crankshaft counter weights
- Thread starter oldspert
- Start date
Pete
BANNED
If you made the weights so they could accommodate several slugs of Mallory, it would be even better.
oldspert
Senior Member
I would buy pre-made weights. Probably from Bert's.
nkaminar
Well-known member
The engine I am rebuilding has the welded on counterweights. It ran smoothly. It had problems with the insert bearings and scored cylinders due to problems with the piston pins. The crankshaft was balanced and that must be done after you weld on the counterweights. If you want to be exact, use the bob weights when balancing, see https://www.fordbarn.com/forum/showthread.php?t=333750
oldspert
Senior Member
That will be up to my machine shop.
BRENT in 10-uh-C
Well-known member
Allow me add some additional thoughts to this a tad. Being a professional welder is definitely helpful however that skill is kinda down on the list based on my experience doing this.
To begin with, you really should Magnaflux the crankshaft to verify there is not any cracks, and then the crankshaft needs to be straightened to ensure when the weights are installed, they will be exactly perpendicular to the crank's centerline.
As for installing weights, IMO you really need a Milling machine with a set of V-blocks to support the crankshaft on the front and rear journal pin. You will need to fabricate a fixture to be able to locate each weight where each web is positioned at 00° centerline (i.e.: at the exact 12 o'clock position), -and that both weights can be installed exactly in the same plane. My fixture registers off of the crank flange dowels. Failure to correctly position just one weight likely causes more issues than all the remaining weights would ever overcome. Plus, when you price heavy metal, you will know why I am saying this.
Next, I have found the arc of the counterweight generally does not have the same radius as the crankshaft's web, therefore you need a way to fit the weight to the web. Basically there are 3 ways I have accomplished this. One is to use the crankshaft grinder to remove metal from web circumference. Another is to clamp the weight onto a faceplate and use the lathe to machine them. The 3rd is to use a boring head on my Bridgeport.
I use the DRO on my Mill to find the centerline of the crank weight. Just use a centerfinder on both ends and scribe the center of each one. At that time, I drill a 0.375 hole thru the weight's centerline for a safety bolt. Next, with the crankshaft clamped to the Mill table, you should be able to find the crank's centerline to match the weight's centerline to the crankshaft. I feel each web needs to be drilled and threaded so that a (a socket allen head) safety bolt can be installed after the weight is fitted. Once the safety bolt has been installed, just fill the socket head with weld and allow penetration into the weight so the bolt cannot unscrew. Then weld each weight at both ends first, then around the perimeter where the four sides of the weight meet the web. A follow-up run thru the wet-mag is generally prudent.
Once all of the above has been completed, recheck the crankshaft for straightness and then on to balancing. Bobweights will not be used during the balancing process. So I trust you now understand why welding skills should not be the priority in this deal. From experience I can tell you this is not an easy modification to make on a crankshaft.
To begin with, you really should Magnaflux the crankshaft to verify there is not any cracks, and then the crankshaft needs to be straightened to ensure when the weights are installed, they will be exactly perpendicular to the crank's centerline.
As for installing weights, IMO you really need a Milling machine with a set of V-blocks to support the crankshaft on the front and rear journal pin. You will need to fabricate a fixture to be able to locate each weight where each web is positioned at 00° centerline (i.e.: at the exact 12 o'clock position), -and that both weights can be installed exactly in the same plane. My fixture registers off of the crank flange dowels. Failure to correctly position just one weight likely causes more issues than all the remaining weights would ever overcome. Plus, when you price heavy metal, you will know why I am saying this.
Next, I have found the arc of the counterweight generally does not have the same radius as the crankshaft's web, therefore you need a way to fit the weight to the web. Basically there are 3 ways I have accomplished this. One is to use the crankshaft grinder to remove metal from web circumference. Another is to clamp the weight onto a faceplate and use the lathe to machine them. The 3rd is to use a boring head on my Bridgeport.
I use the DRO on my Mill to find the centerline of the crank weight. Just use a centerfinder on both ends and scribe the center of each one. At that time, I drill a 0.375 hole thru the weight's centerline for a safety bolt. Next, with the crankshaft clamped to the Mill table, you should be able to find the crank's centerline to match the weight's centerline to the crankshaft. I feel each web needs to be drilled and threaded so that a (a socket allen head) safety bolt can be installed after the weight is fitted. Once the safety bolt has been installed, just fill the socket head with weld and allow penetration into the weight so the bolt cannot unscrew. Then weld each weight at both ends first, then around the perimeter where the four sides of the weight meet the web. A follow-up run thru the wet-mag is generally prudent.
Once all of the above has been completed, recheck the crankshaft for straightness and then on to balancing. Bobweights will not be used during the balancing process. So I trust you now understand why welding skills should not be the priority in this deal. From experience I can tell you this is not an easy modification to make on a crankshaft.
Jim Brierley
Well-known member
Counterweights don't necessarily make the engine smoother, they add to the longevity of the bearings.
Bob weights aren't needed or used when balancing a 4 cylinder, 180* crank.
Bob weights aren't needed or used when balancing a 4 cylinder, 180* crank.
johnneilson
Well-known member
FWIW,
If you really want a counterweighted crank, the option to fit a "C" crank is another way.
It is just another can of worms to open.
PM me to discuss, John
If you really want a counterweighted crank, the option to fit a "C" crank is another way.
It is just another can of worms to open.
PM me to discuss, John
oldspert
Senior Member
The information from Brent is exactly what I was looking for. I have a milling machine in my shop to make sure all is exactly lined up. The addition of safety bolts is a very good idea, never thought of that. I still haven't decided to add the weights until I get into my engine and see what is making it out of balance. I do know the engine has been separated from the bell housing because the bolts are clean and with mis-matched bolts. The friction disk has been replaced because the springs in the disk are clean and bright paint.
Synchro909
Well-known member
I considered doing that years ago but I dilly dallied just long enough for Mr Burtz to come up with a better solution. The biggest challenge was going to be the making of new main bearing caps ($). I was going to run the crank shaft and rods on insert bearings like I did in the diamond B engine in my Tudor. I still think that would be the second best option after a Burtz engine,
All of that said, the engine I used for all of my long distance towing trips was an original one rebuilt with the aim of both more power and as much stamina as I could put into it. It has a new Burlington crank shaft (nearly due for a regrind) and new connecting rods both on insert bearings. They are a work of art. I put a HC head on it, a mild touring cam and a downdraught carburettor. After about 70,000 hard miles, it is now a bit noisy and due for "refreshment". I digress.
Can anyone confirm that Terry Burtz is behind the new rods offered by vendors for many years now?
Pete
BANNED
Everything flexes but not so it bothers anything.
Several of us spin our engines well over 6000 every day.
Synchro909
Well-known member
6,000 rpm! Wow but not for me. With that old and heavy flywheel (even if it has been lightened) spinning near my feet, I'm not keen to try it.
Terry Burtz Calif
Senior Member
Arnold,
I make several parts, but my only involvement with connecting rods are the forged connecting rods used in the "New Engine" which utilize the very common (and cheap) 2 inch diameter inserts that are manufactured by several manufacturers.
The original Model A crankshaft and all Scat crankshafts for Model A and B engines have 1 1/2 inch diameter connecting rod journals and they utilize an insert that has a sole manufacturer, and because of volume, the inserts are expensive.
To minimize crankshaft flexing that causes cracks and eventual fatigue failure, modern 4 cylinder engines have a stiff crankshaft with large diameter main and rod journals with a counterweight on both sides of every connecting rod.
The "New Engine" crankshaft with 2 inch main and connecting rod journals and 8 counterweights can be modified to fit into a stock Model A cylinder block and retain the large journals.
We have sold several crankshafts and connecting rod sets without cylinder blocks to people building race engines that need to utilize a stock cylinder block to follow the rules.
Synchro909
Well-known member
Terry, Thanks for the reply. When I saw the rods in your new engine kit, I noted that they had similarities with the ones I had used in my earlier motor so I suspected you were behind them. Apparently not! They are still a very nice piece of work.
In my inserted B engine, we used the same inserts as you did in the new engine (8-10 years ago) and inserts from some other car for the rods. I can't remember which car "donated" those. That engine is my second most favourite now after your new one.
BTW, those clips for the oil holes are in and working well. Thankyou.
In my inserted B engine, we used the same inserts as you did in the new engine (8-10 years ago) and inserts from some other car for the rods. I can't remember which car "donated" those. That engine is my second most favourite now after your new one.
BTW, those clips for the oil holes are in and working well. Thankyou.
ModelA29
Well-known member
I spotted this beauty on another site. You can see the amount of work to use an original block to stay within the rules. They are very specific on what mods you can do to the block and what welding is allowed.
The red engine was Roy Creel's. He's well known for building some big horsepower B engines. Sometimes even with all that work they still come apart.
My OHV B is running Pontiac rods and bearings from a Perkins diesel. It was originally built before new forged rods and inserting A/B rods were a thing. I picked up a set of new forged inserted B rods for a B flathead I'm building for our Tudor.
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