Miles Posted March 24, 2003 Share Posted March 24, 2003 74 350 SBC ran fine until two weeks ago. It started running rough and would die going over bumps. Condition got progressively worse where the engine would run ok for 10-20 miles and then start surging like it was out of gas and would die at idle. Let the car sit and it would run for a mile or two. Next. I rebuilt the Edelbrock 1406 carb to factory specs replacing all gaskets and adjusted floats etc. Car ran a little better for awhile, but then deteriated back to running rough and surging at all speeds once it heated up. Checked timing. The timing mark jumps around. Engine runs very rough and there is a clacking noise inside the engine. Car has power and is smooth at WOT. Any help would be appreciated. Thanks Miles Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted March 25, 2003 Share Posted March 25, 2003 Is this a rebuilt engine ,or an older engine? If it's old it could be a stretched timing chain. Quote Link to comment Share on other sites More sharing options...
denny411 Posted March 25, 2003 Share Posted March 25, 2003 Is it possible that you have rust or sediment in the tank that is agitated when you go over bumps? This could cause the pickup screen in the tank to become plugged. Or, if you dont have a pickup sceen it might be plugging your fuel filter. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 25, 2003 Share Posted March 25, 2003 Check all the vacuum lines. Replace anything that even looks old. You can use an unlit propane torch or engine starting fluid to check for vacuum leaks around all the carb and intake parts. Could be a stuck EGR valve. The irregular timing and clacking noise are confusing me. You need to track down the source of the noise more carefully. Agree that it could be a worn timing chain. Check for slop in the distributor shaft. Hydraulic lifters will really clack if you are low on oil, but that shouldn't make you run that rough. Could also be a failing fuel pump. I assume you replaced the fuel filter when you rebuilt the carbs? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 25, 2003 Share Posted March 25, 2003 OK. Sounds like you have a dirty gas tank. You start out ok but the contaminant (whatever it is) is being shaken up as you ride and finally doing what you say. When you stop the junk settles in the tank and then when you go again it gets stirred up again and the same thing happens. You better watch out because the mechanical noise may actually be detonation from a leaned out conditionof the fuel. Drain some gas from the tank into a clean pan and see what you got. Quote Link to comment Share on other sites More sharing options...
Miles Posted March 25, 2003 Author Share Posted March 25, 2003 Here is some additional info: engine has no smog equipment, gas tank was recently removed and cleaned (no rust), engine now runs rough at all speeds, when I rebuilt the carb there were bits of rubber hose in the needle valve strainers and fuel bowels. Anyone familiar with Edelbrock 1406 performer carb fuel bowels? I ran the car until it got real rough and then removed the top of the carb to check the fuel bowels. Both had a little over 1/2 in. of fuel. Anyone have a 74 350 sbc engine in good shape for sale in Sacto area? I think I may just replace the existing engine. Thanks Miles Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted March 25, 2003 Share Posted March 25, 2003 What about the fuel lines going from the tank to the carb? Did you blow those out? Could be crud in the line reducing flow. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 25, 2003 Share Posted March 25, 2003 Now let me get this straight.....LOL. You are considering another engine so as to bypass the problem? (Probably not). I would do a compression check to see if a head gasket was going away in between cylinders. I would check the fuel pump diaphram to see if it was coming apart. I would again set/check the carb floats to the required height and etc. You seem to have a funky situation here and poking around everything is in order. The only real clue I have seen you mention is that the engine messes up AFTER it has warmed up. So, it may be pretty safe to say that the source of the problem is heat related and must be searched out after that manner. Also I will tell you a thing.....Ignition coils (if you have one)will sometimes have a crack and cause strange engine performance as they come up to operating temp. In fact, the whole ign. system should be suspect until cleared. One thing for sure is that it either has to be gas related or spark related or a combination of the two. Track these down seperately and completely (with heat in mind) and you will find the answer. I must say that I speak of engine basics and if you are running all the smog junk then use discretion concerning what I have said here. And what about the clicking noise? Just what area is that coming from? If you can, try using a stethascope, large screwdriver or a legnth of broom handle etc. to find that area (one end in your ear, lol, and the other on various points of the engine and other objects) you can pin it down, maby even find it. Quote Link to comment Share on other sites More sharing options...
denny411 Posted March 25, 2003 Share Posted March 25, 2003 Do you have a catalytic converter on the car. I`ve had similiar problems when the platinum inside has broken up and turned sideways blocking the flow of exhaust. this could also account for the clacking noise. It could shift when you hit bumps. This could also cause the intermittent problem since the exhaust would gradually build more backpressure as the car runs, and some of that pressure would bleed of when the car is sitting. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 25, 2003 Share Posted March 25, 2003 Jeez', I just read again and focused on the timing comment this time. Loose distributor, loose distributor gear, condenser going, any fatigue crack in the plastics involved that will open up under heat (valid only if you have such parts). I don't think the jumping mark could be the result of a streched chain, but that might result if your idle speed was low and the cam overlap was aggrivating the situation. The cam gear coming loose (ugh) or excessive endplay of the cam and/or distributor is the only way I can see the jumping mark happening; but again, If you have electronic ignition then I quit talking. Quote Link to comment Share on other sites More sharing options...
Miles Posted March 25, 2003 Author Share Posted March 25, 2003 Things just got worse. Went to start the engine and two puffs of smoke shot out of the carb followed by the starter grinding and struggling to turn the engine over. Now the engine won't turn over and the starter just makes a grinding noise. Could this be a slipped or broken timing chain or loose cam drive gear? This all came on a week or so ago and has slowly gotten worse to the point of engine lockup. Should I pull the timing chain cover or just junk the engine? Thanks Miles Quote Link to comment Share on other sites More sharing options...
denny411 Posted March 26, 2003 Share Posted March 26, 2003 Always inspect for damage before trashing an engine. It`s surprising sometimes how such small things can cause big problems. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted April 5, 2003 Share Posted April 5, 2003 Miles.....LOL; This is a duzzie! I bet your cam chain has given up the ghost, folded up inside the cover somehow and locked up the whole engine, LOL, what a blast! The carb smoke and the lockup are all I need to be ready to place my bet. Hey!, are we mechanics or not? Pull the cover and fix that puppy! Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted April 6, 2003 Share Posted April 6, 2003 I must say I agree with Spiirit, probably that damn timing chain. Time for gear drive! Make sure you put in a good double roller timing chain. It is worth the extra coin! Mike Quote Link to comment Share on other sites More sharing options...
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