To balance engine or not?

[John_Progess]

I am trying to decide if I am going to have the engines rotating mass balanced or not. I don't know anything about the past performance of the engine except that on dissassembly the bearings look like they could be reused but will be replaced and all fits are standard. I am going to have it rebored with +.020 pistons. On a car that will not be driven more than a couple thousand miles per year (one of four LBC's) is it prudent to balance the engine? Thanks for your opinions and have a good day!

John

 

[GregW]

Just my opinion.

 

[Randy Forbes]

I'm glad I had the entire rotating/reciprocating assemblies balanced in my engine.

With a hotter cam, the ability to smoothly rev higher is obvious.

 

[Hedgehog]

Yes! Balance the whole rotating assembly. You won't regret it.

 

[red57]

I agree, it's a small additional cost and all those internal bits are going to be much "happier" with less harmonic vibrations - and your own fun factor will go up knowing you have done a good thing for your motor.

Dave

 

[Bob Claffie]

I disagree. Unless you plan on track time with serious red line driving time forget it. The factory does a fine job balancing engines and what changed since it was new? New pistons are likely closer in tolerance than the old ones. Everything else is the same. Do you want perfection and bragging rights at the pub then spend the extra $$$ but the motor won't know the difference. Bob

 

[GregW]

Hi Bob,
I think trusting that the engine hasn't changed in forty-plus years is rolling the dice. These were sold as sports cars and at least my dad drove it like it was. He introduced me to drifting over thirty years ago. He also towed and launched his race boat with the Healey. All that to say there was a time when people flogged these cars.

When I rebuilt my motor, the big ends on my connecting rods had ovaled and needed machining. Consequently, they needed to be balanced since different amounts of material had been taken off each rod. Weighing the small ends separately from the big ends. Fortunately, the block hadn't warped.

 

[Greg_S]

I say have it balanced while it's down. The rotating parts will work together more efficiently and you're likely to get more out of it.

 

[Michael Oritt]

Every engine is "balanced" in the sense that all parts are manufactured to some standard size and weight tolerances, etc. The question really is how fine that tolerance is to be and whether the reciprocating parts are still within it--obviously the finer the tolerance the more the cost.

 

[healeyneil]

I dont believe that these engines were balanced to a high degree when originally built. I was amazed just how different my conrod weights were
Besides which, I found it very satisfying to bring everything to the same weight. I did each piston, rod and cap seperately, then reassembled each set, and checked the weights again

 

[Hedgehog]

Bob, have you ever hooked up one of your just reassembled engines on the shop floor? The one engine I didn't balance started to walk it's way across the floor. Every engine I've balanced properly and started on the shop floor just sat in one place and ran. That includes a couple of Spridget race engines, TR3, MGTD, Healey, etc. I'll take the smoother running engine any day of the week. But I tend to be overly fussy about the tolerances.

 

[GregW]

But I tend to be overly fussy about the tolerances.

Can't say I see that as a flaw. :laugh:

 

[Bob Claffie]

Am I missing the point here. John says everything measured up to standard spec. No crank grinding, no rod resizing, no decking. Why should this engine be any more out of balance then when it was when new? I have built several MGB, Spitfire, Civic and SB Chevys. The only engines I had balanced were for the Spitfire because it was a RACE car with an extended red line. Never a failure. Is balancing worth it? Sure it's "better" but also totally unnecessary for your average street car. I stand by my previous opinion. Bob

 

[Patrick67BJ8]

I think we need to consider the fact that the rear brake drums can be as much as 6 oz out of balance. They could have been made with the same "factory" tolerances as the engine or maybe not as good...who knows for sure?? My rear drums cam back from Hendrix after being balanced and there was a lot of material added and also removed. Well worth the money because the scuttle shake was finally gone. I did buy new tires and had Hendrix install them on my used rims that were within factory tolerances.

Just a thought.
Patrick

 

[Randy Forbes]

The internal engine parts were/are mass produced, how much care do you think went into matching components for assembly? I think not much.

I can account for rebuilding approximately one hundred (100) engines, probably half MGB, perhaps 25-30 Big Healey (4 & 6 cyl) and the balance being Triumph, Buick V6 and some oddballs (Lotus, Jaguar, ALvis, Riley, etc.). Less than half of those were dynamically balanced, but there was a clear and obvious difference the minute they came to life.

Yes, balancing costs more money and not every engine (or owner) justifies it, but any engine I build for my own purposes will be balanced.

Bob, you're certainly entitled to your opinion, but don't criticize ours.

 

[healeynut]

John -

With the engine out I'd highly recommend having all pieces balanced individually (i.e. rods, pistons, flywheel and crank) then have the whole lot assembled and balanced again as a rotating mass. This is the best money spent on rebuilding a motor.

I did this with my BJ8 in 1985 when I built a new 3000 motor and I can tell you my car runs amazingly smooth, even 80K miles later. Car is back in for a complete strip and rebuild from the chassis, but my mechanic and I both agree to leave the motor as is, as it is still going strong.

:thumbsup:

 

[PAUL161]

I agree with John. We used to race circle track many years ago. Remembering the engines we used, Fords, the most important thing we did to them was have them balanced and blue printed. In the sportsman class, you could do just about anything you wanted to the engine, as long as you couldn't see it. By eliminating all HF vibrations, the B & BP engines would run away from the stock configuration ones. Of course a little porting, polishing and relieving helped somewhat.

 

[vagt6]

Those of you who've paid to balance a Healey engine:

what's the extra cost for balancing, and/or blueprinting?

In my experience, it's not a significant amount and well worth the effort and expense to balance an engine that's being rebuilt if you intend to keep and drive the car.

These 3000 lumps are not cheap to work on, just wondering how much the balancing adds to the rebuild cost??

 

[Randy Forbes]

Those of you who've paid to balance a Healey engine:

what's the extra cost for balancing, and/or blueprinting?

In my experience, it's not a significant amount and well worth the effort and expense to balance an engine that's being rebuilt if you intend to keep and drive the car.

These 3000 lumps are not cheap to work on, just wondering how much the balancing adds to the rebuild cost??

When I built my 3000 engine (29D) to replace the 100/6, around 1984, the balancing operation was about $250.00 (pistons, rods_end for end, crankshaft, dampener, flywheel and clutch cover).

You should be able to get a fairly accurate estimate from your local machine shop; the only variable would be adding Mallory (heavy) Metal to the crankshaft, if required.

Something else to consider (and requiring yet more money in material, and mostly, labor) is polymer coatings. Thermal dispersant, thermal barrier and dry-film lubricants all yield subtle benefits in both longevity and performance/efficiency.

 

[Darwin]

Cost me an extra $165 to have the internals balanced. The guy who did it said it was within 1/2 gram. When I fired the engine for the 1st time I couldn't believe the difference. Idle was dead smooth,coulda balanced a nickle on the valve cover. Throtle response was a lot snappier. Will it perform better? I don't know, but to me it was worth the few extra bucks to KNOW that all was right with the internals.