sdowney717

I have a 17080213 that I am rebuilding
It has a 1/4 inch hose hookup on top of the airhorn on the secondary side and I would really like to know what the purpose would be, is it possibly for a fuel pump vent (clear sight line like when the pump has failed it will pump gas to the carb instead of dumping in the bilge idea) as you would find in a boat?

And I would like to add the little rubber and metal washer to the booster pump shaft in the air horn, any ideas on what could be fabricated, part number to get, etc? The air horn has the recess but never had one staked into it.

Also I have a 17085432 I am rebuilding. I noticed this one has no plastic insert in the aneroid cavity like the other one. Is it supposed to have one and what will happen if it does not?
And on that one, there was no primary side choke pull off, only a secondary. The secondary pull off was bad but I have a good primary choke pull off I can use on it. should be ok? Can you repair those rubber diapragms by prying them apart?

sdowney717

Yes, that is what it is, for M4M series carbs, it collects fuel and or vapor from the fuel pump in a marine carb. marine carbs also do not have the front bowl vent to a cannister, although it might have been a good idea to collect vapors.
I do think new EPA standards for boats involve adding in charcoal cannisters instead of overboard open tank venting to the outside of the boat.
On a 4M series, a port is drilled on the left front going into the front of the venturi for a fuel pump overflow vent. That hole would be right above the fuel inlet.

In this picture you can see the drilled threaded port. I have also seen them with pressed in steel tubes, so I suppose this one was modified.

sofakingdom

iTrader: (1)

That fitting has nothing to do with "marine".

It is the clean air supply to the choke. The choke stat is constantly heated up by the 12V on the electric supply, and cooled down by air flowing through it. In normal operation heating wins. The cooling prevents the heater from burning up. In many carbs this is all accomplished by internal passages in the casting, but in some it's handled by a line that runs from that fitting (which doesn't have vacuum; it's WELL above the throttles) to the choke stat housing.

If you don't need it, cap it.

17080213 is a part # for a 1982-up Chevrolet car carb. Not a Camaro or Firebird, more likely a full-size. Doubt it has anything to do with current EPA standards for boats. No "features from the future". Although you're right, boat standards have tightened up CONSIDERABLY; which is probably just as well, I've seen some SERIOUS fires at the marina caused by gas overflowing from through-hull vents.

sdowney717

thanks for the response.
So if it is not for the pump, then where does the fuel pump vent line go on the M4M series of carbs? I was looking at pictures of marine M4M and many have that fitting and I have a sense that is what they want you to use even if not originally made for it.
I know some of the flame arrestors have this connection built into their sides.

here is a couple of pictures showing these connections.

Apeiron

Are you trying to put this on a boat?

sdowney717

Not this one. But I did email some carb rebuilders and asked about this hookup and they said the "carb will be labeled for the hookup"
So they wont outright tell me and now I want to know.

I think the marine improvements yield safer carbs than stock anyway.

So far my study has found that
Marine carbs have
no canister bowl vent hookup for emissions purposes,
J tubes on the main vent or a slant with a liguid fuel barrier,
may or may not have a fuel pump vent hookup,
may be set richer since the motor is under heavy load,
might have throttle shaft seals some Holleys do have teflon seals or grooved shafts, Quads dont.
generally have rebushed throttle shafts
cant leak more than 0.5 cc of fuel in 30 seconds.

some people talk about slabbed shafts or upside down shafts, that make little sense to me.

Looking at that main vent, I dont even see why it is needed at all. The air horn is vented in the center. Why not just get rid of the tube vent sticking up?
the secondary rods and the long slot on top of the float have plenty of air room for a vent.

five7kid

iTrader: (14)

What year car are you dealing with? www.carbs.net says 17080213 is an '80-'85 truck carb. It doesn't come up with anything directly for 17085432, their "decoder" page doesn't make any sense - are you sure you got the # right?

On my '82 LG4, that airhorn fitting was used for the EGR solenoid fresh air (provides filtered air to the solenoid). On my '86 LG4, that fitting didn't exist.

sdowney717

I will recheck the numbers, the engine is a 1975 350 Chevy Blazer

I picked up 2 quadrajet carbs for parts to get one to work.

So I stripped them down, re bushed the primary shafts, cleaned them up nicely and test fired them on the motor.

The newer one 17085432 was supposedly a dodge truck 360
The older one 17080213 a Chevy truck

They ran very differently. The 17080213 idles extremely well, no nozzle drip but stumbles and wants to die when the throttle is cracked open on the primaries about 1/4 inch. It will catch back again if you rapidly move the throttle and it will run the engine Ok, but the stumble is bad enough that the motor will die. Perhaps running out the idle jets some more?
or raise the float level?

The 17085432 idles kinda poorly, wants to die at idle, if you lower down the throttle plates, seems to have a nozzle drip but has no stumble at all, open the throttle and the engine roars, it runs very well except for the idle quality.

Both carbs I set the float to 3/8. I observed the metering rod piston as they were running (in the driveway) and neither one ever came up. The engine is of course not under a load, so the vacuum wont drop and allow it up, so I assume that is normal?

So I am kinda wondering if 17080213 needs the float raised a little and perhaps 17085432 needs it lowered a little. or something else?
The 17085432 perhaps needs more idle fuel, It is definitely affected by the mixture needles. I also dont think I had it sealed well to the manifold, so I need to play around with it some more and see what happens.

I was impressed with how well 17085432 responded to the throttle.
So any ideas?

Dodge truck on the 17085432
1988-85 5.9L (360") R-4 M4ME 17085414, 17085415, 17085416, 17085432,
http://webcache.googleusercontent.co...&client=ubuntu

sdowney717

a search on nozzle drip found this
Nozzle drip is you look down the primary throat at idle and see fuel coming off the nozzles?
http://cliffshighperformance.com/sim...php?topic=26.0
So it sounds like I need to turn out the screws perhaps a lot more and then lower down the throttle plates. Turning them in and out does affect the engine

I looked at the numbers on 17080213. The jet size is 70, the primary rod is 49M

http://www.arkansaspontiacs.org/tech...ockyQ-jets.htm
reading this makes me wonder if the primary metering rods are on the small side, 70-49=21 thousands for the fuel flow
what is a good source to buy primary rods or can you?
would raising the float level from 3/8 to 5/16 help richen this or not?

After looking around, I am thinking the cheapest easiest thing is to drill out the jets.

EDIT adding this.
I took some plumbing silver solder, paste, and soldering gun.
I cleaned the jets in vinegar, rinsed them off.
put a little paste on the screw side hole.
soldered them shut. ( If you get too much it will flow to the other side, no worry hold it with a hemastat, heat it and shake off the excess. What you want is the hole blocked but you need the slot clear.
held jet lightly with pliers against flat plywood
used variable speed drill and made .073 hole
It worked great, the silver solder is a little tougher than lead solder.

Anyhow, got most of the issues sorted out, no nozzle drip, idling ok, etc...
Just need to run it and look at the plugs.