[FONT=Verdana, Arial, Helvetica][FONT=Verdana, Arial, Helvetica][FONT=Verdana, Arial, Helvetica] A couple of months a go I had probs starting my A, there was a spark, there was fuel and it was timed to perfection but still wouldn't fire...got so fed up I just shut the garage door and went for a beer...anyway due to illness, christmas, and other stuff you have to do today was the first time I got to look at it properly so.... fully charge battery (one idea was not quite enough power to get a big enough spark) try to start it and wont fire but I had flooded it anyway out with the plugs, off with the dizzy cap, clean both, turn over engine to chuck out the exess fuel...go and pick kid up from school (so plenty of time for the petrol to dry off) I have an idea it has to be fuel as the spark is now big and fat. plugs in, check fuel is being drawn from the idle jets when cranking (all OK) stop cranking, neat fuel ignites and blows back through the carb. Try again, crank it over nowt, stop cranking and it blows back through the carb. Do this 3 or 4 times and she fires up and runs like a dream. switch off and re-start 5 or 6 times and no probs but when up to temp she did diesel a bit on final shut down.... Go in and have me tea... back out, wont start but is blowing back through the carb again but is really trying to run and dies when I give it some throttle (then blows back!!) try this several times, finally starts but runs like ****, finally dies and diesels again. I am now really fed up, please help [/FONT][/FONT][/FONT]
What kind of carb? Sounds like junk in the carb to me. I dont know if its old gas or dirt or what, that gets into my needle and seats, but my car (with a 750 holley 4 barrel) will do a similar thing sometimes. Makes it real hard to start, rough idle and wants to die... then will usually floods the carb. I just pull the needle valves out and clean them real good with carb cleaner. Always fixes it. I'd start with that.
make sure your "perfect" timming is in fact that. Sounds like a timming issue with the fact it is running on and poping back out the carb. but i also would not rule out the carb being gummed up. What kind of carb you running? could be a little bit of both
Could even be something like a rotor with a hairline crack or a bad cap. I had a rotor do that once, and the crack was in the metal inside the plastic where you couldn't even see it.
My guess it timing also. If you have an old harmonic balancer, they have been know to slip on the rubber ring. Use a TDC tool in #1 plug hole, turning the motor over by hand. Find TDC and then look at the mark on the balancer. I speak from experience. I had backfiring up through the carbs and timing was off due to the balancer slipping almost 20 degrees.
I'm with sinister on this only it could be too advanced because of it firing through the carb try moving it around a little.
motor is a ZZ4 crate motor..and it has the recomended 750 holly with vac secondaries (with metering plate). It's also the first Chevy I have ever had so I don't really have a clue what to look for or do, other than fuel, spark, timing, etc. Give me an A series BMC and I and could make a basket case run like a sewing machine but a Chevy V8 is totally new to me. I have an idea it's fuel so Ill pull the jets and try that. One theory is that the harmonic balancer may have moved around so the timing marks are out....any possabilities?
Sounds a little like retarded timing. Try rotating the distributor counterclockwise a hair and see if you get a big improvement. If it's a hopped up motor, ignore the timing at idle and set the timing up at the point the mechanical advance maxes out (~2800 - 3000 rpm maybe), and set it to around 34 degrees advance. Plug the vacuum advance line while you're setting the timing. With hopped up engines, you can't usually set the timing to factory timing specs at idle or they'll run like junk. When you hook up the vacuum advance again the advance may seem too high at idle, but it will run better. If it's an old engine, maybe the timing chain is messed up.
is your firing order right?chevy is 18436572 clockwise looking at the top of the cap. front of motor 1 2 3 4 5 6 7 8 rear of motor hope this helps. -danny
What kind of distributor does it have? Does it have both centrifical and vacuum advance? Check that the ****erflies in the back barrels are closing up all the way. Sometimes they'll stick open slightly and it has the same effect as having a large vacuum leak and it makes it hard to idle correctly.
[FONT=Verdana, Arial, Helvetica][FONT=Verdana, Arial, Helvetica]the dizzy is a mallory pro billet with a Holly strip anihaltor ampifier/control box. [/FONT][/FONT]
it sounds like either the dizzy or the box to me. too new for a balancer to go bad and if anything would go wrong with the carb (like clogging) it would stay that way. backfiring throught the carb is ignition (most of the time), is there anyway you can get a different dizzy to try (points would be best), also try checking the neg side of the coil for signal from electronics inside (pick-up coil, module) with a test light. maybe try to wire up without the box.
I haven't read all the replies, but does the car have a roller cam? if it does did you get the correct distributor drive gear? Does the rotor turn an excessive amount while the engine is just sitting there?
Put in some fresh gas.... Put in some fresh plugs...... Never "clean" gas fouled spark plugs on a Chevy engine....only do that on Fords and lawn mowers.
I had this happen on a previous build. Turned out to be the firing order. Double check both timing and firing order. Thats what was causing the blow back in my case.
I wouldn't be surprised if with all the backfiring and popping back through the carb that you haven't blown the power valve in that Holley as well.
I say its a lose timing chain, worn out sprocket or leaking intake manifold gaskets. 1. Take the dizzy cap of and put a socket and ratchet on the crank.Now turn it slightly one way,then turn it back the other direction and see how much the crank moves before the rotor starts to turn. 2. If the intake was installed with silcone gasket sealer , it may have de-solved over a period of time and the intake is leaking.****ters right about the power valve, its probably blown by now.Go head a install a power valve protector while your into the carb.
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