Chevy 350 motor problems
 

I have a 72 gmc with a 350 motor. I'm having some trouble getting it to start. I had it somewhat running. Then I deep cleaned my carborator and tied the vacuumed modulator in with the brake booster in the intake. After I did all these I haven't been able to get it started. It turns over and tries to start but won't. I know it's not the spark so I figured it was the carb. Before I go and by a rebuild kit I wanted to test it with a new carb off another truck but still couldn't get it started the new one was a automatic choke that I didn't properly wire in due to the fact I didn't have enough time to but I got it hooked to a power source but the same results. So should I still by the rebuild kit or could it be something else causing the problem I'm not really sure what to do anymore haha can someone please help. Thanks for reading
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Re: Chevy 350 motor problems
 

What do you mean by deep cleaning the carb? If the engine wasn't running and you sprayed a bunch of carb cleaner down the carb. and it wasn't running to well to begin with you might have a flooded (with carb cleaner) engine.

Re: Chevy 350 motor problems
 

I took the carb off and disassembled it and cleaned it because it had small particles in the chambers ad I reassembled it but I never sprayed carb cleaner in the engine haha
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Re: Chevy 350 motor problems
 

Can you expound on "somewhat running?" Did it run smooth or missed and sputtered?

The reason I ask is to see if it has another issue that may be compounding your problem. Look carefully inside the throat of the carb to see if it's getting fuel when you manually activate the throttle by hand.

Re: Chevy 350 motor problems
 

It ran but missed and sputtered. It does get fuel when I manually activate the throttle which confused me about being the carb. So I thought it was the spark but it has a good spark an all that. And I don't see anything wrong with the block but I could be wrong
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Re: Chevy 350 motor problems
 

Sounds like a timing issue to me.. Has the engine ever ran? Is it a new drop in, etc. ? Did it just start giving you trouble starting? Did anything change? HEI or points ignition?

Re: Chevy 350 motor problems
 

Could be your coil. My grandpa's 64 chevy truck with 350 wouldnt start and finally the battery died after trying to start it over and over. Took the distributor coil to get tested and it was bad. Put a new one in after getting battery replaced and boom it started. No problems since
Now I am having similar problems for the 67 c10 but I have points and Ignition coil might need replaced.

Re: Chevy 350 motor problems
 

It's ran yes I've test drove it a little but the timing is perfect on it and nothing has changed I have the same parts on it when it ran It just started recently and I am Starting to think its something in the block which sucks haha
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Re: Chevy 350 motor problems
 

I tested the distributor with a spark tester an it read that it had spark but I'll test it again to see
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Re: Chevy 350 motor problems
 

Couple of things that I would do since you say it did run, timing is correct, you get spark and carb is shooting fuel into the engine.

Get a one gallon container with fresh gas and buy about a 2½ to 3 foot piece of fuel hose.

Remove the hose going into the fuel pump, attach the new hose and place in the gallon container of fresh gas under the truck. It may be that you're fuel is somehow contaminated.

Other possibility is flooding. Too much fuel being introduced into the engine. Usually detected by a strong fuel smell or dark gray to black smoke coming out of the exhaust when it does try to start. If that's the case, open the choke fully, hold the gas pedal down and crank the engine without pumping the gas pedal.

Re: Chevy 350 motor problems
 

It could be the timing chain is slopy 7 may have jumped a tooth.

Re: Chevy 350 motor problems
 

68gmsee when I'm in the cab cranking it over I do smell a strong fuel smell and only sometimes it will blow grey smoke out of the exaughst when cranking over but if it runs there's no smoke
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Re: Chevy 350 motor problems
 

That's the way a flooding engine does sometimes. It may be flooding when you first start it and the excess fuel burns off after you start it. Check the float level again carefully and make sure the needle valve and seat are not nicked or damaged in any way.

Re: Chevy 350 motor problems
 

Ok I will check then I'll let you know. Thanks for the tips everybody
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Re: Chevy 350 motor problems
 

What is the timing actually set at?

Did you properly set the floats to the specs in the rebuild kit?

You could have also got some junk in the needle and seat area if it wasn't flushed out good enough on the rebuild. This will let excess fuel past the needle and seat and flood the engine.

Also the vacuum advance for the distributor needs its own vacuum sorce, and not "Tee'd" in to the brake booster line.

Gary

Re: Chevy 350 motor problems
 

The timing is at 0 and I haven't bought the rebuild kit yet. I borrowed a carb from a complete truck and got the same result as my carb. And the vacuum is on its own line I ment the vacuum modulator on the tranny.
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Re: Chevy 350 motor problems
 

My mistake on the vac line to the tranny... I would run that seperate too. There is a stock fitting located on the intake behind the carb for that line. The brake booster should be a bigger line that goes into the back of the carb.

Even stock, the timing should be advanced a little more than zero. I don't have my service manual in front of me, but I would look in your service manual and see what the timing spec is supposed to be.

Gary

Re: Chevy 350 motor problems
 

Ohh ok I had the brake booster teed in to the back of the intake haha thank you for letting me know that. Boy do I feel stupid and ok I'll look it up and hopefully that fixes the problem
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Re: Chevy 350 motor problems
 

I had a 72 El Camino with that engine and a Holly 4 barrel quadra jet carburetor. We ran the timing at 2 degrees above TDC because in two different places it gave two different settings. Two degrees above was the correct timing for that catruck, at zero she wanted to die. And yes make sure you check the butterfly floats to make sure they are working properly, for all possibilities it could be bent slightly and you not realize it making it not be at it potential. I've had that happen as well.

Re: Chevy 350 motor problems
 

Don't feel stupid... it's a learning thing. I've been wrenching on rigs for a long time. But there are cats on here that have forgot more than I will ever know. It's always good to get some info that is useful... no matter what your skill level. :)

??? Was it a Holley Spreadbore Quadrajet replacement carb? I don't believe Holley ever made a "Quadrajet".

Gary