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1800ES B20E Crank balanceViews : 502 Replies : 9Users Viewing This Thread : |
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Jan 23rd, 2019, 08:38 | #1 |
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1800ES B20E Crank balance
Hi Everybody,
As part of my rather scary project the engine is completely stripped down. I am replacing rings, shells, mains, camshaft (new bearings fitted) and a few other bits. A friend suggested it would benefit the engine and me to have the crank balanced. Does anyone have opinions about the potential benefits as I have had one quote and it doesn't seem to be a cheap item. My budget keeps getting stretched. Any contacts for this service in the West Midlands (UK) would be gratefully received. My quote was from Wilkinson Dynamic Balancing. If this has been covered elsewhere please post the link as I am not very good at negotiating my way round forum search engines. Thank you in advance Ian |
Jan 23rd, 2019, 09:45 | #2 | |
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From your previous threads I thought you wanted something that was usable - a bit nippy but not especially race tuned. If you want to get the crank balanced then to feel the benefits you need to start considering conrod and piston weights and rotating masses (subtly different), then you'll want to think about valve spring rates and perhaps ported heads then perhaps some sort of gucci custom made cross flow head... ...you've already mentioned a budget that keeps getting stretched... ...if I were you I'd pay attention to various piston and conrod weights (don't worry about rotating masses) so you get a nice evenly balanced combination of parts - ideally each piston and conrod assembly should weigh the same - so approach that combination as best you can with what you've got. Unless something is really different I wouldn't bother to try and remove material. Put the engine back together again with care and love and it will be just fine.
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Jan 23rd, 2019, 09:49 | #3 |
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Alternatively: If you want to do battle with the Honda Civic "My car makes 1000bhp at the front wheels" boasts - then yes a balanced crank is just the beginning - in fact you really need to have some sort of custom (got to be CNC) crank made from some exotic alloy.
Note "normal" machining is no longer appropriate in the world of boasting - it has to be CNC
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Jan 23rd, 2019, 09:57 | #4 |
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Thanks for that. The email reply from the balancers said this
" You need to bring pistons with the rings on, con-rods, flywheel and crank shaft. Benefits of fine balancing will be in reliability of your engine, it will rev up much smoother without vibration and will rev faster. Will drastically reduce the wear and tear on the rotating and reciprocating parts of your engine." It was the reducing wear and tear bit more than anything that made me wonder if it was a worthwhile investment. You can see some indication of my folly in the new profile picture I have added. Try not to laugh too hard. Cheers, Ian |
Jan 23rd, 2019, 10:06 | #5 | |
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Jan 23rd, 2019, 10:23 | #6 | |
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The extents to which you are rebuilding your engine should get you at least 100K miles - so long as you look after it. I personally think buying decent oil and changing it a little bit more frequently than prescribed is a more effective "investment" to help reduce wear. If you are really really worried (as in psychologically paranoid) about wear (which I don't think is necessary) I'd advocate a block heater to get the engine warm before starting in preference to spending a small fortune on balancing a crank (especially if you're not going to match it with other carefully balanced parts)
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Jan 23rd, 2019, 13:56 | #7 |
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In my MGA world, I would balance the crankshaft. I would also balance the flywheel and the clutch pressure plate as a unit. Each would cost about $75 to $100 U.S.
I would try calling around to some other machine shops or perhaps press your shop to just balance the crankshaft. I've not been aware that the rod and piston assemblies are necessary to balance a crankshaft. However, I would also "try" to balance the conrods, the pistons and the wrist pins, to get them as close as possible to the same weight, even if I did this myself. A set of pistons usually comes with relatively the same weights, maybe a couple of grams off one way or the other. They can be balanced to each other by drilling material off from the underside. Wrist pins can be balanced to each other by grinding material off the ends of the wrist pins. Con rods are the hardest. The big ends and the small ends are supposed to be balanced independently. Making a jig to do this is a trick. But you can certainly remove material from the conrod to lighten them if you need to. I would consider taking each part and weighing it (I make a chart), then mix and match (to the extent possible) to get each assembly to the same weight. While you may be unable to swap the #1 conrod with the #3 conrod, you may be able to swap the pistons and/or wrist pins to get the units closer to the same weights. In other words, put the lightest piston on the heaviest conrod, etc. Once you have all of the weights charted, it's pretty easy to see what combinations yield the best results. Then be sure to mark the parts so you can always identify where they are supposed to go when assembled. |
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Jan 23rd, 2019, 14:30 | #8 | |
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Then they'd probably charge you the same kind of cash to take it back off! What do "they" actually do for this kind of money? Is it a static balance check?
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Jan 24th, 2019, 11:30 | #9 |
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In a typical engine build there is no need to re balance the engine.
Volvo tolerances were very tight for the time and usually well balanced to start with. Unless you plan on running the engine at high rpm 7000rpm+ then there is very little point. Balancing is done in a similar way to wheel balancing but first getting the weight of pistons and rods etc equal first |
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Jan 25th, 2019, 08:58 | #10 |
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I would agree what others have said about balancing your pistons and con rods mostly because it's something you can do yourself that won't cost anything. If the crankshaft is the original as classicswede has said they were made to high standard in the first place and has been at the heart of your engine for half a century. What mileage has it achieved already? Remember these engines have a great reputation for longevity.
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