How much can I change on rotating assem. before I need to rebalance?
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11-29-2012, 08:56 PM
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Plus or minus 5 grams is good for the balance under 7500 RPM's. I build race motors, and would keep it closer to 0 if doing a total rebuild, but you are not going to get that number unless your machine shop guy is going to give you man hours. But if you stay within 5 grams total for total reciprcateting weight you are good.
11-30-2012, 01:24 AM
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Plus or minus 5 grams is good for the balance under 7500 RPM's. I build race motors, and would keep it closer to 0 if doing a total rebuild, but you are not going to get that number unless your machine shop guy is going to give you man hours. But if you stay within 5 grams total for total reciprcateting weight you are good.
11-30-2012, 07:05 AM
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Personally, I think "Mild Thunder" is right on the money. I am not sure I read this correctly but you had mentioned replacing your stock rod bolts with some made by Arp if I understood your post corrrctly. If you choose to reuse your stock rods (which I wouldn't suggest. Like Mild Thunder recommended...get a set of aftermarket h-beam rods) and are planning on upgrading your rod bolts. You should have the big end of the rods resized. At VERY LEAST have the bores checked before and after the new rod bolts are installed. What can happen when you swap the bolts out is that the bores can distort, mostly due to the better clamping force of the ARP fasteners. Depending on how distorted the bores are depends on what its going to do to your bearings....and bottom end of your motor!
The good news is that the 502 actually comes with a fairly stout bottom end! The pistons should be forged (made by Je), the rods are Ls6 rods with 7/16th bolts (I would still consider using an aftermarket rod due to cost of reconditioning the stock ones and strength) and the crank is steel and nitrides from the factory. I had my 502 crank and an Ati balancer double keywayed for $175.00 when I was building my bbc last winter.
Best of luck on your project and I hope it goes smoothly for you!
The good news is that the 502 actually comes with a fairly stout bottom end! The pistons should be forged (made by Je), the rods are Ls6 rods with 7/16th bolts (I would still consider using an aftermarket rod due to cost of reconditioning the stock ones and strength) and the crank is steel and nitrides from the factory. I had my 502 crank and an Ati balancer double keywayed for $175.00 when I was building my bbc last winter.
Best of luck on your project and I hope it goes smoothly for you!
11-30-2012, 05:45 PM
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Personally, I think "Mild Thunder" is right on the money. I am not sure I read this correctly but you had mentioned replacing your stock rod bolts with some made by Arp if I understood your post corrrctly. If you choose to reuse your stock rods (which I wouldn't suggest. Like Mild Thunder recommended...get a set of aftermarket h-beam rods) and are planning on upgrading your rod bolts. You should have the big end of the rods resized. At VERY LEAST have the bores checked before and after the new rod bolts are installed. What can happen when you swap the bolts out is that the bores can distort, mostly due to the better clamping force of the ARP fasteners. Depending on how distorted the bores are depends on what its going to do to your bearings....and bottom end of your motor!
The good news is that the 502 actually comes with a fairly stout bottom end! The pistons should be forged (made by Je), the rods are Ls6 rods with 7/16th bolts (I would still consider using an aftermarket rod due to cost of reconditioning the stock ones and strength) and the crank is steel and nitrides from the factory. I had my 502 crank and an Ati balancer double keywayed for $175.00 when I was building my bbc last winter.
Best of luck on your project and I hope it goes smoothly for you!
The good news is that the 502 actually comes with a fairly stout bottom end! The pistons should be forged (made by Je), the rods are Ls6 rods with 7/16th bolts (I would still consider using an aftermarket rod due to cost of reconditioning the stock ones and strength) and the crank is steel and nitrides from the factory. I had my 502 crank and an Ati balancer double keywayed for $175.00 when I was building my bbc last winter.
Best of luck on your project and I hope it goes smoothly for you!
12-01-2012, 02:01 AM
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I've seen only one guy swap out rod bolts on a motor that was already assembled and had been run for a short while. It was a mild 302 ford in a 65 mustang. He did it with the motor still in the car. Just the thought of the damage that could occur made me cringe. On a positive note, it lived for atleast a year being driven occasionally. He moved out of state at that point and we lost touch.
Rod bolts will be your weakest link in the stock bottomend of your 502. The one nice thing about running a 10-71 is that you shouldn't have as bad of a heated intake charge as you would with a smaller blower. There are several things to keep in mind when dealing with a 502. Its argued that they are very limited to overbore size. Gm states that they shouldn't be bored to over 4.500 (30 over). My bore is at 4.530 and I run a b&m 250 blower which is on the small size for a 502 but I haven't had any issues so far. I double keywayed my crank snout and balancer only because I intend on bolting on a bigger blower down the road. The smaller 250 blower doesn't put as much strain on the crank snout as a larger blower does.
Rod bolts will be your weakest link in the stock bottomend of your 502. The one nice thing about running a 10-71 is that you shouldn't have as bad of a heated intake charge as you would with a smaller blower. There are several things to keep in mind when dealing with a 502. Its argued that they are very limited to overbore size. Gm states that they shouldn't be bored to over 4.500 (30 over). My bore is at 4.530 and I run a b&m 250 blower which is on the small size for a 502 but I haven't had any issues so far. I double keywayed my crank snout and balancer only because I intend on bolting on a bigger blower down the road. The smaller 250 blower doesn't put as much strain on the crank snout as a larger blower does.
12-01-2012, 06:49 AM
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Thats kinda what I was thinking. I am looking for someone local here to go thru my bravo just to see if its sound to start with. I don't put many hrs per season on the boat to begin with, nor hard hrs. So Im hoping it will last a couple yrs at least?! Bye the way, congrats on your new build!! Read your dyno forum
If you go with the 10-71, even on the 502 as is, its gonna make some power even at low boost. Now, theres options out there to upgrade the drive. If you plan to run 800HP or more, my guess is your gonna want to look into a Imco SCX, BMax, etc. 700HP is one thing, 700HP supercharged is another. Blower motors are harder on drives.
I'm no bravo guy, but with 750-800hp in your hull, a standard bravo maybe last 20 hours if you baby it?? Mr. Gadgets can probably give a better idea.
