The Stovebolt Site Forums The Shop Area Engine Shop 6 Cylinder runs like Crap

I put new points and set the gap at .019". I replaced the cap, condenser and plug wires. I set the plug gap at .035". I timed the engine at 4 deg BTDC. I rebuilt the carb. Started it and it idles great. But when I give it gas, it starts to miss at higher RPM.
I tried driving it down the road, but again, it ran like it's missing or with no power. This is the first 6 cyl I've tuned so don't know what to do next??

well if it starts and idles ok, then that is a plus.. have you been tinkering with the carb? how was it running before you replace the items that you speak of. done anything to the dist, like move it?
clean fuel filter? any cracks in the fuel lines?
gas tank got any trash in it..

not the it makes much difference, what type of vehicle is this... engine, yr...

Hi Seon,

Did you check the timing with the advance disconnected and plugged and at low idle? May pay to check if the advance is working when you increase the revs.

Cheers mate

Bob

Seon,

I'm thinking along the same lines as Mozzie. You indicate you timed it 4&deg BTDC, and I wonder how you came to that value. Do you have a advance timing light or did you read some little numbers off a plate near the distributor.

The carburetor has a powervalve in it that gives the engine extra fuel when you mash the gas. Although pretty simple to overhaul, if one little ball isn't where it belongs, or a spring is hanging up, things won't work right.

The carburetor to manifold gasket is directional. It must have the slot positioned under a vacuum sensing hole in the carburetor base. Look around a bit more and give us some good news.

Stuart

I recently bought this '59 from the original owner that has low miles but hadn't ran for a long time.

I changed fluids, replace all the ignition parts along with new gas tank, sender and fuel hoses, started it up and engine idled smooth but was missing when rev'd.

Thinking that it may be the carb, I rebuilt it. While the tank was out, I blew the gas line out to clear it with 95 psi from the gas tank end thru to the other end while the line was disconnected from the fuel pump.

I've installed a new gas filter in carb and an in-line clear filter just before fuel pump. Started it, again, idled great but misses at higher RPM. I did put a timing light on it and set timing at 4 deg BTDC by disconnecting the vacuum line and plugging the line and carb. I checked and doubled check the firing order 1-5-3-6-2-4. I check the distributor vacuum which is operating correct.

This is not a my first time tuning an engine... but this is my first 6 cyl tune up :rolleyes:
BTW I did notice that when rev'ing the engine the lower portion of the distributor did rotate but returned when letting off the gas...is that suppose to do that :confused: .

Seon,

It sounds like your vacuum advance is working just the way it was designed to. You know what you are doing so finding the problem shouldn't be horrible.

Valves that are gummy and sluggish from a long nap could be a contributing factor to your miss.

The task at hand is to determine if the miss is being caused by carburetor issues, or ignition problems.

Is the miss a occasional miss or is the engine totally crapping out. If it isn't backfiring through the carburetor, can you slowly choke the air horn with your hand as you bring it up in RPM and see if the extra fuel brings it out of its spasm.

This will tell you it goes lean off idle and might be a float setting issue.

Bring the RPM up very slowly and see where you get into the 'crappy' area.. is it mid throttle or pushing full throttle.

What happens when you road test it under load, does it act differently, or is this not possible running as it is.

I would set the timing back to the factory marks for now. You can always tweek it later.

Stuart

Is your fuel pump okay? A weak/dying pump can make it run exactly like that.

Also, I wonder about the filter in front of the pump. Your pump can handle chunky gas, and should tha filter plug up, you could burn that pump up. Most of us have our filters just before the carb. I'm not saying you should move it, it's just an FYI.

You can tune a piano and you can tune a fish but you can't tune a stovebolt without adjusting the valves.
Just a reminder.
Tom

The fuel filter in front of the pump shouldn't restrict the fuel pump but I'll remove it to see if it cures it.
Regarding valve adjustment, are they hydraulic or if solid lifters, what's the setting?
If those two things don't work, I'll replace the fuel pump :confused:

What if your coil is breaking down on ya? I`ve had it happen on other Chevies and on Harleys. Also i had a 230 six that had a bearing out in the distributor, allowing the rotor to wobble and misfire. Just thinking out loud. Please let us know what you find,.
Have a fun day today.
Slider

Check whether the dwell angle changes at higher rpm. Worn bushings in the distributor can do that.

Just to let everyone know, I've stopped working on this for the time being. With the holidays upon us, the wife says she needs me to drive her Xmas shopping . I'll post after I get back.

Seon,
I recently had a similar problem with a 235 in a 56 Car. It idled great but ran badly off idle and under power. I double checked the float level to specs but it made no difference. I finally tried experimenting with the float level and got it right but it is nowhere near what the specifications called for. Sometimes these things have a mind of their own. Fred

My truck was doing similar, only exception is it was freezing the carb where it bolted to the intake. I had the carb apart 6 times before I finally got the speck of gunk in it out that made it run like hell. Id bet the carb has some microscopic hunk of old dirt in.

Ran absolutely beautiful after that! Dont give up, mine persisted this way for weeks ( :mad: looked like this for awhile)and I went through most everything with spark, fuel and timing to.

Blow out all the passages with compressed air in the carb 1 more time, both ways and try her again. Jeff

I have no carb or running problems,but wanted to comment on the freezing statement. This is common on these old carbs and is normal. As the gas evaporates along with the pressure difference in the throat of the carb the temperture can drop below freezing and cause frost to form on the outside of the carb.It's normal.

When you put the carb back on the engine did you put a gasket between it and the intake? There is a little vacuum passage drilled into the base of the carb that needs to see clear into the intake. A lot of the gaskets in the kits don't include a notch. This keeps the power valve circuit from operating in the carb and causes extremely rich off-idle mixture. If you have a phenolic spacer on the intake you can run the carb with no gasket, or just make sure you cut out the notch with a utility knife.

could be bad plug wires or crossed

Interesting statement...there was no gasket when I removed the carb before rebuilding it, so I didn't install one :rolleyes: . Could that be my problem?