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Calling Small Block Chevy experts

You sure the top of the carb is screwed on snug? not kidding there.

Sudden Sooty Plug Syndrome (SSPS) is a serious public issue. conventions need to be convened. protocals must be prototyped in triplicate. mandates must be...well, I'm not going to go there..so lets round up the usual suspects...aaaand...
dude. unless it's some random chunk of varnish that got stuck in the float needle seat or something obvious, I'm going with re-building a spreadbore for a truck is a waste of time, unless you've got time to waste. get an edelbrock and a square bore holley 600 with a vacuum secondary. made to optimize stock cam profile. end of problem.
http://www.jegs.com/i/Holley/510/0-80457S/10002/-1

You could also source a used 2barrel 350 cfm rig, but then you are back in old carb-land.

How a 68 mouse got an HEI I'm not going to ask...

http://www.summitracing.com/parts/edl-2701?seid=srese1&gclid=CIH-yYWA2cMCFZNafgodozsAzw
 
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I didn't read all the responses, but I had similar issues once. Turned out to be the HEI's amplifier/ignition module (as knucklehead kids we called it the "California piece"). You can quickly diagnose by quickly swapping for another. As most Chevy guys, we always had extra parts lying around to pillage.


Edit: Took the time to read. Now I'm just an older knucklehead who should take the time to read. Sounds like it's not your ignition. Good luck.
 
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catch2otwo said:
haha thanks guys. so old plugs were sooty black but i attributed that to a way over due air filter. Looked into the top of the carb and didnt notice much. It was dirty so I was planning a rebuild at some point, just haven't gotten around to it yet.

Just now got back from taking my dog to the vet. San pablo to oakland and back. Truck runs like shit, wont idle anymore. Pulled the air cleaner off, secondaries (the two bores closest to the cab) were dripping fuel even with the truck off. Turned the truck on to move it to the side of the driveway. Re-opened hood, gas is more than dripping from the same area and now its "overflowing" out of the carb.

Looks like its rebuild time. Guess it moved up a few spots on my priority list.
Click to expand...

It's probably just the float/needle/seat for the secondary fuel bowl
 
OP:
Be sure you dump the oil now. It's likely getting diluted with gas and that will take out a cam and lifters in short order.
 
JesasaurusRex said:
Why not check the fuel pressure before digging into the carb?
Click to expand...

I will have to look into the procedure. But just curious whats your reasoning for thinking the mechanical pump would suddenly over pressurize the system? I thought they were constant pressure. My pump is mounted on the side of the block.

frozenduc said:
OP:
Be sure you dump the oil now. It's likely getting diluted with gas and that will take out a cam and lifters in short order.
Click to expand...

Copy that- didn't know about that thanks

channelcat said:
You sure the top of the carb is screwed on snug? not kidding there.

Sudden Sooty Plug Syndrome (SSPS) is a serious public issue. conventions need to be convened. protocals must be prototyped in triplicate. mandates must be...well, I'm not going to go there..so lets round up the usual suspects...aaaand...
dude. unless it's some random chunk of varnish that got stuck in the float needle seat or something obvious, I'm going with re-building a spreadbore for a truck is a waste of time, unless you've got time to waste. get an edelbrock and a square bore holley 600 with a vacuum secondary. made to optimize stock cam profile. end of problem.
http://www.jegs.com/i/Holley/510/0-80457S/10002/-1

You could also source a used 2barrel 350 cfm rig, but then you are back in old carb-land.

How a 68 mouse got an HEI I'm not going to ask...

http://www.summitracing.com/parts/edl-2701?seid=srese1&gclid=CIH-yYWA2cMCFZNafgodozsAzw
Click to expand...

Im not buying a new carb for this. The truck is getting a motor swap after we move so the sbc will get yanked anyway

augustiron said:
the only proper fix is an LS swap
Click to expand...

Nah, no lsx for me. Cummins power!

fawndog said:
It's probably just the float/needle/seat for the secondary fuel bowl
Click to expand...

Thats what it is looking like.
 
channelcat said:
You sure the top of the carb is screwed on snug? not kidding there.

Sudden Sooty Plug Syndrome (SSPS) is a serious public issue. conventions need to be convened. protocals must be prototyped in triplicate. mandates must be...well, I'm not going to go there..so lets round up the usual suspects...aaaand...
dude. unless it's some random chunk of varnish that got stuck in the float needle seat or something obvious, I'm going with re-building a spreadbore for a truck is a waste of time, unless you've got time to waste. get an edelbrock and a square bore holley 600 with a vacuum secondary. made to optimize stock cam profile. end of problem.
http://www.jegs.com/i/Holley/510/0-80457S/10002/-1

You could also source a used 2barrel 350 cfm rig, but then you are back in old carb-land.

How a 68 mouse got an HEI I'm not going to ask...

http://www.summitracing.com/parts/edl-2701?seid=srese1&gclid=CIH-yYWA2cMCFZNafgodozsAzw
Click to expand...
My '73 C20 has a 350/350 as well, and it also has HEI when it shouldn't. It's a good upgrade from points...

Of course, I have a 750 Edelbrock on mine, which is quite a bit larger than I'd like. 600 or 650 would be reasonably for a truck motor (probably making 250-275, plenty to smoke the tires). Then again, I'm also planning on a swap so I'm not gonna spend the money on a carb.
 
catch2otwo said:
I will have to look into the procedure. But just curious whats your reasoning for thinking the mechanical pump would suddenly over pressurize the system? I thought they were constant pressure. My pump is mounted on the side of the block.
Click to expand...

They're not constant pressure, they're rpm dependent. That being said it's lowest at idle. I guessed you had an electric pump and thought there was apossibility somebody messed with the regulator. Fuel pressures easier to check than pulling acarb apart is why i suggested doing that first.
 
JesasaurusRex said:
They're not constant pressure, they're rpm dependent. That being said it's lowest at idle. I guessed you had an electric pump and thought there was apossibility somebody messed with the regulator. Fuel pressures easier to check than pulling acarb apart is why i suggested doing that first.
Click to expand...

Rpm based makes sense. I'll grab a gauge from work and rig something up. Might as well check while j have things apart.
 
scootergmc said:
I didn't read all the responses, but I had similar issues once. Turned out to be the HEI's amplifier/ignition module (as knucklehead kids we called it the "California piece"). You can quickly diagnose by quickly swapping for another. As most Chevy guys, we always had extra parts lying around to pillage.


Edit: Took the time to read. Now I'm just an older knucklehead who should take the time to read. Sounds like it's not your ignition. Good luck.
Click to expand...

lol
 
If there's no regulator I wouldn't bother. Pull the bowls off the thing and take a look at the needle seat like somebody else mentioned.
 
Charles R said:
Pretty much any auto parts place should have generic Holley kits. this place may be more knowledgeable, and migh have some of the higher quality kits
http://www.gotellispeedshop.com/
Click to expand...


Thanks for the this recomendation. Stopped by there this afternoon and picked up a kit. Great service, old timer behind the counter seemed very knowlegeable and willing to give advice. :thumbup
 
Holley could be the power valve.
 
Have you checked for vacuum leaks? Deceleration lean backfire, rough idle, the black smoke throws me off a bit, but I am thinking vacuum.
 
BEN-ZX-14 said:
Have you checked for vacuum leaks? Deceleration lean backfire, rough idle, the black smoke throws me off a bit, but I am thinking vacuum.
Click to expand...

vacuum is always a lovely diag/fix, but he already said its puking gas...
 
All of the ethanol in the fuel these days really doesn't sit well with older carbs. The Carter AFB in my dad's '70 Chevelle (350 SBC, though with typical modern Vortec stuff) certainly doesn't like it... After a rebuild/clean, it runs well for about a year until it begins to run like shit again. Solution? We're ditching carbs and going EFI with a FAST throttle body backed with Megasquirt. Lots of other changes (fuel tank etc) need to be swapped over to do it properly, but it's nice to have a car that is tunable over the entire range, yet starts every time, no matter the weather.
 
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