Random carburetor annoyances

[mrltd]

and accel pump cams, squirters, etc... Carbs aren't all that cheap to tune..unless you do lots of em and have the parts sitting around.


For the most part though, once they are dialed in they are good. Our 4160 was pretty damn good once it was dialed in, the edelbrock has been as good or better though.

[1987cp]

Sounds then like AFBs really are quite cheap by comparison, and not only in initial purchase price. The $37 #1487 tuning kit for the 1406 comes with a full selection of what's "normally" needed to cover a pretty wide range of tuning contingencies, including five levels of power enrichment springs and nine possible primary calibrations, and no need to order extra parts unless different squirters or fairly radical metering changes are needed. The $50 #1486 for the 1404 allows 12 different primary calibrations, and the $55 #1479 for the 1405 includes 16 primary metering possibilities!

[1987cp]

This is interesting, 500cfm Quadrabog remanufactured by Summit:

http://www.summitracing.com/parts/SUM-BC-Q9M43/

What does it really mean for it to be a "marine" versus "automotive" carb?

[Lincolnmania]

it has been many years since i had a carbed ford, but i always ran holley 600's with excellent success........my 78 cougar 351w used to get 21 to 25 mpg highway.....city mileage was so bad i'm embarrsed to mention, but i used to drive it wot light to light most of the time and it had a 2.73 rear......gas was under a buck a gallon back then, and i didnt care lol
i had a holley 600 on the 351c 2v in my 73 cougar also......i used to get 19 highway with that car.....and around 12 city.......2.73 gears also

[1987cp]

Not bad at all!!! I like the idea of better fuel economy. Should be good for tailpipe emissions and sparkplug longevity, too.

Another thing I should sort out before I have money to buy another carb (though that might be a while) is, what are the exact advantages of having a small BG versus a regular Holley 4150? :p (dang, I'm full of randomly varied and occasionally off-the-wall questions!)

[gadget73]

What does it really mean for it to be a "marine" versus "automotive" carb?

Primary and only obvious difference is the fuel bowl vent setup. On a typical carb, its just a tube sticking straight up, so if the thing floods it sprays gas upward. On a marine carb, its turned downward so it floods the motor out instead of spraying gas upward. There is also a connection between the fuel pump and carb throat so that if the pump diaphram blows, it pumps fuel into the carb instead of the bilge. Other than that, its just in the tuning, but that varies engine to engine anyhow so its not hugely relavent. Choke linkage may be different, usually there is no fast idle cam on a boat. Also, you'll pay 2-3x as much for that USCG approval number on the side.

Tuning a marine carb is actually easier than a car, mostly because you really don't need to be good with a carb. It needs to idle, it needs to run good at WOT, and it needs to run good around 2/3 throttle. Going from idle to WOT needs to be mostly smooth and thats it. You don't need all that fine tuning for constantly varible throttle positions like on a car. Most marine motors will have the throttle in the same position for the vast majority of their life, so as long as it runs good there, nobody cares.

[P72Ford]

Seneeb and Rick have a Qjet on the race box. Not sure if its a spread bore intake, or an adapter on a square bore intake.

There is a 9 second Chevy II at the track I go to, that uses a Qjet. Most of the people that piss on them don't know how to work on them. I have never fiddled with them, but there is one on our wagon, and on my dad's LeSabre. Neither car has a powerhouse engine, but the initial throttle response is much better than it is in my car, with a 1406.

[1987cp]

That does make some sense; it appears that the 1406's primaries are quite huge compared to a Q-jet.


Bilge? http://en.wikipedia.org/wiki/File:Bilge_well.jpg
Yech.....

[gadget73]

Rick has a spread to square adapter on the race box.

Most bilges don't look quite that horrible. Its just a generic term for the marine equivalent of the basement. Its the area between the deck and the hull where the bracing, and whatever else needs to be stashed lives.

[1987cp]

Good info about the adapter, as I'd assumed they were only for running a squarebore on a spreadbore intake and didn't have sufficient clearance for the throttle butterflies. That'd mean I could theoretically try a Quadrajet while still retaining my current Edelbrock 2121 (302) or 2181 (351) intakes. I've got a book on Rochesters coming to my local library through the MELcat system, as well as I think three on Holleys! :banana:

[Pirate]

Good info about the adapter, as I'd assumed they were only for running a squarebore on a spreadbore intake and didn't have sufficient clearance for the throttle butterflies. That'd mean I could theoretically try a Quadrajet while still retaining my current Edelbrock 2121 (302) or 2181 (351) intakes. I've got a book on Rochesters coming to my local library through the MELcat system, as well as I think three on Holleys! :banana:

If you're going to try this, get the open Q-jet adapter, and skip the 4-hole unit. The 4-hole adapter/spacer is a bit of an airflow tragedy.

In addition, if you're going to look into doing this, there are some things you should know:

1. Q-jets occasionally have issues with the bottom of the float bowls having cracks and seeping fuel out while sitting.

2. No rebuild is considered 'proper' unless you get bushings installed on the throttle shafts, where they go into the baseplate. These carbs tend to wear out the hole around the throttle shafts (especially the primary), and cause all kinds of driveability problems. The last time I had it done, it cost me around $100....but this has been a few years ago.

3. There are a few different types of castings....the two basic units are the '4M' castings (pre-smogger) and 'M4' (smogger units), the easiest way to tell them apart is to look at how the fuel goes into the float bowl; the early 4M goes straight into the front, while the M4 (and related) goes into the front, but angled 90 degrees to the right.

More later if I can remember.

[P72Ford]

Michael, if you want a Qjet core, we have tons of them laying around. I know we have some where the fuel enters straight into the front... not sure about all of them though.

[1987cp]

Hmmm......... I'll have to let you know on that once I've read this book I'm getting and done a little thinking!

Do you know whether it's hard to identify a cracked main body as Pirate warns against?

[gadget73]

Start it, then shut the motor down. OPen the throttle plate and see if a puddle forms in the intake. Had one do that, couldn't see the crack when I took it apart but it dumped a load of fuel down the motor whenever it was shut down. I guess you could just pull the top off and fill the bowl up. If it dumps out the bottom, there is a problem.

[Nathan in MI]

I've got one you can have, too - sitting at my mom and dad's house. They'll be out this way July 4th weekend, so they can bring it out if you want it. No idea what casting it is, or the condition of it, but I'm fairly sure it's complete.