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Sand in carburetor

FM Former Member
My speedster is on the road-almost-and I want to thank all of you guys for your help. I borrowed a few of your ideas and outright stole some of them. I've only asked a few questions during my build, but I've lurked, listened and read everything here, and your knowledge and insight was hugely helpful.

Now I have a technical issue that is keeping from getting on the road. I was running very lean, and couldn't get the #1 cylinder to misfire, so I got new jets. When I pulled the carb apart, there was about a teaspoon of what looks like sand in the float bowls. I cleaned the carb thoroughly, rejetted and set the carbs, per the knowledge section. At idle it was running great, but when I went to take it for a spin, it almost immediatly started missing and eventually quit altogether. When I pulled the #1 idle jet, it was plugged with the sand again. The other idle jets were clear.

Some details:

2187cc Scat Zero mile longblock
35.5x40 Valves
Dual 44 Webers
55 idle jets
155 main jets
200 air correction jet
F11 emulsion tube
1 5/8" A1 Sidwinder exhaust

I'm running a CB Performance rotary fuel pump with a filter before the pump and a second filter before the carbs with 3/8" fuel line.

The carb for #3 and #4 cylinders is running almost perfect and is clean.

Any thoughts on where the sand is coming from or came from, and how to solve the problem? I'm in Sachse, TX and there is a little local show I'd like to go to tomorrow night. By the way, I'm also in for the Ennis run with the Texas and Oklahoma guys, if I can get the motor running!
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FM Former Member
My speedster is on the road-almost-and I want to thank all of you guys for your help. I borrowed a few of your ideas and outright stole some of them. I've only asked a few questions during my build, but I've lurked, listened and read everything here, and your knowledge and insight was hugely helpful.

Now I have a technical issue that is keeping from getting on the road. I was running very lean, and couldn't get the #1 cylinder to misfire, so I got new jets. When I pulled the carb apart, there was about a teaspoon of what looks like sand in the float bowls. I cleaned the carb thoroughly, rejetted and set the carbs, per the knowledge section. At idle it was running great, but when I went to take it for a spin, it almost immediatly started missing and eventually quit altogether. When I pulled the #1 idle jet, it was plugged with the sand again. The other idle jets were clear.

Some details:

2187cc Scat Zero mile longblock
35.5x40 Valves
Dual 44 Webers
55 idle jets
155 main jets
200 air correction jet
F11 emulsion tube
1 5/8" A1 Sidwinder exhaust

I'm running a CB Performance rotary fuel pump with a filter before the pump and a second filter before the carbs with 3/8" fuel line.

The carb for #3 and #4 cylinders is running almost perfect and is clean.

Any thoughts on where the sand is coming from or came from, and how to solve the problem? I'm in Sachse, TX and there is a little local show I'd like to go to tomorrow night. By the way, I'm also in for the Ennis run with the Texas and Oklahoma guys, if I can get the motor running!
Alan MerklinAlan MerklinDrclock - Elkins, West Virginia Supporting Member
Since you are getting a huge amount of dirt, a complete fuel system disassembly from the tank on back ie. cleaning the tank, replacing the tank sock, hoses, filter(s) replace the fuel pump and a complete tear down of the carbs are in order to correct the problem, anything less and you will continue with fuel related problems. Be sure to add a fine amount of clean grease along the upper and lower air filter rubber edges to seal any minute gaps. A long day spent correcting this will equate into reliable driving.
FM Former Member
Also, if your car is fitted with one of the little really cute brass insert fuel filters (inside looks like tiny brass balls stuck together) - throw it away and get a good filte. When those brass filters break down, little round bits go into your fuel system and plug up critical parts. I've been left stranded by one of those feeding an Edelbrock in an SBC car. Never again.

angela
FM Former Member
I'm working through the system. The two filters I have, one before the pump, the other just before the Y-block feeding the carbs, are supposted to be pretty good ones. They cost me $35 each. This was the problem I was most trying to avoid! The wierd thing is that it is only one carb. The other is perfectly clean. The sand looks like it came from the casting mold. I think the carb bodies are sand cast aluminum. It almost looks like they just didn't clean it out very well when they broke it out of the mold. It seems like both carbs would be affected if it were sediment from the tank or the fuel lines. It also seems like even a cheap filter would catch particles this big. I'll let you know what I find.
FM Former Member
Rod,
Just read your last post and you hit the nail on the head. If you have new carbs you have a carb that has sand from the sand casting - not nice stuff to get in the engine. If you have old used carbs you got a carb that is metal fatique and is braking down - what does the fuel bowl look like - is it pitted? If so that is the problem. As you stated the other carb is fine so, I agree with you it can't be the fuel system from the tank this would affect both carbs. Recommend you replace the faulty carb or complete take it apart and clean it with air pressure or anything else you can send through all the little orifices. Good Luck.
FM Former Member
Never doubt Master Merklin. I drained the fuel system. The front filter was clogged, and all kinds of crud came out of the tank. I think that was seriously affecting fuel flow and contributing to the stuff in the carb. However, it is a brand new carb, and I think some of the sand was from the casting, so I'm chalking it up to a combination of the two.

Good new is it's running almost perfect now.

Thanks for the help.
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