262XP Day

[SawTroll]

Can anyone tell me what vintage my saw is so I can use the right IPL. Thanks.

1992 week 17.

Remember that IPL dates don't always correspond exactly with production changes - and parts could have been swapped out on older saws, mostly with newer parts, but some times with older. Often the older and newer parts interchange, but not always...

 

[VinceGU05]

Ok thanks. Well at least I can step in the right direction now [emoji106]

 

[drf255]

Randy,

With the low intake and great case pressure, coupled with bridges and fingers to increase flow/decrease restriction/increase cross sectional area of the uppers, why do you go with a 15* blowdown?

The fingers look a bit higher than the upper mains in the photos.

Are you using the factory research of what worked for them to base your changes upon?

Granted, the factory has much more time and money to devote to R&D than anyone else.

I'd imagine with all the flow increase you've created, coupled with the great case pressure, one could run a numerically higher (physically lower) transfer circuit and get better charge filling and less charge dilution. But I guess the factory decided on a low blowdown for a reason with the design.

It appears that you've created a poor man's quad port, but maintained a 2 port's transfer height here.

 

[drf255]

The transfer tops are also much physically closer to the top of the exhaust port than they are before the SB cut and jug drop at the same blowdown amount as before the cut.

Is this just a situation where reality trumps theory?

 

[Mastermind]

Randy,

With the low intake and great case pressure, coupled with bridges and fingers to increase flow/decrease restriction/increase cross sectional area of the uppers, why do you go with a 15* blowdown?

The fingers look a bit higher than the upper mains in the photos.

Are you using the factory research of what worked for them to base your changes upon?

Granted, the factory has much more time and money to devote to R&D than anyone else.

I'd imagine with all the flow increase you've created, coupled with the great case pressure, one could run a numerically higher (physically lower) transfer circuit and get better charge filling and less charge dilution. But I guess the factory decided on a low blowdown for a reason with the design.

It appears that you've created a poor man's quad port, but maintained a 2 port's transfer height here.

The fingers open 2° ahead of the mains to help push the exhaust out. That allows the higher transfer to work without as much dilution. Also, keep in mind that the transfer passage design has wide open tunnels that will be lazy.......yet another reason for higher transfers.

The transfer tops are also much physically closer to the top of the exhaust port than they are before the SB cut and jug drop at the same blowdown amount as before the cut.

Is this just a situation where reality trumps theory?

Not following you here........but I think you are referring to the bigger jump in degree wheel numbers on the transfers, than what you see in change on the exhaust. This is just because of where the port are in relation to crank/rod angle.

 

[drf255]

The fingers open 2° ahead of the mains to help push the exhaust out. That allows the higher transfer to work without as much dilution. Also, keep in mind that the transfer passage design has wide open tunnels that will be lazy.......yet another reason for higher transfers.



Not following you here........but I think you are referring to the bigger jump in degree wheel numbers on the transfers, than what you see in change on the exhaust. This is just because of where the port are in relation to crank/rod angle.

The actual millimeter difference in distance between 15* BD should be much less the more you lower the jug, because of rod angle and piston speed. I just lowered a jug .039 on a 262. The ex roof now at 108, but the transfers are at 130-132 with the same drop.

I'm trying to wrap my head around the entire thing. So an asymmetric upper transfer with small directionally placed lip towards the intake side could conceivably create a similar effect to fingers for a guy who is less skilled (as I am).

 

[Mattyo]

Got another 262xp on the bench, this one's PERTY... very little wear, but low comp... 90. Stuck ring. The transfer extends over to the decomp valve... so i'm thinkin its the decomp... what you guys think?

 

[Mastermind]

A leaky decomp rarely scores a saw. Now the A/T saws like the 562XP score like that pretty easy because they run pretty lean as is. I'd just replace the seals and other rubber bits. After all, it's an old saw.

 

[Mattyo]

will do, bearings feel good... just find it odd that the transfer is on one side, and so specifically STOPS at the decomp opening

 

[Mastermind]

Meh........just a coincidence.

 

[Mattyo]

man, i really thought i was on to something.... oh well ....time to go pop in some seals!

 

[Northerner]

Has the saw in question been sitting for an extended period of time? If so, do the bearings too.
I just learned the hard way on a 55. Saw had been sitting for an unknown amount of time but the bearings "felt" good when I had it apart.
Well, today I took the saw for a test run, not 5 minutes later the clutch side bearing blew......aaarrrggghhh!

Worst part was, I knew I should have done them right away....

 

[Mattyo]

case is seperated... will pull bearings when I can. have this CT GTG in the way of getting this saw done

 

[Mattyo]

case is decked....now to get some timing numbers and do some porting

 

[SquareFile]

Will your 262xp's be faster than your 346's?

 

[Mattyo]

Haven't done a 346....have done a few 350's though.

 

[SquareFile]

Haven't done a 346....have done a few 350's though.

I was referring to the op, my mistake.

 

[VinceGU05]

1992 week 17.

Remember that IPL dates don't always correspond exactly with production changes - and parts could have been swapped out on older saws, mostly with newer parts, but some times with older. Often the older and newer parts interchange, but not always...

welp i had a look and i have the KS jug and 87 carby!! do i win a price

 

[SawTroll]

welp i had a look and i have the KS jug and 87 carby!! do i win a price

You already have the price!

 

[Mattyo]

Did the transfers here in the dental office....



Didn't need to remove much to get to 122 timing. Just extended towards the intake slightly too...nuthin too silly