New Holley 4 bbl

[Mbrown]

Just purchased a 87 Minnie that the previous owner had a New Holley 4 bbl recently put on, went to get the rig smogged and the tech said it was running too rich and it didn't pass. When he did the High rev test the right side exaust from the manifold turned RED HOT. The tech said it was running rich down low but lean at higher rev's and the gas wasn't burning causing the red hot exhaust.
The tech is going to adjust the mixture to hopefully solve this ..
Is he correct is my question...
Many Thanks in Advance !
,

[Mbrown]

tpi wrote:
Can you give the numbers read out by the smog test? Did it flunk the idle portion of the test? By how much? When the manifold was glowing red during the high speed portion, did it flunk that too? For what reason? Nox?

In general, leanness should not cause manifold to glow just by revving up engine to about 2K RPM in neutral. The symptom for leanness there would be lot of popping and rough running as the engine was at that speed with low load. Is the engine running smoothly at the 2K RPM portion of test without popping in exhaust?

A gut guess the red hot exhaust was not related to the carb. Either timing effectively retarded for some reason (more to it than just idle static timing), or restricted exhaust come to mind. The one place where it may be carb related is if it has Air Injection Pump and the rich running engine is causing excessive afterburn in the exhaust manifold.

But to start post your results numbers.

I will...thanks so much

[tpi]

Can you give the numbers read out by the smog test? Did it flunk the idle portion of the test? By how much? When the manifold was glowing red during the high speed portion, did it flunk that too? For what reason? Nox?

In general, leanness should not cause manifold to glow just by revving up engine to about 2K RPM in neutral. The symptom for leanness there would be lot of popping and rough running as the engine was at that speed with low load. Is the engine running smoothly at the 2K RPM portion of test without popping in exhaust?

A gut guess the red hot exhaust was not related to the carb. Either timing effectively retarded for some reason (more to it than just idle static timing), or restricted exhaust come to mind. The one place where it may be carb related is if it has Air Injection Pump and the rich running engine is causing excessive afterburn in the exhaust manifold.

But to start post your results numbers.

[DaHose]

California SMOG law is vicious. Be absolutely sure it is the factory Holley. Mine (1983 Jamboree - Ford 460) needed rebuild. I pulled it and sent it out.

California models have an EGR plate under the carb. The hot exhaust gases cook those gaskets and they are a common smog failure. I replaced all the carb. gaskets and she passed with flying colors.

Jose

[spacedoutbob]

What engine do you have on your motorhome? Also, make sure that your particular Holley carburetor is approved for use in California.

Bob

[PaulJ2]

Mbrown wrote:
Well upon further research and discussion it turns out its an distributer/carbuerator issue

X2, Glowing manifold means either a too lean mixture or--late ignition timing. Check out the distributor first, both mechanical advance and vacuum advance system. By bet is on the distributor as the problem.
Repaired these countless times in my shop days. Mostly GM however.

[Mbrown]

Thats really great info, I'll look at that.

[j-d]

I've heard of intake manifold leaks on the 460. I guess any engine can have them but 460 has come up several times. There are easier things to do than replace one and the manifold is heavy enough that the manual recommends using a hoist.
But what I found ours was that the EGR "Plate" was seized to its studs and the gasket between it and the actual intake manifold was burned through. This was after I found the EGR Valve itself had rusted out and was causing a major vacuum leak. Then I got suspicious of the plate gasket when the plate wouldn't lift off the studs. One stud was rusted solid to the plate. That meant that tightening the nuts holding the carburetor down didn't tighten that corner of the plate. Cleaning it all up and installing new gaskets had it running quite a bit better. Along with a new EGR Valve of course. Our 460 was a 1983 and did not have a cat converter or O2 sensors.

[tatest]

Mbrown wrote:
Have been researching this topic of glowing exhaust on line and some say too rich, others too lean, also possible causes are; catalytic converter clogged, o2 sensor, throttle position sensor, cracked manifold or timing. The timing was off 3 deg but dont think that was problem...
Where to go next ???

Uneven mixture side to side would come from the carb only if one side of the carb feeds one side of the intake manifold. I don't know the distribution for your intake.

Other sources of overheating on one side exhaust can be too much air going in (intake manifold fitting or gasket leaks), or as you've mentioned, air leakage into exhaust manifold or blockage of exhaust on that one side. Anything that is the same for both sides, e.g. ahead of the carb or after the exhaust is joined, would not be the first places I would look.

I would not expect to find O2 or throttle position sensors on a truck without fuel injection, as those are among the inputs to the ECM. O2 sensor is for operating injection in feedback mode rather than off the mixture and timing maps.

[woodgeezer]

Take it to a carb specialist. I had my E350 done years ago and lost almost everything over 50mph. Turns out the spec book was for a 650cfm when it really needed a 750cfm. When properly installed and jetted, it improved my mileage 3mpg and ran great at 65-70 mph. On my 302 Ford van I looked for someone to work on the carb/fuel to pass emissions. Found the right guy at the shop next door, who spoke no English, but was a master with the carb. Result, tested out better than a new carb standard, and had to be run by two different testers before the DMV would accept the results.

[Mbrown]

Well upon further research and discussion it turns out its an distributer/carbuerator issue

[Mbrown]

Have been researching this topic of glowing exhaust on line and some say too rich, others too lean, also possible causes are; catalytic converter clogged, o2 sensor, throttle position sensor, cracked manifold or timing. The timing was off 3 deg but dont think that was problem...
Where to go next ???

[DougE]

X3 - forget the carb, you'll just spend a ton of money to get it right (maybe). Go for the aftermarket throttle body fuel injection system. They tune themselves and give much better performance, especially for an RV.

[dalejiw25]

Holly now makes a bolt on throttle body fuel injection carburetor. That might be something worth looking into for you. I believe Edelbrock may also.

[tatest]

You might see if there is a third party replacement for the Holley that is more tunable (I'm thinking Edelbrock) but even that is going to require some expensive dyno time to get the jetting right for the pattern of use.

Living in California, dealing with CARB emissions standards and testing, can be a pain. In the carburetor era, it was hard to do a tune lean enough to pass emissions when the "solution" was lean burn technology, and still be rich enough under load to function well. U.S. carburetor designs simply did not have enough mixture control flexibility to meet the full. range of needs, particularly for trucks. That led the industry to electronic fuel injection and feedback loops in the control programs, abandoning lean burn for catalytic conversion, which for NOx control needed mixtures rich enough to provide useful power with a little bit fuel cooling.