VCCA Home Forums TECHNICAL - 1945 AND EARLIER Chevrolet Speedsters Counterweights

I believe for speedster/high-speed touring use that a counterweighted crank is necessary for longevity’s sake. That being said, I don’t know how to go about having counterweights installed on a crank. Are counterweights commercially available, or must they be fabricated? I have heard of bolt-on counterweights being used (I think on late Model B Ford engines) - if that isn’t an option for the Chevrolet Four, how should they be installed?

-Dave

Dave,

Check with Herb Kephart (ebtm3) on the other site- he made some for his truck block.

Cheers, Bill

There is a fellow in Portland OR who does it all of the time on Model A cranks. He is adding weights to my '29 Chev crank right now (his first Chev). The Chev cranks are angled at the crankshaft connecting rod journal, instead of flat like the Model A. He is having the weights cast from steel at a local foundry. He and the foundry have been doing research as to what metals are compatabil to a forged crank. After that he is going to jig up the crank and weights for welding. Lastly it will be sent to the crank grinder for balancing, straightening, and grinding to final insert bearing diminsions. For a 4 cylinder they drill the crank and turn it into a center feed with a oil filter attachement. Both projects are quite involved and take longer than anticipated.

Interesting information on the six cylinder, beachbum, thanks. Are you building a speedster with that engine, or is it just for touring?

Mac, I looked through our '28 Chevy thread on that other site, and it appears Herb welded his weights on and states at one point that he doesn't think bolt-on counterweights would clear the insides of the block. Nor is there a good place to bolt them on (I guess the Ford cranks have flats).

I haven't asked him yet, but I'll bet he fabricated his counterweights.

-Dave

This is a copy of my post made on the HAMB Chevy 4 site

Took a while to find this--it is a 223 crank, but the looks and principle are the same



First, if crank is to be drilled for oil pressure, do that before counterweights are put on--it is easier to set the crank up then.

Flame cut counterweights are welded to crank, then machined on sides and OD. Crank will probably have to be straightened, and most certainly need to be balanced. If the engine HP is to be increased to any extent, bolt flywheel to crankshaft and drill, ream and insert hardened ("dowel") pin between each bolt hole.

I have a B&W pix of the 170 crank, finished--but will have to find and scan it.

Herb

Are you fitting counterweights to the centre of the crank only, or on the end throws aswell?

Four counterweights in all. Just picked a couple up and laid them by the crank.

Herb

Here is a shot of the crank from my 170 engine (1927)



Herb

That crank is a thing of beauty, Herb.

-Dave

Ok, so you added a bunch of counterweights, what weight do they counter? and what is the purpose of doing this to a normal 1927 Chevrolet crankshaft? Surely you have a good reason for going to this much work and expense.

The weights are added to counterbalance the reciprocating mass of the pistons, rings, gudgeon pins and the small ends of the connecting rods. Putting the weights on the crankshaft addresses the inbalance of forces at the site of the inbalance, instead relying on the flywheel to smooth out the vibrations and inbalance.
http://modelenginenews.org/etw/etw_bal/p2.html

Hi Jack,

Translated, that mean a smoother engine?

What effect does that have on revving etc?

And last of all, the cost would be?

Cheers

Ray

The addition of counterbalances would allow for a lot higher revs,(due to better engine balance).I can't give you the rpm range , but the nostagic racing guys would probably give you some idea. (particularly Herb whose photo of the 1927 crank was posted earler). The early ford racers used to use the 1928 heads to make their fords somewhat better, (and the three port Olds head). There is a crankshaft manufacturer in Victoria who can make a crankshaft for any vintage auto. He could probably make a counterbalanced chev 4 crank if you really wanted one. I don't remember if they were all cast iron though.

The model "A" F@#$d hot rodders do this all the time. If anyone wants this done, check with them.

Do not turn your nose up at cast--or better nodular-- a form of cast-- iron for a crankshaft. Cast iron is stiffer than steel, and so deflects less = less vibrations. Since it is an amorphous
(without grain) material, it is less likely to develop cracks than a common steel crank, AS LONG AS THE LOADS ARE WITHIN THE STRESS LIMITS OF THE MATERIAL.

This, and the economics of manufacture, are why cranks, and rods for modern cars are made of it.

Herb

WOW!
I figure it would take a whole bunch of knowledge about how much and where to place the counterweights on the crankshaft. Is there a source of data for doing this, or is it just something you have learned from engineering training and experiance? Maybe from being a natural born Hot-Rodder?

Thanks for the explanation guys, That is why I asked! I have a little bit of experiance with balanceing the 235 and 261 engines, but Nada with the crankshafts of the 170 fours, I do have some used 1928 engine blocks, a head, and both of the blocks have crankshafts. One has the rods detached and one has been seized up for years but has a good distributor and the flywheel and clutch. I also have two 1928 transmissions complete with the crossmember attached. I got them from a Ford model T fan that got the odd-balled Chevy stuff when he bought a trailer load of T parts. I figured I might need the parts for my 28, but "Klinkerbelle" is doing fine with her original "completely overhauled engine", transmission and rear end that came with her. Her original (maybe) engine is as clean as a pin inside and runs very smoothly.from an idle up to 55 MPH, lots of whineing noises from the transmission, with 85-140 multipurpose in the transmission, reckon I need to add some Honey oil or STP?. She also drives smoothly after I got the proper 1/8" of toe in set, she came with 3/8" of toe out and was a bit squirrley on rough blacktop roads.

So approximatley how heavy is each counter weight? I assume you need to start a little heavier and then machine down to get balance, once you have got your pistons etc all selected. RAYCYCLED

With a four cylinder inline engine, especially one that does not rev any higher than 3000 RPM, the exact weight of the counterweights in not in any way critical. Make th c/weights as large as possible, but still clear the cam and crankcase. they should be all the same size to start with, and after welding and machining get the crank balanced. With V8 cranks you have to make up weights that clamp on each throw, which must be a percentage of the weight of the piston,upper half of the rod, pin and rings. With an inline four this is totally unnecessary, and if the guy that is going to do the balancing tries to tell you differently, find someone that knows what balancing is all about.

Herb

That is the same information the fellow who is adding c/wts to my '29 crank said. The people he counts as mentors told him that on an inline engine all you need to do is counteract the rotational masses. Longevity and a few higher revs are why I elected to go this route. They are not making the 3.55/1 gear sets for the '29s, so will have to stick with the 3.81/1 and a better turning engine.