May it provide you with many miles of enjoyment. NOTE - S&S offers connecting rod sets which are pre-fit to .892" diameter wrist pins. Norm. These are Federal-Mogul 0.010-under rod bearings. Video of me testing the lower connecting rod journal wear. ... Other blueprinting factors critical to bearing clearances include crankshaft end play and side-to-side rod … Then measure the clearance with plastigauge. Slide the piston to the right and left and repeat in closer proximity to each pin boss. This will allow time for the high spots to wear in and get a good adjustment. Increased clearance provides less sensitivity to shaft, block, and connecting rod deflections and the resulting misalignments that result from the higher levels of loading in these engines. Refer to the manufacturer’s specifications. The connecting rod is required to transmit the compressive and tensile forces from the piston, and rotate at both ends. I determined that the interference is in the side clearance. If the engine was rebuilt using aluminum pistons the rods may not make noise due to the less load of the light pistons ? Was common for all makes that did not use inserts. Been covered here several times and answer is no to both. Well good luck to you and the rebuilt engine. See Figure 1. Use of synthetic oils with their better flow properties can help to reduce fluid film friction. If it still binds remove one layer from the other side intil you get .002 clearance. Vintage Chevrolet Club - Discussion Forum. You can get some prussian blue at the auto parts store, and rub some on the rod and cap. Add or remove shims until you get .0015 clearance and wipe the bearings clean put some oil in the bearing torque the bolts to 35 ft lbs and install cotter pins. Checking the rod bearing clearance is conducted in a similar manner. They didn't even have a torque spec in 1934.It dosen't matter which side odd number of shims are but Chevrolet suggested the camshaft side and was more of a way to remember what side had what. So in case of a main bearing, the thicker shell half would be placed in the main cap while in a connecting rod, the thicker half would be placed in the upper position with the rod. If so peel a layer (a layer is usually .001 thk) from one side and try fit it again. If the connecting rod is overlooked during an engine rebuild, the result is shortened engine life. Thats the advantage of the Chevrolet babbited rod bearings. The wear and fretting in the pin bores that I once thought were caused by inadequate clearance and lubrication are actually due to distortion of the wrist pins. Looking around to educate myself, i find shims for sale from one outfit that are .009" thick, and some other place has .002" shims, with nothing in between. Instead, the critical clearance is between the wrist-pin towers and the sides of the little end of the connecting rod. Dewey. Checking rod side clearance. IF THERE IS A QUESTION/DOUBT KEEP THEM ON THE LOOSE SIDE. Yes, that is correct. Connecting Rod Inspection: Normally the connecting rod is not crooked but can sometimes be bent due to preignition and detonation. Now I know that the wrist pins must be rigid to prevent damage to the connecting rod and piston. Adjusted the rods to the correct clearance like they should have been done the first time and that stopped the rod knock. I have driven the car about 200 miles since it was finished, and everything seems to be ok (no "bad" sounds that I can hear). Any comments appreciated. So between the three potential gaps (con-rod to side of crank, con-rod to con-rod, and con-rod to other side of crank) that value is what is called the connecting rod side clearance. Don't scrape but reverse the cap and check the fit again) Continue this until the entire surface is clean. Connecting Rods. The crank is a forged one, but I don't know if its Chevrolet or aftermarket. Furthermore, they must have round and concentric bores, and the fasteners must also be able to withstand the stresses of that application – whether it’s a performance engine or heavy-duty application. It takes horsepower to mess up rod bushings and pin bores, and that’s wasted power. Then, notice what contact area you achieve with the bearing surfaces and scrape, reshim or lap w/Timesaver as needed. The rod bearings were all adjusted with shims to be "loose", you could move them front-back by hand (about 0.0015-0,002" bearing clearance), because the shop thought this was the correct clearance. (Note, If you notice one side of the rod is clean and the opposite side of the cap is clean, you have the cap reversed. Just do not make them too tight. To be safe, it might be a good idea to drop the oil pan and re-adjust the bearings then, right? I hope you enjoy your 1934 Master as much as I enjoyed mine. We used to tighten them up with crankshaft .002" out of round and they lasted for many thousands of miles. increases with shaft speed. Side bearing clearance This is the clearance between the crankpin and the crank arm (Big end) thrust side. Higher clearance also helps accomodate expansion or the rod, however, I would normally expect the journal to expand more than the rod. This is what you're saying when you say total clearance. A bad rod or rod bearing will eventually destroy an engine. The proper condition of a connecting rod is fairly straightforward: The rod must be straight, center-to-center rod length must meet design specs, the pin bore and big-end bore must be perfectly round, each bore must be sized appropriately for wrist pin and crank rod pin fit and oil clearance and the rod must be free of potential flaws. The “L” means this shell must be installed in the lower half of the connecting rod so that the bearing’s chamfer will be on the same side as the crank radius. After these holes are drilled, the wristpin hole of each rod must be honed to provide 0.001" running clearance. If not too much out of round the rod will stay tight for a long time. Using a marker pen I marked both surfaces, tightend the cap, turned the crank and found interference in the radius on one side. Fillet ride can also cause issues with connecting rod side clearance as it prevents the rod from using the full amount of side clearance available between the journal shoulders. Thanks. You can check this with a feeler gauge or welding rod of the appropriate thickness. pulled 2 rod caps off today had my brother in law the machinist come by lookin at the issue we ended up checking the journal, just one he had a better gauge the journal is fine for width. That is a good time to change the oil for the first time also. Sounds like number 5 needs to be looked at very closely. This creates a situation where under load, the oil clearance decreases on the loaded side so the thinner shell half allows more room for the oil to enter the bearing area and maintain lubrication. By the way, a 1934 engine is the old fashioned 207 engine and shares almost no parts with a 1937 and up 216 engine. “Generally speaking, you want .005- to .010-inch clearance from outer dimension of the rod width to the insides of pin bores. The ends of the rod spin around the crankshaft and the wrist pin of the piston. Fit bearing at the point when it is tight and keep it on the tight side - where tapping with little hammer is required to move it back and forth. Did it have brass shims between the rod and cap. I think that I normally run 0.022" clearance on my Carrillo rods, but I havn't rebuilt that engine for a few years now, so I would need to look it up. (oil thined out). None of the rod connections have up and down play but they all seem to have slight side-to-side play with the #6 cylinder (the one closest to the driver side, where the noise seems to be located) having about twice as much play as the other rods. If you can get it to a shop have then "mike" it to see. As the crankshaft turns, the rod also turns, forcing the piston up and down. will excessive connecting rod side clearance increase the amount of oil thrown around and or increase oil consumption? I have never been into a babbit bearing engine like this. Chevrolet in the 1933 -34 engine and Hudson used the dipper system and babbitted rods on most engines til 1953.The later Chevrolet with dippers and oil jets directly to the dippers was good up to about at steady 3500 RPM. (Note, If you notice one side of the rod is clean and the opposite side of the cap is clean, you have the cap reversed. If they don't line-up at 40 go a little tighter. Then tighten the bolts enough that it is snug but you can still rotate the crankshaft and turn one turn. the rods are fine for size. actually about .012+ clearance. Then it is inspected while fixing it. What is an acceptable range of side clearance? Learned never to take a vintage engine to a local machine shop if it was to be done correctly. The reason for using a mirror is to make certain the clearance doesn’t close where you can’t easily see it or measure it. Engine seizure may occur. I don't know what kind of rods they are as I cannot see or feel any kind of identifying marks or castings. The “U” obviously is the upper insert. Looks like they were trying to restore the fillet radii which was small from a previo Connecting rod side clearance - 332-428 Ford FE Engine Forum If they are the 0.0015, they should be ok. My rods were set up by a local engine shop at .0015" (one was set at .002") on my rebuilt engine and the rods started knocking almost immediately. the bad thing is the radius on the crank is to big and interfering with the side clearance. Just a thin coating. each side of the I-beam into the pin boss as close to parallel with the I-beam as possible. . Sorry the answer is not simple. This was done on a 1987 Kawasaki KX125, but is applicable to almost all motorcycles. since the oil pan is off I may as well adjust the rods, I guess. take a feeler gauge and check side-play in the lower rod bearing maximum side play is i think 0.031 from what i can remember id have to check service manual to be sure, but i know its close to that and you also want to check to make sure that it doesnt move up and down your side play can be in spec and the crank still be bad if it moves up and down on the bearing Then measure the clearance with plastigauge. Yes, that is correct. It works better than what you think. Describing some misconceptions about connecting rod side play. BTW, we might guess several of your bench racing friends warned against increased rod side clearance. Chevrolet installed 4 .001" silver shims and two .002" copper shims on each side if I remember correctly. In a heartbeat the crank can be ruined and the rods damaged with insufficient side clearance for proper lubrication between them. It works better than what you think. Don't scrape but reverse the cap and check the fit again) Continue this until the entire surface is clean. After all of the pistons and rods are installed, use a feeler gauge to check the rod side clearance Figure 15-20. This may be your problem. A rod with too much bend will limit oil clearance from one side to the other and possibly lock up at the pin end or at the thrust face on the crankshaft. Don't know the thickness of aluminum foil but as long as it can be combined to result in 0.0005"-0.001" it definitely will be better than Plastigauge. They don’t have to size the big end to ensure proper side clearance. Scrape the babbit, as you suggest, until the radii no longer interferes. I have taken down the oil pan and started checking / adjusting the rod bearings today. Lightly scrape the parts that are wiped clean and repeat the process. A connecting rod, also called a con rod, is the part of a piston engine which connects the piston to the crankshaft.Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the crankshaft. Chevgene, fantastic technical information!!! BEARING SPREAD Main bearings:.005” (.13mm) to .020” (.50mm) in excess of crankcase bore diameter Connecting rod … Note the stamp “L” or “U” on these shells along the upper stamping. Then remove the cap. Dewey, I have found it to be perfectly normal the have interference at the radii when fitting a rebabbitted, (or otherwise foreign), rod. So for a 2.100-inch rod journal, it's always a good idea to shoot for 0.0021 or 0.0022 bearing clearance. If you re-adjust them for peace of mind I wouuld put a few more easy miles on it and do it at about 400 total miles. S&S also offers .001" yOU MAY BE ABLE TO REMOVE TWO SILVER SHIMS OR ONE COPPER COLORED. Friction and horsepower The connecting rod bolts look to be 3/8 inch but I haven't pulled a nut or removed a bolt to check yet. Should work just fine. Assemble the rod to the piston with the correct orientation and swing the rod to both sides until it contacts the inside of the skirt. The dipper system works fairly well up to abut 3000 RPM. FIGURE 15-20. Regardless of the vehicle’s use, the connecting rod must be free of defects, straight and on-size. If it were mine I would drive it for a few hundred miles and then see if you can hear any rod noise after the oil is good and hot. I am certain I can scrape the babbit and make it fit ok but is this the recommended procedure. Sounds like the rod is slightly undersize of the crank, or you might have the cap on backwards. The way I was taught to do these when a young boy by my father and grandfather was: I agree with some of the others on running it for a few hundred miles first. Never to worry. 406 crank came back from grinding with the rod journals widened. On initial fit up it locked up before final torque. I just replaced #3 rod in my 25 T with a vendor supplied replacement. Connecting Rod Side Clearance. Today’s connecting rods strain under 3,000+ HP in racing engines or as few as 50 to 300 HP in a passenger car. I have found Plastigauge to be very inaccurate with thicker babbitt bearings such is Chevrolet 6 cylinder engines 1929-1953. 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