SU Piston test

[Hap Waldrop]

BTW the whole float chamber wiggles a bit more on this carb then the other.

There's old trick here, all of us professional rebuilders use, put a extrra 5/16 flat washer on the bolt that hold the float bowl on, just position it behind the rubber and brass washer, it will allow you to tighten the flaot chamber up enough to keep it from wiggling. Make sure you have the odd shaped washer that goes on the float chamber, just before the rubber alignment grommets also.

One thing unique about the HS2 is they only have two dashpot retaining screws and they are concentric, so that means you can put the daskpot on backwards if you will, revert the dashpot 180 degrees and see if the piston/s drop any better.

On the jets dropponing form the choke mode, alot of the time the choke arm linakge, (the one that goes form the carb side linage to the jet itself) can get slightly bent, and if it does it will cause the jet not to drop or spring back into postion correctly, sometime you have to slightly tweak that chocke arm to get good fluid motion.

Another thing on HS2 carbs, is when repalcing the throttle shafts it is real easy to over tighten the throttle disc screws and slightly warp the shaft causing the disc to bind, sneak up on tighten these, start on one, tighten a little, then go the other one, then back and forth until snug, don't over tighten or you will damges the shaft. Most professional rebuilder do not rely on the split on the bottom of the throttle disc screws to retin themselves, most of use a drop of lock tite here, you don't want to digest a throttle dis screw into the motor.

Another thing on repalcing the throttle disc on HS2, 95% of time you only need a new stadard size throttle shaft to renew the HS2s to a ggod fit and seal. Unlike the HS4, HS6, and HS6, HIF4. etc, the HS2 has no brass busing in the carb body for the throttle shaft to ride against, in ther HS2 the throttle shaft rides directly on the aluminum of the carb body, since ther aluminum is harder, the shaft tends to take all the wear, very seldomly do yu ever have to bush a HS2 carb body or use a oversized shaft.

Hope this helps.

 

[jvandyke]

SUs are looking good. I do have Grose jets, they were both "sticky" using a "blow through the line" method, but air vs. gas, you'd think liquid pressure would be a better test then air. I'll clean them up and run them. These carbs have not been run since probably '87 (there's a receipt from the PO showing purchase of the Weber kit from VB $259.95 vs. $699 today!)
I stuck the hose end of my house vacuum on the head side of the intake, just to see the pistons move, they do if I block the other side. Neat. . Regarding K&N Scroll to the bottom for conclusion.

 

[jvandyke]

BTW the whole float chamber wiggles a bit more on this carb then the other.

There's old trick here, all of us professional rebuilders use, put a extrra 5/16 flat washer on the bolt that hold the float bowl on, just position it behind the rubber and brass washer, it will allow you to tighten the flaot chamber up enough to keep it from wiggling. Make sure you have the odd shaped washer that goes on the float chamber, just before the rubber alignment grommets also.

Do I really need to care if it wiggles a bit? I wasn't going to tear these down anymore than I have if I don't have to. I suppose if the chamber jiggles from vibration it could froth up, throw off the level or something....?

 

[jvandyke]

Here's a picture of the welded intake. Should I clean up the inside, is that flow inhibitor/disruptor? or no big deal?

 

[dklawson]

Were that my manifold and it was off the car, I'd use the port polishing sanding drums to remove any high spots and blend the two surfaces together. I don't know how much restriction the welds produce (I can't tell how high they are from the picture) but since the weld bead is accessible, why not remove it?

 

[jvandyke]

Alright, I'll touch it up a bit, got a new set of Dremel bits for Christmas anyway. Then I'll let them be while I convert to negative ground, install the Crane Cams XR700, get timing good, valves good, play with the Weber until it's as good as I can get it, then I'll put the SUs on for fun and comparison.

BTW
On a '63 1098 the valve cover was vented to the air filter housing, with my Weber that didn't provide a enough vacuum, I tapped the intake and that helped with oil leaks tremendously. Going back to SUs means going back to a filter housing hose. There's probably more vacuum in a OEM filter can then the dorky little foam filter that sits on the Weber now, so I'm hoping that'll work okay? Otherwise, has anyone tapped a stock intake to get a source of vacuum?