Well mine came back with .030 rods and .020 mains, it's a light forged corvette style 283 crank Under normal circumstances i wouldnt worry, but this motor WILL be abused its a 301 with Scat H-beams, chevy offroad 140 grind, gear drive, late 327 block w/spacer bearings, and 10 to 1 compression Should i worry about the crank especially at rpm??
Did they leave a nice wide radius on the journals ??? That's were the"I MEAN ANTI FATIGUE" strength is !! >>>>.
Its all about the journals ad the radius on there from the shop that did the grinding. If they made a nice wide radius, the crank will actually be more crack resistant than the factory stock crack at std/std. Strength is not the issue really - fatique life is. Cranks with a wide radius on the journal will be much more crack resistant that a crank with an undercut radius or a square shoulder. The downside is you might have to shave your bearings to get them to fit without interferance. Most race bearings are already clearance anyways since most aftermarket cranks have a nice wide radius.
A reputable local sprint car engine builder swore i should go 350 type block with spacer bearings because of the webbing, and since my 327 block had been stolen and a deal fell through on an original DZ large journal crank i decided it would be the easy route
bearing spacers are not a good idea in a motor that will be "abused". There are heat transfer problems, stability issues, and it just adds one more item to fail in an area that sees quite a bit of stress to begin with.
Something to keep in mind with engines that will be work HARD is that more the crank is turned the thicker the bearing materiel has to be. The steel backer stays the same, so the soft bearing material takes up the space. Fairly easy to 'hammer' the bearings if they get too thick. With the Jaguar engine .010 is max for an engine destined to be 'abused' and standard is much better for a long lived engine. Personaly I would look for a .010/.010 crankshaft.
Coupla things...historically, Grumpy Jenkins used spacers made from bearings in many of his race engines, like 331's using early crank and late block. Read his books on his fitting details. He used actual bearings, not the purpose made spacers, and line bored them after fitting to his preferred crush level. On thickness, there are undersize bearings avaialable from some suppliers made with thicker steel backing and normal soft-metal thickness. Have not messed with Chevies in a long time, cannot remember who. And...some serious engine builders suggest on stock-crank based race engines that they be turned to max (based on bearing availability) undersize in order to allow big radii to be formed. Yunick's books show some tricks for fitting bearings to large radius journals.
webbings? hell ive seen more 350s break apart at the track then old blocks. i run a 301 in my nova the crank is 30-20 i have had no problems in 5 years and thats on 13:1 compression with stock rods!!! arp bolts of course. its a steel crank as well. im using a 1964 283 block .125 over with 2 bolt mains and have not had an issue there either. i routinley shift at 7500. you should be fine.
Is it clean and is the fit right. That is all that matters. Don. Backing is not always the same by the way I have peeled a few Clevlites just to see. Hove run 030under in experimental engines that saw stuff we would never execpt out of a normal deal . Was pleasnatly surprised that even in these potentiually throwaway experimental deals never had a failure of an 030 under rod bearing depite some absolutley unreal abuse
Did somebody mention main bearing webbings breaking ???? I just couldn't help but to post this >>>>. 1500 posts yee-haw !!!
I thought the number 1 rod was the weakest point in chev's. Farthest from the oil pump! Got two blocks inthe scrap pile where the number 1 rod let go.
I don't think you have anything ta worry about as long as you assemble properly and set all your clearances. I've seen many 377's (400 block w/ 350 crank & spacer bearings) last a long time. And these engines seen 8,500 to 10,000 rpm use. If your gonna spin it that hard it would be worth the money ta have the rotating assembley balanced.
This is true in engines with babbitt bearings, the babbitt has to be finished thicker the more the crank is cut. Insert bearings maintain the same overlay thickness regardless of undersize - the backing shell is thicker to make up the size. Some .060 under bearings (usually old industrial applications) have thick overlays that can be refinished all the way to standard and it will say so in the manufacturers catalog. I fought this myth thru 25+ years of crank remanufacturing. I'd rather use a shaft that's ground and polished correctly at .040/.040 than a lot of the .010/.010 hack jobs I've seen. Correct size, roundness, lack of taper, correct radius, straightness and finish are way more important than bearing size. By the way, Jag cranks are nitrided - if you grind more than .010 you grind through the nitride, that's the reason for no more than .010 under.
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