VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1931 Engine rebuild

I am about to rebuild my 194 engine soon and have seen some of you talk about replacing the babbit rods with ones with insert bearings. What year rods would I need to look for to fit my crankshaft and pistons.

I think that the original type rods are used and they are machined to take the insert bearings. My 37 has insert rods in it. It was done a lot in the 50s and 60s. Places like JC Whitney and Sears used to sell crankshaft and rod kits that had the insert bearings. I don't know where one would get them now but possibly a machine shop specializing in old car engines could do it if bearings are still available. I'm not sure there is much advantage in inserts over the original babbit rods in an antique car.

I live in south Georgia and not sure if anyone around here could rebabbit mine. I guess I would have to send the crank and rods to someone to rebabbit and fit. Any good prospects to do this?

I'm sure that some of the guys on the forum can recommend a place to have it done. When I rebuilt the engine in my 33 I bought a set of new old stock rods out of Hemmings Motor News but that was in about 1980 but I bet there are still some around.

I really don't think my rods are bad. Not knocking or worn looking. What kind of cleareances should I get on them.

Well, I would have to look that up for sure, my memory isn't as good as it used to be, .002" to .003" comes to mind but I can't remember for sure. I bet chevgene or a lot of the other guys can tell you off the top of their heads! I think they used to say to take out shims until a "light tap of an 8? ounce hammer" will take the end play out and then add a .001 shim. I never liked that method too good but I think it worked for the really experienced mechanics. I usually used plasti gauge.

The rods should be about .001".

Just looked in my 37 shop manual it says "Remove shims, an equal number from each side of the bearing, until the rod can not be snapped back and forth by hand, but can be tapped back and forth with a light blow of an 8 ounce hammer. Then replace one .002" shim, being careful to keep the number of shims on each side equal if possible.When the bearing is properly fitted, it should be possible to snap the rod back and forth on the crank with one hand." I think a 1931 would be about the same.

For the pre 1937 engines shims are removed until the rod can not be moved back and forth by hand but will move with a tap of an 8 ounce hammer. This is due to the smaller journal size (Chevrolet says)....so they are fit a bit tighter than a 216 engine.
At .002" they will be making noise.

MyChevy,

You better go by what JYD and CheveGene say, they are more on top of it than I am. I don't remember how I fit my 33 rods back in 1980 but fortunately it is still tight and quiet but it only has about 3500 miles on it since then.

Hi
Before you start the rebuild on your engine, you should have a shop manual. If you don't have one for your 1931 Chevrolet, Gregs Online has them for $10.00. Here is the link http://www.gregsonline.com/eshop/Shop_Manuals/31PSM.htm to see it. Here is a link http://chevy.oldcarmanualproject.com/shop/1934/index.htm to the 1934 shop manual which in the located in the Old Online Chevy Manuals link http://chevy.oldcarmanualproject.com/ which is also loaded full of other information like service letters and parts catalogs. The engine section of the 1934 manaul shows exactly how the main bearings are line bored and set up.

Replacement babbitted main bearings shells come in .060 inch undersize semi finish. These are installed in the engine with shim packs consisting of 4 ea .002 inch shims under each side of the main bearing cap which are then bolted to the engine block at the appropriate bolt torque. Depending upon the undersize the main bearing journals need to be ground on the crank shaft ie. .010, .020, .030 inches, determines the undersize the main bearings shells or inserts need to be line bored. The clearance is what Junkyard Dog suggested at .001 inch running clearance. I would suggest using plastic gauge to check the journal clearance on the rod and main bearing when installing them or setting up the engine as this is a more accurate method but to an experienced mechanic the old way would still suffice as it is done by feel. You will end up taking the engine block and crank shaft to a machine shop to have this done. You may be able to reuse your original main bearings and connecting rods if they are not excessive worn. The main thing to look for on the main and rod journals is spalling, roughness, taper and out of round. Most engines of this age need to have the crankshaft reground as years ago the maintenance of these engines was not to good.

From my experience the connecting rods for the 194 engine can not be cut for an insert bearing. The local machine shop that I use does any engine in anything including high performance. He has done a few 194 Chevrolet engines in the past. I had him check on the possiblility of refitting the 194 engine connecting rods with inserts but he could not find a proper available sized bearing insert to install after the old connecting rod would be machined out to accept an insert bearing. To have these bearing shells specially made would be cost prohibitive.

Hope this answers your questions.

If you need parts for the rebuild on your engine, please visit our website www.marxparts.com or e-mail me at bob@marxparts.com as we have some or most parts in stock for these engines.

Bob

thanks for the info. i have a manual and will be checking with my local machine shop