porting specs

[bansh450]

Personally on my port jobs, I do a full reshape of the intakes...but, enlarge them only enough to clean up the casting flaws. I try to enhance flow characteristics as much as possible without slowing down intake velocity. This is one area where a lot of builders disagree. Ask any five builders what intake size/shape/texture works the best and you'll likely get five different answers. I have experimented a lot with auxillery ports and found that they actually slow my engines down some. There are builders who swear by them, but I haven't found them to give any advantage in my portwork. I know what works best for me, but what works best for someone else may be different.

 

 

does 30mm exhaust and 44mm transfer ports sound right for a stock cylinder?

when i grind down to 26.78 on th exhaust do i also remove the same on the bottom of the exhaust port?

ive already cleaned up casting flaws and sharened up the the transfer port ways.

now what size dome would work good with the cool head 110 gas 35mm carbs, cpi and this port work also what would you set your timing plate at? thanks.

[Wildcardracing]

does 30mm exhaust and 44mm transfer ports sound right for a stock cylinder?

when i grind down to 26.78 on th exhaust do i also remove the same on the bottom of the exhaust port?

ive already cleaned up casting flaws and sharened up the the transfer port ways.

now what size dome would work good with the cool head 110 gas 35mm carbs, cpi and this port work also what would you set your timing plate at? thanks.

Yes, those are the stock roof heights. You will lower the port floors only 2mm from where they are now, that will put you at @56mm from the port floors to the deck. This way your piston crown will be flush with your floors at BDC. Your domes will have to be custom stroker domes, the machinist building them will want to know your exhaust duration ie: 196 deg. and that they are for a -2mm deck height. The size will depend on altitude, 19 or 20cc domes will work well with 110 at sea level. I would recommend no more than +4 on the timing with 19's no more than +6 with the 20's. Hope that answers your questions.

[J-Madd]

Personally on my port jobs, I do a full reshape of the intakes...but, enlarge them only enough to clean up the casting flaws. I try to enhance flow characteristics as much as possible without slowing down intake velocity. This is one area where a lot of builders disagree. Ask any five builders what intake size/shape/texture works the best and you'll likely get five different answers. I have experimented a lot with auxillery ports and found that they actually slow my engines down some. There are builders who swear by them, but I haven't found them to give any advantage in my portwork. I know what works best for me, but what works best for someone else may be different.

 

When you drilled the ports through the intake, did you also remove an area of the transfer wall on the other side? I've only seen a few sets of ported stockers, but the one that ran the best had the boost ports on the intake that went all the way into the middle of the transfer area, if that makes sense. This engine made 84 rwhp on the dyno untuned. We didn't get to dial it in b/c it welded the ball to the rod on the first pull. Probably makes around 90 hp. Runs 4.20s all day with 190 lb rider...has run teens with a lighter rider.