Is it possible to balance and blueprint a single cylinder two stroke engine? I saw an engine in Ebay advertised as "balanced and blueprinted" and I don't understand what that means in an engine with only one reciprocating part and one rotating part. Just balance them to each other and call it a "balanced" engine?

Sometimes the usefulness of what they did is doubtful. I would not buy that engine.

Single cylinder engines are hard to completely balance anyway. If you change what's there, they'll probably be out of balance at some point in their rpm range

Balancing and Blueprinting. That term has come to be used over the years for a high performance engine. Meaning it is 'better' than a stock engine.

What it means to a machinist and engine builder is that the reciprocating parts have been balanced. Yes, you balance a single cylinder engine. That is what the counterweight on the crankshaft is for. A multi cylinder engine has all the rods and pistons weighing the same and crank weights properly counterbalancing the weight of the reciprocating mass.

"Blueprinting" the engine means all technical specifications of the engine design have been met. That is not a big deal though. Because engine specs allow a tolerance, a variation of dimensions. Ideally, the dimensions are held to the minimum. But if they are anywhere within the envelope the engine is technically "blueprinted."

Blueprinted also to some means that the all of the ports, manifold's, Headers and all are matched. My old Blueprinted and Balanced VW 16V GTI (former SCCA car) also had the deck milled, and the head milled to Factory Max's. The Bearings clearances were also opened up along with every little thing that would pass an SCCA tech inspection. I purchased it from the local VW Dealer who raced it for 1 season. I have to say that was the most fun car I have ever owned, to bad it was when I was young and did nott realize you cannot pound the car every single day. I did get 140,000 miles on it. That's not to bad considering it had 9,000 miles of track use when I purchased it. It was raced at Road America, Sears Point, Mid Ohio, and many other tracks along with competeing @ Daytona on the Big oval in the VW Cup series.
OOp's, I guess I was just supposed to reply to Blueprinting and Ballanceing.

There was an article in one of the RCmagazines in the last 5 years on balancing an engine. For the life of me, I can't remember which magazine it was or even the approximate date. I subscribed to MAN, Model Avaiation, FlyRC and RCModel World. I'm sure it was one of the first three though and if it was over two years back, it was one of the first two.

If I remember correctly, the blanceing didn't yield any more power, but did result in a little less vibes.

Don

You can alter the counterweight, but the factory normally has done what they could like W8YE said. This would not be a one day operation in most cases. Be sure to have a spare crankshaft on hand before going at the mods.

I wouldn't buy an engine with those mods unless I knew a lot about the person doing the work.

Hummmm I was just thumbing though some of these posts and happen to come across this one.
Ok for one you can not balance a single Cyl engine ,you can match the counter weight to the reciprotating parts, but the side force harmonices is always there.
As far as blueprinting it , To what ????? there is just one cylinder, you can port and polish and change the squish area's, change the port timing, but thats about it.
Real blueprinting goes alot farther than anyones even touched on here and no there is no variables or tolorences when its comes to a true blueprinted engine. Every cylinder is the exact same as the others, the crank is indexed ground to insure the throws are the exact degree and stroke the blocks are milled so each piston comes to the same height ,rods are reworked as well as pistons. The heads are measured to insure the combustion chambers are the same, the ports are either machined out or hand ground to the same configurations. The manifold of choice is matched to the cylinder heads so the ports are in perfect alignment. Theres more but this covers a good amount.
If Balancing a engine didn't gain anything why does everyone insist on doing it to there Hi Perf Engines??? Nonsense !

Most of the r/c engines reviewed by Clearence Lee were balanced about 80% of the piston and rod. If they were balanced to 100% of that weight would they be smoother?

Keith Baker said one way to balance an engine without increasing the counterbalance size would be to press tungsten rods into it.

Even multi cylinder engines are never perfectly balanced. The term does not mean the balancing is perfect, but that it is better than stock. But it is the blueprinting that makes more power, especially matching the ports. Often a higher volume and pressure oil pump is installed and the journal clearances are widened to match the new pump. This decreases friction of the spinning crank and pushrods.

I had a friend who balanced K&B marine motors by drilling the crank counter weight and pressing sections of carbide(?) rod into the holes. I believe he used 60% of the weight of the rod, wristpin and piston. Carbide is denser than steel and helped get the motors closer to balanced.

Actually Blueprinting refers to the original factory blueprints for measuerments rather than using any tolerances. When the engines were designed, an original set of blueprints were developed for them and these are what manufacturing companies used as a baseline for manufacturing engines but because no two castings are exactly the same ( near all engines of any sort start with a casting ) they introduced tolerances to allow non a slight amount of non conformance to the original design.
Example: Chevvy smallblock originally called for a deck height (crank center line to top of cylinder) of 9 1/2" , but most I've measured come out over and up to 9 3/4" . To properly blueprint that block, I would have to mill the deck height parelell to the crank at 9 1/2" because that is what the original blueprints called for. This process leads to performance because carefully measuring and machining these dimensions makes sure that all the cylinders are exactly the same as what the original designer wanted with all the variences taken out.

How can this be? This would reduce compression ratio by a a tremendous amount! There is no way a block ends up .250" out of tolerance these days. Are there not variants of blacks for different strokes and such?

Yep, You're dead right, It does reduce the compression ratio. This is just one of the areas you pick up performance by blueprinting an engine. These mass produced engines aren't madeas thousands of special one-offs. To last 200,000 miles and not leak and run consistantly day in, day out, an engine doesn't need to be perfect . It just needs to seal properly, have good compression , and mechanical integrity (from a design point of view). To mass produce them cost efficiently, it doesn't matter if EVERY engine is perfect, as long as its within their tolerances and will make at least the baseline power requirement. To make EVERY engine of a particular model run accurate to the blueprints (rather than the tolerances) would cost in machining terms more than any gains they would achieve so they dont do it.
Exapmle: They have a run of castings come from the foundry. These castings deck height are running at 9.75" raw cast. To get a good seal area for the cylinder head the machinist only does 1 run and takes the block down to 9.625". Rather than follow the blueprints and re-run the block down to 9.5", he pushes that one along and sets up the next one. This means that for roughly the same amount of time he has done 2 blocks acceptable to tolerances instead of 1 block acceptable to the blueprints. That extra .125" wont worry compression to the point where ITS the reason the engine wont make acceptable power. Cams , heads and fuel type /ignition will make a lot bigger difference at this stage.
Also , yes you probably wouldnt get a .250" varience in modern engines but my example was a chevvy smallblock, a design running back to the'60s. This also is another reason why "blueprinting" USED to be a big power gaining method.
Hope I've helped you understand at least a bit better.

Its been a while since I did a blueprint job on a 350 chevy small block, but they sure as heck are not any 1/4 of a inch out of specs .020-.040 on the tall side I can believe. Just depends on the block and what it was origanlly in.
Cut off a quater of a inch and I guarante you will have some serious interference problems. Sort of hard to put the head on with the piston sticking out of the cylinder, also the manifold would never fit, let alone match the ports up. I reman the 350 engine alot, but blueprint very few due the cost, people just won't pay that for a 350 when you can go with a , 372,383,406 and even a 427 small block. All the small Blocks have about the same deck height from the 265 up to the 350, and maybe the 400 It's been a while indeed since one of those has crossed my door.

Sport you gain better oiling to the bearings by cross drilling the crank and chamering the holes larger, but if a Splash guard is not installed with the mod you will lose anything you hope to gain from it, which is not much to start with. As far as clearance go's yes that will create less friction, but also can make a short life engine from doing it. You add up the pump plus more clearance and less area on the crank and you get a leaker thru the rods, sometimes Iv'e actually seen them run way low of oil pressure due this type of thing.
The tolerances on the crank & rods has best be there or else it won't live for long.
When I have a crank index ground for a hi perf engine I always ask for it to be on the bottom of the givin tolorance in the book, I'm still in the specs and don't usually have any leaking problems internally, plus I don't wind up with a unhappy customer due to engine failure.
One thing I do to a few is plug off the oil drain holes in the valley of the block, that will stop alot of the oil from hitting the crank, HP gain is 5-7 horse, again depending on the engine.
As far as blanceing go's, if someone that dosen't know what there doing you are correct, but a person that knows the correct way to balance a engine will have all the throws and rod&pistons within a couple of grams. Been then and done that when I worked for other places, but now since I don't own a balancer I have to send them out to a trusted reliable source.
Not one person has mentioned degreeing the camshaft,*S* thats also done to a Blueprinted engine. It's a little tougher on a 2stroke ,I can never find the cam for some odd reason,*LMAOROTF*

 I wasnt trying to steal the post and take it to an automotive area, but using this as an example to explain what proper blueprinting was and why all engines arent the same as the original blueprints.
 I did do 1 block once for a person that came out at around 9.675, had a 4.125 bore . That aint too far off 9.75 . Was out of  a truck as I recall.  Those pistons when I lifted the lids were a lot more than 3/16 down the bores, top ring damn near half inch down. 

 If you go right into it I think you will find in block designs all sorts of modifications to cam heights, crank diameters, bores , web thicknesses, and the list goes on.

I havent rebuilt car engines now for quite a few years ( fix caterpillar now) but memory still pretty good.

Not sure but I think the taller deck height may be the 400 sized small blocks.

Truck engines have a taller deck height.

This was done with dry sump systems and very large pumps. It was for drag racing applications. We didn't need no stinking long engine life, because lots of other things broke it a lot sooner!

It doen't have to be the original manufactures blueprint. It can be the modified prints of a good racing engine builder.

Quote:

ORIGINAL: JollyPopper

Is it possible to balance and blueprint a single cylinder two stroke engine? I saw an engine in Ebay advertised as ''balanced and blueprinted'' and I don't understand what that means in an engine with only one reciprocating part and one rotating part. Just balance them to each other and call it a ''balanced'' engine?

JP,


Single-cylinder engines of the type we use in our models, cannot be balanced!

Please read [link=http://www.rcuniverse.com/forum/m_4936657/anchors_4936657/mpage_1/key_balancing/anchor/tm.htm#4936657]this thread[/link] and [link=http://www.rcuniverse.com/forum/m_780489/anchors_780489/mpage_1/key_balancing/anchor/tm.htm#780489]this one[/link] to understand... I remember a few more threads, but my search did not bring them up, for some reason or other.


These facts make the ad you are referring to rather nonesensical...

Dar I thought I said that, but I am glad you gave some reference to some important info on the matter. I agree the guy on sleezebay was trying to pull a fast one.
Good job THUMBS UP !!!!!!!!

CW,


I was by no means taking credit for what you wrote in post #7...

I just thought the reason for it not being possible, warranted explanation...



I just underwent LH CTR and Ulnar nerve procedures... So, it is rather difficult for me to retype the whole explanation...

To be fair to the seller on Ebay, "balanced and blueprinted" is a term that is liberally tossed around for a range of things.

You can't balance a single cylinder engine perfectly, but you can get it as close as possible.

My synopsis of the matter, if its Says "Balanced and blue printed" it means beware.

There is a natural tendency in the human being to explore and experiment. So many people cannot wait to disassemble their engine or to change something about it. Many times it is just for the sake of change. Many times the results are more like how much better your automobile runs after you wash it.

If you try to trade in a car or truck on a new one, If the dealership gets the impression you modified it from original, they will not take it at any price.

The same goes for a model engine. I've been looking at model engines for close to 60 years and some people foul them up royally.

There are some people (also on RCUniverse) that I would trust if they were selling a model engine. But just someone out of the blue - I would let it pass . . .

I bought a OS 48 four stroke. The guy said that he had ported and polished it. He did do a nice job of blending the valve pockets into the runners and matching the intake runner to the intake manifold. It even had a OS 52 carb. I had previously seen some of his Harley work so I figured he didn't foul it up. The OS 48 did run nice with no problems but didn't have any more noticeable power than a regular OS 48.

I see a lot of modified model engines on the Internet. Some are modified just for the sake of change. Some of the mods serve no real purpose in performance and may possibly be detrimental to overall operation.

Quote:

ORIGINAL: blw

You can't balance a single-cylinder engine perfectly, but you can get it as close as possible.

Barry,


My point was that not only is a perfectly balanced single-piston engine unheard-of. 'As close as possible' is also a moot point - a far cry from reality...

As long as there is any reciprocating mass to balance, it will have to be counteracted with a rotating counter-balance; which essentially means no balance at all.
So, if you want perfect balance; out goes the entire reciprocating mass... No crankshaft counter-weight required either...


This is why I wrote 'single piston'. An imaginary zero-mass piston and con-rod will obviously never be.

If you can have a single-cylinder engine, with two counter-motion pistons; a perfect primary balance can be achieved... Engines like that do actually exist.
...But there is no way of converting our single-cylinder engines into them.

And trying to balance an existing engine 'as closely as possible to perfect', entails a piston that might fragment (like in the TT 1.30 - discussed here recently) and a similarly fragile con-rod...
I don't think anyone would want to go there...[X(]