Porting questions

Blaner

Your Friendly South African Ambassador
Mar 26, 2008
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East London, South Africa
Hey guys
A few questions with regards to porting.

Will shaping the piston bottom skirt to match the transfer port shape and matching the intake holes in the piston to the intake ports have any weakening/unbalancing effect on the piston?

I have discovered that auxillary ports can be drilled to link the intake chamber to the transfer ports below the piston. What size drill should be used here and can someone explain the exact function of these holes and does adding them have any worthwhile gains? do they allow constant airflow into the transfer ports when the main intake ports are blocked as the piston moves up and blocks them off? surely on a stock motor the intake air movement is stopped as the intake ports are shut off resulting in poor air flow?

I also see that when at BDC the piston does not fully drop below the transfer ports entering the cylinder. I think the piston stops about 1mm short of being flush with the bottom of the ports. A spacer plate would fix this by raising the barrel but that will mess up port timing?? also this would mean the top end would need 1mm skimming to correct compression. Does using a spacer plate have any worthwhile gains or does it cause more trouble than its worth?

Just trying to clear these things up before i start!
Thanx guys!
 
From my research i have heard good things about the auxiliary ports,look at this site,"macdizzy.com" it is full of info.
 
hey yes iv been using mcdizzy.com but he doesnt really say in the end how the blaster rebuild performs since the dude crashed on the 1st ride! my main concern is the base plate spacer, im not sure i should raise the barrel, i feel there are too many things to go wrong, any thoughts? anyone done this?
 
hey yes iv been using mcdizzy.com but he doesnt really say in the end how the blaster rebuild performs since the dude crashed on the 1st ride! my main concern is the base plate spacer, im not sure i should raise the barrel, i feel there are too many things to go wrong, any thoughts? anyone done this?

I think that one of the builders (Flotek?) on the site said in another thread that there was not enough of or any benefit to adding a spacer (from memory, please forgive me). My thoughts are if it was worth the effort that they would use this technique for everyones engines. However, if you are doing to work yourself it may be worth it- the builders have to consider the cost/benefit ratio to the customer. I also say try it and report back to us the results! :D
 
boysen ports do help i add them to every blaster cylinder ,look at every modern reed frontal intake design 2stroke they all have these ports for a reason .how and why they are done is best left to seasoned engine builders and also you may end up with unwanted extra holes going out the side of your intake box (sadly ive seen people do this !)the pisto nand intake performance gains are marginal in comparison to the transfers and exhaust port,thats mainly where the big gains will be found.raising the jug on a *stock stroke is a bad idea it will make the ports even worse and increase squish clearance which already is poor,i realize your in another country and maybe even o na tight budget to send things out but it may be a good idea ot seek the help of another source or do more research. a good intake flow shape and size can add some benefit for sure but dont be overly concerened on the intake manipulation becuase theres much bigger roadblocks that need addressed ,these are things veteren builders can spot and fix that he average guy simply wouldnt know to do .