The Stovebolt Site Forums The Shop Area Engine Shop Rochester "b" #7004600, what size metering jet?

Hey guys (and gals), I was wondering if anyone knows the metering jet size for a Rochester "b" #7004600. I am looking for the oem size. I have received input from 51bolt, that he uses a .051. Anybody know if that is the oem size? If it helps any, I'm at sea level in a sub tropical climate most (9 months) of the year. Thanks to all. Mannymoejax

Can't help you Manny, but a guy named Carb King should be along shortly.
Mark

Thanks Mark, I'll wait for the king. Martin

I guess I should have asked, what size jet for a Rochester #7004475? #7004600 is actually a unit Part # that would incl. carb (7004475), gasket and Insulator. This is all new to me, so sorry for any miss communication. M.

I'll try to help while we wait for the king. You didn't say what size engine it is but the 216 usually has .052-.053. The 235 is about .058. I had to drill mine out to .062 to get it to run right.

I'll try to help while we wait for the king. You didn't say what size engine it is but the 216 usually has .052-.053. The 235 is about .058. I had to drill mine out to .062 to get it to run right.

My engine is a stock 216ci. I don't believe it matters but I think it's the original 1953 block and head my truck came with. I was also wondering if a #51 Rochester metering jet is in fact .051?

Thx. M.

The original jet was a 52 (0.052). If you live in an area where our benevolent government has mandated E-10 fuel, you might try a 53 (0.053).

Jon.

Thanks. I guess I should have added that the truck seems to be running way too rich. Black inside the tail pipe and all. Yeah, I'm in FLA and 10% ethanol seems to be commonplace unless I visit a marina.

Manny,
According to my manual (1951) 216, the standard is .051, one step lean is .050 and one step rich is .052. Can you tell us what you have?
Mark

You can lower the float just a touch to lean out a carb.
I would go through it and give it a good cleaning, set the timing a few degree higher then stock, check the dwell, and clean the plugs all before going into the metering changes. One jet size either way will not make a drastic change. Black pipe and soot is a sign of bigger problems or tune up out of whack.
E-10 should lean it a jet size all by itself, and as stated above, you really should be one step higher if running any fuel thats not 100% pure gasoline.

joe


Joe

Very rich running is often caused by a weak ignition.

However, if the vehicle is equiped with a Rochester "B", very rich running is normally caused by warped castings which creates an internal vacuum leak resulting in the power valve always being open.

However, the white tailpipe which many of us knew from childhood to be an indication of a well-tuned engine actually was lead deposits inside the tailpipe. The tailpipe of a vehicle running todays no-lead fuel is black. However, it should not be "sooty".

If the engine is excessively rich, an observer behind the vehicle might guess you are "fogging" for mosquitos.

Jon.

Don't know yet what jet I have, I assume (you know what they say about assume) I have the stock spec. I'll have to diss assemble carb to find out. I can tell you it's running rich (black soot at tail pipe). Thanks to everyone. Don't know what I'd do without friends like you guys (and gals)! M.

What can I do if it is a weak ignition? M.

I have a .051 in my Rochester on my 216. A .058 makes more power but turns the plugs a sooty black.

Manny,
Let's see what jet you have and if your floats are set correctly. As long as you have the top off, blow out every port you can find to clear any junk from the idle circuit. See if there is any change. By the way, have you put a kit in this carb? If not, it may be a place to start.
Let us know.
Mark

I would make sure your vacuum advance is working.

if it's running way too rich, make sure the vacuum hole on the bottom of the carb is not blocked off by an incorrect spacer or base gasket. This will cause the carb to run too rich, even with the correct jetting

Weak ignition comes from coils giving out due to age or heat, dirty or worn points, bad condenser, worn distributor, old wires to the coil, worn ignition switch, pretty much anything to do with engine electrical. Start with the basic's, distributor tune up. Then work back to the coil, and from there back to the ignition switch. Check wires and terminals and any contact points. Also, be sure the ignition switch is providing full battery voltage to the ignition circuit. For testing, you can wire straight from battery to the coil, bypassing the whole key circuit. Late timing effects the fuel burn in the cylinders so check that while you are at it. A little advanced will help. Short drives with the resister wires bypassed to the coil will not burn out the points, may over a long period it would, but not short tests. This will provide maximum voltage to the coil.

Joe

Well everybody chimed in and I can't tell how much I appreciate all the good advice. Some stuff came up I had to deal with, so I am embarrassed to say I haven't been able to get to it yet. I did do some interesting reading and I did purchase a carb kit. OK, almost 2 years ago I bought my truck. Unbeknownst to me, it seems the carb was installed with both a riser and a gasket below the throttle body. So I did some research, and found where GM says that my '53 Chevy 216 motor should have a riser under the throttle body but not a gasket. The book goes further and says some models should have a gasket and not a riser, in fact, it says the two should NOT be used concurrently. It also says that if you do, the power piston of the carb will always be in the open position causing the engine to run rich and rough. Now I haven't tested this info yet, but my truck does have both concurrently, and it is running rough and rich, so there could be a connection. I guess it's true what they say about the last place you look. This info was right there, but I never knew. Thanks to everybody, I will update very soon.

Geskets on both sides of the spacer are fine but like Bolter says, make sure there is a passage from the hole in the bottom of the carb to the inlet chamber. It must get vacuum like the book says for the power valve to work. You may have to cut a little hunk out of the gasket.

yes, rochester's stamped sizes are that size in thousandths of an inch. example stamped 51 on jet is the diameter of .051"