372 builders, port numbers any idea's how she will be?

[trappermike]

Well there are so many variables when different people build saws,the of course cc size dictates what can be done too. Smaller saws like little extra in. dur.,and like extra compression,but for more performance a little more ex. dur. is needed to make more power.
Lostone- To make it short more ex, dur. will build more top end power, more comp. will build more midrange power in a no too modified motor.When going to a higher performance level more port timing will win the day over comp.,all race motors are built this way. But when building modded work saws,it's a combination of everything,finding what port timing,compression,carb size etc. that will do the job best for the application and cc of motor.Do not go excessive on any of these things,find a happy medium for what you want.
But to climb the ladder toward high output power more ex. timing is the key,not compression, but transfer and intake dur. must be good too.
In work saws I use a little more ex. dur. than most guys with no problem,but I always bore the carb larger to get more fuel in to feed that hungrier ex. port.

 

[trappermike]

Yotaismygame ,I like some of your knowledge and specs and being open,but for max. power I would go farther on ex. dur. ,ex. 170 to 172 .Try to keep compression 140 -180.

 

[Yotaismygame]

I’ll have to try that sometime. But I don’t build for max power. Just hot work saws. For a exhaust duration of 170 what do you like for the intake? Similar duration?

I post a lot of my work on this forum and YouTube. If people ask me questions I tell them. No reason to keep it to myself.

 

[trappermike]

For lotsa torque,not racing I wouldn't make intake duration too long,a little more than stock but widening the port A LITTLE helps without killing low speed power if the cyl. and piston permits it. Intake dur. cannot be as much as ex. dur.
For 170 ex. dur., I think around 160 in. dur. could be good as a start.
Too much intake duration can really kill pulling torque at mid revs.

 

[Yotaismygame]

For lotsa torque,not racing I wouldn't make intake duration too long,a little more than stock but widening the port A LITTLE helps without killing low speed power if the cyl. and piston permits it. Intake dur. cannot be as much as ex. dur.
For 170 ex. dur., I think around 160 in. dur. could be good as a start.
Too much intake duration can really kill pulling torque at mid revs.

Agreed. Case compression good. Only saw I’ve had near that was at 97/122/80. Ran pretty good.

 

[Yotaismygame]

What about for racing? Yet to build a race type of saw so I’m not sure what numbers exactly but I’m sure I could figure it out.

 

[trappermike]

Well the numbers you just said are definitely racing numbers, and are pretty damn good, but I wouldn't go beyond those,because you can run into other problems that are very difficult to solve.

 

[AUSSIE1]

I wish i could find my book. The wife is good at filing things away, bad at remembering where.

I cant remember any of my numbers but i used to lift the transfers till i reached the torque i was chasing with the 372 (BB). Out here in the South East of Australia, we need all the torque we can get for our hardwood.

I used to spend the most time on the transfers. Alot of time. There is so much you can do to them.

 

[Ketchup]

I wish i could find my book. The wife is good at filing things away, bad at remembering where.

I cant remember any of my numbers but i used to lift the transfers till i reached the torque i was chasing with the 372 (BB). Out here in the South East of Australia, we need all the torque we can get for our hardwood.

I used to spend the most time on the transfers. Alot of time. There is so much you can do to them.

Were you raising the exhaust with the transfers or shrinking your blowdown?

 

[AUSSIE1]

Were you raising the exhaust with the transfers or shrinking your blowdown?

This is with the aftermarket 52mm barrels.

It was something like 10 years ago so im hard pressed to remember. Timing numbers i def wont remember. I do remember the timing on the exhaust was equal to about 1mm when the base gasket was removed. I would slowly bring up the transfers till i found that perfect for me torque x revs. Widened exhaust and matched to the muffler. The inlet was cleaned up and flaired at the bore. Port matched of course.

I did an immense amount of work to the transfers. I never enlarge. Velocity is key. Use a base gasket as a template to match the barrel to the cases. There is so much work here. I would clean up in the transfer ports. Then i would do plenty on the uppers. Alot of time for intricate work. I used a right angle dentist drill and modified bits to fit.

I modified a Stihl 064 piston, run backwards with only one ring.

It was a torque monster that could rev.

I never did get around to trying out the 385/390 carb/manifold. It runs the stock carby.

Ill see if i can find some pics. I took alot of my work. Also i have vids that show the before and after of raising the transfers only.

 

[AUSSIE1]

The 50/52mm Huskys could rev with the base gasket removed. Comp wasnt over the top.

This 372BB had a bored carb that at the time of the vid i was unaware had a pin hole leak.

 

[AUSSIE1]

Prior to raising the transfers.

 

[AUSSIE1]

Then with the transfers raised.