I'm putting a 406 small block in my '86 TA with a T5 World Class.
1. Will a 168-tooth flywheel fit in the stock bellhousing? The answer I have seen just about everywhere is no.
2. Will the stock 1-piece rear main flywheel from a 1990 Firebird fit the 400, given that they are both externally balanced? Are the flywheel bores the same? Or do I need to go shell out a few hundred for a Ram clutches flywheel that will probably be way heavier than a stock 16lb T5 flywheel?
3. The Dart heads on the 400 have raised ports. Will a header/y pipe kit for a standard engine fit or will I have to fab a new y pipe for them? (And does anyone in the northeast US want to trade non-emissions headers for a set with emissions hookups?)

 

1. No. There's a reason you've "seen that everywhere". The BH won't even go on over it, nor accommodate the starter for it. (stock BH that is) To run a stock T-5 BH and starter on a 400, which of course will require a 12.8" (153-tooth) FW, you WILL HAVE TO drill the hole circled in magenta in this photo of the 400 I had in my 83 L69/T-5 car for many years. I drilled and tapped this hole myself with a hand drill, using a stock T-5 starter as a template. Note the special larger diameter entry to the threads; this is REQUIRED so that the starter bolts, which are SPECIAL themselves, can act as dowel pins to locate the starter exactly positively perfectly aligned to the block. Aftermarket starters may not need this butt it would be bald-faced bone-headed STUUUUUUUUUUPID not to include it so that a stock starter can be used in a pinch if nothing else. Any of the aftermarket "dual pattern" starters will then work, as well as a stock one; NONE can POSSIBLY work without this hole.



2. No. The 400 is externally balanced, while the 305 & 350 are internally balanced, with the 86-up INTERNALLY balanced ones having the rearmost little bit of INTERNAL balance weight that used to be on the crank flange, moved to the FW so that the crank flange can be round. Bolt patterns are also QUITE different as well as the center pilot being different. This is what a 85-back crank looks like; in fact, this is that same 400 I spoke of above. Easiest way, using stock parts, to go about this, is to get a stock L69/LB9 16 lb flywheel (NOT LG4 or L03 unless you want the heavier 22 lb part) "unbalanced" to the stock 400 balance. Easiest way to do that is to drill about 20 - 25 ½" dia holes about ½" deep on the appropriate edge of the FW and use a rig like a lawn mower blade balancer in conjunction with a STOCK 400 flex plate turned exactly 180°. IOW something you could theoretically do yourself if you're patient and talented with a drill press. If your 400 is balanced to the STOCK 400 SPEC, and the flywheel is ALSO balanced to the STOCK 400 SPEC, then there is no need for any "special" balancing; and neither the engine nor the FW will be required to be present, let alone altered, in the process of balancing the other. The stock 400 "unbalance" is approximately 24 in-oz with the weight removal centered exactly opposite the dowel pin.



3. Probably not. LOOK AT how the Y-pipe fits under the oil pan, and imagine raising the pipe by the ½" or whatever it is. Headers might fit or might not; Y-pipe DEFINITELY will not.

 

2.1: In the even that you can't find a sufficient/affordable replacement FW for F-body application on a 400, You can use the stock 1-piece rear main flywheel from a 1990 Firebird, have a machine shop bore the center, drill "2 piece rear main seal" bolt patter, staggered to the '90 1 piece bolt pattern, and then either have that machine shop balance that FW to 400 spec, or you can buy a 400 counterweight from Summit etc for about $18 that sandwiches between the FW and the crank. I did this years ago to run an LT1 FW on a 400, cost me $80 and worked great.

 

I already was aware of the holes for the starter and whatnot. It currently uses a dual pattern 350 starter anyway, no big deal there, it's fine, don't need to worry about that part, hence why I didn't ask about it.
All the information I can find about the 86-up 1 piece rear main engines says that they are externally balanced engines from the factory with manual transmissions, hence why every option for those engines on summit shows as "externally balanced." Provided that is not the case, I'll have my local guy unbalance the flywheel to match the 400 spec and all will be right with the world, because I noticed that the 400 flywheels in 153 tooth all come in high weights, like 26-30lbs unless I way overspend on an aluminum unit

 

The 1-pc rear main seal engines are NOT "externally" balanced. They are INTERNALLLY balanced, same as all other stock SBCs except the 400. The reason you see them called "external" everywhere, even though they're NOT, is because the whole industry got sick of arguing with ignorant people who DON'T UNDERSTAND how balancing works or why, and they glance at the parts and one looks "internal" because it's all but invisible (being that funky shape on the back of the crank), and the other looks "external" because it's attached to a different piece. I assure you, that is NOT what the terms "internal" and "external" balance refer to.

However all that may be, it's quite eeeeezzzzzzy to unbalance a stock 305 FW to the 400 spec, as I described above; something you could potentially do yourself even. One piece of advice, if you decide to have it done by a "shop": DO NOT let your FW and your rotating assy exist in the same shop at the same time with the notion of "balance" in play; because what WILL SURELY HAPPEN, as it has to so many others, is that they'll take the eeeeezzzzzzyest possible road FOR THEMSELVES, which is, to leave the ENGINE at whatever random balance it happens to be at, and create a "custom" balance for the FW. Well guess what... if you EVER have to change the FW for WHATEVER reason, it is now IMPOSSIBLE, because your FW is a COMPLETE ONE-OFF balance. Same thing in reverse, if the engine requires bottom-end work for any reason. DO NOT let anyone tell you otherwise NO MATTER HOW HARD they argue and tell you they're the "expert" and they "have to have it" and all that bull plop. IT'S NOT TRUE. Have the engine balanced to the STOCK 400 SPEC, and accept no excuses for why they "need" the FW; then, once it's back in your possession, hand them the FW and tell them you want it set up to the STOCK 400 SPEC. That way, ANY 400 part you ever buy or make in the future, interchanges freely.

 

I bought a $20 off the shelf 400 flex plate and gave it to the machine shop for use as a flange template and for a balance template, if they so chose to use it that way.

 

Per the earlier message, the 1990 flywheel will also need to be redrilled for the 400's bolt circle as well, correct?

 

No.

Won't fit.

There's PLENTY of stock 83-85 flywheels available. No reason to dink with the other.

 

Damn. Well. I have one out of a 1990, only reason

 

Correct. Price an early 80's flywheel plus "400 balancing" vs. drilling, boring and balancing your flywheel.

 

https://www.summitracing.com/parts/pft-50-6516 for example

 

I forgot to ask:

Which size flywheel is on it with this setup?

 

Yep. ^That, plus machine shop balancing to the 400 requirements, or ^that plus THIS, will work.

 

Factory 1 piece seal small blocks and 4.3Ls for that matter are factory externally balanced on the rear. It has a counter weight thus externally balanced, very basic and simple concept to understand. Some Fords used a bolt on counterweight and those are also considered to be externally balanced. If it has a counterweight that bolts on externally it is external balance.

It is possible to internally balance a 1-piece rear seal engine using $$$ Mallory metal and many high reving performance engines with 1 piece rear seal setups get internally balanced. Many companies make flexplates and flywheels for the 1-piece rear seal setup with neutral balance. I can tell you exactly what happens if you mistakingly use a 1-piece rear seal internal balance flexplate in place of an externally balanced one. The engine shakes like a paint shaker over 2,000 rpm.

GM even acknowledges the fact they are externally balanced in the rear with a 1-piece rear seal. The only exception to that rule that I know of is the 8100 Vortec. It is internally balanced despite a 1-piece rear seal and requires a neutral weight flywheel or flexplate for an internally balanced 366, 396, 402 or 427 when replacing the factory 8.1L unit.

 

Who ever's righter than whom, GM created an f'ed up situation when they went from an engine(s) that was literally, internally balanced, to one that literally, is not....then tried to call it "internally balanced" b/c of whatever stupid reason. That all they did was "move some weight that was on the crank, to the FW, b/c of the 1 pc seal". (?) Or whatever dumb reason they used. The fact is, when you bolt a counterweight on the outside of an engine to make the thing neutral balanced (not vibrate like a sumbitch), that is what the industry calls, "Externally balanced". Fords, SBC 400's....externally balanced. They need chunks on the FW to run right.

It's kind of like how GM mis-names the thing on the other end of the crank, that prevents the crank from becoming a torsional tuning fork. The "Harmonic DAMPER". It's a damper b/c it dampens torsional vibrations. It is NOT a "harmonic balancer" for two reasons:
1. You can not "balance" away...harmonics.
2. Except for the SB 400, it balances nothing; engine would run smooth as ever, w/o it installed at all.

BUT GM erroneously calls it an Harmonic Balancer in some tech literature....probably to remain consistent w/calling an externally balanced engine, "internally balanced".

 

See what I mean...

Even GM has had to give in to the mass confusion in the aftermarket when publishing their aftermarket marketing materials to the aftermarket, because people in the aftermarket who DON'T UNDERSTAND WHAT THE WORDS MEAN think that just because a balance weight "looks" "like" it's separate from the crankshaft, that the balance is "external". IOW, like Van Man with his GM aftermarket ad, they lack the knowledge to cut through the confusion between the visual of "external mounting", vs the technical meaning of "external balance".

An engine is INTERNALLY balanced when the crank counterweights COMPLETELY balance the rod journals they adjoin. Engines like the SBC 400 and BBC 454 CANNOT do this, because the counterweights must be made smaller than the "ideal", so that the pistons don't hit them when they're at BDC (which is also of course when the counterweights are at "TDC", directly opposite the rod throw). For this reason you can spot a stock 400 crank in a roomful of SBC cranks from 100 yards away, due to its "flat cut" counterweights while all other SBCs have round (circular) CWs. This causes the rotating assembly to no longer have the optimum "dynamic" balance, which a rotating mass CANNOT POSSIBLY correctly balance against a reciprocating one ANYWAY, butt the "correct" INTERNAL balance at least minimizes this effect, such that vibration only occurs at RPMs that the assy never reaches, and at all other RPMs the vibration is contained WITHIN the crankshaft, which is commonly called "harmonics". Invariably, when EXTERNAL balance is used, it also means that balance weight must be added to BOTH ends of the crankshaft, i.e. both the flywheel and the crank damper (in a car situation... engines for generators or pumps or whatever might have different parts that handle this).

This property is NOT changed from the 2-pc rear-main-seal design to the 1-pc. All that changed was, the rearmost INTERNAL counterweight, which is that funky-shaped flywheel flange pictured above that was used in SBCs with heavier rods than the original "small journal" size, had to be moved to the flywheel, so that the flange could be made round, for the 1-pc seal. It would theoretically be possible to balance these motors by drilling holes in one side of the ROUND flange and filling the other side with heavy metal, butt that would be costly at best, and might require heavier metal than can be readily obtained; so, bolt it to the flywheel, was the obvious, cheeeeeep, and eeeeeeeezzzzzzzzy solution.

The 1-pc RMS SBCs have a neutral balanced crank damper, thus showing the most obvious sign that they are INTERNALLY balanced.

Aftermarket 383 cranks, even though they have the same stroke as the stock 400 crank, CAN BE made internally balanced if desired, given other compatible parts choices. In the case of the stock 400, the factory chose to make the pistons have what they considered to be the minimum compression height in the SBC (the 267/305/350 height), with the same ring spacing and width as all the others, thus requiring the shorter 400 rods, which in turn limits the counterweight size, which then requires EXTERNAL balance. Aftermarket 383s can have longer rods than stock 400s or even those of all the other SBCs, and/or pistons with lower compression heights, and/or ring packages that are shorter and mounted higher on the piston than factory 400 ones, thus allowing enough room for the CWs. GM, for whatever reason, was not willing to compromise the ring setup in the 400 that way, thus requiring EXTERNAL balance. The same is not true of the INTERNALLY BALANCED 1-pc RMS engines.

None of which is really material to the matter at hand anyway. No matter how the terms "internal" and "external" balance are defined or merely CONFUSED, the fact remains that the 400 is balanced COMPLETELY differently from the 1-pc RMS motors. They are not interchangeable. (which incidentally, the SBC 400 and BBC 454 balance weights aren't strictly interchangeable EITHER... about 24 in-oz for the 400 vs 28.5 or so for the 454) No matter what, regardless of drilling and boring and all that, the balance of a 1-pc RMS flywheel WILL NOT be correct for a 400; even if all that were done, which I'm not sure it can be since the holes might overlap, it would STILL require a different balance weight. And, given the low cost of a neutral-balance 2-pc RMS flywheel or flex plate, coupled with the ease and low cost of "unbalancing" one of those to the stock 400 balance spec I gave above, makes fiddling around with a 1-pc one economically suicidal. Like so many other things, just because it "can be" done if it even can be, doesn't automatically make it A Good Idea, let alone The Right Thing To Do.

 

I know how words work....and thus, I completely agree with you. ^That^ was beautifully stated.

"Crank counterweights". Crank. You didn't mention flywheels, flex plates, dampers, or other bolt-on devices that live outside of the engine.

But more technically, what you just typed about the proximity of the balancing mass to the rod journal. I like how you recognize that relationship. Looked at that way, perhaps that means that "external" is probably more correct, for ALL SBC. Let's examine: since even the Gen I two piece engines have counterweighting added to the flange of the crankshaft....that flange and the associated balancing mass is definitely not "the rod journal they adjoin". It's well outside of that journal. It's outside the journal, adjoining that journal. It's outside of the block "bay" for that journal. Heck, it's outside the rear main seal....outside the pan...outside ("external" to) the entire engine.
I think that it's safe to say that even calling a gen I, 2 pc seal engine "internally balanced" is dubious; there is counter balancing mass outside of the main bearings of the engine, outside of the engine -exactly like the counter balanced dampers on 400's, Fords, AMC's, etc. that are all.....externally balanced.

Explain to me/us how the counter weight on a 400 flywheel/flex plate differs, or more "external", than the counter weight on the one piece engine's flywheels/flex plates? Or....OR, If I buy THIS CHINGADERA and tack weld it to my 400 crank flange....is the 400 now "internally balanced", since "the crank counterweights COMPLETELY balance the rod journals they adjoin"? . How would that weight tacked on there be functionally or nomenclaturally(not a word) different than GM slapping mass on the crank flange? (I think, starting with the 283)

As I said above....

....possibly when they called the original engine internally balanced but had balancing mass outside the engine. But definitely, once they moved that mass to a bolt-on location, that is outside of the engine. That is the literal definition of "external".

 

Of course not. Internal vs external balance is a property of the crank, rods & pistons. All those other things are incidental.

Yes it is; or at least, as close as it can be, and not hit the oil pump. It's the same, functionally, as the front-most one, except that it happens to be on the far side of the bearing. It's still right where it needs to be, and is the correct weight, just like all the others. The fact that there's more crank length between the throw and the weight doesn't alter that.

I already did.

The counterweights ON THE CRANK, adjacent to the rod throws they balance, CANNOT be made large enough to properly balance the rod throws. This is UNLIKE all the other SBCs.

The funky flange on the large-journal motors (besides the 400) are the rearmost INTERNAL counterweight for the rearmost (#7 & #8) rod throw. This CW is EXACTLY where it belongs, as is the one on the OTHER side of the rod throw. On the 400 that weight is the same as the other motors, only, it's not large enough either, just like the other CWs. The factory COULD HAVE made it GIGANTIC if they felt like it; are you trying to say that would make it "internal"?

No.

In ALL other SBCs, ALL the counterweights on the crank, are exactly where they need to be (in between and/or adjacent to the rod throws they balance against), whereas in the 400, they are NOT. They CANNOT be because there isn't enough room. This makes all the others INTERNALLY balanced. Including the later 1-pc RMS ones: the rearmost INTERNAL weight, which is right exactly where and how heavy it needs to be to optimally counterbalance the rearmost rod throw, is EXTERNALLY MOUNTED. Again, and over and over, the difference between "visual" and "technical". The engine is still INTERNALLY balanced because all the CWs are right where they need to be and are the correct optimum weight; from ONE END of the engine TO THE OTHER.

No.

If you do that like the factory did, then ONLY that counterweight "might" qualify as "internal". ALL THE OTHERS, including the one just in front of the rearmost rod throw, are too small to fit between and under the rods & pistons they're supposed to counterbalance.

No.

The original 265, 283, 302, & 327 – the "small journal" motors", up to 67 – had a ROUND crank flange.

Regardless, it's not material to the OP's situation. He simply needs to buy a 2-pc RMS flywheel and either "unbalance" it to the stock 400 spec, or buy a "pork chop" weight to go with it. Personally I prefer altering the flywheel rather than the other butt in the end either will work. His biggest concern is going to be the starter, since virtually no 400s whatsoever (only potentially the last couple of years of them) have the correct inner bolt hole for the 12.8" wheel introduced in 1978 or so, so that a starter whose shaft is located about 5/8" inboard of the one in the starter for the 14" wheel, will be able to be installed and not have a bolt try to go RIGHT DIRECTLY THROUGH THE MIDDLE of the starter drive. He's got his head in the sand about that with the "dual pattern" starter business, and most likely will end up like practically all of the others on this forum that have tried this swap, put their motor in their car, went to bolt up their "dual pattern" starter, and discovered that they can't; and now have to either pull the motor back out, or lay up under the car on their back and drill the hole in place. Ignorantly arguing the finer points of the definitions of balancing terminology doesn't get him any closer to a finished project.

 

O.K. Then....
What's the diff between the "pork chop" and the "Funky Flange"? Other than that one is bigger?


Exactly. How would that be less "internal" than the "funky flange" that is already there on the smaller "internal" engines that have weight located...externally? "GIGANTIC" is subjective. The Chingadera (aka "pork chop" as you call it) is not what *I* would label, "GIGANTIC"....especially the all caps, part.


Once again, we are in complete agreement.

 

About 24 in-oz, and the fact that the one, on an INTERNALLY balanced large-journal SBC, is ONLY ONE of all the CWs FROM END TO END of the crank, all of which are of their correct weight and in their correct place adjacent to the rod journal that it COMPLETELY counterbalances.

I'm not really sure how to explain this any more clearly. Tom, usually you're one of the more knowledgeable and willing-to-learn people on this board. It's unclear how something THIS FREAKING SIMPLE is causing so much controversy.

Weight BETWEEN AND ADJACENT TO the rod journals that it balances FROM END TO END of the crankshaft, such that EACH AND EVERY journal is COMPLETELY balanced individually to the optimum degree possible, aka INTERNAL balance; vs weight that CANNOT BE in that correct type of place because there isn't room for it, and therefore has to be placed "externally", aka NOT in the optimum location, OUTSIDE OF the correct location. NONE of this has ANYTHING to do with whether some portion of the CW is molded along with, bolted to, or otherwise attached to the crank, or to any other part; nor is it related to which side of a bearing, block, oil seal, or parting line between 2 parts, that it's put. I'm struggling to understand how this is hard to understand.

And, my comment about "GIGANTIC" was referring to the concept of making the crank flange ITSELF large enough to contain the extra 24 oz-in of balance weight for a 400, rather than it being something added on elsewhere.

If this is all about appearance, as in, the weight "looks like" it's "external" because you can see it with the engine assembled, then... a certain shiny yellow metal is trading at somewhere around $4400 - 4500 an ounce today. I have a lump of shiny yellow metallic-looking stuff I'll be glad to sell you at the low end of that range, for $4400 an ounce, even though I'm gonna tell you it's iron pyrite. After all, who ya gonna believe? Me, or your own eyes?

 

Good question. How did the name Internal and external come to be? Is external, not external (outside the oil pan?). Is "internal", not internal (inside the engine)? On an AMC, it's wicked obvious; if you don't bolt parts on to the crank, outside of the engine, the engine can not be run (not for long) w/out damage, and IF run, it would shake like a ****. You have to bolt on external parts, (like dampers and flywheels that are out of balance/counterweighted) to balance the assy and use/run the motor. Whether these counterweighted bolt-on's end up in the "perfect" location to balance the assy or not doesn't really matter, as it relates to where they are placed, from a naming stand point; they're outside the engine. Maybe I'm sofakingdom that I can't understand words, but to ME, since those parts complete the balance....and...they're outside the engine ("external")...that makes them "Externally balanced". No?
So, Skool me on where the terms "internal balance" and external balance" originated please, so I can be lessfakingdom.



Did you not just describe the "funky flange" of the standard 2 pc seal crank?


Simple, you're ignoring wicked simple questions.

Let's brush up on some history. Starting with the early, 3" stroke small journal crank you stated had a round/neutral balanced FW flange, right? 100% of the "balancing" of that engine happened w/in the oil pan...."inside" the engine. We know that b/c the damper was neutral balanced. The FW was neutral balanced. and the FW flange on the crank was neutral balanced, b/c it was...round. Any balancing of that engine was inside the engine aka "internal" and literally, right next to the rod bearing and piston mass that it was attempting to ideally balance. Right? RIGHT. Moving to the later, large journal 3" stroke crank, that has the "funky flange". What happened there? Why did GM add or remove weight from the flange along with that change? Both engines were 302's or 327's with the same bore and stroke...so why the "funky flange"?

 

Exactly.

No.

Go revisit what I've said over and over. Focus your mind on the concept of FROM END TO END. That means, in a V8 of the design that the SBC is, that the #1 & #2 rod throw has the CORRECT balance weight on either side of the throw; that is, half of it is "in front of" the throw, and half is behind it. Then the same thing applies to the #3 & #4 throw: half of its CW is in front of it, and half behind it. And so on, all the way down the crank. FROM END TO END. Each throw, each CW, they're all exactly "optimum". Of course, between the #1/#2 and the #3/#4 throw, there's only ONE CW, which is exactly right to be the "optimum" for both; at each end, i.e. in front of #1 and behind #8, the CW really only has to balance out THAT ONE throw.

The 400 IS NOT like that. The pistons come too close to the crank CL at their BDC, for the opposing CWs when they're at "TDC", to FIT, if they're made of the same metal as all the rest of it (misc alloys of Fe). It's not possible to fit enough CW under the piston for the INTERNAL balance weight to be adequate. Consequently the crank assy is NOT "internally" balanced. In ALL other SBCs, it IS.

No I did not. That flange is the rearmost INTERNAL balance weight for those engines. Keep in mind, not sure how many times I have to say this, it DOESN'T MATTER which side of bearing, block, seal, bolt-up, WHATEVER, it's on; it's EXACTLY the right angular inertia to counterbalance the rearmost crank throw. Just like the weight that's IN FRONT OF that rearmost crank throw. That makes it part of the INTERNAL balance system for those motors. Doesn't matter what your eye sees; it's still INTERNALLY BALANCED.

Because the "large journal" 67-85 engines had LARGER crank throws (larger dia, aka heavier) and rods (larger altogether, aka heavier) that required balance weights (heavier) that wouldn't fit inside where you couldn't see them anymore. No worries; they were still INTERNALLY BALANCED.

I would also add, the rod throws were drilled though the center, all along, in all SBCs, to LIGHTEN the rod throws, so that the CWs could be as small as practical. Again, for whatever reason, in the large-journal (67-85) engines, GM decided they couldn't just drill a yet bigger hole in the rod throws, maybe thought it would make the rod throws too thin, and instead, opted to handle that last bit of balancing via the funky flywheel flange. Maybe they drilled the front one larger: and maybe that's why those motors tend to break their cranks where the #1/#2 rod journal meets the "throw" between that and the front-most CW. 400s are even worse about that (speaking strictly as someone whose has broken 400 cranks just exactly like that).

And so were the later large-journal motors, up until the 400. EVERYTHING you could "see" with the oil pan installed, except for the FW flange on the crank, was neutral balanced. This was possible because they were all INTERNALLY BALANCED. (which is not necessarily the same as "neutral balance", just as "external balance" doesn't mean "you can't see it") The 1-pc RMS motors didn't change this, except that the weight of the "funky flange", had to be moved outboard, so that the flange could be ROUND. The basic balance of THE ENGINE stayed the same and DID NOT CHANGE. They are all INTERNALLY balanced.

Ready to buy that shiny yellow metallic stuff off of me yet because it looks like gold? It "looks" just "like" it, even though I'm telling you it's something else. Who ya gonna believe? Me, or your own eyes?

 

Not you...if you can't explain it or answer my questions directly. "Butttt", we're starting to get somewhere....

Agree. ALL of the weight required to balance the assy won't fit inside ("Internal") the engine. So it's "externally balanced" b/c that excess weight had no where to go, but OUTSIDE ("external") the engine. COOL...we're all good then. We agree.

Awe SH|T! I thought we were all good! On the same page....but then you went and said this:
Well!! That is very weird, indeed! It's almost...ALL-MOST....as if you're saying the the exact same reasons for the same movement of the same weights (not the exact same value), to the same place (outside the engine) for both cases. So b/c your advice hasn't sunk in yet, and I'm still sofakingwetoddit, explain this to me like I'm a 5 year old: Why is the addition of mass to the crank flange on one engine, called "internal"...but on a different engine the same technique and location of weight addition is called "External"? It's almost like we need to....

...so that we can then understand why one engine with weight bolted to the FW (b/c it won't fit INside) is called "Internal" and another engine with weight bolted to the FW (b/c it won't fit INside) is called "External". Maybe wetoddit people like me don't know what "internal" and "external", means. Why are Fords "Externally balanced"? I mean, they require balance weights (heavier) that wouldn't fit inside where you couldn't see them anymore. Right? I mean, on a Ford....
So a Ford must be internally balanced too then....right? Becauuuuusse....^^^^


Right? Totally! Buuuttttttt....so it is on the flywheel of a 400. So....ahhh... That must be internally balanced too, right? Since it DOESN'T MATTER which side of bearing, block, seal, bolt-up, WHATEVER, it's on?
I'm So confused.... I guess I'm just ain't smart 'nuff to no whut werds meen. Hick hick hick....You got me sum dat 'gold' there, pard??

Since we have two same-brand, same-platform engines that have moved weight outside of the crank case to have neutral balance (not shake), yet one is referred to as "internal"balance and the other is referred to as "external balance"....and in BOTH engines, it DOESN'T MATTER which side of bearing, block, seal, bolt-up, WHATEVER, it's on?.....then I think....I THINK, that at this point in the discussion, we simply need to know what the word "internal" and "external" mean....
Oxford? Meet Sofa. Sofa....Oxford.

in·ter·nal
/inˈtərnəl/
adjective

1. of or situated on the inside.
   "the tube had an internal diameter of 1.1 mm"
   Similar:
   inner
   interior
   inside
   intramural
   central
   middle
   Opposite:external

noun

1. inner parts or features.
   "all the weapon's internals are well finished and highly polished"

-----------------------------------------------------------------------------------------------------
ex·ter·nal
/ikˈstərn(ə)l,ekˈstərn(ə)l/
adjective

1. 1.
   belonging to or forming the outer surface or structure of something.
   "the external walls"
   Similar:
   outer
   outside
   outermost
   outward
   exterior
   surface
   superficial
   visible
   extrinsic
   extraneous
   Opposite:
   internal
2. 2.
   coming or derived from a source outside the subject affected.
   "for many people the church was a symbol of external authority"

noun

1. the outward features of something.
   "the place has all the appropriate externals, such as chimneys choked with ivy and windows with jasmine"

 

I think this really all boils down to post #15:

...and/or WHICH AUTHORITY you choose to listen to/believe. Since you won't believe what your own eyes can see...I have lbs of real gold that I know you're not interested in having for free....b/c of course it can't be real even if it looks real, right? The easy position to take is what "GM says". My personal problem with that is knowing what words actually mean. I know that I won't be changing GM's (or your) mis-use of words and likewise, Sofa, I'm TOOWETODDIT, & TOOFAKINGOLD to change my thoughts on the matter.

 

A 32 pound 168 tooth.

 

After taking in all of the information and referencing my current flywheel, it isn't off a 1990 in the first place. Oops.
It has the earlier larger bolt pattern, which tells me that it's an early model unit (that and the part number on the back referenced against a summit listing). So I'll have a machine shop balance it to 400 spec when I have it resurfaced, and that'll be that.

 

Nice. Easy button.

 

I feel like GM called it internally balanced when all the necessary weight was cast or forged as part of the crankshaft which is an internal part even if additional weight was part of the external flange. It becomes externally balanced as soon as an additional counter weighted part is added to balance the rotating assembly. That is the only way I am going to look at it and I have been doing this long enough my mind is set on that concept as well. GM service literature has always considered the 1pc RMS SBC engine externally balanced in the rear because of the counterweighted flexplate/flywheel required for it in factory production form. If you order a flexplate or flywheel for an engine that was counterweighted externally it better be for external balance. As I said I have made that mistake, bolted on an aftermarket flexplate for internal balance to a 1 pc RMS SBC and the engine ran like a commercial paint shaker mixing up a 5 gallon can of paint.

 

I've done it too. It was bad. Above 2000 RPM? BAD.

MERRY CHRISTMAS third gen'rs!!! 🎅

 

MERRY CHRISTMAS back at everyone.