Some porting help

Discussion in 'RC General & Getting Started' started by niky133, Mar 4, 2003.

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  1. niky133

    niky133 New Member

    Hey guys.I've a pile of old engines & i'd like to learn how to port.I've never done this before.What should i do.As far as i know the inlet and the exhaust ports are made wider for better flow.Also the timing is changed.Any tips how to do this.As far as i uderstood the crankcases are also modified.Why?Are there any ports added.
    PS An experienced driver will be helping me =).
    Any help will be be highly aprecieted.
    10x gyus
  2. rockn82

    rockn82 Marx Brother

    Well porting should not be taken lightly. First don't worry about anything but porting for now. The procedure is really pretty simple but doing it can be tricky. You will need a dremel and a small grinding stone. First, take one of those old engines and place the sleeve inside the case (make sure it is aligned correctly) and look at the exhaust port. Looking through the port you can see the sleeve. That part of the sleeve that is visible is the part that needs to go. Pay attention to the way the port in the sleeve is angled as you will want to try and keep the same angles. Use a c-clamp to hold the sleeve in the crankcase so it doesnt move (but dont overtighten and warp your case). Grind the Sleeve until it is flush with the port on the case (remember those angles). Do not grind the sleeve any higher toward the top of the sleeve than what the original port was at. Doing this may cause the engine to have 0 compression because the exhaust port has to be closed for compression (yeah i know DUH) Give that a whirl and let me know how it goes. By the way, make sure the engine was a running engine because you have to be able to start it to test it. LOL This is really hard to explain in writing, so if you can watch someone who has done it before you should. If that is not possible, you can follow this but follow it carefully. This is just porting the exhaust and you should do this first as it is the easiest to do and there is less chance for you killing an engine. You'll try try to do that in Part II LOL. We'll go though porting the intakes. By the way it also helps if you have the basic knowledge of how the 2 stoke works. You may want to read up on that before you start if you don't already know. Before reassembly of the engine make sure you clean the engine out throughly. You don't want any pieces of metal to get into those bearings. Also use afterrun oil generously during reassembly. After porting the exhaust you will notice that it sounds different telling you you did a good job.

    Good LUCK! And good grinding.
  3. niky133

    niky133 New Member

    I know how 2 stroke engines work and i also have some working engines.A friend will be helping me.He have been racing speed models(the ones witch travel in circle) and have done all kind of modifications to original engines but not porting.He have also made 1 or 2 engineshimself. Thanks for the info.I'll try it and tell you what happened.I hope i'll kick some butt at the track(those stupid O.S. engines have no chance onroad=) ).
  4. Jacko

    Jacko New Member

    Hello Rock
    I have a 21 bb that in my eyes is to weak but it still runs so I have a project engine to start with ...
    I would Really enjoy learning to port an engine
    my first task is to remove the sleeve ... it will only come up about 1/16 of an inch and makes a Hard stop I have tried pushing up on the bottom of the sleeve with No Joy other then the 1/16

    I have read the post you made about the exhaust port
    the 21bb has no angles on the ports they are all 90 deg.
    but the Exhaust port on the case is round on the top and bottom
    and the sleeve port isn't do I grind the sleeve out until it is round on top and bottom as long as the highest point towards the head does Not go any higher ???

    if so please post part 2
  5. rockn82

    rockn82 Marx Brother

    Well Jacko the .21 has a round exhaust port (yeah i know) so you are right dont go any higher on the sleeve than it is already at. As for getting the sleeve out use some WD-40 or penetrating oil and let it sit for a couple minutes and try again. If still you find no joy set the oven to 220 degrees and cook the whole thing (minus all meltable stuff, seals, gaskets, heat sink, carb and screws) for about 5 or 10 minutes. Dont use a torch or a heat souce of the like because you can warp the crankcase due to uneven heating. IF that still doesn't work Grab the top of the sleeve with a pair of pliers (not touching the inside of the sleeve) and give it hell. LOL. It'll come out. As for porting the rest try the exhaust port first and see how it goes. Maybe you wont want to do the rest LOL. You can also enlarge the port on the case to make and even larger exhaust port in the sleeve. Just dont go higher than what it was at.
    Porting is basically allowing the fuel/air mixture and exhaust gasses to move more fluently through the engine. That allows the engine to "breath" easier increasing the engine's output. So when you get the exhaust port perfected your ready for the intakes. The inside of the crankcase has (if you have a 4 port) three intake ports and the exhaust port. So you will notice the three depressions in the sides of the crankcase where the sleeve sits. As the piston comes down from its compression stroke there is a vortex created in the cylinder. At the point where the piston clears the intake ports is when the fuel/air mixture is sucked through the depressions and into the combustion chamber because of the vortex (like a vaccuum). What we are looking to do is to allow a smoother flow of fuel/air into the cylinder. So we have to angle the intake ports on the sleeve down towards the bottom of the sleeve. OK here's where we get to kill the engine :) lol. At this point try not to enlarge the inside of the port on the inside of the sleeve (that may throw off your timinig). We are only looking to take the angle down from the inside of the sleeve to the outside of it. Try that and see how it goes. NOTE: when you port an engine it is easier to overrev it and therefore break the connecting rod or other parts. So don't listen to it scream and say "wow, man that thing is flyin". lol. Anyway if you still have an engine when your done. (this is really hard to explain in writing and being its your first time). Let me know how it goes and we can move to Part III (enlarging the ports and the depressions) and part IV (increasing overall crankcase sealing, which allows more vaccuum from the piston to suck more fuel/air. And if you really, really, really feel like it when you are done we can go on to increasing the size of the intake port on the crankshaft (under the carburator) and Enlarging the carburator venturi and butterfly valve. The possibilities are endless and as you become more efficent you will become quicker at doing it. Make some money off your friends.
    NOTE: As I said in the above post (Part I) Use a dremel and a grinding stone. Well I have found a much nicer little attachment. It's a high speed carbide cutting bit for hardened steel for the dremel. Got it at Wal-mart for about 8 bucks. Makes is easy but you have to use a little more caution. Good Luck, and let me know how it goes.
    Happy porting.
  6. Jacko

    Jacko New Member

    well the wd didn't work but the oven did
    so I got the sleeve out and will follow your steps tonight and let you know how it goes ...

    Thanks Rock I think this is going to be Alot of fun :c)
  7. Jacko

    Jacko New Member

    Hey Roc
    got the exhaust port done in about 10 minutes ... Really enjoyed it too ... I like doing stuff like this
    now fo the sleeve ... it has 5 ports counting the exhaust port
    two of the ports are angled two are not ?!?! do I angle all 4 or just the two that are already angled

    I'm going to go ahead and do the two that are angled and will wait to hear from you on the other two ... man I love this stuff
  8. Jacko

    Jacko New Member

    Ok Roc
    I got the two ports across from the exhaust port angled
    Kind of surprised me it looks very good :c)
    I did not make them any bigger just made the outside of the sleeve slope evenly into the angle of the port also made them come into a point and am thinking now I should widen the point out so it flows better ???

    Also do I need to take the taper on the outside of the sleeve down to the bottom of the sleeve I have it only down about ¼ inch at this time

    … now do I want to shave the other two the same way ??

    if so I can do that in about 10 minutes and ready for the next step … I did not run it after the exhaust port or the intake port … do I need to see if it will start at this point ?
    If so it will be the weekend before I can … I loaned out the carb

    This weekend I will take some photos and send you to see what you think of what I have done already

    Roc I can’t thank you enough for the time this is taken you
    Hopefully I will be able to pass along what you are giving me
    Surfs up Dude lets Roc
  9. Jacko

    Jacko New Member

    Yoo Rockn ... she Still runs ...lol.. so I guess so far so good ... I don't have it mounted in the truck just yet I will tomorrow to see the differents .. it started right up if you get the chance to post the next step please do I would like to get started on the next step as soon as I can :c) ... I'm hooked ... If this one turns out well I have an 8 port that I'm planing on doing next then stepping up to the picco 26 Grinz ...that pup Already has Crazy power can't wait to see what it does in the Savage

    say Rockn thanks Again
    Jacko
  10. Jacko

    Jacko New Member

    Hey Rockn
    I ran the engine you are helping me to port ... I was a bit disappointed in it ... it had a very bit More power but seems LAZY as **** engine did seem to be alot smoother running ... do I tear it back down or do I need to play with it and fix what is making it lazy ... also I ran it with the stock savage pipe... was that what made it lazy ?... to tell the truth I have been running Much stronger engines so I do not recall just what the power was like

    thanks for your time
    reply when you can
    Jacko
  11. rockn82

    rockn82 Marx Brother

    Ok Jacko, I would guess that the carb is a slide carb. So you won't be able to do a whole lot with it. However you can do these steps.
    Look at the carb from the top (through the venturi) You can enlarge the bore through the carb. Do this by completely disassembling the carb and enlarging the bore in the carb casing. Don't go too big though as you will weaken the top and bottom of the case. Does your carb have the pinch bolt or does it have the two screws? If it has the two screws you can wrap some teflon tape around the screws and seal any vaccuum leaks from there. Also look at the bottom of the carb. When the aluminum is cast imperfections occur. You want to make sure that the inside of the base is nice and round and as large as the largest part of the top opening (keeping the whole bore through the carb the same size). Yeah kinda confusing. Once that is done you can try a little controversial step. :) Make a carb spacer. That will take some ingenuity but it is not difficult. Try to use hard plastic for the space because that will act as a heat resistor from engine to carb and allow a colder airflow (colder air is denser and thus there is more air in the same volume). 1/2 or 3/4 of an inch should do the .21. On the inside of the spacer run a tap through it and create a spiral pattern on the inside to create a swirling effect help air/fuel atomization. And that will about do it for the carb. Let me know if you have a rotarty type and I will go through that one.
    Ok, time for that crankshaft. When the piston is just after BDC (Bottom dead center) the port on the crankshaft is just opening. When the piston is moving up on it's compression cycle it creates a vaccuum inside the the case, thats when the port on the crank is opening and allowing air to flow through the carb. As the piston moves down it creates a vaccuum in the cylinder and moves past the ports to allow that vaccuum to suck in the air/fuel that is inside the case. Make sure you look at this and understand what I mean before attempting this. The port on the crank is open for about 180 degrees of rotation. We want to increase the duration that the port is open. Not the point at which it opens. (thats bad). This step is going to require you to halfway assemble the engine and look at the piston in the sleeve and the crankshaft (through the carb mount) at the same time. Rotate the engine so that the piston is at BDC (bottom dead center) Then look at the crankshaft through the carb opening. You may have to rotate the engine a couple of times to understand. What I mean. See the crankshaft port moving under the carb at the same time the piston is moving up and take note to which side of the port opens and which side closes (and make sure you are rotating the correct way). The side that closes the port is the side that you are going to enlarge. (allowing more air to enter the engine) Don't make the port too big (don't have it open any further than when the piston starts to leave TDC or you will kill the engine and need a new crank). Also don't enlarge the port so large that you weaken the crank because there is no longer enough metal to keep it together. You will notice that the piston is at TDC when the crank port closes, but if you rotate the crank just a little more the piston won't move because the the connecting rod is at TDC and that makes for a little play in the crank/piston connection. However the crankshaft will move just a little further. Doing this you can see just how much you can take off the closing side of the port. Remember that when the piston just barely starts to move back down you want the crank port to be closed. The best shape to make the enlarged port is in the shape like this [> kinda making it look like a cone of ice cream with a flat scoop (for lack of a good description). That will allow you to enlarge the port all the way to the point of the piston moving and still retain the cranks strength.
    One more thing to look for is the porting on the side of the case. Like I said before casting causes mistakes. So make sure that the ports are open on the bottom and not blocked by stray bits of aluminum.
    As this has taken me over an hour to write, it may be confusing so if you have any questions let me know.

    Some other tips for an engine to perform are:
    -buy a lightweight Flywheel
    -get rid of the pullstart and use a starter box
    *getting rid of the pullstart will increase the crankcase seal since you will no longer have a leak from the starting shaft going through the rear adapter.*
    -try to use the minimum crap on the crank such as flywheel and clutch assembly
    *all the above will create less rotating mass for the engine to rotate allowing it to rev quicker and idle down faster. The more weight you add to the engine the slower it will respond.*

    Want more. Shave a little off the inside of the heat sink (not the part that goes down into the cylinder but the part that sits on top of the sleeve). Dont take too much off or your piston will hit the glow plug or the heat sink. Doing this will raise the compression of your engine and increase the horsepower.

    Still more... Take a set of calipers to the hobby store and buy a connecting rod from another engine that has the same size crank and piston pin bore but has a longer distance between them making the piston travel higher in the sleeve. That will also increase the horsepower and be carfull of the glow plug and piston meeting :)

    Happy porting and let me know.
  12. rockn82

    rockn82 Marx Brother

    Oh by the way you are gonna have to do some major tuning to her when your all done. Now that you have the engine beathing easier and sucking more air you are gonna have to run it a little richer than normal. I have an old OS .15 that I have found some big problems with. Like having only one working intake port because of some unmilled aluminum at the bottome of the case. LMAO. So I just ordered a bunch of new parts for it so I will try to take some pictures and post them to my website in a step by step type thing.
  13. Jacko

    Jacko New Member

    well !@#$%^&*()_+

    brought eveything on the trip to do the carb but forgot it and the dang engine... Ill work on it monday night

    Rock I can't tell you how much I appreciate all your help
    will let you know how it goes asap

    Thanks again
    Jacko
  14. Jacko

    Jacko New Member

    Say Rockn ... I can't go with a starter box on the savage so I was wondering if I can cut some off the flywheel to make it lighter ?? if so do I cut it down to just a bit bigger then the clutch bell ??

    also the head has a washer/spacer to move the head up away from the piston would removing that be to much or do I just need to try it and see if the piston still clears ? I am GUESSING it to be about .030 of an inch thick
  15. Jacko

    Jacko New Member

    Okay
    got the crank cut out SOME I didn't go all the way because I wasn't 100% sure that I hadn't gone to far because I didn't make the hole come to a point on the closing side but more like a hmmm 1/4 moon.
    (my cutting tool wouldn't let me bring it to a point)
    so I still have some to cut if needed ... as for the carb I hope this is good news and it maybe to big but it fits .. I have a ofna 25 carb that fit right in place and seeing I am doing this at almost midnight I couldn't make the carb spacer BUT I Will... I wish I didn't live in town because I would be firering this pup up now :c) so tomorrow will Have to do :c(

    unless this thing just blows my mind I will take some photos tomorrow after I tear it back down to show you what I have done and see if there is anything more you think I should do ...
    btw I left the head spacer in place for now
    I maybe wrong about this but did opening up the crank give it More compression ??... it seems a Good bit harder to turn over could it be suckign more air just by turning it by hand ???
  16. Jacko

    Jacko New Member

    I had hoped to run this engine over the weekend how ever I broke the rear drive shaft and awaiting parts...
    I did start it holding it in my hand and played with 2 different carbs ... the 25 ofna carb had No top end ... maybe 30k rpms
    But the picco 26 carb Now that dude this lil engine Will REV!!!!!!
    very Jumpy ... can't wait

    Rock ... you Da Man
    thank ya thank ya thank ya

    btw still waiting to make the carb spacer ... by chance do you have a photo of one ???
  17. rockn82

    rockn82 Marx Brother

    Well I don't have a photo of a carb spacer right now but I can make another one (seeing as every time I make one and show some one the Engine the say how much?) lol. By the way don't remove the spacer for the heat sink it is actually the head gasket....But if you can find a thinner one... anyway, glad to hear the engine is kickin'. Also Yes having the crank port opened up is allowing more air to enter the engine and having the porting done you are allowing more air to enter the cylinder causing a higher compression ratio.
    And just a note, well more of a I have a bad reared engine, LOL.
    I just put my OS .15 in a HPI MT that I rebuilt against a brand new OS .21 RX in a Duratraxx AXIS and I kept right up with it. In some cases (when I got the jump on him) I would pull ahead and stay there. HEHE

    Anyway I'll try to make another spacer tonite or tomarrow and send you a pic. Remember when you get it in the savage and up and running your gonna have to retune the engine. It will fly.
    just add wings LOL.
  18. Jacko

    Jacko New Member

    A different matter

    COOL RocK ... Thanks BUddy I Owe you a big one ... and I do pay up
  19. doberman

    doberman New Member

    Hey did this thread die or are parts 3 and 4 still comming? This is great!

    doberman
  20. rockn82

    rockn82 Marx Brother

    Nope the thread didn't die I just ran waay skimpy on time. If you have any other questions I will be able to answer them a little more regularly now.
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