this way come loose or fall off while working on the crank while it's placed on a firepit for heat soak:
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Nov 17, 2017 8:37 pm

With the first cuts made to get 4.082" stroke, Milo and I were both kinda proud the crank came out 'straight', with no need for any crank straightening work.

Evidently I became overconfident and decided to build up the first cheek between main bearing #1 and the first crankpin journal... without placing the crank on the pit...

After making several other small welding touch ups, I took it back to have the final cuts made.

Milo called and told me... it's not straight, and asked if he could go ahead and try to straighten it.

Of course I said 'yes'.

The next call, Milo tells me how he fixed it by welding up the crank snout and re-cutting all the mains .020"...I confessed and told him what I'd done... (built up the front cheek, not on the firepit)

So... there it is; for anyone else who'd like to know, it was another lesson learned: expect to distort the straightness if you weld on a cheek when it's not heat soaked on a firepit.

Milo said he was able to rebuild the crank snout on a conventional crank welding machine but to cut keyways he'd need to refer me to another shop.

I said thanks & I'd try to cut the keyways myself.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Nov 17, 2017 8:52 pm

Milo said he tried using a press but it was so hard he couldn't budge it. Milo confessed 'when I was pushing on it to straighten it, it popped out of the press and landed on he floor. He said the loud 'bang' when it happened scared everyone nearby pretty bad!

Now all final cuts are made and the stroker crank is .020" on the mains and the rod journals are standard size (2.248") whew/scary... we made it though...
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Nov 17, 2017 8:58 pm

At this point in the process I was under the mis-impression that I had a crank that was somewhere close to final balance... man was I ever wrong!

In reality, I had a lot to learn about balancing two plane V8 cranks!
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Sat Nov 25, 2017 5:23 pm

Two pics, after crank pins cut to final size (std.) with 1/8" radius & more detail grinding to refine the shapes of the cheeks:
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Thu Dec 07, 2017 1:03 am

So at this point, having the journals cut to final size, I have something to take to a machine shop and have them run it on their balance machine.

I took where the crank grinder (Milo at E & E) told me to take it: Duffin Machine Shop in San Antonio Tx.

(Duffin was where Milo learned to grind welded up tractor pull cranks for one of the Duffin brothers)

(this might be a tip for anyone else 'out there' would might have welding skills and enough ambition to do their own custom welded crankshaft; contact 'tractor pull people'? They might know a local crank grinder in your area?)

So Duffin ran my crank on their Stewart Warner balancing machine. (what a beautiful sight that was for me to see my crank on a balancing machine!) He told me- 'Hey, this thing is way out of balance!/it almost jumped off the machine!" and pointed where he'd have to add mallory metal 'way over here' (off one side of the rear large counterweight) ...and said 'it smoothed it some by adding the damper on the front'. He made marks with a black sharpie on the big front and rear counterweights and told me how much weight I'd need to add in order to get internal balance... wow... about 620 grams on front and 640 grams on the rear... So paid him their fee to simply run it on the machine ($75) & took it back home to work on it some more.

Now what?

First thing of course is to look it up on the Internet; review every article online about adding mallory metal and look at other stroker cranks to see what 'the Pros' do. I spent hours on end looking up and reading every article I could find telling about crank balancing.

I found a few good articles on how not to install mallory metal; 1) you can't just push it into one of the pre-existing lightening holes and weld it in like that: the mallory metal does not weld well at all and it most likely will come out like a bullet (not good for the engine when that happens!) 2) The 'slug' (which is an appropriate term for weight by the way) needs to go into a hole drilled sideways through the counterweight... and it can't be too close to the edge (as tempting as that may be because the further out the weight is from the centerline of the crank, the more centrifugal force/effect it has) ...rather, the drilled hole to receive the 'slug' needs to be at least 1/4" in from the outer edge of the counterweight to 'hold it in' ...and it needs 'press fit' (I'd say about .0015" like a press fit wrist pin but get a second opinion) ...then a few welds won't hurt to keep it there for 'cheap insurance'.

In the course of looking up articles on how to balance a crankshaft, I found two articles on flywheel explosions.

Eg: One was showing pictures of a drag raced manual transmission 390 V8 AMX with rather large torn holes in the windshield cowling, just ahead of the lower edge of the windshield. They said it also took out part of the headers on the driver side but the owner/driver of the car was ok. The other article was a forum comment made by a guy who put a 'cheap' clutch on his drag raced AM 360 V8 powered Javelin; he said it tore a hole out of the back of the block (catastrophic damage) and had to replace the engine.

As a long term AMCer myself, I know both these engines came external balanced from the factory. I'm also familiar that most low buck engine builders don't re-balance their rebuilt engines... moreover people will swap externally balanced engine parts like a flexiplate or a harmonic balancer with little concern for finish balancing; like... if it came off another 360 its good to go on their 360 engine... like there is no more concern...

Then I found some really obscure original AMC information which told about 'replacement dampers and replacement flywheels' (for externally balanced '66-'91 AMV8 engines) That source said 'the factory replacement flywheel/flexiplates and harmonic balancers were made to have a 'middle weight' calculation which would serve both the heavier and the lighter balance variation on the factory built engines, but in ever case the factory recommended to keep the original flywheel and harmonic balancer on it's original engine if at all possible.

...to be continued.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Dec 08, 2017 9:54 am

Here's a few pics I took of the crank prior to doing any balancing work.

The stock weight of the crank is perhaps most important, helping to defend against those who always say 'Rambler V8 is too heavy' (implying needless excess weight because the designers were ignorant)

The new weight of the 'welded up' crank is basically trivial, but surprising to notice I put at least three 5 lb. boxes of Lincoln welding rods on it but after basic grinding work it only weighed about 1.5 pounds more.

Rough guessing, considering 3/8" stroke was added to the stock journals, since one typically doesn't use the whole electrode when arc welding, but throws away 'the short' before they put on a new rod, this translates into about four pounds of added weld material for every 1/8" more stroke, then after grinding, about 1/2 pound more for every 1/8" added.
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Sat Dec 23, 2017 11:31 am

Back to the external vs. internal balance debate:

AMC's high performance modifications book named "Performance American Style" recommends that all external balanced '66-'91 AMV8s should be internally balanced for higher performance use.

"P.A.S." recommends swapping the forged steel 390/401 crank and rods into the cast nodular iron crank and rod 290/343 & 304/360 engines and even provides a chart showing the alternative stroker combinations for the smaller CID engines.

Past 6500 rpm, "P.A.S." recommends a custom billet steel crank should be made & recommends Moldex Crankshaft Company by name. And they recommended having custom rods made by a company like Carillo.

This makes a strong statement against running an externally balanced crankshaft by quoting the AM engineers who wrote the book.

Furthermore, whenever I search the Internet for information on crankshaft balancing, the articles seem to unanimously agree that internal balancing is preferred vs. an externally balanced rotating assembly.

This appears to be indisputable, without need for further explanation.

So why would a manufacturer ever choose to make an externally balanced rotating assembly in the first place?

My first reaction to answer this question is 'to reduce the cost of making the engine; they can eliminate the time it takes to detail balance the internal parts'.

But is that true? That's the whole answer; cost reduction?

Nope. And here's an answer to what 'they' never say:

There is a very real advantage to an external balanced rotating assembly, even a power making advantage... for engines that are run in the rpm levels below the stock factory 5000 rpm redline.

What all the 'engine balancing articles' never say is this: when we take a balancing weight and move it further away from the center axis of the crankshaft, that weight effectively becomes heavier. By Newton's Laws, this means the crank and rod rotating weight can become lighter and have a lower moment of inertia and this will require less power to accelerate, reducing parasitic loss, with a corresponding increase of the engine's efficiency level.

Put in layman's terms, 'external balance' is a sneaky way to lighten the rotating assembly so the engine can 'wind up' faster.

I don't think you'll read this anywhere else (I never have, anyway)

The basic understanding of the concept can be described by visualizing two same-weight fat boys sitting on a see-saw, each one the same distance, about midway from the fulcrum.

As such, the see-saw is balanced.

(move one fat boy in or out on the see-saw and it easily goes out of balance)

~But~ we can alternatively balance the see-saw by replacing one fat boy with a lighter weight boy, by moving the lightweight boy further out -further away from the fulcrum.

The lighter boy, seated further away from the fulcrum has more leverage which makes him effectively heavier, but the total/combined weight becomes lighter.

This is the basic concept anyway and the net result is a lighter rotating assembly having a lower moment of inertia which is easier to accelerate, which is based upon Newton's Laws & the rather simple geometry of mechanical advantage.

Moreover, by reducing the total weight of the rotating assembly, the engine becomes a few pounds lighter which increases the basic power to weight ratio of the car.

The main problem is 'crankshaft flex'; more flexing strain is placed on the beam of the see-saw since more leverage is used to replace the weight of the fat boy who was seated closer to the fulcrum before.

What is less obvious and forces the see-saw analogy to be abandoned is the increased tension between the external balancing weight and the internal parts as they spin.

Then we need to use a 'round the world' yo-yo analogy; spinning the weight of the yo-yo applies tension to the string. The faster we spin the yo-yo 'around the world' the more tension it puts on the string (until the string breaks)

For any given speed of rotation, if we make the yo-yo's string longer, the yo-yo's circular path becomes longer and in order to travel the longer distance the yo-yo's speed increases, increasing tension on the string. Likewise, the shorter we make the string, the less tension there is on the string. -this makes the string weaker or stronger depending on length.

This is why for race applications, the AM engineers recommend internal balancing; to shorten the length of the yo-yo's string effectively makes the the rotating assembly stronger -the closer we can place the weight of the yo-yo to the center the stronger the string becomes -which is speed related.

So an externally balanced crank even has a higher performance advantage over an internally balanced crank in the lower rpm ranges -which works out great for going to the grocery store where the engine is never made to spin more than about 3000 rpm (never approaching 80 mph in first gear!) The engine will be making more power by reduced moment of inertia in the lower rpm ranges and not apply excessive tension to damage it's internal parts (oversimplified but true)

But if we are going to race the engine and force the yo-yo to spin as fast as possible on a regular basis, we definitely want to increase the strength of the string and this is alternatively done by shortening the string's length -or what is done by internal balancing.

Hence, while external balancing can be used for performance advantage in the lower rpm ranges, for race engines that will be made to spin in the higher rpm ranges, internal balancing is how we keep the parts from sending the yo-yo into orbit; ie: how to avoid catastrophic engine failure at high rpm -past the stock 5000 rpm redline.

All this expressed in the simplest terms possible (with much oversimplification) but the gist of the debate is made understandable:

Despite what all the engine balancing articles say (or don't say) external balancing does have a power making advantage for engines that won't spin past their stock 5000 rpm redline by reason of lower moment of inertia.

But for a race application, internal balancing is mainly done to effectively strengthen the rotating assembly to avoid catastrophic engine failure in the upper rpm ranges past the stock redline.

The internal balanced engine will have slightly more 'moment of inertia' but much more resistance to parts failure in the higher rpm ranges.

Scientifically speaking, internal balancing is actually a disadvantage for a lower rpm engine because external balanced rotating assemblies are designed for reduced moment of inertia -which is not done to 'cheapen the engine' as one might initially suspect.

(the engineers are going to calculate the harmonic frequencies of the crank in either case and make the correct torsional absorber for either type... in most cases! -there are notorious bad examples but this is not the target topic of internal vs. external balance differences)

It's a subtle nuance to describe, but I've never read any engine balancing article that explained why external balancing can be used for high performance advantage on lower rpm engines. Assuming basic component part strength is not compromised by the use of inferior materials, it's simply less efficient to lug the extra weight around in the lower rpm ranges where most average consumers run their engines.

Thank you SpeedTalk for the space to talk about speed.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Sat Dec 23, 2017 12:08 pm

I know there is a mistake to the argument by using an arbitrary 5000 rpm 'speed limit', but it's case sensitive, using the '66-'91 AMV8 for an example.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Sun Dec 24, 2017 12:49 am

For this application, where welded stroker cranks are notorious for stress cracks, reducing centripedal forces by internal balancing is an obvious choice -to reduce tension in the cheeks of the built up crank pins.

But where internal balance cranks tend to be heavier than external balanced cranks, the higher challenge of this crankshaft project was to make the stroker crank lighter than the original... to make the 'best' crank possible within my ability.

At this point in the process, I made two more discoveries which may be helpful to anyone else attempting to do this:

1) Make a 'crankshaft stand' to hold the crank in a vertical position.

-this makes most of the detail grinding sanding and polishing work much more ergonomic. Bolting on a flywheel is not good enough; the crank is still too awkward to handle and you can't flip it over... need to show a pic of how I made mine (easy to make)

2) Make a set of parallel bars.

-placing an internal balanced V8 race crank on parallel bars separates truth from fantasy; it's either right or wrong, static and dynamic, before and after final balancing. The final holes drilled in the over-weighted end cheeks are only done for correcting the added weight of the connecting rod big ends (using the 50% rule) -they do not violate or change the inherent balance of the crank. This is what I'm calling 'precision balance', as opposed to 'perfect balance' which technically cannot be done because of the irregular motion of the pistons etc.
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Thu Dec 28, 2017 9:55 pm

All benefits of external balancing aside, custom welded stroker cranks are notorious for stress cracks so internal balancing is the only way to go IMO -to get rid of as much unnecessary flex and torsional twist as possible.

For this example, this crank required much time spent lightening the outermost areas of the crank pin cheeks & this was proven effective by trips to the machine shop & running it on their crank balance machine.

For the benefit of anyone else who might be interested in modifying a stock type external balanced crank for the purpose of internal balancing, to increase the engine's durability in the upper rpm ranges, the awkwardness of detail grinding the cheeks on the crank while laying on it's side in a horizontal position was much relieved by making this tool to hold the crank 'standing up' in a vertical position ...I'm calling this tool a 'Crankshaft Easel':

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Re: AMC 327 - 443 XRV8

Post by FPV_GTp » Fri Dec 29, 2017 5:46 pm

Try copper ( pipe or sheet'ing, secure with copper wire ) splatter and weld resistant. cheers

Ps Merry Xmas & HNY2018
F/S - Heenan and Froude G490EH engine dyno http://speedtalk.com/forum/viewtopic.php?f=35&t=22982

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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Wed Jan 03, 2018 10:26 am

Yours would be the first comment I read anywhere saying to wrap the journals with metal 'ribbons' for protection during welding on the crank... strange absence of this info in other 'welded crank' articles...

...Only after many hours of searching on the Internet did I find an obscure welding website that told about 'welders tape'; apparently welding supply companies sell non-adhesive backed aluminum tape for spatter shielding on critical surfaces adjacent to a weld area.

In my experience, simple DIY cut strips of inexpensive 'roofing tin', wrapped onto the journals and secured with 'tie wire' offered the most protection for making 'touch up' welds on the crank because the tin has a slightly higher melting point than a soft metal like aluminum (I did not try copper, but I think copper would melt at a lower temp like aluminum)

-whatever material one chooses to wrap onto the journals for protection during welding there is concern for potential weld contamination also... depending on how close the weld is to the shielded area.

Thank you for your valuable comment on the uncommon subject.
XRV8 Race Parts > for AM's '56-'67 Rambler V8: http://amcramblermarlin.1colony.com/favorite_links.html

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Re: AMC 327 - 443 XRV8

Post by mk e » Sat Jan 06, 2018 7:19 am

amcenthusiast wrote:
Wed Jan 03, 2018 10:26 am
In my experience, simple DIY cut strips of inexpensive 'roofing tin', wrapped onto the journals and secured with 'tie wire' offered the most protection for making 'touch up' welds on the crank because the tin has a slightly higher melting point than a soft metal like aluminum (I did not try copper, but I think copper would melt at a lower temp like aluminum)
Copper does melt at a low temp but it conducts heat twice as well as aluminum so copper is what always saw the welders use when I worked in a fab shop (I was on the machining side). They would make little SS brackets that needed a bead on the edge and would use a copper block on the back side. Purge bloacks too...xray quality welds on SS and any welds on Ti needed to be back purged and they had a selection bronze filters wrapped with copper with a piece of tubing soldered on to attach an argon hose too then they laid or taped to the back of the weld. I saw copper roof flashing at times too. Normally I use whatever I can grab at the local hardware store when I realize I need something so aluminum flashing...... and then add layers depending how scared I am about the splatter melting through :)
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Re: AMC 327 - 443 XRV8

Post by amcenthusiast » Fri Jan 12, 2018 9:20 am

Thanks for your contribution, for context of information. -where heat always travels to the cooler material and the copper or aluminum will shed heat more rapidly -excellent reminder.
--------------------------------------------------------------------

The 'crank easel', used to hold the crank in a vertical position, is a very useful tool to drill lightening holes in the crank pins, in order to obtain internal balance.

Since this crank was calling for more weight on the rear, I drilled these holes progressively deeper from front to back, using a hand drill, sharpening all my bits DIY, measuring the depth of the holes with a veneer caliper.

This is an alternative to adding mallory metal, to internal balance an external balanced crank.

Since the built up journals added about 3/8" stroke, I tried to drill into the welded up area only, to keep the grain structure of the original steel forging intact as much as possible. Final hole size on these is 7/16" diameter. The deepest holes on the rear crank pin/journal do not intersect but stop about 1/8" short of 'going all the way through'.

Here's a pic of how I drilled the lightening holes. (the digital camera is another tool, along with a magnifying glass, to examine the finish quality of the work):
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