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 > California SMOG related question - 1983 Jamboree

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DaHose

No. Cal.

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Posted: 01/19/13 05:39pm Link  |  Print  |  Notify Moderator

Hello fellow RV'ers. Feels pretty good to say that.

I have a 1983 26 ft. Jamboree with a Ford 460 that failed smog. This motorhome is new to me, so I did a full tuneup and replaced the passenger exhaust gasket. It runs much better now, but I was told it didn't help and it looks like vacuum leaks. I also discovered that stomping on the throttle will cause a stall, but I slowly go to full throttle and it will pull pretty well. Idle is a bit rough.

From what I have read, it seems that this year/model engine is prone to drying out the gaskets between the carburetor, EGR plate/spacer and manifold. That leads to cracking and vacuum leaks.

I have thought of doing a leak test with brake cleaner, but truth be told, I don't have a problem just changing out those carb./spacer gaskets since it is a known issue. What does concern me is that I also read that the Holly carburetor on this model RV can be really hard to tune and leak prone. Since I have to take off the carb. to replace the gaskets, now would be the time to either rebuild myself or purchase a rebuilt. If this carb. is a pain to work with, I would lean toward paying a rebuild service, but $200 or more is nothing to sneeze at.

The questions I hope someone with experience can answer are as follow.

1.) Is my carb. with less than 60K miles on it likely to need a rebuild?

or

2.) Would you just replace the carb gaskets and expect it to pass smog?

Thanks for any all help offered.

Jose

TyroneandGladys

Chandler AZ

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Posted: 01/19/13 05:45pm Link  |  Print  |  Notify Moderator

We had to rebuild our carb due to varnish buildup from the previous owner not using a fuel stablizer while stored. The way the vehicle is "driven" during the smog test can effect it also as a result you should have it tested at a test center that is in an area with more older vehicles.


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Coach-man

Florida

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Posted: 01/19/13 05:57pm Link  |  Print  |  Notify Moderator

You seem to "know your stuff", a rebuild kit for that carb should not be too expensive, replace the gaskets and rebuild the carb. Clean it real good since varnish build up may be a problem while it is apart.

K Charles

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Posted: 01/19/13 06:01pm Link  |  Print  |  Notify Moderator

A bad accelerator pump could cause the "stomping on the throttle will cause a stall" but won't make it fail the smog test by itself. I would go with a vacuum leak at the carb or more likely at the manifold. You may not find it with brake cleaner because it may be leaking on the inside as the 460 manifold also serves as the valley cover.





smkettner

Southern California

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Posted: 01/19/13 07:03pm Link  |  Print  |  Notify Moderator

What were the smog readings vs specs?

Honestly I would get a replacement Holley if it needs a carb. It is not so much that it only has 60k miles but the fact that it is 30 yo.


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DaHose

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Posted: 01/19/13 07:39pm Link  |  Print  |  Notify Moderator

The readings we got were ...

HC - 2000
NO - 9PPM
CO - 0.18%
CO2 - 6.8%
O2 - 11.0%

I don't know what the limits are. They aborted the test due to sample dilution. That is why he said it was a vacuum leak.

Yes, Coach-man I have a pretty strong mechanical background.

OY! So are you saying (K Charles) that you would take off the intake and replace that gasket too? That means breaking loose the thermostat. That's "let someone else deal with the headache and mess" territory. I do think the RV came with a carb. rebuild kit in the spares. I suppose I should take that as a hint.

Completely rebuilding a carb yourself still leaves the tuning hassle. Most of the places that do rebuilds flow test and then tune on an engine. Maybe I could just replace the diaphragms and O-rings on the accelerator circuit, with the thought to order a rebuilt if that doesn't fix the stalling problem.

Jose

tpi

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Posted: 01/19/13 07:46pm Link  |  Print  |  Notify Moderator

Stomping on gas stall does indicate bad accelerator pump.

Rough idle could be vacuum leak, idle mixture adjustment, idle speed setting, or could be uneven compression. Check all vacuum hoses for leaks, particularly power brake booster and PCV valve.

If the carb job doesn't smooth it out, I'd check compression. In fact I'd check it first except your flat spot sounds almost surely like accelerator pump.

If equipped with catalytic converter, it is possible to have lost effectiveness. I'd start with obvious roughness and compression first.





smkettner

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Posted: 01/19/13 08:16pm Link  |  Print  |  Notify Moderator

I am going to assume the 2000 HC is the issue. Idle a bit rough has me thinking lean misfire. I would probably put a new carb on. But first check the firing order that all plug wires were replaced correctly. I assume it has electronic ignition.

woodgeezer

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Posted: 01/19/13 09:15pm Link  |  Print  |  Notify Moderator

Just out of curiosity, is this the original carb? Regardless of mileage, has it been replaced with a smaller air capacity model. My old Ford Cube (1984) had fuel problems about 75,000 miles. The "new" emissions requirements were a little in flux. I bought one of the first cutaways approved by the EPA, it didn't have all the limits on smaller engines, but I think Ford fudged. My unit was built up by Utilimaster, a division of Holiday Rambler.Basically a Box van or Motorhome chassis. It needed a huge carb. As I remember a 750cfm or larger. If your carb has been replaced, it could be a more common smaller 650cfm like they tried to do on mine. Did not work, forced the tinkering with the timing to the extreme to pass emissions. I would think that if you are close, you would do well to check the size, and settings first. Also, I would go down and get a fresh oil change. That engine used about a quart every 1,000 miles when new, so,you don't want old oil adding to your problems.

DaHose

No. Cal.

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Posted: 01/19/13 11:39pm Link  |  Print  |  Notify Moderator

Thanks for all the feedback so far.

Sounds like the consensus is pull carb. and rebuild. Since the carb. is already off, replace the intake gasket because I am already into it that far and the everything will be solid.

I have tools and ability to do the work. What I don't have is time, but labor rates in my are are $175 per hour for heavy duty vehicles.

BLAH!!!!!

Jose

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