Ok so i have an 84 firebird with a '72 350 sb that i recently purchased and its been giving me a bunch of problems since buying it..

the biggest of problems was a tapping sound that didnt seem to bad at first.. almost sounded like an exhaust leek.. after eliminating that factor i checked and adjusted the valves. also concluded that it wasnt the problem.. over time it seemed to get worse.. maybe a lifter.. all were fine.. a few people suggested it could possibly be the fuel pump due to the fact it was mechanical.. so i switched it to an electric fuel pump to eliminate a cam lobe problem.. wasnt that.. i then decided to pull the engine after pulling it all apart i found that it was a rod bearing.. go figure.. i was bad enough to score the crank but it didnt spin or anything.. the cylinder wall seems fine still smooth and no signs of markings from the piston.. now the crank is already .020 under so is it possible to get it cut to .030. and if so would i be able to do it to the one journal and leave the rest at .020.

this problem was actually cause by a bad carb. the bowls were overflowing and poring gas cause my oil to wash.. then at one point my oil pressure guage line hit the header and melted lost oil pressure and the first bearing went.. lifes a bitch.

engines already bored .060 over so im glad that i might be able to save this one because the cylinders are okay.

 

You can take the crank down to .030". Do all of the same type of journals (rods, in this case) to the same undersize. If the mains are clean, you can either leave them be or have them polished.

 

I would avoid cutting that crank any further, mainly due to the cost of a cast crank is about what a shop will cut it for, unless it is a forged crank. If you did cut it I would say to do all of the rod journals and also have the mains checked, if it lost oil they may be hurt also. sux that you got a turd

 

yea it sucks that people will scam you like that. but also this is another reason im questioning things a little bit.. even though i did loose oil i only lost about a quart or so. im actually wondering if there was a problem with the crank and the dude just put new bearings on it and sold it before it started tapping again.. all the other bearings are fine.. including the main bearings..

maybe ill just look to buy a new crank.. and change out all the bearings.. that way i wont have to worry about anything..

any suggestion on a good crank.. never built an engine before.. this is actually my first time takin one apart so its a learning experiance

 

You need to take the entire engine apart, remove all galley plugs, and thoroughly clean all oil passages before you start putting it together again.

 

Ive seen bearings up to 60 under, i wouldent use them but some people do.
If you dont trust it get another crank they arent too expensive. You can even order a kit with the crank and berings IMO it makes life a little easyer. www.partsamerica.com/ has kits with reman cranks starting at $140.

 

If you want a stock type replacement crank, a local auto parts store may be able to get you one, but I would look for a store with parts guys that seem to know what they are doing, autozone usually doesnt fit that lol. If you want something a little better than stock, but not too pricey a cast crank from scat or eagle is a little stronger, summit or jegs , or if you have one a local speed shop can get those. If you have a machine shop in town, ask them what they can get, most of the better shops will give you a good price on the parts so you bring them the machine work, so its worth a try. As previously stated, since there was a bearing failure, all the oil passages must be cleaned thoroughly to prevent damage to new parts. If you are not sure what you are getting into, swing by the book store and look at a book on small block chevy's there are a ton of them out there so I wont say look for this book, or only this book is good, however if you see one by dave emanual, thats my ride on the cover, he sold it after writing that book and some articles on his project (hard rock camaro). Engine repair is not a beginners job so make sure you know what you are getting into. also a service manual for the car isnt a bad idea

 

yea ive been reading a lot lately.. and i actually getting into the motor is helping me absorb information.. and i work at pep boys.. but im not really tryin to get a stock crank.. and was just lookin through summit for a new crank..

just curious how long would you say this might take me if i do it the right way.. i hate people throwin **** together.. thats kinda how im at where i am now

 

umm....Ill put it this way, use as much time as you need, make a check list, so you know what you did, then after everything is cleaned and checked for debris, start assembling. i usually keep a silver sharpie around to mark things that are tightened as im doing it so i dont need to remember. It is not a race to build it, thats later lol (well i did almost run out of time building the engine in mine now..I think i did ok, first started it tuesday before the event, put it on the bumper sunday lol so much for break in time ) Also use a quality torque wrench to tighten things, you may need to ask a favor from somebody, but a good one will be more accurate. I dont really recommend the Taiwanese ones for that. If the budget will hold it I would upgrade the fasteners on the bottom end, mostly since you dont know the history of them, the previous owner was clearly a hack.