crustydemon Posted April 12, 2008 Report Share Posted April 12, 2008 I really need some help and I know I shouldnt be doing this myself but Im going to. I'm putting in a 4 mill long rod and do not want to use a plate and need to know a few things. As I understand it I need to lower the transfers and exhaust 2mm but do I need to raise them 2mm also?What about the intake and boost ports?I know the risks involved and the effects of transfer angles and port widths but just cant find any info on port heights for a stroker.Also is it a wise decision to assemble the engine and match up the main transfer and exhaust floors to the piston crown at bdc? I've also seen people say that if your cylinders have been ported for a stock stroke they may be ported too far for the 4 mill. How can this be when you got an extra 2mm of stroke each way? Quote Link to comment Share on other sites More sharing options...
blowit Posted April 12, 2008 Report Share Posted April 12, 2008 I really need some help and I know I shouldnt be doing this myself but Im going to. I'm putting in a 4 mill long rod and do not want to use a plate and need to know a few things. As I understand it I need to lower the transfers and exhaust 2mm but do I need to raise them 2mm also?What about the intake and boost ports?I know the risks involved and the effects of transfer angles and port widths but just cant find any info on port heights for a stroker.Also is it a wise decision to assemble the engine and match up the main transfer and exhaust floors to the piston crown at bdc? I've also seen people say that if your cylinders have been ported for a stock stroke they may be ported too far for the 4 mill. How can this be when you got an extra 2mm of stroke each way? You missed the book on port timing. Anyone that ports a cylinder bases on mm's is going to have problems. You either need to work the trig or do some more reading regarding timing. Brandon K, that sounded harsh, my bad. Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted April 13, 2008 Report Share Posted April 13, 2008 Where you want your peak power to come on and what supporting bolt on mods you plan to run will decide if you raise your ports at all with the stroker crank. I would not recommend cutting ports with the engine assembled. You will need to lower the port floors 2mm for the increased stroke, that will increase your port duration itself...raising the exhaust 2mm with the 2mm lowered floors will put you somewhere in the mid 190's in degrees of duration, this would be a dune type port. What type of port are you trying to achieve here?? My honest recommendation with the ?'s you are asking is to have a professional do the portwork. Not trying to be a naysayer or discourage someone from the learning experience of cutting thier own ports, but you have a lot of studying to do before you pick up the dremel my friend. Quote Link to comment Share on other sites More sharing options...
IrideA250R Posted April 13, 2008 Report Share Posted April 13, 2008 look at it this way, you can either send it to someone who knows what they are doing and pay for the porting now, or after you screw it up you can send it to someone who knows what they are doing + pay for new cylinders. Your choice, don't do it yourself! Quote Link to comment Share on other sites More sharing options...
crustydemon Posted April 13, 2008 Author Report Share Posted April 13, 2008 I know ive got alot to learn, Thats why Im asking. I dont use a dremel and just wasnt sure about what had to be done. Ive got a couple good books on performance 2 strokes that im reading but they didnt really go into stroking.The cylinders that I was going to use already have a trinity pro mx port and if all I had to do was drop the floors I would do it myself,other than that I would send them out to get done.I just dont want to use a spacer plate. A dune port would be nice but anything with a good mid range punch with decent upper would be good.I got PT mids,Noss head but havent ordered the domes yet because I dont know if I want to run race gas,34mmPJs,dyna cdi,etc.(1500ft) You'll never learn anything if you always have someone else do it for you. Quote Link to comment Share on other sites More sharing options...
MILO Posted April 13, 2008 Report Share Posted April 13, 2008 You'll never learn anything if you always have someone else do it for you. i agree, but i also agree that this is something that is such a fine line thing to be messing with that you better have your ducks in a row before starting into it or it will inevitably end in disaster. i'm not saying that you don't, but it's your money and your ride, so have at it if you like. good luck bud, i hope it works out for you. :thumbsup: Quote Link to comment Share on other sites More sharing options...
blowit Posted April 13, 2008 Report Share Posted April 13, 2008 I was not trying to discourage but merely pointing out that more homework needs to be done. I remember when I was learning porting and asked the guy who I started learning from how much duration will make a certain 250 happy. He replied with, "about 2mm". I knew at that point that i had learned what I could from him but I was getting over his head. He learned from the school that most did and that is, keep going until it runs like crap. Then you have found the limit. Those theories make absolutely no sense especially when real math is applied. You can calculate to a nats ass what your engine will do if you have a calculator and know how to use it. That being said, if you do not understand fluid dynamics, there is another book in there to read. I think everything came together for me with my OEM performance schooling. That is not an option for everyone but there are plenty of books out there that have NOTHING to do with porting that will educate in port flow behaviors. In short, aerodynamics, fluid dynamics, and thermodynamics. I would say anything less would be working ports old school and blindfolded. Brandon Quote Link to comment Share on other sites More sharing options...
crustydemon Posted April 13, 2008 Author Report Share Posted April 13, 2008 I totally agree with that and Im working on learning about it ( just started). I have devoted my whole life to studying 4 stroke engines and started out the same way as you guys did with the 2 strokes, with an old guy teaching you everything he knew and then taking some of that knowledge and expanding it with your own studies, whatever but I dont know anyone around where I live that knows anything about it to learn from. I dont have 500 sets of cylinders to cut up to find out what works nor do I want to but I do want to learn how to do it and do it right. Its not going to be a one time deal, I am afraid this is an addiction that Im not going to be able to shake.But for right now I just want to get it together so I can ride. Quote Link to comment Share on other sites More sharing options...
blowit Posted April 13, 2008 Report Share Posted April 13, 2008 If it makes you feel better, I have never scraped any cylinder in my life and my first banshee port job pulled 55HP on an inertial chassis dyno. Enough study on the subject before you ever touch a tool is key. I will admit there is an "art" or more appropriately called, "experience" in operating porting tools accurately and in a controlled fashion. You sound like you are going about it the right way so keep your nose in the books and don't tackle the whole job at once. Take it one port or area at a time. :thumbsup: Brandon Quote Link to comment Share on other sites More sharing options...
crustydemon Posted April 13, 2008 Author Report Share Posted April 13, 2008 Thank you for all the help and advise. I will do more reading before I start cutting. Its just something that I am quite interested in and would like to get into. Four strokes just dont cut it for me anymore! Justin. Quote Link to comment Share on other sites More sharing options...
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