Silver72

I have a 72 rocket 350 and last time I drove it I was getting off the hwy and took off about 1/2 throttle it popped what sounded like through the carb then started running rough. At idle it runs good but every so often will miss but bring the rpm’s up to 1500-1800 it misses and vibrates. I’ve checked for broken rocker and springs and done compression test all good. Could it be carb? I have a 650 edelbrock that I have rebuilt twice in the past 2 years. And every now and then before this instant sometimes under acceleration like getting on the highway it would pop but never run rough.

Gpc1

I would suspect maybe it jumped time, check the basic timing to see if it’s moved. Put the crank at 0 then open the cap to see where the rotor is pointing. Note it could be 180 degrees out depending on which stroke the engine is on. Just move it one full turn.

oldcutlass

If the engine is 180 out the rotor will be pointing to #6.

edzolz

The loud "pop" may have blown a vacuum line off somewhere. Sounds like it is running lean to me.

Fun71

I would say check the condition of the points, the coil, and the resistor wire. The engine can idle OK with a weak spark but any load causes misfiring.

Destructor

Will an Old's engine run after jumping timing, more so will it start again and keep running after jumping timing.

Sugar Bear

Check the inside of the distributor cap closely for carbon tracking causing a crossfire. It will look like heavy pencil line drawn on the inside of the cap. The timing chain did not jump, nor is the distributor 180 out or it would not be idling ok. When was the last tune-up, plugs etc.?

Good luck!!!

Gpc1

Yes it will I’ve had it happen.

joe_padavano

No, it will not, so don't waste your time on that. Check he timing with a timing light. The more likely cause is fuel or carb.

69CSHC

When i first got my car after a good 1/2 hour of smooth driving at speed i would get off the highway and come to a stop. Wait at the red light, light goes green, i give it some gas nothing even remotely aggressive and car would pop and shut off. No drive time it was immediate. Not a loud pop more of a subtle poof.

It would instantly start right up and drive fine again.

Early on when i would make 1/4 mile passes with her, she would occasionally do this midway and further out during pass. Obviously under hard acceleration, sometimes 2-3 pops in a row. With each pop it felt like something was pushing the car back for a split second, or pausing it so to speak, almost felt like it was being fuel starved...

Luckily the track at the time sold race fuel by the gallon. After a few gallons added it ran additional 1/4 mile passes without issue...


My car has always been in tune since day one, I bought it with a fresh tune and new carburetor just installed. New points cap rotor etc. With factory set timing always.

The carburetor was the issue, needed plenty of air fuel mixture and idle adjustment . Also replacing small cracked / brittle hoses and replacing rubber caps on ports. I personally fiddled with this for months till i found what i consider a sweet spot. The car currently runs very well in my opinion.


My car still does this from time to time, if by miss you mean subtle pops (poofs) during idle while shifter is in park. For whatever reason i did not really notice this early on in ownership. Very inconsistent, let it run for a mechanic and ask him to listen and of course it doesn't do it... In my case I always felt this was partly due to poor gas quality. Even though she is fed a steady diet of 93 octane high test. 93 is lousy compared to what it required factory new in my case.

Again this issue is very inconsistent, and seems to disappear once you throttle up. Also don't notice it while in drive in stop and go traffic. Its probably less than ever at this point, likely due to fine tuning the carb, etc.

dragline

Hard to armchair since it could be a couple gremlins. What ignition are you running? Can you post a picture of the engine bay? A fuel gauge you can read while driving will let you know if there's a problem with fuel pressure. A vacuum gauge is good to read while your driving also. Ignition problems like cross arching in the cap are common. A cracked spark plug will also cause problems.

Destructor

I will not be checking timing, my engine runs fine.

Silver72

The car fires right up yesterday I put new plugs in it made sure they were gapped correctly went for a drive and it ran awesome. On my drive home which is about 30 min when it got good and warm it was kinda surging at a light then while I was going especially up a hill it started to pop again through the carb then this morning went to turn into the road and gave it gas and it popped and fell onto its face. I’m kinda thinking my fuel pump is starting to go out. It doesn’t have points anymore I have upgraded to hei

oldcutlass

You need to start trouble shooting. Check fuel pressure, check timing, make sure you have full battery voltage at the HEI, and go over your vacuum lines to make sure they are connected and no cracks.

stan 65 cutlass

just another thought, my dirtbike pops when i have water in my gas