Thread: New 496 wont run??

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Hey guys, I need some help or guidance, I have a newly pro built 496 for my 1969 camaro, it was originally dyno’d by the company it was built by so it has been run. it got shipped to us and We installed it into my camaro, its mated to a 700r4. When I first got it running it would run but not very well. It had about 6 inch of vacuum at idle. And didn’t like off idle much and would be around 700rpms and the exhaust would burn your eyes. It has a quick fuel 830 carb with electric choke on it and a msd hei ignition with mech advance. I first tried to tweak the carb setting the floats and then the mixture screws but no change. I changed out the fuel with fresh 93 and started messing with the distributor. I found that the cap was damaged so I replaced the cap and rotor, set the engine on tdc, at 0 on the crank verified it was on the compression stroke but I can’t get the distributor to point exactly to #1 cylinder, I can get close but not exact when at zero on the crank. i have verified plug wires are in correct location with running order but now after all that it starts and now dies right away. I’ve pulled all plugs they were wet with fuel mostly likely, I cleaned them took the carb off and reset everything I could see but still nothing. I am new to old school carbs and distributors, I am use to obd stuff, please help thanks!

Also some more info :
I have tried to adjust the timing by turning the distributor both ways and still no change. I am
running a mechanical fuel pump. I am waiting for my fitting to come in so I can install a gauge and see my pressure. My carb has sight glasses so I can see the float levels and they are set to just below half way. Right now I have the card choke set to be closed when starting. I have tried to adjust the idle throttle screw from full closed to slightly open with no change. My issue is I am not sure if it’s a timing issue or fuel issue. Once I pulled the plugs and reset the timing the engine fires right up but then dies a few seconds later. I talked to the engine builder and they told me that I should have around 14 inches of vacuum at idle. The timing should be 13 initial and 36 total. Not sure if it’s running to rich and flooding the cylinders, when I bore scope number one I have a little fluid built up in the corner of the cylinder wall on top of the piston but I don’t know if that’s oil or fuel. I am assuming it’s fuel because the plug is wet and smells like fuel not oil. I set the idle mix screws to 1-1/4 turn out from stop which is even leaner then what it comes from the factory. I was told that the engine parred with this trans should run rich but I have a feeling it’s too rich but I don’t know how to find that out or what to look for.

What is your fuel pressure?

Can you close the idle mixture screws completely and the motor still run?

Thanks for the replies, I will try to attach photos. As for the set up on the carb I have been messing with it so much that I don’t know where anything is right now other then the floats and the mixture screws and I am pretty new at tuning a carb so that doesn’t help. I have the choke set right now closed with a low temp opening. I will try running the mixture screws in and see if that helps. EDC55227-E370-472F-922D-B43959C4D630.jpg

Originally Posted by DennyW

He said in his post that: I am waiting for my fitting to come in so I can install a gauge and see my pressure. My carb has sight glasses so I can see the float levels and they are set to just below half way.

No disrespect meant, but we know he has an excess idle fuel delivery problem. While I missed the "waiting on a gauge" part buried in solid block of text with no paragraph breaks, my bad. However, excessive fuel pressure is a #1 suspect and should be checked first. Regardless of where the sight glass shows on a motor that won't run long enough to adjust properly.

My second question "Can you close the idle mixture screws completely and the motor still run?" While an overly rich condition (burning eyes) could account for the low vacuum (6hg), it could also be indicative of a vacuum leak or transition slot over exposure and closing the idle screws can confirm this.

It has always been my intention to help.

Denny, I read your statement as sarcasm, and due to a bad day over reacted, for that I apologize and will edit my last sentence.

you are in Miami .. wire the choke wide open till you figure out what`s up ..unhook and block off the fuel line with the carb full and see if it clears up before it runs out of gas ..

I realize this is not exactly a Holley Carb, but it's based on one.

Fuel level on a Holley is set so the fuel level is at the BOTTOM of the sight hole. Above that level the carbs flood.

If it was me I think the first thing I would do is drop the fuel level (in hot climates with todays gas I have found running the level even a bit lower to compensate for fuel expansion also helps



.

Okay guys, I didn’t want to cause a fight, I just wanted some help. So back to what I have done, last night after the car sat all day I went and turned the mixture screws in all the way and backed them out only half a turn, opened the idle screw up a bit and tried to start it and it started instantly and ran at about 2200rpms. I let it run for about 4-5 mins and shut it off. Checked for leaks and then started it again, it was idling way too high so I closed the throttle screw a bit and it ended up dying again.

After that I pulled number one plug and Bork scopes the cylinder and found just a tiny bit of fluid built up on the piston. I opened the throttle a little bit and it ran again but at a higher rpm, I can’t get it to idle very well at regular idle but I didn’t have much time to let it run and warm up though.

Curious to hear what you fuel pressure is at idle when you get your fitting and gauge installed. Where do you have the vacuum hose to the distributor hooked up, ported or full vacuum? I ran a similar carb on an E-85 engine and ended up using a vacuum referenced fuel pressure regulator to keep the engine clean at idle, hard to say until you get an accurate pressure reading. Is this the same carb that was on it when dynoed? My two cents worth would be to get a fuel pressure gauge on it and see where the pressure is, check your needles and seats to make sure some little pieces of gunk aren't holding them open, then perhaps a fresh set of plugs. Cleaning them is good, but doesn't necessarily guarantee the plug is firing clean, once they've been fuel soaked they don't always get cured with just cleaning. Also, what are the plugs and what do you have them gapped at? You might also want to consider an initial timing at 10 or 12 degrees and back the total off to about 34 to get the initial run in on the engine. Just my 2 cents...

Thanks and yes I have watched that and other videos but most are on the same line as that one where it tells you what the adjustments are but not what they do and the effects on the carb and engine running performance when you do change them. I haven’t really found a video that really covers this well so I can really understand what I am changing inside that carb when I do those adjustments.

Originally Posted by Dave Severson

Curious to hear what you fuel pressure is at idle when you get your fitting and gauge installed. Where do you have the vacuum hose to the distributor hooked up, ported or full vacuum? I ran a similar carb on an E-85 engine and ended up using a vacuum referenced fuel pressure regulator to keep the engine clean at idle, hard to say until you get an accurate pressure reading. Is this the same carb that was on it when dynoed? My two cents worth would be to get a fuel pressure gauge on it and see where the pressure is, check your needles and seats to make sure some little pieces of gunk aren't holding them open, then perhaps a fresh set of plugs. Cleaning them is good, but doesn't necessarily guarantee the plug is firing clean, once they've been fuel soaked they don't always get cured with just cleaning. Also, what are the plugs and what do you have them gapped at? You might also want to consider an initial timing at 10 or 12 degrees and back the total off to about 34 to get the initial run in on the engine. Just my 2 cents...

I should have the fitting any day I am curious as well but truthfully the engine builders dyno’d the engine with everything on it already it was almost turn key, the carb, ignition, fuel pump, all came with it and had been run with it. Not that something can’t break in between then and now, I did find my distributor cap damaged which I replaced.

As for the plugs I have to measure them I don’t know what the gap is, but I agree it’s probably a good idea to change them.

Originally Posted by Mike P

I realize this is not exactly a Holley Carb, but it's based on one.

Fuel level on a Holley is set so the fuel level is at the BOTTOM of the sight hole. Above that level the carbs flood.

If it was me I think the first thing I would do is drop the fuel level (in hot climates with todays gas I have found running the level even a bit lower to compensate for fuel expansion also helps



.

Yes I would agree but I read the manufacture information on this carb setup and they state that seeing it has the sight glass you should set the float level as a base where you can see half in the sight glass.

With only 6hg vacuum, I would be suspicious of the power valve opening and flooding, another reason I suggested closing the the idle mixture screws.