Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

The real truth about fixing 'nozzle drip'

<< < (2/3) > >>

Cliff Ruggles:
Marine carburetors are required to have an approved flame arrestor in place, that's about all that a USCG Boarding Officer is every going to look at on your engine.  They will check to make sure that you have a working ventilation fan in an enclosed engine compartment.  At least in regards to engine room complicance on small I/O watercraft.  Of course vessels are catagorized by length, and type, so make sure you check specific regulations that apply to your vessel.

In any case, we recomend to install bronze shaft bushings on all builds.  The factory clearances between the primary shaft and throttle body are relatively "loose", and they only get worse with time. 

There is no need to install bushings on the secondary shaft, as the throttle plates are designed to be self centering and seal off when closed.  The shaft must "float" slightly for this to happen.  If/when secondary shaft bushings are installed, this more often than not tightens up the shaft to a point where the throttle plates will NOT seal off effectvely.......Cliff

makomark:
Actually, the knowledge of most of the 'kids' that perform this role is pretty high. My query was based more on USCG compliance (read this as insurance/investigator/surveyor)  than a boarding related check.

I know the carb has at least two requirements on it - the vents must 'drip ' internally (the infamous holley inverted J tubes) and if flooded, must not permit more than 5cc outflow in xx minutes (i can remember the specific value). The second item is the root for 'stabbing and slabbing'. BTW, these are independent of the vessel size; they are based solely on the fact that there is a permanently installed engine (inboard or I/O).

I'm sure you would have seen any difference between a true marine Qjet and the auto types when disassembling the base plate. If you haven't noted any, then I'd suspect my info doesn't apply to the qjets.

thanks, again,     mark

makomark:
Correction - the phrase is "grooved and slabbed". I found this link:

http://www.boatsunlimitedny.com/tt_marinecarb.php

which has the same text as one of my old Holley catalogs.

If I get time, I'd take out the shaft from an old baseplate that is from the marine Qjet and post a picture. Hopefully, having a reference, one can determine if Rochester did anything different.

bigvette1:
Like to comment and jump on the issue of "dripping fuel" at the boosters...
1st - Is this acceptable to drip at idle???

2nd - The carb is new.y rebuilt so that should not be an issue.

3rd - Vacuum at idle is 17", the CR is 9.25:1 an the cam is a Crane 218/218,  LCL is 112 and lift is .500 so that appears not to be very radical.

Next as a note -- the carb at idle is sucking enoromus amounts of air - loud to say the least.  As a point to prove, I installed an Edlebroch 1901 that I had on the shelf and the amount of sucking air is nothing compared to the carb we are questioning.  The vacuum at idle is the same 17-18". 

Last, if this is not a normal condition and assuming the float is set right - where do I go to approach this issue.

All comments are welcomed.  Thanks

bigvette1:
Let me add something that maybe useful.  After running the car for sometime and pulling the carb off the floor of the intake manifold is wet with gas, maybe even some oil being sucked in.  I thought this was supporsed to be dry for all purposes. 

FYI

Navigation

[0] Message Index

[#] Next page

[*] Previous page