283 chevy PROBLEM... again.

So I recently have been having the most fucked up luck with my car. The car is back firing/popping thru the carb. I have replaced the points, dist. cap, plug wires and vacuum adavance. The dist. is in great shape. The points are adjust prop., the timming is not perfect but it is ok.(my timing light recently broke) the car idle's great, but when the motor is under a load it starts popping. But when I shift it to second and hit my cruising speed it is fine. (on a side note I just started dating someone, and all the problems started at the same time, you think my car is jealous?)

 

Too lean a mixture?
(Maybe it needs bigger jets)

Maybe float is set too low?

 

(on a side note I just started dating someone, and all the problems started at the same time, you think my car is jealous?)

I'd check down the carb to see if there are any panties stuck in there.

 

.... or your own balls!!!!

JH

 

sounds like a fuel problem, or timing is off. back fires are usually a sign of wrong timing. i also had a problem just like your good under minor load but terrible under heavy load. this was on a 305 chevy. it had blown head gaskets. the give away for me was super hard starts after it hit normal temp.

 

too lean is my guess. Might need a jet change or at least richen the idle mixture just a hair. That always fixes the off-idle stumbles with Holleys for me also

 

Thanks for the input! I guess i should of also mentioned it is an all stock 283 w/ a 500 cfm edelbrock carb. The car has been running great for five years with this setup.

 

Then it might be a blocked or parially blocked jet?

Have you a fuel filter fitted?

 

Is it possible that the timing chain has jumped a tooth?

Hmmm...didn't realize the issue was sporatic...ignore my previous thought.

 

Hi, this is a little off the wall, BUT i had it happen to me! Check the drive gear at the bottom of the Distriutor, I had a roll pin shear off and the gear would jump back and forth, it would idle fine but put it under load and it would miss all over the plasce but back off the gas and it would jump back into timing. Worth a quick look.
Bob V.

 

thanks again for the quick input! I am thinkin of replacing the the dist. There is NO abnormal movement in the dist. I do have a filter and it is a bit dirty. i am gonna pull out the jets and look as well

 

I believe it MAY BE starved for fuel.

I had a 283 with the same issues. The fuel filter was partially clogged.
I blew out the fuel lines and added a NEW filter and the issue was CURED.

 

Another possibility (however remote) is you may have a cam lobe going away. It will usually appear when your accelerating and it pops in the intake or when cruising at higher speed you hear it in the exhaust. If all diagnosis proves futile you might give the valvetrain a check for consistant movement of the rockers.

Frank

 

Hi I had a engine which would idle great,give it gas and it would start to break up,...I checked the wires,points,cap,rotor,fuel and carb jets,...I also checked the ohm reading of the wires,coil all checked out good,..checked adjusted the timing to no end ,still same problem,...I let it run got it hot ,...then I removed all of the wires which were connected to the coil,..I then check the coil while it was hot using the ohm meter and found that it was shorted out,,current was running from the inside of the coil to the out side of the metal case,.I checked the coil again when it was cold and it showed that it was good,...changed coil engine runs great...Miller

 

Valves set to tight ?

 

Water in fuel?

 

*ding* *ding* *ding*........ i think we have a winner.
or at least that's what i think.

 

x 2

 

x 3. Had it happen on a 327 a few years ago. New cam made it alllllll better

 

this was my problem.after checking dist
/setting time.carb and everything else you can think of.new motor.it was when we first started hearing about the lack of zinc in the oil. maybe it won't be. good luck

 

Well I am fearing the worst, blew out fuel lines, changed filter, checked the dist. gears, new points, dist cap, plugs, and wires, cleaned jets... The one thing I was thinking is maybe the resistant wire for the dist. (I think thats what it is called) I think that the cam lobe going out sounds right and makes A LOT of sense. The motor is 100% stock internally never even looked at the valves. It really bums me out cause it is my only car... I will hopefully look into the cam and valve train later on this week. Thank you ALL for offering your suggestions, now I am off the the R.J. cruise in Oakland, albeit in my lady's Yota'

 

Check for a broken valve spring. I had one that was broken and would walk. Same symptoms.

 

Man, hang in there. I'm dealing with a similar (but much worse) situation at the moment. I can't get mine above an idle after 10-15 minutes, then it's nothing but clanking and backfiring...loss of power, etc. Let it cool and then I can start it up...rinse, repeat. Chasing these ghosts sucks, and while it *may* be a bad cam lobe, keep your mind off it. As much as some guys on here want to help, there *are* those others who spooge their britches at the chance to say "it's toast" "yer f*cked" and "flat cam lobe". There are debbie downers among us.....ignore that sh*t and break on thru!!! GOOD LUCK!

 

If it never goes away could be the cam or spring. I have seen both make it backfire. Carb might just be intermittent. Pull the valve covers, you may be able to see a flat lobe by less movement at the rocker arm. Could be looser too. It is probably on an exhaust valve. Look at the springs close as they sometimes get back in place and are hard to see. If it is broken and shifted you will be able to see it. Hope this helps.

 

A bad intake valve will have the same symptoms as a cam,only seen it a couple times as a bad cam is more common.

 

O. k. I know this is an older post and I hope he has resolved his problem. But in the first post he mentioned that his timing light was broken and his engine is set up with an Edelbrock carb, right? He also went on to say things were fine when he got up to cruising speed. Is it possible that he was trying to check the timing, disconnected the vacuum advance, and hooked it up to the wrong port? Hooking it up to manifold vacuum would advance it fully at idle, and gradually retard it as RPMs increased, at which point the centrifugal advance would have taken over. I.E. too much advance in the low end, and fine or slightly retarded at cruise. Seems to simple to me.

 

Ya I have not taken care of this issue yet. This car was my daily for awhile. My usual daily(o/t mitsubishi pick up) took a major shit. So ALL my cash was dumped into that. The car did get worse from the last post I made. Back firing through the carb always. Barely will do 25mph. So she waits patiently for me too get back too her or I maybe selling her soon...

 

Pull the valve covers and look at/measure the valve springs when fully open. A bad lobe should show up pretty clearly as the spring will depress either a lot less or not at all.If you have a spring that is moving a lot less there should be your problem.

Another possibility is the heat crossover between the heads and through the manifold is plugged which will give you a pop through the carb on acceleration. Your symptom sounds somewhat more severe but if you have to pull the manifold it would be good to clean it out.

 

I wonder if the heads were ever reworked for hardened seats??? Being that's a 283 and running on unleaded fuel will probably wear out those old exhaust seats...

 

Bad cam lobe or too lean ...