Porting a Husqvarna 351

[Mastermind]

This is my first post in the Hotsaw forum. I've used the search function without success. I've ported several saws with good gains, but all have had closed transfer ports. The 351 on my bench has open transfers and I'm at a loss. What can be done to improve flow and in the cut power on this type of transfer?

Here's the port timing numbers without a base gasket. Squish is .021.

Intake 72* abdc
Exhaust 108* atdc
Transfers 121* atdc
Blowdown 13*

Here's a few pics of what I've done so far, I figure on getting flamed for my crappy looking work so don't be shy, I can handle it.

Stock.

After widening the ports and changing the intake timing to 78*.

It's the transfers that have me puzzled, what to you guys think?

 

[MechanicMatt]

file or dremmel?

Im in the middle of doing up my 50 it has the same open port design, I'll be watching your post closely as i too was wondering what to do with the sides? Did you use a dremmel tool or a file or both when widening? And what do you think the ideal timing is? thanks for any help. I want to put a p5000 head and piston on my 50 but untill i find one im gonna play with the stock stuff. Matt

 

[Art Vandelay]

And you're the "Mastermind".

 

[Mastermind]

Im in the middle of doing up my 50 it has the same open port design, I'll be watching your post closely as i too was wondering what to do with the sides? Did you use a dremmel tool or a file or both when widening? And what do you think the ideal timing is? thanks for any help. I want to put a p5000 head and piston on my 50 but untill i find one im gonna play with the stock stuff. Matt

This is a pretty old thread, that saw has been back with it's owner for months.

He is pleased with the gains that we got, it's pulling a 18" .325 very well.

I use a dremel with different sizes and shapes of carbide burrs. I also use sandpaper wrapped around an 1/8" drill bit for a flap wheel. Attention to detail is most important on port work.

As for ideal timing numbers, that's a good question. I've ruined a few jugs trying to find out the answer to that one. To much intake timing and you lose torque, but gain rpm. Raise the exhaust without compensating for the compression loss and you've ruined the jug. I started porting by just widening the ports, after I read everything I could find on the subject. Good luck with your 50.

 

[MechanicMatt]

what did you do with the transfers? thank you for all the help this is the first saw i've tried to port. -matt

 

[Mastermind]

what did you do with the transfers? thank you for all the help this is the first saw i've tried to port. -matt

There's not a lot that can be done to the transfers. If you widen them much you add to the case volume, I don't know what that does for torque. On some saws I've ported since with open transfers I widened just the top part of the transfers and angled them towards the intake port. (The amount that is open with the piston at BDC).