Went out to find my low speed jets on an 89 Merc 40. Was shining all over
around in there with a flashlight. Couldn't find them. Saw the plug on top
of the oil injector tank was loose, and went in there to tighten it. Of
course, I only knocked it off, now have to take off the tank to find the
plug which had fallen into the abyss between the tank and the intake
manifold. Which I should have done in the first place to get to the carbs.
As I look over the carbs after I have moved the tank, I notice there are two
holes through the tank specifically aimed at the jet screws. Reachable with
a thin blade long screwdriver.

HAH! Glad it was not a Ford, or I would have probably had to take off the
starter and loosen the motor mounts to do it. So, on the next cruise, I'll
set the jets. Bottomed them out, and came out 1 1/2 turns for now.
Adjusted a couple of hoses that had kinks in them from being cut too long.

Hope to take it out this weekend.

Steve

On Tue, 5 May 2009 18:19:31 -0600, "SteveB"
wrote:

Went out to find my low speed jets on an 89 Merc 40. Was shining all over
around in there with a flashlight. Couldn't find them. Saw the plug on top
of the oil injector tank was loose, and went in there to tighten it. Of
course, I only knocked it off, now have to take off the tank to find the
plug which had fallen into the abyss between the tank and the intake
manifold. Which I should have done in the first place to get to the carbs.
As I look over the carbs after I have moved the tank, I notice there are two
holes through the tank specifically aimed at the jet screws. Reachable with
a thin blade long screwdriver.

HAH! Glad it was not a Ford, or I would have probably had to take off the
starter and loosen the motor mounts to do it. So, on the next cruise, I'll
set the jets. Bottomed them out, and came out 1 1/2 turns for now.
Adjusted a couple of hoses that had kinks in them from being cut too long.

Hope to take it out this weekend.

Let us know how that adjustment works out. Personally, I've never had
any luck with carb idle jet screws, 2 or 4 barrel, Carter, Holley or
Rochester.
In my experience they come adjusted to the correct turnout from the
factory or rebuilder, so when you bottom them and turn them out the
correct turns you're back where you started.
And I don't recall any other adjustment being better than that.
Then you've got the throttle idle screw itself to tinker with, which
affects RPM and ear test.
I have had some engines idle better with the screws further out than
spec, but then you're risking washing the cylinders with a over rich
mixture.
IMO without an exhaust gas analyser idle jet screws are a losing
battle.
I'm glad I've tinkered with my last carb long ago.
Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.
I settled for tinkering and a minor gallop.
Balancing dual carbs is an even bigger PITA. You really need air flow
meters. But maybe I'm just too "perfectionist" and carbed engines
don't allow for that.

--Vic

On Wed, 06 May 2009 06:29:32 -0500, Vic Smith
wrote:

Balancing dual carbs is an even bigger PITA. You really need air flow
meters. But maybe I'm just too "perfectionist" and carbed engines
don't allow for that.

They used to put SU carbs on everythilng from Austin-Healeys to
Volvos. Everyone had a cheap airflow meter.

Casady

"Vic Smith" wrote in message
...


Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.

That Rochester quadrajet (aka "quadrabog) has got to be the most miserable
carburetor to rebuild ever designed. Had one on a boat that despite the
best efforts of several people to rebuild, adjust, repair, etc., never ran
right.

Had one in my '67 GTO that was fine however, so I never touched it.

Eisboch

On Wed, 6 May 2009 09:55:50 -0400, "Eisboch"
wrote:


"Vic Smith" wrote in message
.. .


Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.

That Rochester quadrajet (aka "quadrabog) has got to be the most miserable
carburetor to rebuild ever designed. Had one on a boat that despite the
best efforts of several people to rebuild, adjust, repair, etc., never ran
right.

Had one in my '67 GTO that was fine however, so I never touched it.

I only fully rebuilt one carb. A single-bbl. Didn't notice any
difference after the rebuild. Just happy it worked at all.
Of course I'm an amateur, and didn't even tank it. Used the kit.
Poured Gumout on it and blew out what I could.
After that I just bought a rebuilt when I couldn't fix it.
My carb successes are limited to float valves, floats and accelerator
pumps. In fact an accelerator pump cured the quadrajet from bogging.
Same with a deuce I had on a Ford 352. Think it was a Carter.

--Vic

On May 6, 9:55*am, "Eisboch" wrote:
"Vic Smith" wrote in message

...

Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. *By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.

That Rochester quadrajet (aka "quadrabog) *has got to be the most miserable
carburetor to rebuild ever designed. *Had one on a boat that despite the
best efforts of several people to rebuild, adjust, repair, etc., *never ran
right.

Had one in my '67 GTO that was fine however, so I never touched it.

Eisboch

I agree! You would think that your carb is crapped up because of poor
performance, and rebuild it, and it'd run the exact same afterword! I
learned early in my gearhead days that the perfect fix for a Rochester
Quadrajet was a Holly 650 double pumper!

wrote in message
...
On May 6, 9:55 am, "Eisboch" wrote:
"Vic Smith" wrote in message

...

Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.

That Rochester quadrajet (aka "quadrabog) has got to be the most miserable
carburetor to rebuild ever designed. Had one on a boat that despite the
best efforts of several people to rebuild, adjust, repair, etc., never ran
right.

Had one in my '67 GTO that was fine however, so I never touched it.

Eisboch

I agree! You would think that your carb is crapped up because of poor
performance, and rebuild it, and it'd run the exact same afterword! I
learned early in my gearhead days that the perfect fix for a Rochester
Quadrajet was a Holly 650 double pumper!

---------------------------------------------------------------

The '46 Ford street rod that I had with a 454 chevy had a Holly 650. I
liked the color coded springs that you could swap for different performance
settings.


Eisboch

wrote in message
...
On Wed, 6 May 2009 09:55:50 -0400, "Eisboch"
wrote:

That Rochester quadrajet (aka "quadrabog) has got to be the most
miserable
carburetor to rebuild ever designed. Had one on a boat that despite the
best efforts of several people to rebuild, adjust, repair, etc., never
ran
right.

Had one in my '67 GTO that was fine however, so I never touched it.

Eisboch

I had one in my Corvette that I couldn't get right, until I replaced
the float.


They had some orifices or holes that many recommended using epoxy to close
in order to get them to run properly. All I know is that if they were
"right" they were fine, but a bear to try and fix if screwed up.

Eisboch

"Vic Smith" wrote in message
...
On Tue, 5 May 2009 18:19:31 -0600, "SteveB"
wrote:

Went out to find my low speed jets on an 89 Merc 40. Was shining all over
around in there with a flashlight. Couldn't find them. Saw the plug on
top
of the oil injector tank was loose, and went in there to tighten it. Of
course, I only knocked it off, now have to take off the tank to find the
plug which had fallen into the abyss between the tank and the intake
manifold. Which I should have done in the first place to get to the
carbs.
As I look over the carbs after I have moved the tank, I notice there are
two
holes through the tank specifically aimed at the jet screws. Reachable
with
a thin blade long screwdriver.

HAH! Glad it was not a Ford, or I would have probably had to take off the
starter and loosen the motor mounts to do it. So, on the next cruise,
I'll
set the jets. Bottomed them out, and came out 1 1/2 turns for now.
Adjusted a couple of hoses that had kinks in them from being cut too long.

Hope to take it out this weekend.

Let us know how that adjustment works out. Personally, I've never had
any luck with carb idle jet screws, 2 or 4 barrel, Carter, Holley or
Rochester.
In my experience they come adjusted to the correct turnout from the
factory or rebuilder, so when you bottom them and turn them out the
correct turns you're back where you started.
And I don't recall any other adjustment being better than that.
Then you've got the throttle idle screw itself to tinker with, which
affects RPM and ear test.
I have had some engines idle better with the screws further out than
spec, but then you're risking washing the cylinders with a over rich
mixture.
IMO without an exhaust gas analyser idle jet screws are a losing
battle.
I'm glad I've tinkered with my last carb long ago.
Geez, I remember in '76 I could get rebuilt 2-bbl Rochester for 25
bucks, a quad for 50. By '90 I couldn't find a Rochester quadrajet
for my 350ci for less than about 400 bucks.
I settled for tinkering and a minor gallop.
Balancing dual carbs is an even bigger PITA. You really need air flow
meters. But maybe I'm just too "perfectionist" and carbed engines
don't allow for that.

--Vic

I've had decent luck, and have a good ear for them. My plan is to slightly
increase the idle, then adjust until the idle starts crapping out, then back
off until if smoothes out of picks up. It's hard to describe, but it's a
combination of getting it to run rough and smooth, and counting turns so you
can put it half way inbetween. Whatever is going to be better than what it
was. It was continuously stalling at low speeds.

Steve