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Which bearing sizes you need depends on how the crank mains measure. All new cranks are not created equal when you're talking thousandths of an inch.
Specs for the new crank:Stroke:3.622"Main Journal Diameter:2.559"Rod Journal Diameter:2.100"
As for the main bearings, I'm seeing my options as standard, 0.010 undersized, 0.020 undersized, and 0.03 undersized...so im trying to figure out which ones I need for this particular crank
To do this correct, your machinist/engine builder will need to measure the journals on the crank, then measure the connecting rod big ends and the engine block with the main caps installed and then determine what work needs to be done, and what size bearings that you need. Ideally, if the crank is new, and machined to factory specifications, standard size bearings should work, but there are tolerances and if you are planning on higher power, it is best to do it right.
Specs for the new crank:Stroke:3.622"Main Journal Diameter:2.559"Rod Journal Diameter:2.100"
As for the main bearings, I'm seeing my options as standard, 0.010 undersized, 0.020 undersized, and 0.03 undersized...so im trying to figure out which ones I need for this particular crank
Those are the specs. There is always a tolerance around the specs. You buy the crank, measure the mains, and then determine the bearings you need to hit the clearance you want. You're going to need to do the same for the rod bearings.
What the engine is being built for also plays into the specs you want. Stock? Boosted? Normally Aspirated but a bunch more hp?
You don't say what bearings you're using, but I've never seen a brand not offer standard size bearings, besides under and over. If you're using a bearing that is coated, the coating can affect what the clearance should be.
Those are the specs. There is always a tolerance around the specs. You buy the crank, measure the mains, and then determine the bearings you need to hit the clearance you want. You're going to need to do the same for the rod bearings.
What the engine is being built for also plays into the specs you want. Stock? Boosted? Normally Aspirated but a bunch more hp?
You don't say what bearings you're using, but I've never seen a brand not offer standard size bearings, besides under and over. If you're using a bearing that is coated, the coating can affect what the clearance should be.
The engine is being rebuilt due to oil breakdown, as a rod bearing had spun previously, so I am having it being replaced as stock, basically to what it was before. It has a base stock engine, and I'm not sure if the new crank is coated or not. I'm hoping standard size will work
The engine is being rebuilt due to oil breakdown, as a rod bearing had spun previously, so I am having it being replaced as stock, basically to what it was before. It has a base stock engine, and I'm not sure if the new crank is coated or not. I'm hoping standard size will work
:sigh: The crank is not coated. Some *****bearings***** are coated.
I do not understand why you would not take the crank and block to a machine shop and have them measure everything and set the bearings up. You may be fine with standard bearings. You may get the opportunity to rebuild it again. Why would you not spend a few hundred dollars to be sure? Too tight and instead of a new crank you ventilate the block and get a new engine when the piston comes out the side.
The engine is being rebuilt due to oil breakdown, as a rod bearing had spun previously, so I am having it being replaced as stock, basically to what it was before. It has a base stock engine, and I'm not sure if the new crank is coated or not. I'm hoping standard size will work
I'll also add that my mechanic already replaced the rod bearings and didnt decide that the crankshaft needed replacing until he put the engine back together, ran it, and realized that there wasn't enough clearance with the old crankshaft in there, and said it needs to be replaced. He said I need standard main bearings. I just wanna make sure he knows what he's talking about..
I'll also add that my mechanic already replaced the rod bearings and didnt decide that the crankshaft needed replacing until he put the engine back together, ran it, and realized that there wasn't enough clearance with the old crankshaft in there, and said it needs to be replaced. He said I need standard main bearings. I just wanna make sure he knows what he's talking about..
The fact he just slapped it together tells me this is a low-buck hail-Mary rebuild or the mechanic is clueless.
Two sayings apply to engine building...
You can have it right or you can have it now, but you can't have it right now
Crankshaft main/thrust bearings question
Too tight and instead of a new crank you ventilate the block and get a new engine when the piston comes out the side.
