11 replies to this topic

[fuzzypumper]

Hi,
I have a Rochester off a WB which has its idle mixture screws sealed with a caps/covers from the factory
for anti pollution purposes. I want to remove to gain access to the mixture screws.

Can anyone tell how to remove them? has anyone done it?
I think the these covers are made of titanium because the hack saw, the drill punch or a drill bit wont even
scratch them or put a dent in them.

[76lxhatch]

As far as I know, they can be drilled out: http://www.aussiev8....ning-carbi.html

Never had to do it myself though as I always seem to come across carbs with this already done.

[warrenm]

The cups are hardened steel so they can't be drilled.You need to drill base plate about 6 or 8mm back from the end of the cup with a small drill until you find the end, tap the cup out.

[fuzzypumper]

Thanks guys, I'll give that a try.

[Struggler]

WarrenM is on the money.

Back in the day we would just flip them over and grind the bottom of the base away until the plug fell out. The drill and punch is a much neater option.

In this day and age I am really surprised you found one with the plugs intact !!

[fuzzypumper]

Struggler, It was probably left untouched because it came off a WB Statesman and not a Commodore.

Here's what I did:
I had a picture of HZ rochester throttle body so it gave me an indication of how far I could grind & cut into the body
without damage.

I ground the front of the cup off with an angle grinder. and then removed the idle screws with a pair of small long nose pliers
so I wouldnt damage them when I started drilling. (Screws where 10 turns in).


I found the cups are 11mm deep from the front so I scratched a few guide lines and drilled with a 2mm bit, 12mmm in,
behind the cup and around the side towards the front.


I then used a screwdriver to breakaway the alloy and lever out the remaining cup.


Then I cleaned up around the holes with the angle grinder and file.


I also hack sawed a slot in the idle mixture screws heads so I could use screw driver to easily adjust them later.


Thanks again for your help guys.

Edited by fuzzypumper, 24 December 2009 - 12:41 AM.

[Struggler]

Nice work, those plugs are a real PITA.

Slotting the screw heads is a nice touch. You can buy the appropriate screwdriver from Repco etc. You will need it to adjust the part throttle screw as well.

[fuzzypumper]

Thanks AJ, but what is the "part throttle screw" you are referring to?

[76lxhatch]

In later model carbs there is a little plug under the air cleaner at the front, usually drill halfway through and pull it out with a little ez-out. Underneath is the adjustment for the primary metering rod stop, known as the part throttle adjustment. It determines the maximum distance that the rods can be pulled into the jets by vacuum and thus the leanest that the primaries can operate.

[fuzzypumper]

Ok. Thats the bit I was gonna ask about next because I forgot to take note of its initial position when I pulled the carb down.
Ive just put it back 1 turn from the bottom at the moment, but what is the actual procedure I use the adjust the part throttle?

So by taking the plug out youre not opening the vacuumed section?

Edited by fuzzypumper, 24 December 2009 - 09:18 AM.

[76lxhatch]

It opens up the float bowl, you need to replace the plug before driving again. See post #24 in the AussieV8 link above for more detail and recommended tuning practice (# turns etc)

[Struggler]

76lx has it sussed.

I used to run a 1/8 NPT tap thru the hole and screw a plug in while the top was off.