Carb Rebuild issues, please help!

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sciabola13

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Hey crew.

71, H code, Fmx, 2v, 2100 with electric solenoid.

Car is in beginning stages of resto and tackling getting her running better. The car did run prior. Rubber hoses were trashed and leaking gas around base gasket and air horn. A vacuum gauge showed between 12 and 14.5 inches of vacuum before I pulled carb.

This is my first carb rebuild, I went slow and checked myself between instructions, manual, and YouTube. Was very thorough on taking pics throughout but I have a few mistakes I regret, more on that below. I was very intense on keeping things clean, spraying the openings with carb cleaner and compressed air. Only spare parts were an extra check ball, a dime sized felt gasket and an extra needle gasket I think. There were two in kit and I put one on. It was a NPD kit btw. The carb base gasket in kit was different so I ordered the fel pro one that was laminated with steel center like my original.

The issues is that car backfired 3 times with flamage through the top of carb in getting her started.

I again, turned the idle/air screws all the way in and then out 1 1/2 turns. I also adjusted the hot air choke a little bit.

Car started and ran for 30 seconds or so idling very slowly...as slow as an engine could idle I bet! Anytime I let foot off accelerator, she died. No subsequent backfiring.

Looked down into intake and fuel is pooling beneath along with some seepage around base gasket.

Pulled #1 plug and she was fuel fouled.

Waiting about 5 minutes after and pulled airhorn off. Fuel bowl was about 1/3 full. Not really sure how much to expect....

Car does need spark plug wires, ignition attention but I wanted to tackle carb first. She ran prior to carb rebuild, not spectacular but it would crank and run almost immediately and idle decently up to temp.

During rebuild I did take off throttle plates and accelerator linkage. I didn't take good photos of that and not sure if throttle plates should be fully closed or have some space when installed. Big error on my part.

I also wish I had gotten a baseline for the timing on the vehicle prior to making changes. I plan on new cap/rotor/wires and a pertronix igniter II once I get the fuel system straightened out.

So, I am not sure how to proceed. I am fairly worried I destroyed the power valve with the backfiring.

Any advice on a procedure to get her started and not burn my house down would be appreciated!

Thanks!

Jeff

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NG8264723

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The issues is that car backfired 3 times with flamage through the top of carb in getting her started. THis happens

I again, turned the idle/air screws all the way in and then out 1 1/2 turns. I also adjusted the hot air choke a little bit. Sounds good

Car started and ran for 30 seconds or so idling very slowly...as slow as an engine could idle I bet! Anytime I let foot off accelerator, she died. No subsequent backfiring. Sounds like a vacuum leak

Looked down into intake and fuel is pooling beneath along with some seepage around base gasket this I do not understand, Where> Send a pic of what you got

 

delawarebill

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i agree with NG. u said u pulled the plates, i'll assume u also pulled the shafts too. and if did were they really easy to remove and any slop will give a vac leak. the plates should be closed and idle vac sucks gas through the orifice and mixture screws u adjusted. yes i would pull the power valve for they don't take much to kill. as far as leaking, been several yrs i did a 2 brl but i recall and ball check. maybe u didn't put it back or the seat is still dirty.. i'd suggest pulling it and doing it again.

 

sciabola13

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Thanks guys. I replaced also all the vacuum hoses since they were a mess. The plates and throttle shaft were pretty tight fit in and out. I was really thorough on keeping stuff clean!

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sciabola13

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Turned idle/air 1/4 turn each out and tried again. A few tiny "sputtering" out of the carb she ran for about 30-45 seconds but died again and shot some flame out of top of carb again.

Doesn't look like fuel is pooling inside manifold like last night.

Here is a photo of fuel level right after, could be float is way too low? Would that cause the backfire? I cranked her over a few times with my remote start switch with air horn off and fuel is shooting up out of needle/seat but looks like air bubbles are in few stream. Not sure if that is normal.

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sciabola13

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Also, I do not have the solenoid connected or the choke setup.

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I am no carb expert but when something is not going right I would take it off and go through it again. Continuing to start the car and get the same results will not fix it. Something is not right in the rebuild. I have overlooked items in the past just go through it again. It looks like the carb was bead blasted. You should never do that tiny glass beads get into places that you cannot clean. Only soak in real carb cleaner that you get in gallon bucket not the spray cans. Denatured Alcohol also works pretty good to get any build up of residue from the gas.

Always keep a fire extinguisher and a 5 gallon bucket of water on hand when trying to start. Much better to have and not need that to have to run and get it. Never pour gas in the carb. use a squirt can to be sure it cannot backfire and catch it on fire then you throw it across the garage and there she blows. I was at the burn center in Georgia with my mother and saw several people come in the 3 days I was there that got burnt pouring gas in carb.

Carbs are a PIA for sure. Some of the staked in balls are very difficult to get out so you can clean the passages.

 

sciabola13

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I am no carb expert but when something is not going right I would take it off and go through it again. Continuing to start the car and get the same results will not fix it. Something is not right in the rebuild. I have overlooked items in the past just go through it again. It looks like the carb was bead blasted. You should never do that tiny glass beads get into places that you cannot clean. Only soak in real carb cleaner that you get in gallon bucket not the spray cans. Denatured Alcohol also works pretty good to get any build up of residue from the gas.

Always keep a fire extinguisher and a 5 gallon bucket of water on hand when trying to start. Much better to have and not need that to have to run and get it. Never pour gas in the carb. use a squirt can to be sure it cannot backfire and catch it on fire then you throw it across the garage and there she blows. I was at the burn center in Georgia with my mother and saw several people come in the 3 days I was there that got burnt pouring gas in carb.

Carbs are a PIA for sure. Some of the staked in balls are very difficult to get out so you can clean the passages.

Thanks for the info. I had rags and fire extinguisher on standby, good call on 5 gal bucket...

Carb wasn't bead blasted. Soaked in cleaner overnight, scrubbed down real well and sprayed with Eastwood carb renew.

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sciabola13

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Update; I pulled off PCV hose and put a vacuum cap on the port on base of carb. That would be most obvious vacuum leak.

I looked over my build instructions again and I think I put a gasket on Venturi bolt that sits over check ball and weight that wasn't supposed to be there. I pulled off that little gasket and put it back together.

Got the car running immediately and no back firing. Engine was definitely laboring a bit but she ran for a few minutes.

When I opened up throttle she died, but no flames! That is a relief. Shot a quick pic of vacuum gauge, she was running between 11-15 during those few minutes but didn't really get up to operating temp.

Still feel like my float is set too low. I am taking a break now to regroup. Will hookup my external tach to get a rpm reading and try and get the idle smoothed out.

Any advice on getting the idle dialed in? There is definitely an art to getting these things running well.

668566fff551540023fda5d487a400fa.jpg


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I would cap off a vacuum lines at the point of connection to manifold. The brake booster is a big leak point. I have a bad one right not on 73 and it will not idle at all. Vacuum canister can have rust hole in it also, air conditioner controls etc.

If it idles with them capped then start to hook them up one by one to find the bad one. You can spray carb cleaner around where the intake gasket to head is to see if you have manifold leak there. It will change the idle when you spray if there is a leak.

Forgot to mention. If you have one of the hand pump brake bleeders it is a very handy tool for checking your vacuum hoses and things like the canister for leaks. You can check the vacuum motors on the heater box with it also and your fuel pump diaphragm. They are cheap and very useful tool.

 
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sciabola13

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Update!

Main culprit for backfire was PCV valve and epic vacuum leak from the hose. Once I capped that off and set the choke up, she ran a lot better.

In course of tracing the fuel issues, I discovered lots of issues with ignition system. Going to pause on more carb adjustments and pivot to ignition.

I have new plugs, wires, cap, rotor, and Pertronix II coil and unit on the way.

Big issue now is that timing needs to be adjusted as well but the distributor will not rotate or budge at all. Got her soaking in PB blast and will keep that up for a few days.

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That is a pain when they stick but PB is best choice. Just keep soaking it and let it gradually work. Don't break the Dizzy. Light taps on the vacuum diaphragm to try to rotate also but give it time. If you pull out to clean be careful with the oil pump drive shaft can fall into the oil pan then more work.

 

Mikes73

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I have good luck using an oil filter wrench to turn and remove a seized distributor, do at your own risk. I had to throw in the disclaimer :)

 

sciabola13

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Thanks! Two day soak with PB Blast and intermittent gentle love strokes with a 2lb dead blow hammer and she loosened right up. Patience is the key with those situations!

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sciabola13

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Update! She Runs! Please watch, feedback welcome!


Backfire was caused by combination of ignition timing being off and major vacuum leak at the PCV valve. I regrouped and tracked down any extraneous vacuum leaks and then started tackling the ignition system. The cap, rotor, wires, and plugs were in horrid shape, not to mention the points. I put in a Pertronix II system, with new plugs, wires, cap, and rotor.

Some fresh valve cover gaskets actually took care of a pretty bad oil leak that I thought was coming from somewhere else, the PO had no VC gasket and just a mushy goop of Permetex blue in place of a proper gasket.

This was my first carb rebuild, but I learned a lot. My choice to rebuild the carb prior to the ignition system was not a good tactical choice. Way too frustrating trying to chase carb issues with questionable ignition. I learned that now.

This is probably it for this thread, but I wanted to post a followup for future folks who find themselves in a similar predicament.

Next I will dial in the timing and adjust the idle air mixture screws on the carb as well as tidy up my wiring for the spark plug wires. Also need to get my PCV valve and hose situation lined up as I am restoring the air cleaner next.

Thanks everyone for the help!

 

thomas1984

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Good job and thanks for sharing your experience! :)

 
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