I'm going to try and get some numbers for the 268 and 372 pistons today and I'll post them. I have a degree wheel so I'm going to do a little reading on the right way to do it, I've never done it before.
Fist time porting question (372)
- Thread starter Ronie
- Start date
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Too many variables. The 268 piston gives a bump in compression, but also messes with timing. The skirts are narrower, so maybe there's a freeport issue on the intake or exhaust. Maybe the coil. Maybe too much intake duration. Or maybe it's a pos FT cylinder. It could be one or many things. Hard to tell
This is what I got for the 268 pop up piston.
Exhaust 106
Intake 82
Transfers 129
I'll get the numbers for the 372 piston after lunch.
Exhaust 106
Intake 82
Transfers 129
I'll get the numbers for the 372 piston after lunch.
I don't think it's your numbers that are holding the RPM back. Usually the a.m. ports are smaller. If the transfer ports are small and don't have good direction, it's just not going to rev up. But it may produce more torque which will help offset the lack of higher RPM horsepower
One thing I noticed is that it looks like the transfer ports are not opening all the way.
Thanks for taking the time to look at my numbers
Yotaismygame
Juiced Saws #GetJuiced
The 268 pop up I ported was a screamer. Easily could hit 15k. I saw your most recent video on youtube and to me i'd suggest working on your chain filing before getting into port work. Not trying to be an ass here.....
Are you talking about this saw with the black starter cover? I sharpened it on a chainsaw chain sharpener. It's pretty sharp but the rakers are low.
Yotaismygame
Juiced Saws #GetJuiced
Pretty much all your videos. Rakers are part of the whole equation. I guarantee you all the porters here tune their chains perfectly when making videos for future customers to see. Take a bad ass saw with a chain setup wrong and it's not going to look bad ass at all. I see this kind of stuff a lot on youtube. Guys modding saws but still running safety chain. Whats that!!!
I understand what your saying. I don't own any bad ass saws or safety chain. Maybe one day I'll build one. I'd like to have a saw that would turn 14,000-15,000 to play with.
Yotaismygame
Juiced Saws #GetJuiced
I'm just saying, get your chain squared away first. Probably find more gains from that alone. On this saw though, try raising your exhaust a hair to bring the comp down to around 180psi, and gain some RPM. Is the muffler modded?
Mufflers modded, 3/4 pipe
I got the numbers with the 372 piston.
With Gasket
Exhaust 100
Intake 74
Transfers 129
Without Gasket
Exhaust 102
Intake 76
Transfers 125
With Gasket
Exhaust 100
Intake 74
Transfers 129
Without Gasket
Exhaust 102
Intake 76
Transfers 125
The 268 piston 372 I did will not 4 stroke above 13000, I've been running it about 13200, the plug is a rich brown color. When I first started it (new 390 carb) it was reving pretty high and I had to open the screw a lot to get it to 4 stroke.
I've got deep snow and no big wood to work with now so can't work the saw.
I'me used to running 372 at 14000 up and I think this one will go higher than it is but if it won't 4 stroke I gotta be keerful.
I've got deep snow and no big wood to work with now so can't work the saw.
I'me used to running 372 at 14000 up and I think this one will go higher than it is but if it won't 4 stroke I gotta be keerful.
I'd be shooting for 98°-100° on the exhaust, 18°-20° blowdown, and 78° on the intake.
Port timing it only part of the puzzle. There a lot to port shape and size as well.
Port timing it only part of the puzzle. There a lot to port shape and size as well.
Thanks for the numbers I should be looking for.
So, I put the cylinder and 372 piston on the clone saw without the gasket. I don't have high hopes for it, squish was .034-.035, but we'll see how it does. I have another Farmertec cylinder and a couple of crankcases so I'll keep trying until I get it right. Thanks again for the tips I'll post how it turns out.
Transfers are probably limiting the rpm. I’ve not tried any aftermarket jugs. I did use an oem piston and added windows once to compare to stock piston. Both had chambers cut and ported to the same numbers. I never liked the windows. Seems like it was higher revving and less torque.
World renounce traveler eh?
I would be happy to meet abroad in Europe?
And she better have a friend. Haha
Come see me in 'Winston Churchil's
Island' some day
Well I tried it out this morning. It ended up having a disappointing 140lbs compression but i guess that to be expected with the high squish. It should rise a little as it brakes in. It's running around 14,200 rpm and four stroking a little, it's hard to hear in the video but it is. My bar quit getting oil so I've got to see whats up with that. I have a new bar and chain so I'm going to put that on, turn down the rpm to around 13,500 and go from there. I also got to ind some more wood.
