Hey everyone, my new 350 got trashed a week ago. Some foreign debris got into cylinder #6 and destroyed the piston and damaged the head. :( The head looks repairable with heliarching, but I will be replacing that piston/rod/bearing on #6 after doing a quick hone on that cylinder. The block itself appears to be perfectly ok.
My question is that if I decided to say screw it and put forged rods/pistons in instead of just replacing that single piston/rod/bearing/rings would I have to remove the whole engine and send the rotating assembly off for balancing?
Coolant in oil? HMMM ... blown head gasket let coolant into #6 cylinder ... cylinder hydraulicked ... damaging piston/head ... blown HG also allowed coolant into oil ... or when hydraulicking, coolant forced past rings into lower end.
BTW, if you haven't already done so ... get all the coolant out of oil/lower end/cam right away. Normal driving temps will evaporate off the water ... but NOT the coolant ... it'll etch bearings/journals/lifters/ etc.
BTW, if you haven't already done so ... get all the coolant out of oil/lower end/cam right away. Normal driving temps will evaporate off the water ... but NOT the coolant ... it'll etch bearings/journals/lifters/ etc.
The car has been parked since it happened. Within 24 hours I drained the bad oil with coolant in it and filled the engine with clean stuff. I then pulled the distributor and primed the oilsytem for a few minutes with a drill.
Yesterday when I pulled the heads off I also quirted oil through the lifter bores all over the cam to make sure it was covered.
I would certainly rebalance at the minimum. Mostly beause I'd be scared that getting fluid in the chamber, under compression could bend or even break/fracture a crank shaft. Not to mention split cylinder walls and bend rods or reshaping of the barrel etc....
Scorp,
I'm going to take some flack here, but oh well. If you are not going to be reving 7000+rpm on a regular basis, you will not need to have your engine rotation balanced. If you look back into the 60's-70's stock car/drag car/ muscle car eras, you will find many many engines running fine with nothing more than "equal part" balancing. What is meant by "equal part balance" is that the rods all weighed to within .5-1.5gms., pistons weighed... etc. The factory high perf engines were built without balancing the rotating assy, just matching componant weights. If you want to go with the forged rods and pistons, just ask when you order them to get a metched set. I've run an aluminum rod, cast crank, forged piston 406 in a stock car, this was a low $ deal, for 2 1/2 seasons without anything more that factory weigth metched parts. Manley rods were within .3gm! The pistons were used trw units, and I weighed them on a paint scale and they were within .6gm. The motor did end up breaking a rod, and I called manley to ask them why.... after telling them this thing had in the ballpark of 750+ laps on it, they told me that they recomend replacing the rods somewhere between 300-400 laps! As for balancing, it is something that if you want to do it, and plan on severe rmp/hp abuse, is a good idea but not a necessity. I'm sure that there will be many guys here that will disagree with me, but so far I've only had 2 engines rotating assy. balanced, and have not had any break because they weren't. It's up to you, but as far as I'm concerned you'd be better off with the forged rods and pistons no balancing than you are with stock rods and pistons and put back together! :cheers:
Re: Would it have to be rebalanced? (sinistervette)
I'm not going to give you any flack, just try and sway you a little. You are right about the RPM and balancing and if I was building an engine for dropping in a truck to haul trash I probably would not worry about the balancing. In the old days we didn't balance because of the cost. Technology has come a long way and the initial cost of the machines have dropped and the accuarcy increased. If you put a crank on the machine with a factory balance you'll see just how crude the factory does it and you can get many miles on a new factory engine. But for me the cost of the balance, between $125 and $200 depending on who does it is worth the extra cost. Watching the crank spin once its balanced might make you change your mind. Plus with the balance there are a few more rewards like less vibration in the drive train and a much smoother running engine.
I have done that. What you need to do is put the correct bob weight on that represents the weigth iof the rods and pistons you are going to use. If you keep everything static balanced to within 1.g. you will see a great improvement. Keeping static weight to within .5g. no need for anything more. If Scorp were to weigh each rod, and weigh each piston and make sure they all weigh within the .5g. he'd be all set. I just like to save all I can if I'm not going to be abusing the rpm range. I'm currently building a 302 sbc for a friend that will be running in the 8500-9000 rpm range. This one will be spun balanced no questions asked! :cheers:
Location: NCM Drag Racing coordinator, Spring Hill, Tennessee
Re: Would it have to be rebalanced? (scorp508)
Brian, I've been where you are now and it's never a black or white answer. It all depends on how much you want to spend and how much your going to expect out of of the motor.
Brian, I've been where you are now and it's never a black or white answer. It all depends on how much you want to spend and how much your going to expect out of of the motor.
Corvette Store
Would it have to be rebalanced?
