rpsmith
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| posted on 7/8/07 at 08:05 AM |
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Piston / Con Rod Balancing (Blueprinting)
I was wanting to balance my pistons and con rods on my Pinto, (by that i mean weigh each one and get them all down to the same weight), but from my
previous post about removing the gudgeon / piston pin, and posts on other forums, it seems like it is not an easy thing to do, and i don't want
to damage anything trying to knock them out.
So my question is, can i balance the piston / con rod assembly as a unit, and has anyone else done this sort of thing before
I believe that this is a form of Blueprinting an engine, but i could be talking rubbish
Cheers
Rich
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02GF74
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| posted on 7/8/07 at 08:30 AM |
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As far as I can remember, blue printing is matchng up the engine components to be as per the deisgn and entails parts are same size and weight
so thing like combustion chamber size matching, piston hieght etc...
the blanacing you are talking about then making pistons smae weight as each other and then the rod same weight is static balancing.
next step is dunamic blanginc so you want the weight so the conrods distribute the same way. i.e. if you say put the rod on a kife edge to balance
it, the point where they lie on the knife is the same for all rods.
I have seen a DIY verion of this by bolting up to con rods by the big end in a stright line and then pacing the bolts on 2 knife edges - if the rods
are perfrectly match, the arrangement will stya horizontal otherwise it will tip over.
search the web for this stuff.
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nick205
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| posted on 7/8/07 at 08:30 AM |
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I don't see why you shouldn't weigh and balance each piston/pin/rod as a whole. You'd do well to read up on where best to remove
material from the con rod if necessary as you could cause weak spots by reoving material in the wrong place or in the wrong way, particularly if
you're intending to use high RPMs with the finished engine.
If you want an easy to read and practical book, try Des Hammill - How To Power Tune Ford's SOHC Pinto Engine. It's well written and
illustrated and covers the type of activity you're considering.
Edit to say....
1. Good comments above re: dynamic and static balancing. For true high performance applications, all rotating parts should be dynamically statically
and dynamically balanced. This could be difficult to achieve without specialist equipment and experience - cue a decent engine building shop.
2. Also consider the big end bearing shells and piston rings as part of the assembly. Their weight may be nominal compared to the overall weight of
the assembly, but for accuracy and completeness they are still part of the rotating assembly/mass.
[Edited on 7/8/07 by nick205]
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rpsmith
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| posted on 7/8/07 at 09:15 AM |
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Cheers for the replies, i have actually got that book, but this was just an idea i had that is cheap and fairly simple way to get a bit more out of
the finished engine build, as they say "every little helps"
I'm on a tight budget so i won't be going down the engine build shop route.
I know i need to be careful where i remove material, i was hopeing someone on here might have done this to give me some pointers
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cadebytiger
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| posted on 7/8/07 at 10:53 AM |
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whenever i read post like this it makes me worry because i don't think we had anything balanced when we re-built the engine. Is this likely to
be a problem?
It's a pinto BTW - around 140bhpish
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rpsmith
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| posted on 7/8/07 at 11:08 AM |
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I dont think it should be a problem to have an unbalanced engine, that is how Ford made them
But i just figured that while the engine was in bits, i may aswell just weigh everything and get them all to as close the same weight as possible
"Every little helps"
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nick205
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| posted on 7/8/07 at 11:21 AM |
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Ford manufacturing tolerances should be perfectly good enough - it's when you're looking to run at higher RPMs that balancing becomes more
important or shows more effect. By higher RPMS on a Pinto I mean up in the 6-8k range. Then camshaft choice, engine breathing and fuelling etc are
equally as important.
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bimbleuk
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| posted on 7/8/07 at 11:48 AM |
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I do static/dynamic balance my engines especially if I'm mixing manufacturer parts.
From experience Toyota engines are usually very well balanced/matched. My 4AGE 20V engine was particularly good when checked recently.
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rpsmith
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| posted on 7/8/07 at 12:21 PM |
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Does anyone know a safe place to remove material from the piston or con rod
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02GF74
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| posted on 7/8/07 at 01:00 PM |
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quote:
Originally posted by rpsmith
Does anyone know a safe place to remove material from the piston or con rod
depends on what you are trying to achieve 
think of tit this way; cponsider the two comboination below.
a) conrod 200 g, piston 150g
b) conrod 150 g, piston 200 g
both weigh the same on the scales but once they start whizzing around, the heavie piston is going to create a lot more force - it is non linear -
sqaared? so although they are dynamically balanced, it would be a bad engine.
If you dont believe me, take a walking stick and put a bag of sugar o nthe end. hold the end opossite the bad and spin it - that will be harder to
get going/.stop than if you tried the same but holding the bag end.
.... but to answer your qyestion; I have seen conrods with small drillings into the big end part to remove weight so would indicate a good place and
the underside of the piston.
going back to maybe your previous post, you probably should be looking to keep the wieght of rotating stuff equal the frutest fro mthe point of
rotation i.e. the pistons - so may need to tke them apart.
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clockwork
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| posted on 7/8/07 at 01:16 PM |
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I was under the impression that blueprinting was getting the engine to within tolerances of the manufacturer, but in such a way that the tolerances
were used to "improve" the performance of the engine. I.e. using the +- (x) to your best advantage.
Am I wrong?
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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ned
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| posted on 7/8/07 at 01:40 PM |
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Blueprinting is matching the ports, done using engineers blue, hence the name.
Friend of mine built a race pinto and balanced his pistons and rods. He used his lathe to cut the skirts of the pistons down, this probably marginalyl
accelerates bore wear but on an engine that isn't going to do loads of miles is perfectly acceptable imho.
If working on conrods always use abrasives (file or wet n dry etc) up and down the length of the rod, never across it. Take off the flashing down the
sides and clean up any sharp angles, you should get a bit of weight off enough to even them up and can actually improve their strength by removing
stress raisers this way.
If going the whole hog it's a good idea to get the crank, then flywheel, then flywheel and clutch then whole lot balanced. If you ever have a
problem and have to remove and change clutch and/or flywheel your engine will still be correctly in balance.
You could always skim the head for a bit of extra combustion, but check valve tolerances.
Ned.
If you're getting really pedantic it's amazing how much weight can be saved from the block by reshaping the webbing, taking off unused
lugs and generally stress relieving. I know people who've spent a bit of time ona block and saved a good few kilo's this way.
[Edited on 7/8/07 by ned]
beware, I've got yellow skin
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rpsmith
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| posted on 7/8/07 at 02:10 PM |
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Thanks for the info guys
As i am aware , Blueprinting contains all of the above, balancing, tolerances etc, it basically involves rebuilding an engine in the best way possible
to the tightest tolerances available (this will also include component weights)
The main reason for the static balanceing i am wanting to do is that is cost nothing, and should improve the effeciency of the engine
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ecsjwhi2
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| posted on 7/8/07 at 02:17 PM |
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quote:
Originally posted by ned
Blueprinting is matching the ports, done using engineers blue, hence the name.
No it isn't.
See rpsmith reply for correct definition.
Cheers
JohnW
[Edited on 7/8/07 by ecsjwhi2]
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Confused but excited.
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| posted on 7/8/07 at 02:22 PM |
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quote:
Originally posted by ned
Blueprinting is matching the ports, done using engineers blue, hence the name.
If that was true, 'How to Blueprint Your Engine' would be a thinner book than 'The Encyclopaedia of French Victories'. 
Tell them about the bent treacle edges!
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ned
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| posted on 7/8/07 at 02:43 PM |
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Well my understanding was that blueprinting was the accurate building of an engine, using engineers blue to match ports and accurately assemble engine
components to as close a tolerances as poss. It would appear to envelop this and more, including lightening and matching the wieght of components so
to that end I happily stand corrected. I would still maintain (from what I was taught) that it got the name from the use of engineers blue to achieve
this.
wikipedia's definition:
---
Blueprinting
Blueprinting is the remachining of components to tighter tolerances to achieve better balance.
Ideally, blueprinting is performed on components removed from the production line before normal balancing and finishing. If finished components are
blueprinted, there is the risk that the further removal of material will weaken the component. However, lightening components is generally an
advantage in itself provided balance and adequate strength are both maintained, and more precise machining will in general strengthen a part by
removing stress points, so in many cases performance tuners are able to work with finished components.
---
Ned.
beware, I've got yellow skin
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MikeRJ
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| posted on 7/8/07 at 05:54 PM |
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quote:
Originally posted by ned
I would still maintain (from what I was taught) that it got the name from the use of engineers blue to achieve this.
Blueprinting is building the engine by hand, slecting or modifying parts to the most favourable end of the tolerance range shown on the original
blueprint (i.e. detailed engineering drawing).
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clockwork
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| posted on 7/8/07 at 10:07 PM |
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Funny how we all think slightly different.
I agree with MikeRJ though, or he agrees with me. Must be a Devon thing :-)
"Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." Benjamin Franklin.
"Well if you have nothing to hide, you have nothing to fear" Morons the world over.
Locost/Kit builders info and FAQ website:- www.carbuilders.info
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rpsmith
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| posted on 8/8/07 at 06:57 AM |
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Thanks for all the info guys.....
..... but does anyone actually know how to remove the piston / gudgeon pin from the Pinto piston / rod assembly
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NS Dev
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| posted on 8/8/07 at 07:16 AM |
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quote:
Originally posted by cadebytiger
whenever i read post like this it makes me worry because i don't think we had anything balanced when we re-built the engine. Is this likely to
be a problem?
It's a pinto BTW - around 140bhpish
don't worry!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 8/8/07 at 07:19 AM |
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PS MikeRJ et al are correct, blueprinting is building an engine to "standard specification" i.e. within factory tolerances, but at the
"beneficial" end of every tolerance.
Its an awfully expensive excersise, painfully time consuming and a pain in the arse. Regulations that call for "standard production
tolerances" are some of the worst to follow in racing, and most expensive to win under.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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