Carb Kits

[campjer]

Anyone know of a supplier for Rochester 4-Jet (Quadrajet) carbs from 1959? I don't have a carb # as they only printed them on the copper tags and never stamped the carbs (and obviously someone has removed them! argh!)

Alternatively - anyone know where there are any NOS Rochester Quadrajet carbs?

[Wood Commander]

Edelbrock got the rights and tooling to build Q- jet carbs brand new, but I think they stopped building them now. You might be able to find leftover stock somewhere.

However, a 4- jet is not a Q- jet! The 4- jet is the predecessor to the Q- jet. One of the differences is that the 4- jet has all four barrels of the same size. Whereas the Q- jet is a "spread bore" and has smaller primaries and larger secondaries.

The Q- jet is a complicated carb but works well when used in the right application and tuned correctly. it has the added advantage of being more economical to operate if you can resist kicking the back two barrels in, because the front two barrels are actually smaller than the barrels on a two- barrel carb.
Due to it's spread bore design, you would have to use an adapter plate turned upside down to use a Q- jet on a square flange manifold. Or you could get a replacement Q- jet, spread bore- type manifold.

4- jets are also good carbs and rebuild kits are still available for them. They came stock on some Chris Craft F engines. I've run 4- jets on my own boats before and found them to be a good performing and economical carb. And they are less complicated to rebuild than a Q- jet.

I believe that at some point in the production of Q- jets, Coast Guard regs started calling for special marine carbs.
From what I can tell, marine Q- jets such as those found on Mercruiser engines, have a special tube going through the air cleaner/flame arrestor flange on the top of the housing for an overflow vent from the mechanical fuel pump to vent into the carb in case of a fuel pump diaghram failure. This would prevent fuel dumping into either the engine crankcase or the boat's bilge, and causing a pesky and unpleasant explosion on board your boat!

There is a great need for safety and caution in this area!

I don't think that there are any other special features of a marine Q- jet, but I don't know that for sure.
If anyone does know about any other differences between marine Q- jets or any other carbs and their automotive counterparts, please let us know!

[campjer]

Thanks Bret - I was curious if the 4-Jet and Quadrajet was actually the same carb or not. What I have are the original 4-Jet Carbs.

I was able to find a general purpose rebuild kit with everything matching perfectly except the plunger (my old one was fine anyways). They are a pretty easy carb to rebuild - one doesn't need a degree in rocket science, or even grade 9 science to properly rebuild these.

I'll do some more digging in attempts to get another kit - though from what I understand, I received the last one in the Province of Ontario. Think I'll have to stock up on a few if I find a supplier!

Are you saying that the 4-Jet's do not have a different bore size between the front and rear barrels - as mine definitely appear different in diameter.

...and thanks for the safety tip regarding the flame arrestor flange tubing - I'm 99% sure mine has no such thing but if I upgrade to Quadrajets - I'll ensure the model has this improvement.

[Ocean Scout]

Try Danny Cook-former engineer CC Engine Div, great supply of parts and expertise 740-446-3339.