Ignition or fuel issue?

[vetteguy76]

Hey everyone, I'm new to the forum. I've been beating my head against the wall trying to solve my issue... Here it is.

1976 Corvette

496 BB stroker 10.1 : 1 comp.
th400 trans
quickfuel 850 carb
quickfuel reg set to 7psi
quickfuel hp155 pump
msd 6al box (replaced)
msd pro billet distributor (noticed rust on pickup, have not replaced yet)
pt# 8361
msd hvc blaster coil (replaced)
ohmed all superconductor msd wires and they check out 40ohm/ft
new ngk plugs gapped .040
timed 36 deg total advance 18 in motor 18 in distributor

Car ran great for about a year and a half in Chicago. Moved to Florida (Tampa). Drove the car for a couple days and it started acting up...
From a stop, if the car idles at a light, if I leave the light hard it sounds like it is breaking up. Accelerate through 3rd and the motor chokes and dies. Can't even feather the pedal to keep it going. Need to stand on the accelerator to get it fired up again. Spits fuel out of the primary vents of the carb.
Also, noticed when sitting at idle in park, it is fine. When I bring the Rpms up around 3000 the engine sounds like it is dropping a cylinder and the rpms drop sharply about 3-500 rpm and never regain through acceleration.

Would rust on the magnetic pickup inside the distributor cause something like this?

For the longest time I thought it was a fuel issue... The car originally had a mechanical pump. The first thing I did was replace the mechanical with an electric one. No change. Replaced fuel line. No change. Added a heat shield to the bottom of the carb, no change. Sent the carb back to quickfuel to be rebuilt, no change. Replaced plugs multiple times, no change. Ran new ground from battery to frame, battery to bell housing, 2 straps from frame to engine block (cast iron heads) no change. Replaced 6AL box, no change. Replaced the coil with a Blaster 2 coil, no change.
Short of replacing the distributor or carb, I don't know what else to do besides rip the interior apart and rewire the whole car.... Or go EFI! I should be able to figure this out... I won't stop till I have!

Ideas???? Please help me figure this out! I've been at this for almost a year and have spent way more than I wanted to all for no reason so far!

[36 sedan]

Check your distributors mechanical advance, make sure it is not binding or sticking.

[jerry clayton]

Spits fuel out of the primary vents??

First off Chicago area has different fuels than other areas of country-----

A holley carb won't hold 7 psi pressure------electric pump? turn off to see if it will clear up---- sounds like you are flooding it out pretty bad

[techinspector1]

A holley carb won't hold 7 psi pressure------electric pump? turn off to see if it will clear up---- sounds like you are flooding it out pretty bad

You guys kill me with your fuel pressure settings. No modern 4-bbl carburetor needs more than 5 psi to keep the bowl(s) full. You need VOLUME, by using large diameter lines (1/2" or larger), but you do not need high pressure. All that will do is to overpower the needle and seat and allow the pump to blow raw fuel into the intake manifold, creating a tuning nightmare for you. This is not EFI, where more pressure will support more horsepower.

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[twolaneblacktop]

I agree with the Inspector. You do not need to hear much more than the system psi and that gas is coming out the bowl vents to understand that you are flooding the engine. The other tip is having to hold the throttle wide open to get it to re-start. I think that you may also have pre-ignition issue due to poor gas. Have you read your plugs? Pull your plugs, keeping in mind with came from which cylinder. I'll bet you will see black deposits on the center insulator and they may even be wet. Take a look and they will tell you all you need to know. Google "Read spark plugs" and you will get great photos that will help. If this has been going on for a year, you may have to reset the floats and check the needle valves as they may be off at this point. The rusty pick up may contribute somewhat to the misfire issue but you have to fix the fuel issue first.

[rspears]

It's no skin off of my nose, but vetteguy76 posted his lengthy explanation and question, then two minutes later logged off and has not been back. This means that he's not yet read any of the four responses unless he's lurking w/o logging in. Not a problem to me, but maybe we need to give him time to come back and respond to what's been suggested. Maybe he's one of those "instant gratification" guys who expects an immediate answer to any question, but maybe he just went home to visit Mom for Christmas.

[twolaneblacktop]

Well I found an article for him. http://www.crankshaftcoalition.com/w...ng_spark_plugs
Fun to talk about any way
Happy New year!

[techinspector1]

Well I found an article for him. http://www.crankshaftcoalition.com/w...ng_spark_plugs
Fun to talk about any way
Happy New year!

Thanks for addressing the reading of plugs. I usually do that also, but failed to mention it this time. I like to suggest a Longacre lighted 10X loupe and making a full-throttle run, then going to neutral, chopping the ignition and coasting to a stop, where the plugs are pulled right there. Idling or driving after the full-bore pass will re-color the plugs and the plug reading is worthless.
Longacre Racing 50884, Longacre Tools and Pit Accessories | Longacre Racing

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[techinspector1]

I doubt this fellow is coming back. He probably asked the same question on 10 other forums and liked the answers he got somewhere else.

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[twolaneblacktop]

Well, for me I do not care if he returns or not. It was very enjoyable to think about his issue, knock the cob webs out, and discuss the issue with you folks. I am an old drag racer that has been away from the sport for twenty plus years. My son saw the old photos and fell in like with the strip. He built an 88 super coupe himself. I made sure that it went straight when it went, did not catch fire, and that it stopped when it needed to. Don't know how I raised a ford kid......

[techinspector1]

Well I found an article for him. http://www.crankshaftcoalition.com/w...ng_spark_plugs
Fun to talk about any way
Happy New year!

I just realized that article was written by Mark Ritter, an old friend from Atlanta, aka Cobalt327.

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[jerry clayton]

He's a check writer

[vetteguy76]

Hey everyone, thank you for all the responses! I am a Realtor in the Clearwater Beach area and I focus on property management/rentals and I have been swamped right before the beginning and just after the new year with check ins and check outs. This is the first chance I have to respond to everyone. First Happy New Year! And I am so grateful that all of you have taken the time to share your experiences with me! I have not had a chance to mess with the car too much... Since I have posted my initial Thread, I have changed my magnetic pickup in my dist. which was rusty. I have also replaced the msd 6al box with no change in issue. Quickfuel has told me to run the carb at 6.5 - 7psi. In speaking with the techs there, I question their competence. I have tried to bring the car up to 3000 rpm (in park) while the motor is chugging and shutting the fuel pump off and low and behold the car smooths out. I plan on dialing down the fuel to around 5psi. I also checked my power valve this morning which is a 5-6. The car has 9in of vac at idle in drive (th400 trans). I will be replacing the valve with a 4-5 either tonight or tomorrow. The plugs have been fuel soaked the last few times I have changed them. It's been extremely frustrating dealing with this issue for the past year... however I have learned so much about the other components of the car! I love hearing feedback from others... I am not afraid to say I don't know that much about cars but I am learning!!! I will post an html to photoshop of my build. This is the first car I've built. The only things that were done for me was the engine and trans were built by professionals. I have done everything else myself.

Corvette by jpalasky | Photobucket

Please let me know if the above link works!

[twolaneblacktop]

Well son I have to say that based on your posts, I think you have more money than sense. Quit spending money and put your brain in gear. You have fuel squirting out the vents, wet plugs, and clear symptoms that the carb is loading up. You are dumping fuel down the carb and choking the engine. Take The Inspectors advice and install a fuel pressure gage. Adjust fuel PSI to 5. I believe that the carb is damaged. Find a local carb shop, they still do exist, and have them review the carb or IF you want to spend some more money buy your self a real HOLLEY.
At that point you need to look at the distributor. How did you get dampness in the distributor?? Is the cap in good condition? After you fix the fuel issue look for a vacuum leak.

[johnboy]

The link works.
Nice car!