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 The strong smell of exhaust!
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 07 Apr 2010 :  11:33:33 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Maybe it's me. I've had this complaint for years now. But I find the exhaust from my engine to be quite "smelly." Granted not one of my other vehicles is without cats, and none of them sport a racy cam (Comp Cam 276AH-10). However the "thick smell" of exhaust to me is terribly strong.

After running the engine, checking the idle and doing some tuning to overcome the rich AF mixture my clothes reek of exhaust. I realize the overlap with that cam is significant, but is this condition one that all hot rodders have or is this continued evidence of a very rich AF mixture?

Greg Miller, Tom Worrall, Dan Steward, Corey Thompson--any of you experience this?

Bill


"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.

Edited by - Bill Boyle on 07 Apr 2010 3:21:49 PM

Vid
Kicking Horse

USA
1685 Posts

Posted - 12 Apr 2010 :  9:23:50 PM  Show Profile  Reply with Quote
Bill, when I start my wagon at my house (on two acres of horse property) I hardly notice the exhaust smell. When I start it at my condo (with neighbors homes in close proximity) I think the fumes are pretty strong and I am concerned that I am stinking my neighbors out! No one has complained yet, but if I idled it for long peroids like during tuning, I am sure someone would complain and rightfully so. Not everyone thinks race gas fumes smell like Chanel #5, hahahahha But to answer your question, YES I think the smell is strong with these big overlap cams.
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Armadillo
Cochise

USA
223 Posts

Posted - 12 Apr 2010 :  11:42:44 PM  Show Profile  Reply with Quote
Yes, I have smelled it. Makes my eyes water at times. Right now I just started my engine for the first time and it was bad. I have some adjustments to do. Leaning the Idle a little with the A/F screws is what I will work on. We ran it for a 1/2 hour last night to do a heat and leak check. I have 2 other things to work on before I worry about the exhaust smell.

TOm

Will I ever be done?
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 13 Apr 2010 :  07:27:47 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
After thinking about this on and off for days now, I'm pretty certain the strong exhaust smell is from the overly rich condition of my q-jet. I'm working on that problem right now. When the plugs are showing a normal burn, I believe the stench will be pretty much gone.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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rad400
War Paint

USA
1251 Posts

Posted - 13 Apr 2010 :  09:23:08 AM  Show Profile  Reply with Quote
Bill if the smell bothers you than you are getting to old and need to sell your T/A. lol

Conrad
79 Trans Am 400 auto Crower 60210 Torker II Holley 750 vac sec. #12 heads,3500 stall.
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 13 Apr 2010 :  10:14:44 AM  Show Profile  Reply with Quote
No, don't sell that piece of junk. I will fly down and take it off of your hands for free.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Christ
Howling Wind

USA
1808 Posts

Posted - 13 Apr 2010 :  7:35:42 PM  Show Profile  Visit Christ's Homepage  Reply with Quote
quote:
Originally posted by Phil

No, don't sell that piece of junk. I will fly down and take it off of your hands for free.




This sounds like you all have rear end problems and should wear some depends!
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Vid
Kicking Horse

USA
1685 Posts

Posted - 14 Apr 2010 :  10:33:40 AM  Show Profile  Reply with Quote
Bill, for the record my plugs are looking sooty too, but I am not sure how much of that is due to the carb being over-rich or the restrictive exhaust manifolds (stock log type) that clearly do not work with my cam (Comp 041 repop). Once I get my RAIII manifolds and X pipe on (soon), then I will really work on tuning it up. No point in fine tuning it until I get the correct exhaust system installed.

Good luck!
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 14 Apr 2010 :  2:34:45 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
When I drive around in my smoking jacket and yachtman's cap I like to smell good. What's wrong with that? You guys are tough on me.

----
Vid--I don't believe a better exhaust will cure sooty plugs. My new exhaust did nothing for it whatsoever.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 14 Apr 2010 :  3:48:30 PM  Show Profile  Reply with Quote
To quote Sam Mallone: "Hey, I'm smokin' in ANY jacket"!

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Vid
Kicking Horse

USA
1685 Posts

Posted - 16 Apr 2010 :  01:53:19 AM  Show Profile  Reply with Quote
Bill, I agree with you, the soot is coming from upstream no doubt. That is a project I will tackle after the new exhaust is in. It is choking on it's own exhaust. There is now way it can't be.

Did you ever resolve the issue with the secondaries not opening? As good as my car runs, I don't think mine are opening, or not fully anyway, because I'm not getting that Q-Jet secondary sound (or power) when I stab it, we all know the sound - bWaaaAAAAAA!

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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 11 Oct 2010 :  7:28:08 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
This is an older thread from earlier this year.

I haven't driven the TA much at all. I've too many other things going on right now to deal with it.

Tonight, in between activities, I decided it was about time to take the car out for a short drive. (Got to keep the charging system working). With the change in weather (cooler air) the idle dropped from 800 to 600 rpm. My biggest complaint is that my clothes reek of exhaust after driving it. None of my other vehicles do it; all have converters in place. I'm convinced that only cat converters treating the gases is the only thing that will make a difference.

The car has been outdoors now and the sun just bakes it. The small patch of clear coat on the roof that was breaking down has now spread to the entire roof. The clear on the hood and trunk is now beginning to break down. It won't be long until I start seeing evidence on the upper part of the doors. Considering the hundreds of hours spent refinishing the car in the early 90s, it is disheartening. Refinishing the car is no longer a thing I can do myself. I don't have the "garage" to do it as I did before. The cost of having a professional do it the way I want it is expensive. So I'll have to save up for that.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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dgray
Crazy Horse

845 Posts

Posted - 11 Oct 2010 :  8:51:08 PM  Show Profile  Reply with Quote
Yeah the sun is almost as hard on paint as the winter is. (I'm not talking about road salt- just being parked outside). The Southern sun is death on the interior too. I guess you need a really good cover. I have a friend who put up a tent-type garage 4 years ago and it still looks good and I'm talking about the Michigan winter here too. I think he only has about $500 invested in it, including an OSB floor.
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Kiwi Mal
Crazy Horse

New Zealand
690 Posts

Posted - 12 Oct 2010 :  12:48:24 AM  Show Profile  Reply with Quote
quote:
My biggest complaint is that my clothes reek of exhaust after driving it. None of my other vehicles do it; all have converters in place. I'm convinced that only cat converters treating the gases is the only thing that will make a difference.



Bill, that seems strange to me, just because you have no cat's on your exhaust dosn't mean you should have a strong smell inside the car. You have dirty air coming into the car somehow. I would check to make sure there are no places for fumes to enter the cabin, lost rubber bungs etc. Is your exhaust exiting where it should, and at the right angle. Sometimes fumes can be drawn into the cabin when the window is down.
Cars never ran cat's for years before they had to for emissions.
I remember you had header seal problems, but you sorted that problem out, so that should not be the cause.
I would drive it with the windows up( not for to long though), see if you can smell anything. Then try down.
Good luck.

Edited by - Kiwi Mal on 12 Oct 2010 03:30:00 AM
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Mark S.
Cochise

USA
432 Posts

Posted - 12 Oct 2010 :  01:18:22 AM  Show Profile  Reply with Quote
Consider the 10% ethanol factor? That does give the exhaust a different "fragrance" than 'ol plain unleaded used to have...

PSP Member since 1996

Never enough cubes...

"The difference between genius and stupidity is that genius has its limits." - Albert Einstein

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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 12 Oct 2010 :  07:44:26 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
The sun is brutal. My 77 corvette project car that I still can't get rid of, sits under a custom cut car cover and after 1 year in the weather is breaking down. This is a heavy duty cover and it can't cut it for long.

I think one of the problems with my paint, at least the clear coat, is that it was wet sanded, buffed out to perfection and gave a car show shine. The reduction in thickness of the clear coat probably allowed the sun to do its destruction more easily. For years the car was fully projected in the garage. This kept the exterior from the elements and allowed me to have a "looker" any time during the week. Car shows were always easy to attend. I polished and protected the car like it was a fine piece of expensive cut glass. Things changed obviously and that change has made a difference.

The stink of exhaust has been evident since the original GM converter was removed and headers were installed. I used to drive the car with AC daily to and from work and was one of the family cars. That was between 1979 and 1984. I put a mere 30K miles on it during that time and 17k since. The AC has not functioned for decades now so driving is always with the windows down. Now that fall has arrived in south Florida and low 70 degree temps are here, driving in the early morning or late afternoon is pleasant, except for the exhaust.

Mal, there is no header leak at the head or at the collector. There are no grommets missing under the car that go into the cabin. Whatever exhaust is coming in reaches me because the windows are open. To make sure, I will drive the car again today with the windows up and see if that makes any difference.

Mark, I know that most cars did not sport converters before 1974. Those early cars did not have an exhaust smell that I recall. Even those that spewed crank case gases under the car--pre PCV. Clunkers with sludge build up would smell, and you could smell those engines when they weren't running. The mixture of gas today is also different from back then. Gasoline seems to constantly evolve--at least the concoction of ingredients. Whether ethanol is a factor in adding a "fragrance" to the mixture is a possibility--don't know.

All I do know is that I'm dissatisfied with the exhaust smell. If you put on a clean pair of jeans and shirt and go for a drive, you and your clothing shouldn't smell as though you've been outside doing the lawn on a riding mower etc for 2 hours. I don't believe I'm overly sensitive to this as others in my family have commented about it to me.

This whole thing stinks.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.

Edited by - Bill Boyle on 12 Oct 2010 07:45:19 AM
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 12 Oct 2010 :  11:25:49 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Just took the TA for a drive and ran with the windows up. No smell of exhaust inside the car. However, when I parked and got out--smelly exhaust. So, there is no leakage inside. What exhaust comes in enters via the open windows.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 12 Oct 2010 :  1:17:41 PM  Show Profile  Reply with Quote
It's the performance cam and carb smell. It's part of the "ride".

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Kiwi Mal
Crazy Horse

New Zealand
690 Posts

Posted - 12 Oct 2010 :  2:11:07 PM  Show Profile  Reply with Quote
Some fumes must be being drawn into the cars window from the exhausts exit. Is the exit in the stock location ?. Mine exit at the rear of the car now, mainly as thats how the exhausts tail pipes were and to change then would have needed a lot of work. No smell in the car.
You were contemplating putting performance cat's on at one stage wernt you ?.
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jambros1
Tribal Scout

USA
18 Posts

Posted - 12 Oct 2010 :  4:24:45 PM  Show Profile  Reply with Quote
Bill, I had the same strong gas/exhaust smell on my 79' T/A. I lowered the carb. float level by 1/16" and it helped. I think that I was pulling gas over the boosters. Since I made that adjustment my spark plugs have gone from sooty to a tan color burn.

Jim Ambrose
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 13 Oct 2010 :  07:40:00 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Mal--the car has the splitter exhaust pipes, albeit those larger than stock ones from Pypes. It is all essentially in the same location as stock. Yes, as to contemplating performance cats, one for each bank, located behind the collectors, and before the X pipe crossover.

Phil-- don't recall RAM Air 4 engines is stock form with the 041 cam spewing such nasty fumes. Maybe I just haven't dialed in the carb quite right following Cliff's rebuild. The whole thing sure puzzles me. Let me know when you plan on vacationing down here...you can help me sort it out--it would be grand vacation.

Jambros1--carb may still be an issue for me.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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jambros1
Tribal Scout

USA
18 Posts

Posted - 13 Oct 2010 :  11:00:01 AM  Show Profile  Reply with Quote
Bill,The inspiration to lower the float level came to me after reading page 50 of Jim Hand's book. If you can look down into the carb. with the engine running and see even a few drops of gas dripping from the boosters it will make adjusting mixture screws or jetting useless. The 79'400 uses a fairly high pressure fuel pump if equiped with air conditing (5-6 psi) which can over-ride the needle and seat causing flooding at the worst or the "strong smell" at the least.

Jim Ambrose
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Vid
Kicking Horse

USA
1685 Posts

Posted - 15 Oct 2010 :  12:46:38 PM  Show Profile  Reply with Quote
I am running the 041 cam and my car definitely makes plenty of stinky fumes. To top it off, I am running 50% pump premium blended with 50% LEADED 110 race gas. I really doubt that any amount of tuning will alleviate the condition in my car, but maybe Bill's will be different. I almost feel like I should splice in a couple of Cats to the system simply because I feel a bit "guilty" for the cars behind me in traffic. Is that crazy talk or what?! LOL
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 15 Oct 2010 :  2:58:00 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Who hasn't been stuck in traffic behind some old car that is either burning oil, leaking oil and gas, running on only a few cylinders and stinking the place up to high heaven? I usually get stuck behind someone like that every day. Usually it's an old work truck.

Vid--you're not running AC are you? If not, how do you keep the stink out of the car's interior? With window open it has to be as delightful as mine. It's probably less costly to install high flow dual cats than to issue gas masks to all the cars behind you.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Christ
Howling Wind

USA
1808 Posts

Posted - 15 Oct 2010 :  11:33:39 PM  Show Profile  Visit Christ's Homepage  Reply with Quote
quote:
Originally posted by Bill Boyle

Who hasn't been stuck in traffic behind some old car that is either burning oil, leaking oil and gas, running on only a few cylinders and stinking the place up to high heaven? I usually get stuck behind someone like that every day. Usually it's an old work truck.

Vid--you're not running AC are you? If not, how do you keep the stink out of the car's interior? With window open it has to be as delightful as mine. It's probably less costly to install high flow dual cats than to issue gas masks to all the cars behind you.





Don;t you dare do it. I love that smell! Reminds me of my car!
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Vid
Kicking Horse

USA
1685 Posts

Posted - 16 Oct 2010 :  1:36:07 PM  Show Profile  Reply with Quote
Bill, no a/c on my ride. I don't have much of a problem with fumes in the car unless I lower my wagon's tailgate glass, then - phew! The tailpipes exit through chrome turndowns under the back bumper so when the tail glass is down, you'd better have the front windows open otherwise it could get downright deadly.

My car also has the front "wind wing" windows which work well for ducting in fresh air. Maybe that is the difference. Unfortunately, I deleted the lower butterfly floor vents when I installed custom kick panels with stereo speakers in them.

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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 19 Oct 2010 :  11:15:55 PM  Show Profile  Reply with Quote
Bill, thats a deal but you are second in line as I have to go irritate Cobrabill in Tucson first.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Mark S.
Cochise

USA
432 Posts

Posted - 21 Oct 2010 :  09:25:25 AM  Show Profile  Reply with Quote
Bill,

Just wondering, is your trunk weather stripping still sealing? You may be getting fumes into the car from that source.
I recall having a similar issue with my GTO after I installed the tail pipes... For me, the top and sides were sealed fairly tight (I never had water in the trunk after a wash) but the trailing edge was not as tightly sealed. I had to get into the trunk to see the "light" gap. That won't be as easy to do for you on your T/A!
I put some strips of rubber from an inner tube in the channel and the weather strip sealed up fine afterwards, and I had a lot less exhaust smell in the car.

FWIW

PSP Member since 1996

Never enough cubes...

"The difference between genius and stupidity is that genius has its limits." - Albert Einstein

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Brandon
Two Feathers

USA
76 Posts

Posted - 22 Oct 2010 :  09:54:35 AM  Show Profile  Reply with Quote
Wow, what a timely thread for me. I was just logging in after an 18 month hiatus to ask about the very thing Bill brings up here. I'm glad I'm not the only one. We have noticed in the last 2 years that the exhaust smell is awful in the firebird as we drive. We don't remember it when we bought the car 5 years ago. What have I done since then? Rebuilt engine and dropped from the 041 cam to Edelbrock's version of the RAIII cam, put RA branched manifolds on with X pipe 2.5" exhaust, and changed the 1/4 panel exit to a rear exit tip like a '70's FB. I'm really thinking that the exhaust change might be the issue. I was behind a grand prix one day when it was cold out. I happened to be looking at its exhaust pipes and noticed the "smoke" curling right up the back of the car and over the trunk. When it accelerated, this became even more noticable for a short time. After that, I changed my bad trunk seal which leaked every time I washed the car. I thought the smell diminished. However, now that we have opened and closed the trunk several times, I smell it again. We reek when we get out of the car.
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 22 Oct 2010 :  11:09:31 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Brandon--welcome back.

It is still very possible that my Q-jet is still running rich. After installing the 62 heads, larger duration cam, the carb would not allow the engine to idle. It was sent off to Cliff for "tampering" and he modified it so adjustments could be made accurately. I got it to idle and worked the two front mixture screws. Yet the engine spews out smelly rich exhaust. Part of it could be from the overlap on the cam, however, I still believe installing cats will cut the smell down considerably. I must run 93 fuel now. Most of the gas contains up to 10% ethanol here in South Florida. It hasn't caused any issues with my more modern cars, and I don't expect it to be behind the smell.

If I had AC running and the windows up, my clothes would not reek after driving. However, once a new system is installed, it pretty much precludes me from" toying" with the engine, like I do so often.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 23 Oct 2010 :  09:36:37 AM  Show Profile  Reply with Quote
Bill, don't waste your time with cats. You'll burn them out in short order as I believe the cam has alot to do with it. Have you contacted Cliff for any ideas?

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 23 Oct 2010 09:38:30 AM
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 23 Oct 2010 :  7:05:34 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
No--I haven't spoken to Cliff. When time allows I may tweak the carb a bit more. With the amount of miles I put on the TA--Cats would last many, many years.

[Unrelated--my project 77 Corvette will soon be in the hands of a fellow Pontiac enthusiast who will do what I couldn't do to restore it. My hopes of restoring it fell apart a few years ago and now at least the car gets another chance. Tomorrow is will be trailered and on its way north. My wife says I should have donated it, but I'm sure it would have found its way to the crusher then. This is a far better thing that I do.]

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.

Edited by - Bill Boyle on 23 Oct 2010 7:14:02 PM
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 23 Oct 2010 :  9:29:23 PM  Show Profile  Reply with Quote
I still think that fine tuning the combo will result in more reduction of hydrocarbons, and thus the smell.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
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Vid
Kicking Horse

USA
1685 Posts

Posted - 25 Oct 2010 :  5:22:22 PM  Show Profile  Reply with Quote
Went to a Halloween shindig last weekend with my friends' band The Ghastly Ones. There was a hot rod hearse club showing off a few of their amazingly transformed hearses. Caddilacs, Hudsons, Lincolns, you name it. I couldn't help but notice the older hearses (pre 1970 or so) had the exact same aroma Bill and I are experiencing. So, I think we just forgot how pungent older car fumes can be.

Of course I forgot my camera but there was a sweet mid 60's Bonneville hearse in the show... so if you gotta go, you can go out with Pontiac style.
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Phil
The Great White Buffalo

USA
7238 Posts

Posted - 25 Oct 2010 :  10:13:41 PM  Show Profile  Reply with Quote
Unless you guys look like Spicoli piling out of a smoke filled Microbus I wouldn't loose any sleep over it.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 25 Oct 2010 10:15:07 PM
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BVR421
Cochise

Bahamas
245 Posts

Posted - 09 Nov 2010 :  10:14:33 AM  Show Profile  Reply with Quote
lean idle circuits (basically stock carbs) and big cams will really raise a stink
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Bob Kaplan
Cochise

USA
419 Posts

Posted - 19 Dec 2010 :  12:54:24 PM  Show Profile  Reply with Quote
Hi Bill, I'm reading this post and I know the idle circuit will need a tweaking. I modified my QJ using Cliffs book and it idles fine. Pull the carb and look at the position of the throttle plates and idle slots. The slots should be no more than half exposed. If they are fully exposed you are idling on the main nozzles. Give Cliff a call or modify your carb to his stage 2 specs.

The surgeon general said nothing about smokin a chevy...
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455 Formula
Cochise

USA
244 Posts

Posted - 06 Jan 2012 :  1:45:44 PM  Show Profile  Reply with Quote
Bill,

I had a similar problem. My wife has Asthma and the old car exhaust smell really gets to her, even when we pull up behind one at a stoplight!!!

It takes a lot of work to get the exhaust cleaned up on a Pontiac. One of the things I have noticed on Pontiacs is how much cleaner the exhaust is when less exhaust duration is used and I have checked the tailpipe emissions with Dad's old Sun Exhaust Gas Smog Machine.

On Pontiacs, I run no more than 4 to 6 degrees of exhaust duration with headers and good I.E. ratios over 80% (as a rule) and a single pattern at 90% and up.

My Pontiac 350 used a custom UD camshaft with 220/226 @ .050 on a 111.5 degree LSA. I also did a lot of work to the Q-Jet including modified air bleeds, idle tubes, restrictions, etc., to try and get the fuel curve as flat as possible. I also used a double-hooded secondary divider, bushed secondary throttle shafts and bypass air (via the hot air choke bleed only) added to keep no more than .050 of the transfer slots exposed at idle. I do not enlarge the idle discharge ports under the mixture screws.

Running dual taper metering rods (from Cliff) and running them high up in the jet (about 5 turns out on the APT) seems to give the best overall fuel control. Currently, I am running .070 main jets with a .045 dual taper rod with the APT set at 5 turns out.

The #1 problem I see with Q-Jets is incorrect power piston (PP) spring rates. I set these units up exactly like a Holley by dividing the lowest idle manifold vacuum in half and selecting a PP spring with that value as a starting point and I drop the value from there with stopwatch and seat-of-pants testing.

I believe the practice of selecting a power valve or PP spring that opens 1-2 in/Hg below idle vacuum, and long exhaust durations of 8-10 degrees and sometimes more, are contributing factors to the dirty exhaust issue.

On my Pontiac 413 with 231/235-110 UD, we only used a 4 degree spread becasue my I.E. ratio on the ported 6X-4 heads was approaching 86%. I am running a factory PP spring that opens around 3-4 in/Hg. I bought a bag of (10) of them back in 2005 and at the time they were available under part number 7029922.

I also run around 46 to 50 degrees to total timing via ported vacuum advance. The MSD #8412 low resistance carbon button is another SOP. I use R42TSX plugs with a minimum spark plug gap of .060 which really cleans up tailpipe emissions.



(I ran R46SZ on the '092' headed Pontiac 350 gapped at .080 FWIW)

Plug color is hard to judge with modern fuels, but I have no blistering, no pinging and very good coloration in consideration of our modern fuels. With a 4 row radiator and 5 gallons of coolant on board, the car actually runs slightly cooler the harder you run it.

I will probably still put dual cats on the Formula, in consideration of my wife's asthma, but the car burns so clean now, I think I will be able to run cats without keeping them glowing all the time...Robert

Edited by - 455 Formula on 06 Jan 2012 1:48:23 PM
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Bill Boyle
Horse Feathers (Charter Member)

USA
4904 Posts

Posted - 10 Feb 2018 :  3:01:17 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
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"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
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