I am rebuilding my 350/350 h.p. engine in my 69 vert. I took the block, crank, and heads to the machine shop today to get some work done. He was explaining how balancing blocks is important and recommended that I should have mine done. My question to you guys is, is it really that important and should I have it done on my block, or is he just trying to make a few extra bucks? :confused: I am sure some of you out there know or have experienced this same thing/decision. Suggestions/comments would be appreciated.

 

I was replacing pistons,crank and/or rods I would have it done. If it's just for daily cruisin and you're reusing existing parts and take them out and put them back the way they came out, personally I wouldn't bother but that's me.

If you're gonna rev it, balance it. My .02.

 

If he wants to balance your BLOCK go find another machine shop. You balance the big moving parts of an engine: crank, rods, and pistons.

As to whether or not to balance, what are you going to do with the engine? If you're just going to drive it around town, it's probably not worth balancing. If you're not replacing anay of the above, and the engine was ok before the rebuild, it's probably not worth balancing. If you're replacing major components, and you plan to do any high performance/high rev driving, it's a good idea to have it balanced.

 

Personally, I would (not sure how you'd balance the block though ;) ). As our engines are rubber mounted we don't notice any small vibrations from them. If you were to connect your seat & steering wheel directly to an unbalanced engine you would notice the vibration (you may even enjoy it :eek: )! All mass produced engines are gonna vibrate due to out of balance forces - some more than others. So, even though you may not notice, it is still there & it is not good for the engine or anything connected to it.
There is an excellent engine balancer here that I got to balance one of my engines last year. He told me that the crank had been perfectly balanced statically across the flywheel, but was out of balance axially which he dynamically balanced. The rods are weight matched (all big ends & small ends are matched), along with the pistons & pin assemblies, before the crank is balanced (so that he can get the true balance factor, rather than the theoretical eg 85% of the rod & piston assembly weight from the book is different to the actual weight once these items are balanced). Anyway, to cut it short, the engine ran smoothly b4 I had it balanced. Now it's been dynamically balanced it feels like it's floating along. The cost of all this work? £60-00 (about $80-00). It would have been a bit more if he had to increase flywheel weight in a certain spot by inserting Tungsten slugs. After having this motor done, & feeling the b4 & after effects, I wouldn't hesistate to balance any other engine that I have apart. It is money well spent - as well as the comfort factor (if you haven't got the luxury of rubber mounts), it gives your motor a better life. The only reason I haven't been doing this for the last 20 years is that somebody once told me it was expensive to do & didn't make any difference. How wrong he was. I wouldn't strip down a V8 just to balance it, but if it's already in pieces then go for it :yesnod:
:cheers:


[Modified by UKPaul, 10:42 AM 2/22/2002]

 

Thanks for all your guys input. I believe that I am going to go ahead and have it balanced. I just said block balancing to be short without saying pistons, crank, connecting rods, pins, etc... I figured everybody would get the picture!!! :lol: Sorry I will make myself more clear next time. :lol: :lol:

 

Steve, if you don't mind me asking? What is the shop hitting you up for the balancing and the rest of the machine work to your block, rotating assemblies, and heads?
I am weighing the choice of the rebuild vs crate motor.

 

Steve,
it is money well spent.Will show up later when bearings are still great with many miles.Assuming the motor does not detonate.

I would suggest having the wrist pins "pin fitted" as well.Takes the notchyness for lack of a better word out of them for long life.$16.00 is the price.

In my opinion I would buy a new GM Harmonic balancer whether your looks good or not.

 

I just took my engine to the machine shop to be looked at. I guess I should have had him look at balancing everything also. I was under the impression that getting it balanced would be expensive also. That $80 price doesn`t seem too bad though. I will check into it.

 

Bal. rec., you could have said rotating assembly or even short block.

 

Eric,
He is charging me $500 for all the machine work. I was also weighing the option of a crate motor, but the fact that I have a #'s matching 350/350 hp motor was the decision maker. I didn't want to get in the phone book and just pick out any machinist. Several people refered me to him, so he must be pretty good. I was just unsure of the balancing.

 

Double check to see if they are going to "deck" the block. If so, that may very well erase your matching numbers from the engine. To many this would not be a problem, but if you are looking to keep it matching numbers, it makes it a little more interesting.

 

He told me everything he is going to do the engine, and I can't remember anything about "decking" the block. Exactly what do you mean when you say deck the block? I think the only thing that he is gong to do to the block is bore if needed, check align bore, press old cam bearings out put new ones in, take old freeze plugs out and put new ones in, and clean/magnaflux. I may need to check into this if it is important.

 

Decking the block is shaving the surface were the head meats the block. This is done to true up the surface so the head seals good. Very similar to milling the heads only on the block.

 

My motor was decked and took off my matching numbers :(, they said it need it so I did it. However since that time I heard that some shops can deck them and leave the numbers. Which makes sense because nothing sits on top of the numbers.

 

Steve Adkins,

Do not let them deck the block and lose those numbers. It will really drop the value of your car, I would get on the phone quick.

 

Already taken care of. Just made sure that he is not going to loose my #'s. He told me that if he did deck the block that the #'s would be safe. Thank's guys for letting me know.

 

The block can be decked without damaging the numbers. It just takes a lot more work. I believe they have to stop and reset the machine at each pass rather than let it just run across.

I believe "decking" involves more than just making the surface smooth. I'll quote from a magazine here, MUSCLECAR CLASSICS, October, 1989, "The Rat that Roared" by Wayne Scraba. The article is about blueprinting and balancing an L-88 short block.

Here is the quote:

"Next step in the cylinder block machining operation is DECKING. This process squares the block (the block will now be dimensionally correct from both deck surfaces to the crankshaft centerline), and it also establishes the correct deck height (distance from the crank centerline to the top of the deck).

 

Definitely pay the extra $ for balancing.
Just went through the same thing with my engine.
My total paid to the machine shop was around 1600$,
but most of that was for my heads.

 

If you don't mind me asking what all did the mchine shop do to your engine?
My bill is not going to be that much. I was just wondering I might have left something out!!!