Young friend of mine is rebuilding a Chevy 350 and he needs a crank. I have a 305 crank in the shop I will never use. I'd be happy to give it to him if it will work. I know that both engines have the same stroke and journal size and that, from a physical standpoint, they will interchange. What I want to know is if there are any other differences, such as balance, that must be addressed when swapping cranks from one to the other. I don't want to give my friend an unnecessarily expensive or unworkable solution to his problem. I did a search and there is a lot of info about Chevy cranks and various bore and stroke combinations. But nothing authoritative, as in "I have done it and it works," or "This is what I had to do to make it work," when it comes to 350/305 crank interchange.
The only thing is, is one or the other newer than an 1985? there are two different rear main seals, 1 piece and two piece. You can swap them, but its easier to use the right one. All but the 400 are internally balanced, and interchange pretty easily, but it doesn't hurt to have a machine shop balance the whole rotating assembly.
They are not balanced the same. A few years ago, I gathered up everything I need to put together a 350 rotating assembly (305 crank) and took it to Wayne Calvert for a balance job. He had to do a lot of work to the crank to get it balanced right. Larry T
I've done it. May not have been balanced right but I never noticed it. I got several tickets running that engine. Maybe the strange vibrations set off their radar guns or something.
The casting numbers are the same. The problem is with balancing. You will notice the 305 has DEEP balance holes. SOLUTION: just get the new engine balanced and all will be fine. Mike I do this for a living.
I seem to recall that there is a balance hole in the ends of the crankpins on the 350, but not the 305....but it's been a few years since I did it for a living.
We ran a 350 crank in a 305 for several years. My teenage brother wore out the car sold it to a neighbor who pulled the engine and dropped it in an Impala. Last I heard he was still running it. Was it incorrect? Maybe, but we never had any problems with it.
I have read that there is the balance issue between them. However I've put them side by side and everything looked the same, even the depth of the balancing holes. But it wouldn't hurt to have it balanced rather than risk issues down the road.
Balance is the issue. About 100 to 130 grams of difference in the rotating bob weight on each rod journal. This will make it shake like a dog shittin peach seeds>>>>.
i have used stock 305 cranks in stock 350's several times and no problems. both are internally balanced engines and the cranks are neutrally balanced. and as far as piston and rod weights are concerned, as long as the new ones are within specs the crank doesn't know whether it's spinning 2 lbs or 3 lbs (hypothetical weight). If any doubt still exists, call greg at marion performance.he'll tell you the square of it. (870)-739-1773
<TABLE cellSpacing=0 cellPadding=0 width=375 border=0><TBODY><TR bgColor=#e6e8ed><TD vAlign=top width=2> </TD><TD vAlign=top width=71>part number KVL1000</TD></TR></TBODY></TABLE> at autozone 98.99 remanufactured with rod and main bearings,use the 305 crank as a core
Crank class 101. Ok class if you really want to step on your foreskin!!! Go to the crank rack and pull down a crank out of a chev 267 cu-inch. Cast# 442 same as 350. Put that in your fresh 350 and call me in the morning with the results. G-M cast and marked all the 3.48 stroke cranks with 2 piece main seal all the same. Balance was different for bore size and weight of pistons used per cubic inch. Class dissmissed>>>>.
actually i do but on this i was thinking about the way a 4 cyl operated as far as balancing goes, but i have ran ran several of the cranks in a stock configuration with no problems and if anyone has ever done this and had a problem it would probably be because of a heavy piston weight.
If you use lightweight pistons, the 305 crank saves you some work. Engine pro is on the money with the 100-120 grams. The way I used to tell them apart is the 90º notch in the counterweight. One was radius and the other square. I always have to look in the crank rack to remember...
We used to look for 267ci cranks to use in the street stock 350's so we could run lightweight pistons. You were not allowed to rebalance the cranks in that class. A little extra weight on the crank will not hurt anything as some analysis has shown that overbalancing a crank a few percent (2-4% actually helps dampen some harmonics. However, being 100-130grams a piston off ends up being over 1000grams of imbalance in the rotating assembly....thats the same as a stock rod and lightweight piston assembly! That is a lot of imbalance. Production balance jobs are generally held to 50grams of imbalance, and competition balance jobs to 1gram or less.
also a 305 rods are lighter and the beam is smaller than 350 units. The best that my old mind can recall both engines come with rods marked X and O. I used a 9/16 open end as a go no go gauge to tell which is what .
Yes this is a common misconception. I guess they can be made to work but it can be a big mistake if you don't balance!
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