262XP Day

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I'm taking video of my rebuild process ... I've got enough parts to put together 3 of them I think... eventually i'll have a bolt for bolt vid like my other vids.

I'm not cutting squish band on these, just cutting the chassis down to optimize squish while retaining a gasket. Anyone have some timing numbers I should be shooting for? I think MM said somewhere in the 103 deg for exhaust, but what about blowdown and intake? around 78 sound ok for intake? I may not touch the transfers at all. who knows :)

-Mattyo
 
if the 262 won by .1 with a 20" b/c vs 562 16" b/c I still want to see a video of same b/c combo head to head. The 262 should obliterate it's younger competitor. :buttkick::chainsaw::rock:

It might still be misleading to an extent, as we don't know how close to optimal the work on the different saws are - and only one combination of gearing, bar, chain and wood won't tell the full truth anyway. Results will be different with other combinations....

Actually, there are no way at all to find the "final truth" - although it is very easy to get closer than was done here. ;)
 
FINALLY am getting around to this saw. I cut the chassis down a bit so I can run a tighter squish and retain a gasket. I'm at .019 right now... timing numbers are 103, 125 and 68. Seems like I'd wanna tighten the blowdown a touch and take the intake to 78 or so... no? I'm not planning on touching the exhaust timing... maybe just do a little widening and shaping. thoughts?
 
Think of it like this......

The intake is a valve. Once it closes......pressure builds up. Until the transfers open. Keeping the intake short.....like the designers did, allows you to raise the transfers higher without losing case pressure. The early jugs only have about 12° of blowdown.
 
Don't add too much intake........72 seems to work well on these saws. I'd take the uppers way up......to 118.
Randy, I remember reading in another thread about raising the roof of the intake instead of the floor to gain duration. What's your take on this?
 
Randy, I remember reading in another thread about raising the roof of the intake instead of the floor to gain duration. What's your take on this?

I use that, and width to gain area. Remember, the porting on these engines is measured in Time/Area. If you keep the time short.....you need more area. You'll still be able to fill the case, but you can trap, and transfer more. Really what we are seeing is a more efficient engine. Less spitback, less fuel usage, same power, if not more.

Ok...so let's say you fingerported it...does that mean you could have more intake duration or does that mean that you need more intake duration?

I still use 72° on this saw. With or without fingers.

The more pressure you can build in the case.....the more aggressively the charge will be forced thru the transfers.
 
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