440 Internal or External Balanced
- Thread starter BMosely
- Start date
fastmark
Well-Known Member
There are lots of possibilities when you have a combination of unknown parts. I think that is what you have here. The possibly that you have the crank and rods out of a later model (72-78) truck motor that had the steel crank, heavy rods, and neutral balancer, is remote. Especially considering the block and balancer is a 68. Then add the fact that you have aftermarket pistons that are the same weight as those low compression oem 72-78 pistons? The chanced it is correct is almost nil. It would not be the first motor built that was not done correctly. The last four BB mopars motors I’ve done for customers in the last two years, all had poor machining or parts combinations that lead to failure.
My advice is to buy a new set of rods( I like Molnar) because the cost of resizing, new rod bolts, pressing on and off of the pins and the extra time spent by a really good engine shop on equalizing all the rod weights for a good balance job, cost almost as much as a set of real good rods. The balance job will cost less if you have already balance rods( or should). I see no additional balancing on that shaft in the pictures you have shown. I have a motor at the shop right now that was a 75-78 motor home crank, heavy rods and balancer. It had aftermarket pistons installed at the last build. The balance job required a little bit of heavy metal welding into one of the factory holes and a plug installed. I know the engine and builder. It did not vibrate.
If it were mine, new rods and a balance job, and it will be good to go. Pretty simple stuff.
My advice is to buy a new set of rods( I like Molnar) because the cost of resizing, new rod bolts, pressing on and off of the pins and the extra time spent by a really good engine shop on equalizing all the rod weights for a good balance job, cost almost as much as a set of real good rods. The balance job will cost less if you have already balance rods( or should). I see no additional balancing on that shaft in the pictures you have shown. I have a motor at the shop right now that was a 75-78 motor home crank, heavy rods and balancer. It had aftermarket pistons installed at the last build. The balance job required a little bit of heavy metal welding into one of the factory holes and a plug installed. I know the engine and builder. It did not vibrate.
If it were mine, new rods and a balance job, and it will be good to go. Pretty simple stuff.
Thanks for your comments/help
My motor build is essentially what you suggested
New lighter rods, higher compression CF pistons
Cam and Adj roller rockers were reused
906 heads had been ported , with good valves and springs
Heads milled a bit block bored .030
Timing set oil pump water pump all upgraded
Nice smooth runner.
Heavy rods and pistons resold
Solid advice ,not smartest in room comments
Thanks again
mopower440
Active Member
can someone explain how a vibration from an un-balanced engine would feel/act? I know an engine with a mid size cam loping kinda shakes while idling so how do you know any movement from the engine is actually from a balance problem?
1 Wild R/T
Well-Known Member
Engine balance problems are typically RPM specific, above or below that RPM it smooths out quite a bit but typically still isn't truly smooth... And often the vibration will show up at a second RPM band...
It'll vibrate in neutral or in gear.... Though it typically vibrates more under load (in gear)....
Vehicle speed has no bearing...
It'll vibrate in neutral or in gear.... Though it typically vibrates more under load (in gear)....
Vehicle speed has no bearing...
I made this mistake over twenty years ago, with a 73' 440, that was removed under warranty, at the dealer because of a persistent rear main leak. This was a complete long block, but no balancer. I was driving a 69' Coronet with a 383, four-speed trans. Pulled the 383, and used the balancer off it on the 440. Ended up with a vibration that oscillated through the whole boy. You could stand outside the car and see it. Had I known back then I would have fixed it. Even the alternator and power steering brackets are all different.
So bringing myself up to my present problem. A 440 motor home engine. Low miles, but the crank was damaged. Bought a regrind crank. All was good, however, when I put the crank in, alone it rolled over effortlessly. Started hanging pistons and rods, and it progressively got harder to turn. Stopped, pulled off the pistons, and alone the crank turned hard. Hmmmm? Started plasti-gag- ing the mains bearings, when I noticed the was no end play on the crank. Looking at the number three cap assembly you could see there was very little clearance, so small I couldn't get a 008 feeler to gauge it. Removed that cap and bearings and the crank was turning free. I think I was sent the wrong crankshaft, as there is not room enough on the crankshaft journal. Looks like I need a cast crank. I'll get the numbers off this one later.
Last edited:
There is 2 different size thrust bearings. Narrow for old motors , wide for newer. I think 74 and up? Take a look at the crank thrust, and where the bearing goes in the cap.
markrr
Well-Known Member
This is all very interesting.
33 IMP
Well-Known Member
Yep. Later large #3 main thrust flange in a earlier motor is trouble.
This is a 1978 engine. This replacement crank number is: 4027175-3, Is this a cast or forged crank?
Since this problem came up, I didn't know there was a difference in crankshafts. This engine is externally balanced and uses a cast crank. Maybe this is an older model crank?
Last edited:
33 IMP
Well-Known Member
Auggie, look at the cheeks of the rod throws. A sharply defined line will be a cast crank. If there is a roughly 1/4-3/8" wide line, it's a forging.
Another way to tell. The cast crank counterweights are squarely shaped, with defined corners. A forged crank will have more rounded edges.
Another way to tell. The cast crank counterweights are squarely shaped, with defined corners. A forged crank will have more rounded edges.
1 Wild R/T
Well-Known Member
When you install the center main cap your supposed to tighten the bolts to a low value, maybe 4-5 ft/lbs then you force the crank fore & aft to set the main cap location... .008 movement of the cap when bolting it down means no end play... You need to center the cap by shifting the crank, torque the bolts to spec then recheck end play.... It's best to use a dial indicator but a feeler gauge will work...
A 78 block will be cut for the wide flange thrust bearing so either the wide or narrow will work....
A 78 block will be cut for the wide flange thrust bearing so either the wide or narrow will work....
H Series Main Bearings STD - RB Engine - SMALL THRUST
Size: STD / Series: H / Material: TM-77 / Journal Size: 2.750" (RB Engine) / Oversized Fillet Clearance Champher: YES / Oil Groove: 3/4" narrow. Originally developed for Nascar racing, H series are made of TM-77 material, however they are not flash plated with the lead/tin apparently in an effort to help them seat better. They also have enlarged champhers to help them clear bigger crankshaft fillets. They also have a medium level of eccentricity. A good overall performance bearing.These have the smaller thrust surface, which was originally designed for 1973 and earlier RB engine blocks, but will fit RB engine blocks of all years.
Is this crankshaft I have is it a 1973 or older?
The stock crankshaft had rounded corners as you said. So I might have a forged crankshaft, as these are square.
1 Wild R/T
Well-Known Member
One thing I found is that 73' on back has a thinner thrust bearing. 74' on used the thick one.
This engine is externally balanced, is my crankshaft the one I need? Going by the information I found, about the thinner thrust bearing, do I have an older crank that's internally balanced?
This engine is externally balanced, is my crankshaft the one I need? Going by the information I found, about the thinner thrust bearing, do I have an older crank that's internally balanced?
Thanks for this picture, it's two AM here, will check the crank in the AM. I'll see what you suggested in installing that thrust-bearing cap helps.
The crank I have does have 440 cast on it, and square edges. So it must be cast. I must have an older crank going by the lack of clearance on the thrust bearing. Is it externally balanced? I'm afraid it's not? I'm learning a lot here, learning that parts people are interested in a sale, not the right part.
1 Wild R/T
Well-Known Member
Cast Crank = External Balance
The side walls of the thrust should be machined to the same dimension whether it crank is cast or forged...
I read a few paragraphs the info appears solid..
www.enginelabs.com
The side walls of the thrust should be machined to the same dimension whether it crank is cast or forged...
I read a few paragraphs the info appears solid..
Blueprint Series: The Thrust Bearing And Setting Crankshaft Endplay
Crankshaft endplay is a critical tolerance to pay attention to when building an engine, and Jeff Smith shows you the checking and setting process.
OK, that was valuable information. I considered doing the same, but unsure how.Cast Crank = External Balance
The side walls of the thrust should be machined to the same dimension whether it crank is cast or forged...
I read a few paragraphs the info appears solid..
Blueprint Series: The Thrust Bearing And Setting Crankshaft Endplay
Crankshaft endplay is a critical tolerance to pay attention to when building an engine, and Jeff Smith shows you the checking and setting process.
I rechecked the thrust bearing clearance, with a 006 feeler gauge and it wouldn't go in that gap.
I'm thinking I have an early seventies crank. Which would be internal balanced. Which means
I have to come up with a flex plate and balancer. Have seen a number chart to identify these crankshafts by year?
My number is "4027175-3". From what I read the external balanced crank came to being was 1975.
Thanks again
