If you got full vacuum at the ported nipple, it means your throttle plates are open too far at idle. You may have problems in the idle circuit in the carb. If the throttle plates are open that far you will be drawing some fuel from the venturi which shouldn't happen at idle.
You'll hear people say there's no vacuum signal to the distributor at idle, but that's really only true if the RPM is set to factory specs. Many people like a faster idle, most likely because it starts pulling in more ignition advance and smooths it out quite a bit. Put a timing light on it at 600+ RPM and you'll probably see 20° or more.
I had a stinky exhaust Y-Block for a time, somewhere in the tuning process. I spent a long time learning about Tune-Ups. A lot of people (myself included) are inclined to believe throwing a new cap, rotor, plugs & wires on it constitutes a Tune-Up. There's waaay more to it than that. I agree "more" ignition advance is better or bestest than "less", but there's a gazillion things that have to work with each other, or put another way if you change one thing it will affect other parts of the tune. Unless you're an Ace mechanical genius and smarter than the engineers that designed it the best you can usually do is return the baseline adjustments to factory specifications, or exceed them in terms of tolerances +/- and then go from there. A big part of being a mechanic on the old iron is often simply un-fvc&ing previous mistakes. One thing I didn't see mentioned yet is engine temperature or thermostat. When I first picked up the Y block I put a 160 °F t-stat in, because I'd heard that was best. That ain't necessarily so. I use a 195 and it runs a lot better, among other things, and the heater works in the wintertime. Never had any vapor lock or things like that.
Report: “Stank” is history! Installed a fitting for manifold vacuum, was able to adjust from 17” of vacuum to just under 18.5”. It doesn’t feel like it runs any better, (it ran great before this tweaking) but that acrid smell is gone. Thanks for all of the great input guys. Be well Jeff
Do we all get a Pizza & a Glass of Beer ..??? With all the Answer's You should Keep Track for The Next Time.! Dom. Just my 3.5 Cents Live Learn & Die a Fool
Right you are Dom! I’ve have been keeping track and so far by contributing your “3.5 cents worth, you’re entitled to a topping of your choice. Not a complete topping, a mushroom, a slice of sausage, Pepperoni or a sliver of cheese. Kidding aside, who am I kidding? Thanks to you and all the other contributors.
Glad you found something Jeff. Just in case there's some residual stink, now would be a good time to take it on the highway and blow the cobwebs out of her.
GREAT!!!.....Vacuum gauge is a wonderful tune-up tool. We should all use it more often. I guess it just seems "too-simple" to rely on!? I mean....come-on-man! it ain't expensive....it ain't complicated......it ain't hard to put on......it ain't hard to read.......it ain't noisy.....how could a vacuum gauge possibly be worth anything??! Come-on-man! (you a junkie?!) Glad you got it!! 6sally6
Hi Modagger I'd start by starting it and give a couple snaps of the throttle then shut her down pull a plug ( any cylinder and smell it
If plugs smell the same then you need to pull radiator cap then pull gas cap and check for same odor . Cats or other animals may like your radiator and it's a remote chance but after awhile will damage complete coolant system so turn the heater on and check odor there also . If all seems ok I would start with lining the gas tank and if plugs do not smell I'd put money into exhaust
All great tips Freddie! Thankfully all it took was a vacuum gauge, the proper fitting and a carb adjustment to get rid of the offending stank. Whew! Be well Jeff
Great news indeed thank you for sharing the antidote . Safe and Drive well , FF Sent from my 5032W using The H.A.M.B. mobile app
Ask a silly question, but how did you adjust the carb to increase vacuum? a) by resetting the idle position (butterfly more closed at idle), or b) by richening the idle mixture screw (for a Holley, turning the screw out), or c) by leaning the idle mixture screw (for a Holley, turning the screw in)? Each of these indicates a different cause of the stank. Cheers, Harv
If all of that fails , check to make sure you do not have a brake fluid leak from the master cylinder to the intake through the booster , a pinhole will let enough through at idle to stink horribly , with only a very slow brake fluid usage. Test by dripping a drip of fluid on a hot exhaust to see if it matches the smell.
The actual Afrikaans word for a stinky smell is "stank." It's pronounced "stunk," though. Glad you got it sorted out.
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