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4mill crank stock cylinders... port timings


SlowMoe

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Okay I am getting a 4 mill crank 115 rod with long rod pistons for my stock cylinder banshee.

 

I am going to port it myself but I would like to get the port timings as close to optimal as possible using spacer plates.

 

The port timings I am after are roughly that of a driveline assasin HP cylinder. I realize I may need to go a little higher with my exhaust port to have close to the same blowdown as an HP cylinder. Looking for about 198/ 126-126

 

That said, off the top of anyones head can you tell me the approximate port timings on this engine using a 2mm spacer, a 2.5mm spacer, and a 3mm spacer.

 

Thanks in advance

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Take your time, and pay attention. I wouldn't use a spacer plate, but that's my opinion. To each their own though. Keep the curious updated.

 

 

 

Sent from my SM-S820L using Tapatalk

I would feel much more comfortable acheiving the desired transfer duration by raising the cylinder, since I dont have the skill/ PATIENCE to cut the transfer roofs myself. If I have to go more than 2mm to achieve this, I will deck the top of the cylinders to compensate.

 

Before you get ahead of yourself, do you plan on running stock pipes?

Got jokes now, do we :D CPI or shear. Probably CPI since I am also putting a turbo on my YXZ and I need to be a cheap ass.

 

But seriously. ABOUT how much will i need to raise the cylinders/ ports to get to 126? Any clue? I do have a degree wheel but I'm wondering if I need to get a thicker spacer than 2mm to put me in the ballpark...?

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If you have the ability to rechamber and cut the head to get desired squish go for it. Get a cpl head gaskets and do it up . 2 mm spacer and .020 bases gaskets will get u up around where you need . With the 4 mill crank you don't need to raise transfers much but I do like my blowdown a lil different than others

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and mistakes are part of learning.....

 

Sent from my SM-S820L using Tapatalk

 

yes indeed but why put the cart 100miles in front of the horse. logical thinking can prevent a few fuk ups. even before grinding up some niche I would spend alittle time on some unusuables. make a quick template on paper and trace it to the bore wall. spend a weekend, week, month, whatever it takes, and go through the motions. but in the end he'll have to decide when its time to proceed forward

 

spacers can be good but they have their time and place. this isn't the time or place imo

 

raising the exh to make it bigger isn't equivalent to having 3 ports. fyi

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moe you seem lost. why not tinker with some junk parts before you make a cobbled mess of your good stuff

Ive done my fair share of junking cylinders lol. I feel good about this set. Can't hardly go wrong raising the cylinders as long as you have a degree wheel and keep an eye on squish and such. I got this holmes lol

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raising the exh to make it bigger isn't equivalent to having 3 ports. fyi

 

 

I understand that. But to have close to the same blowdown as a set of tripples at 196 degrees, a lot will have to be done to widen and re shape the exhaust port and it will need to be raised as wel in my opinion.

 

Hopefully there wont be much transfer work in this build and I can focus my very limited time on perfecting the exhaust ports.

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