Adrian Worman wrote:Mates please help me out of this one; 440 steel crank just come back from machine shop and contrary to my instructions to inform me of how much grinding it would take to clean up, they went ahead and cut the mains less .030 and the rods less .040. Have I got an expensive paperweight? Keepin' my fingers and everything else crossed.
Adrian
Yeah, it's scrap Adrian send it to me for long term future analysis. LOL
Seriously, it wont hurt anything at all. Less diameter means more horsepower, less friction due to the smaller size while still providing ample strength. Pro-Stock 1600 H.P. 500" engines use 1.888 Honda Rod journals and they rarely come apart even at 11,000- 12000RPM'S!! Offset ground stroker cranks for a 400 using a 440 crank involves cutting the mains down to 2.625 which is a .125 cut and the rod journals are ground even more to increase the stroke and is cut .165 on one side of the rod journal,(the inside of the rod throw) to increase the throw or stroke. In your situation, I would measure the rods and main journals carefully and then determine if bearings are available at the size they cut. They should be and
www.440source.com has a list of potential bearings and the different sizes they come in. Dont worry that the .030-.040 of metal removed weakens the crank appreciably. IT DOESNT so relax. But I would also measure the width of the journal they cut on the rod journals, too wide a cut will give excessive oil clearance on your rods and throw more oil around on the bottom end and may cause low idle speed oil pressure when warmed up,(an adjustable oil relief spring would cure that), no biggie there either but you should aim for .010-.018 clearance for good oil control on the rod side journals,(in between the 2 rods at the center). Another thing Adrian, did they cut the rod journals with a full radius or the stock undercut? With a full radius cut you MUST use chamfered bearings for the rods. If stock udercut journals then standard bearings can be used at the proper size of course.,,This is vital, if they cut the radius, make sure it's the right radius, a bearing mockup with one cylinder hung,(2 rods this way you can check the rod side clearance and the bearing to radius interface) and some lipstick or grease will tell you for sure, it should turn freely and leave a "wear pattern" in the grease "showing& contacting" all sides of the radius but providing clearance to the chamfer on the rod and the crank itself. It should turn freely with no binding. If it does there is something wrong and it must be corrected before continuing on with the build,(either the radius or chamfered bearings are at fault). The last 2 engines we have done had this exact same procedure done to it. The cranks were reground. They both came back with the wrong radius that was cut at too steep an angle and caused binding.
We found a new crank shop to have our machine work done!
Engine machinists are sometimes difficult to deal with,, for this I have no answer.
Oh, one other thing I thought of,,,make sure the crankshaft thrust area,,located on the #3 main bearing and has a flanged surface, make sure this flange is highly polished and you cant feel any maching marks on it. If necessary polish this surface with fine emery cloth and get it has 'slick' as you can. It aids the thrust bearing in longevity.
Posted: 04 Apr 2009 14:37
(The .040 rod bearings might be a tough one to procure)