455 stage 1 emission and tuning problem

Hi everyone,

my engine is 455 stage 1 fully restored and overhauled, camshaft Howards 550121-12 and distributer original 1112521 3H 2, intake from 69 430 engine with no emission device, heads are from 67 400 engine with bigger ports I changed it to stage 1 specs with stage 1 valves. carburetor early Themoquad 100% overhauled and tuned OK and canister is connected. I set the initial timing to 12 degrees (manual says 10 degrees), vacuum advance connected to the intake manifold (with a Tee to transmission vacuum line), Idle speed 800 RPM and in gear 600 RPM according to the manual. I checked the initial with digital timing light shown 33 degrees on Idle at 800 RPM (initial+vacuum). than tuned the Idle mixture with vacuum gauge It won`t go higher than 14-15 but engine is smooth and brakes are good.

My problems are now:
1- Emission! you can not stand behind the car, emission is high, there are not visible smoke but emission is high as all your cloths will smell after standing behind the car. when I disconnect the PCV for connect my vacuum gauge emission is going down a bit but after connect it again emission going higher and I checked the PCV and cleaned it seems OK.
2- Engine seems to need even more advance specially on middle RPM, In middle RPM it revs a little bit better with ported vacuum, maybe in middle RPM I have better vacuum on ported?, however I have no extra place to connect to manifold vacuum, I should use a Tee to the transmission vacuum line and with connecting to ported I can not tune the idle with only 12 degrees initial. I should open throttle and car will go for dieseling and other problems.
3- engine after siting at night starts very hard with some cranking and spraying and playing with gas pedal. choke and fast idle are set and working.

Power and acceleration is OK but I should solve those problems specially emission is annoying.

please let me know if you can see what is the problem or what can I do to tune it better.

 

Are you used to standing behind vehicles that have catalysts in the exhaust? With no catalytic converter, of course the exhaust is going to be stinky.

Another cause of stinky exhaust is over-rich exhaust; including exhaust gas that has excessive hydrocarbons (HC) due to misfire for any reason including lean misfire. Carbon dioxide, and carbon monoxide are colorless and odorless. You're not likely to have excessive NOx emissions at idle. That pretty-much leaves HC emissions which burn eyes and smell terrible. Adjusting the idle mixture screws "lean" from the highest vacuum/highest rpm position can help a lot while not affecting idle quality too much.

20 degrees of vacuum advance is probably too much--but to do that right you'd also want to curve the centrifugal advance as well.

Does the '69 intake manifold have an open heat-channel under the front of the carburetor? Some older Buicks did; and Chevy up through '69 did. But I don't know about '67--newer Buicks.

 

when I turn the idle mixture down after one turn it start to idle rough and all the way down engine rpm is going down and engine will shut off.
I connected the only intake vacuum port on behind of the carburetor to AC/Heater flaps system like original Buick Quadrajets and on early Thermoquads there are no other manifold vacuums.

Today I set initial to 10 degrees and a Idle mixture half turn down and power piston one turn down, shown little bit change but I notice a leak on exhaust too that it will cause also emission.
also the spark plugs are AC 44TS and gap set to 0.045, I don`t know it is correct or not but one old GM dealer guy told me years ago that GM on manual told that gap is 0.060 but all HEIs had problem so than GM told them to set them on 0.045 and based on this information I set them on 0.045 don`t know if I should go for higher gap or maybe AC 45TS.

 

Two degrees of initial timing, or one heat range hotter plugs is very unlikely to make a difference in exhaust stench, unless the plugs are fouled and causing misfire.

Changing the gap of the plugs is unlikely to make a difference in exhaust stench, unless the ignition can't fire the larger gap, causing misfire. If this "original" distributor is NOT an HEI, you won't get by with a .060 gap, in fact the .045 is pushing it beyond what I'd recommend.

 

What are the cam specs?

 

Camshaft Use:
Street
Camshaft Manufacturers Description:
Good idle & throttle response. Designed for engines with improved intake, 4-barrel carburetor and a upgraded exhaust.
Basic Operating RPM Range:
1,200-5,200
Intake Duration at 050 inch Lift:
215
Exhaust Duration at 050 inch Lift:
225
Duration at 050 inch Lift:
215 int./225 exh.
Advertised Intake Duration:
269
Advertised Exhaust Duration:
279
Advertised Duration:
269 int./279 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.474 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.496 in.
Valve Lift with Factory Rocker Arm Ratio:
0.474 int./0.496 exh.
Lobe Separation (degrees):
112
Computer-Controlled Compatible:
No
Valve Springs Required:
Yes

 

My carburetor is Thermoquad so I can see that giant power piston goes down when I start the engine, I inspect everywhere with flash lamp when engine is running and found no float maybe I should inspect more, also I inspect today a oil smoke in driver bank`s exhaust, It will go away in cruising, It happens just today after hours driving up the mountains and back again, I should change the oil with different one to see the result, maybe oil is going to combustion chamber and make emission and when I put the car on the load it becomes worse. maybe one of the valve stem seals is out of position, maybe when I installed the heads I deleted that original inner springs out and it cause gits wear, I just don`t know yet!

 

I forgot to say that 69 manifold have that open heat channel too.
HEI was standard on 1974 Century 455 stage 1 Gran Sport Buicks. distributor number matches the shop manual

 

If you have the open heat channel in the manifold, BE CERTAIN that the channel is covered with a heat shield and sealed with a gasket. Even if you block exhaust-gas flow across the channel by pounding steel pins or screwing bolt shanks into the exhaust gas passages , you can still have air-leak (vacuum-leak) problems.

It's very possible that the heat channel and your Thermoquad have an incompatibility that allows a vacuum leak, or worse--an exhaust leak into the incoming fuel/air stream. I have seen carburetors ruined by folks who left-out the heat shield, so the base of the carb was exposed to exhaust heat. (The engines ran really bad, too.)

The original system had a high-temperature gasket on top of the manifold, with a thin, stainless-steel heat shield on top of the gasket. Then the Q-Jet carb sat directly on the heat shield.

Folks tend to put the gasket on top of the heat shield, which is incorrect. Or they add a second gasket on top of the heat shield, which is also incorrect.

The shape of the heat channel in the manifold, and the shape of the carb base, all make for a situation where either air or exhaust gas can mess-up the incoming fuel/air mix.

Chevy, Pontiac, and Buick used this open channel in the intake manifold. I don't think Olds or Cadillac did. And I don't promise that there weren't some variations in the gasket/shield for different applications or model-years. I just don't know.

Examples:
Steel heat shield:
https://www.carburetion.com/Products/ProductDetails.aspx?part=G796

Original-style high-temp gasket:
https://www.carburetion.com/Products/ProductDetails.aspx?part=G581

But how either of those would work with your Thermoquad, I can't say. Depending on what you find, you may need to switch to a Q-Jet; or modify / replace the intake manifold with one that doesn't have the channel.

Additional info, but missing the Buick applications:
https://cliffshighperformance.com/simplemachinesforum/index.php/topic,874.0.html

 

Sorry, it was my misunderstanding, you mean that two small passages that send exhaust gas directly to the bottom of the carburetor, 1969 intakes they do not have them but 1968 and earlier do, On 1969 they have a big exhaust chamber right and left and they are completely close. Is there any possibility that they leak from main intake gasket to crankshaft chamber or to one of the intakes?

 

problem is I can not understand whats going on here, I changed the oil with different type of oil for test and emission was gone, than engine start pinging on uphill, I disconnect the vacuum advance and connect it to ported (I know it only effects idle and low RPM). no difference it pinging but only uphill, I checked the initial again it is 10 degrees. and when I start to tune the engine again, emission is back! I guess my problems are multiple and because of it I can`t find it, or maybe my new timing light is bad and shown wrong degree.

I can not tune it with vacuum gauge because in highest vacuum I have emission, with lowering down Idle mixtures vacuum and emission are going down together, I want to test tune the distributor with vacuum gauge but I guess it will ends up as emission too. want to put some fancy race oil on it to test the differences too.

 

Oil change won't help with hydrocarbons at idle. Sounds like you have a multitude of issues. Try to tackle them one at a time.
Checking the carb thoroughly probably needs to be done.
Ignition needs to be verified also. Your balancer may be off giving false timing gun readings.
Distributor may need a look for operation. How old are the components inside of it? How much advance is it giving? Is it giving good spark?

 

But apparently the '69 doesn't have that under-carb exhaust channel.

It's possible for the manifold to crack between the main exhaust crossover and the air/fuel passages. Not real common, though.

My concern is that this is all normal; folks are used to catalyst-cleaned exhaust when this vehicle wouldn't have a catalyst.

Beyond that, I wanna see 3- or 4-gas exhaust analysis results.

 

I know engines with no catalyst will stink (Not all of them), I have classic cars since 1998, European and US models both but this engine is abnormal for example compare to my 1970 Riviera 455 that the engine is not restored at all since the car left the GM factory my Gran Sports`s emission is double or maybe more, and it is not stable, it comes and goes away! and I can not use the car like this, I can not roll the windows down after one hour driving those gases gives very bad headaches. I have exhaust leak too that I should fix it too end it cause more emission too.

What I understand misfiring or weak spark theory could be true because the engine is v8 and on cross plane v8 it could misfire a bit and you won`t notice. spark plugs that I use now is designed for point type distributors and gap on them was 0.035 I changed it to 0.045, I will go back to longer TS45. wires are new but I will check all of them. also yesterday`s knocking only should be cause by misfire or weak spark.

Maybe carburetor could float and stop floating again? for example on uphill and down hill, I don`t know, but maybe I should go for fuel injection, I don`t know yet.

for such camshaft I don`t know how many intake vacuum will be normal, it is now around 15 with vacuum advance attached to manifold and 13 with attached to ported.

also it could be possible that exhaust going to intake somehow from heads or even maybe to crank case and than from PCV to intake.

also I`m now searching for that oil burn too, It is gone now but I should find the problem, If exhaust leak somehow to the crank case it could cause big damages in future.

It should be how many degrees in witch RPM?

 

Sounds like carb issues