Exhaust on fire! Intake/carb. problems?

[cjshag]

1048716

My '80 CJ-7 has a rebuilt 304 V-8. The engine was bored over .030 and has an Edelbrock Performer intake, Edelbrock Performer carb.(500 cfm), a mild Competition Cam, in-frame headers, and dual exhaust with cats/flowmasters. My re-occuring problem is the header tubes turning "glowing red" after 5-10 minutes of idling. I have done numerous replacements of the intake gasket. It was running O.K. before I took the body off for some work. Now it is acting up again. I just finished another intake gasket job. Now different tubes are "glowing". Any suggestions? I'm going to check for leaks today. Never had this problem with stock carb./manifold before the rebuild.

[addsig]

 

[Tug-n-pull]

1048717

Sounds like you my have a clogged up cat. Either remove it or replace it! I run without one but if you live in an area that has no testing. Take the cat off and empty the core out and let that beast breath! Welcome to the boards and good luck in the fix. Later Tug[addsig]

 

[BigBlackJeep]

1048719

Yup, sounds like the cat is clogged, get that thing either changed or gutted. That should clear up your problem I would think.[addsig]

 

[MudderChuck]

1048757

What goes in, must come out, if the cat is plugged, it should show low intake vacumn. A vacumn test at the intake manifold, might be helpful. If I had glowing headers, my first thought would be lean, lean can kill a motor in a big hurry. Check your low speed jets (idle jets) opening them up a bit won´t harm anything, but your gas mileage and maybe some sooty plugs. The next time you have the intake off, take a thin feeler gauge and run it around the sealing surface of the intake. Are your valves lashed correctly? Does a compression test show all the cylinders the same? Retarding the ignition, often helps. I always retard my ignitions a bit (when possible), helps the motor last longer, cost a few horses, but most times actually improves torque. Hope your cam is timed correctly. When your TDC (cylinder 1 most motors) the rockers should be a little loose (wiggle a little).



Lean usually shows up as white plugs. Put your hand at the outlet of somebodies exhaust, then put your hand at the exit of your exhaust. Lean will often be hot enough to burn your hand. And you can feel hanging or partially open valves as a thump.[addsig]

 

[cjshag]

1048760

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font class="pn-sub">Quote:</font><HR></TD></TR><TR><TD><FONT class="pn-sub"><BLOCKQUOTE> What goes in, must come out, if the cat is plugged, it should show low intake vacumn. A vacumn test at the intake manifold, might be helpful. If I had glowing headers, my first thought would be lean, lean can kill a motor in a big hurry. Check your low speed jets (idle jets) opening them up a bit won´t harm anything, but your gas mileage and maybe some sooty plugs. The next time you have the intake off, take a thin feeler gauge and run it around the sealing surface of the intake. Are your valves lashed correctly? Does a compression test show all the cylinders the same? Retarding the ignition, often helps. I always retard my ignitions a bit (when possible), helps the motor last longer, cost a few horses, but most times actually improves torque. Hope your cam is timed correctly. When your TDC (cylinder 1 most motors) the rockers should be a little loose (wiggle a little).



Lean usually shows up as white plugs. Put your hand at the outlet of somebodies exhaust, then put your hand at the exit of your exhaust. Lean will often be hot enough to burn your hand. And you can feel hanging or partially open valves as a thump.

</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR></TD></TR></TABLE>



Thanks for the response everyone. My only reason to initially doubt the converters is that this problem started just after the rebuild and new exhaust. I installed new gasket(s) and eventually cured the problem for a term. Why it shows up again after the motor has been sitting during body work? I don't know! Checked my timing today. It is at 8 degrees before TDC. Tightened the carb bolts a little. Started it up. At dark I started again. It took about 7 minutes before the center left header tube started to glow. Temp. gauge was normal. Shut it down! Very frustrating. Tried to spray carb. cleaner around intake to hear RPM change. Really couldn't notice anything. Will try MudderChucks suggestions.[addsig]

 

[cjshag]

1048855

Still trying to solve my problems. May be a bad seal at carb. base! Parts guy gsold me a Edelbrock carb. base plate. I also got another new gasket. This plate is a thin metal plate. My carb. came with a (riser?) about 1/4 " thick. This is made of a hardened card board type material. Do I trash that in favor of my new plate and gasket. Anyone ever use this combo.? I'm going to try it this afternoon.[addsig]

 

[MudderChuck]

1048890

Just thinking out load. But I want to run a few things by you. The spacer/insulator, helps keep the carburator a little cooler, thus helping the air gas density a little bit. But a warmer carb. will atomize a little better and idle a little smoother.

Does your intake have a coolant crossover? I´ve had trouble with Chevy´s in the past, they occasionally replumb them or reroute the coolant by changing the openings in the head and intake gasket. What works for peak horses, doesn´t neccessarily translate into uniform cooling of the motor. Now I always check the new gaskets, against the old, to make sure the cutouts and plugged passagways are the same.



The bigger the carb. the less the intake velocity. Less low end torque, poorer atomization, worse idle. Raising the idle a little might help.



Give Edelbrock a call and ask for there advice. On initial timing @ what RPM.



I had a hot rod dodge PU that used to make the headers glow, but that was usually after a bonzai run up the autobahn.



I used to periodically check my header outlets with a electric thermometer, The motor was supercharged and I was always afraid I´d end up with valves that resemebled asparigus.



A cam with too long a duration, will sometimes overheat the valves, they need the seat contact to give up the heat. Can also happen if your lash is set to tight.[addsig]