Hey guys. I am running a nearly stock jetted 750 double pumper Holley. Even with a warm engine, the exhaust is gross. Do you think that a mildly modified Q Jet would be cleaner? Standing behind my car running makes your clothes smell! Yes, I am running a good size cam, and that makes a difference. I want to clean it up where I can. Coff coff, hack........
The car runs fine, it just smells. For ignition, I have run an HEI with a MSD 6AL. Now it is an HEI with Accell race module and coil, new wires and plugs. I don't think that it is a power valve - it has been stinky for years.... Are we saying that with a cam and a Holley, that this is not a common probem?
Probably.. Are you running any vacuum advance? And if so, it is ported or full vac? Only reason I'm asking this, is because I switched to manifold vac on my dist, and it instantly made my car smell god-awful. It ran so rich, my eyes burned in the garage.
Interesting! No, I am not running any vac advance. I do have light springs in the distributor with an advance curve kit. One other thing - ALL of the heat is blocked off from the intake crossover.
I had a similar problem on a stock engine (with Holley) until I fixed the choke - it burned way too rich, but only until it warmed up.
I think that the choke is opening all the way, but I will check it. I am still wondering if this is fairly normal - And if it is more common with the more race oriented carbs like the Holley Double Pumpers?
I've got an 850 dp and mine is stinky too. The choke is disabled, but it's the same when warm. The cam is the 288-96H and it idles around 800-850 rpm.
My wagon's exhaust is stinky too. But I don't care cause it runs so good. You could always buy & add some of that Bubble Gum sented fuel additive :laugh: Beth
Thanks Steve and Beth! That is what I am geting at. If the car (and carb) is operating correctly, then I know that I have to either ditch the carb, or the cam. The cam stays, So I wonder how much better (and less stinky) a Q Jet would be over the Holley DP. I am very open to all of your Buick opinions Thanks!
Andrew, I have a Q-jet on the wagon, I also have the Car Craft Hydraulic cam, .525 lift, 231/234 duration, 110 LC. We may just be stuck with the stink. It's kind of fun to drive the wagon in traffic & watch all the people in there cars roll up the windows at a stoplight, cause of the smell or the noise, or both. :laugh: Beth
Thanks again, Beth! That's exactly what I was trying to figure out. Your cam is a little more radical than mine. I am running .480" I and .500" E 112 L.C. unfortunately, I only remember the advertised duration, which is 278 I and 282 E. I guess I won't bother with spending the scarce fund$ on a Q Jet, unless one falls in my lap at the Rod Run in Daytona next week. It's funny that you mention the smell AND the noise, because mine is the same way! The older I get, the louder it seems to be! Occasionally, I add a little burned rubber smell to the mix as well
running rich With a holley and a hot cam You need to take a vac guage and see how much vacume you have at idle and then get a power valve that will stay closed above that point. otherwise the power valve thinks that you are on the throttle all the time and stays open. Another thing is the cat pee we get for gas now days. :rant:
OK doc, I hear you. I believe that my Power Valve is set fairly low from the factory. With a stick trans, my idle vac is actually not that bad. For example, the Idle set screws do work, where I can tell where to set them on a low idle ~ 600 rpm warm. I have a vac gauge and will post back what the idle vac is. Furthermore, I have a Holley book that will tell me that my carb has as a primary power valve rating, I think (somewhere in the cobwebs of my mind) that my power vave is stock opening at 6.5 inches of vac. The car has around 10 inches at warm idle. Lemme make sure about that though. I will let you know. Thanks!
Actually the vacume you have at idle doesn't effect the powervalve at all since they are on a differant circut. So, if you have only 8lbs of vacume at idle, you can run a 9.5 PV and it won't be open at idle. The PV will not open until you are using the MAIN circut and the Vacume drops below the number specified on your PV.... Just thought you all might like to know.
take it to a shop with an emmissions tester and see what its doing at idle and cruise. your cam is small wth that vaccume so should be easy to set correctly. timing is critical and so is over all tune-up if you can play around while on machine you will see a big increase in emmissions with timing advanced vs retarded at your altitude the stock jetting may be too rich also try 2 sizes smaller and see what happens at cruise and idle if too lean go one size etc. also if running to lean at present exhaust will "stink" smells more like lighter fluid than gasoline burned good luck
