Hello all. 1977 Chinook 20r. Non cat. model, Trying to pass oregon emissions, was idling rough and hydrocabons were through the roof.

Prelude:
Replaced exhaust from manifold back, Comp test was within tolerance, cleaned the carb, added new cap rotor wires and plugs, adjusted the valves, set the thing to TDC, installed new points to spec and upon startup, found the running timing was about 50 degrees advanced. looked at the carb and found a dead jet, also couldn't adjust idle/mixture screw enough to change RPMs and keep her running at 800 rpm. so I figured Stock carb was crapped out and I installed a 32/36 weber.

Idling better than ever now (stock settings Idle is at about 850-900 RPM and timing is at 8 degrees) but when I throttle it heavy I gets a nasty backfire though the intake and the timing retards itself about 5 degrees. I haven't found any vacuum leaks. Am i running too lean, timing might be too far advanced for such an old engine? I don't get it. any ideas?

 

Back your timing down a bit my weber likes to do that with six degrees or more of advance get a few hick ups more so when the motors cold but try retarding your timing a bit

 

Well tried retarding it and problem is just as bad. Tried enriching the mix to no avail. :/

 

Took it in and had it timed and adjusted. Runs like a champ. However after failing the test 5 times today with various lean tunings and different timing configs, I hate to say it I think I am going to have to bear down and install a Cat to pass this danged test.

 

AZ Dave...Just curious, what did the shop do that you hadn't?

 

Well a good deal of my trouble looking back was that my harmonic balancer had the 2 timing marks of a 77 but the tab for the timing marks on the block were from a 78 so I was having trouble timing it just right, although the mechanic said I was close. Also I was following the weber install to a "T" and not giving it as much Idle as this particular application wanted.
Also the anti-backfire valve in the air injection system was faulty so we just deleted the whole hose and tube that lead from the smog pump to the Exhaust Manifold and welded it shut.

The Emissions numbers are no worse than before I deleted the system and installed the weber, but sadly they are about the same. Thus I think I am going to have to go with a high Flow Cat. to get my Tabs.

A 35 year old vehicle has to pass emissions, what a joke.

 

Added the Cat converter and the Poor thing still isn't passing. I guess it's time to register it or sell the thing across the border in washington where it has no emissions.

 

Don't have any friends of friends that might help you out? Would not be right to have to sell her due to a rediculous smog test...

 

Heh I'm looking as we speak hahahah, however that also involve proving my adress and getting a Washington drivers license, what a Pain.

 

I'm sayin someone that can "smog" it for you in your state...

 

Unfortunately in where I live you have to go to a state run testing station operated by the DMV and DEQ. You can't go to an exhaust specialist and do the secret squirrel handshake and pass unfortunately. Stinkin' hippies.

 

Dang that sucks!!!

 

Last ditch tomorrow is a quart of Denatured alcohol in the tank otherwise drastic measures!

 

Any news today?!?!?

 

Ran the truck around town until the tank was down to about a 16th and threw in 2 quarts of alcohol, made sure the thing was running hot as hell for the cat and then tested, sadly the numbers were no better. I drove it around the block and idled it for another 15 minutes, added 2 more quarts, leaned of the carb about a turn and a half of the mixture screw and retested. Guy was like "I dunno what the hell you just did but leave it adjusted where you have it, I've never seen numbers this low on a vehicle this low!" ran to the gas station immediately and filled her with premium ran to the DMV, Got new tabs and all's well

 

Nice!!!!

 

wow, that is quite a story. I guess I can try that, although I have a fall back of getting a non-metro area address that requires no emissions (colorado). Still at only $15 per 2 tests, I might try the alcohol thingy. Where do you get it?

 

if the numbers are that bad have you thought of rejetting the carb? How does it run?

 

Denatured alcohol you can get it anywhere Walmart/lowes /home depo
But if your running real bad or. CAnt get a good tune you might wanna try some re jetting what sea level are u at in Colorado .

 

Bwjunkie I bet your carb is jetted for sea level...a rejet could really help your situation.