Engine misfiring/ rapid sputter

[cameronsaddress]

Sorry if my terminology is not correct, but I am going to try to explain the symptoms. My truck was running better than it ever had after replacing the PCV valve and installing a needed breather cap. I also put a bottle of lucas fuel system cleaner in with a new tank of gas. All of the sudden 2 days later it started running really rough. At idle, it seems like it has a very rough cam ( i have a mild cam). When I step on the gas it seems to sputter verry rapidly.

It was running very smooth but now I can barely drive it. I actually parlet it today.

Im gonna try to check timing tonight, but could that get out of whack all of the sudden? Also does anyone know what my timing degrees should be on a sb350?

...Where else should I look?

 

[scottishdave]

Did you tighten the nut on the Dizzy after adjusting timeing??? I have seen guys (Myself) forget to tighten that properly after setting timeing and within a day the dizzy will turn.

 

[78Chev]

if you put a fuel cleaner in it and possibly had some gunk in the tank/lines then might check your filter. have had engines drop out on power/sputter when the fuel filter gets clogged. similar to diesels when going from pump diesel to the mixtures etc of it.

 

[cameronsaddress]

Anyone know how to check a filter that is inside the carb? Sorry I've never done it before. What do I do with the flow of gas when I unhook the hose from the carb? Can I just clean the filter or will I need to buy a new one somewhere?

Thanks!

 

[sponsoredbydad]

Hopefully there is one (Fuel Filter) inline poss somewhere near the tank as well as the carb if not put one there. They are cheap under $10 . But if not the carb one should just come out and you should be able to clean it with carb cleaner and a air hose. You need to remove the fuel line and then remove the big nut looking thing the fuel line went into. There should be a metal filter that looks like it was made with small micro metal BB's (Sorry if that description is not clear) should not be too much fuel coming out (Nothing a couple rags can't deal with.

 

[cameronsaddress]

Thanks for everyone's input!

Well it turns out that I got a bad tank of gas. I had a hunch so I ran the rest of the tank out and refilled from a different station and viola... problem solved!

Runs better than ever now!

Damn easy fixes... always elude me.

Thanks again

 

[sponsoredbydad]

I would still think about installing a in-line filter just after it leaves the tank

 

[cameronsaddress]

Will do. How should I do it on steel fuel lines? A hack saw and fittings?

 

[Deuling]

Tubing Cutter, like what they use for copper tubing and stuff for plumbing, just the little mini one though. No hack saw that leaves burrs and nasties

 

[sponsoredbydad]

Isn't there a short piece of rubber hose coming out of the tank? I don't think I've seen the hard line going into the tank on the 1st gens. The hard line runs down the frame on the pass side. Somebody could chime in if that info is incorrect.

 

[scottishdave]

There should be a length of rubber hose from where the hard line ends at the front crossmember and runs to the Fuel pump. I have an inline filter right there.

 

[sponsoredbydad]

Yea, I have one there as well

 

[72blazerguy]

There should be a length of rubber hose from where the hard line ends at the front crossmember and runs to the Fuel pump. I have an inline filter right there.

x2 on that. No hard line to cut, easy to see.

 

[cameronsaddress]

Well, it wasn't a bad tank of gas after all. It has happened 3 times since the initial issue. It's very strange because it is sporadic. It will run great for a few days and then it will start to miss really bad. When it is running like crap it is difficult to start. I have to practically floor the gas pedal to get it started up.

I have added a fuel filter and just checked it again. Nothing in it.

Installed a new fuel pump as well.

Where else should I look?

 

[cameronsaddress]

Plugs, wires, cap?

 

[Z71paramedic]

That's where I'd start. My bet is there's corrosion on the inside of the cap. Get a new cap/rotor and check your plugs and wires to see if they look like they need replaced. Hopefully you get it tracked down.

 

[Greg72]

Check under the dizzy cap...

Bad cap or rotor maybe... check plugs for oil fouling. Check for shorted spark plug wire (melted, etc) Basics first.


-G

 

[cameronsaddress]

I believe that I have an HEI distributor as there is a coil in the top of the cap. Do I need to replace the cap with another hei cap? Autozone says that an hei distributor does not fit my engine... wtf?

 

[onetonbb74]

When replacing the cap, the coil comes off the old cap, and you reinstall it on the new cap making sure you skrew the ground strap on one of the bolt holes.

the HEI will fit your engine, just wasn't designed for that bodystyle truck. I bet its pretty close to the firewall, but it fits. First year in the trucks for HEI was 1975 iirc. My 74 came with points...a 72 would have the same points dizzy stock. Most people upgrade to HEI.

 

[ashman]

that sounds like an HEI to me. the parts store is going to tell you there isn't one that fits because our trucks never came with HEI, but it's a common upgrade. I have HEI on mine as well. just tell them any mid-'70's truck with a 350 and I'm sure it will fit.

or just take your cap in with you and match it up.