Fuel System: running rich

[Ron Dame]

Here is what I am dealing with. Looking for all ideas!

Hi XXXX
I spoke with you on the phone about a month ago concerning the Carter AS on my 1963 Studebaker that (great company) remanufactured about 5 or so years ago. It's been running very rich, and always has. What I sent was a carb with no tags on it, so it is/was a mongral.

You were unhappy with the Pertronix ignition I installed and suggested that was the issue. I reinstalled a used, but not badly worn distributor with points, new non-resistor plugs, but retained the 40kV coil, wires, and cap. I verified correct voltage and resistance to the coil. There was no change whatsoever.

I spoke with Dave Thiebault (sp) about it, and installed an old RBS that I had used, but never was happy with. The rich running went away, but power is way down.

Dave suggested that the engine modifications may be an issue: The engine was originally a Studebaker 170 OHV. It was rebuilt with a crank from a 185 flathead, increasing the compression as well, and a somewhat mildly modified cam with .305” gross lift (I&E), 225 degrees duration @ .50, .460” valve lift and 288 degrees duration at running clearances.

Given this mix, does the carb need re-jetting, and to what? Or can you suggest something better as a carb? Please help me get this running as it should.

Thank you!


What do you all say here?

[jclary]

Hey, Ron, Just a wild guess on my part, but I'm thinking timing... ignition, dwell, & valve adjustment? It would seem to my backyard tinkerer mindset, that somewhere between the mechanical changes you have made to your engine and the factor specs may need a little tweaking? I'd like to see Jack Vines respond to this.

By the way...are you going to try to make the Maggie Valley "cruise-in" Saturday?

[tootie]

Well , it sounds like you do not have an ignition problem , which is where I always start at . But the carb running rich and always has makes me think I would go with the rejetting of this carb. Nothing is good on a street car if you are adding too much fuel to a good motor with good spark and good timing . You said you changed the carb and power was down but can you explain this a little more perhaps , and why you feel it is too rich .Are you seeing the plugs go black?Plugs will tell you the truth about lean or rich . I had a 360 amc that was running really rich and some dude had installed some hi dollar Holley 750 that it sure did not need or like . Swapped to 600 Edelbrock and 360 became a great running engine. I am a points and condenser guy and you sound like you are also.Good luck !

[Ron Dame]

Vacuum at idle is 18" and steady, we are at 2400 feet above sea level, so it's not too bad. The rest of the vacuum readings are normal as well. I know it is rich by 1) soot on the plugs, 2) soot on the back bumper and 3) it smells rich.

The engine is fairly fresh, about 20 on the build. With the RBS, I can't pull hills in overdrive like I did, and acceleration feels weaker too. The throat of the RBS is smaller than the AS,and I suspect this is why the truck is lower on power.

John I probably will be there for a bit, I'm not sure how the cruise through will work, but since I am picking up kitchen cabinets in Canton, I will probably stop by. I hope to see you there!

[christophe]

I wonder if you got any reply from the guys at Daytona Parts...
Your vacuum reading seem a bit low to me. If I recall well, I got 22-24 on my rebuilt OHV6.
If the throat of the RBS is no smaller than the AS, it should be able to feed your engine properly.
You have now to increase gradually the size of the main jet (you'll need special reamers for this) till your engine is happy.
Nice day to all.

[jclary]

OK...I think I understand the concept of running rich. Too much fuel and too little air, right? And, if the installed jets are wrong, it is possible that the air/fuel ratio adjuster can't make up for the disparity. For me, one telltale sign is the smell of the exhaust. The odor of insufficient burned fuel. However, there are two additional instances that give similar signs of fuel not burning completely, and that is old contaminated fuel and valve timing where the valves don't remain closed long enough to allow complete cycles to properly burn the fuel efficiently, right?

In any of these scenarios, hard starting, loss of power, bad exhaust odor, and sooty exhaust smoke are symptoms. You have devoted a lot of time and effort in this vehicle. I really have enjoyed your postings regarding the project, have seen the truck, and like it a lot. I am certainly not the expert my postings sometimes seem. (and I have other postings that prove I'm not an expert.) If I was all that good, all of my vehicles would be perfect, sadly, none of them are.

Regardless of my opinion, or anyone on a phone, or the internet...you are the expert on yours. I look forward to how you solve this current issue.

[PackardV8]

FWIW, the cam specs are to be considered. That's equivalent to the optional R3 cam for a 305" V8. Having 288-degrees seat and 225-degrees duration at .050" is quite a lot for a 185" engine. The OEM intake manifold and single 1-bbl may not be playing well with the increased overlap.

That much cam duration really wants a custom intake and custom exhaust headers. Since no performance intake manifolds exist for the OHV heads, has anyone ever built an intake to mount two 1-bbl carbs on one or built a long ram intake for a 2-bbl?

While the new Holley Sniper 1-bbl EFI would be a very expensive solution, it may be an answer. A friend now owns my Sunbeam Tiger. He put a similar longer-duration camshaft to yours in it and could never get the carburetor tuned to his satisfaction. His garage always stunk of gas when the car came back from a run. He had an Edelbrock EFI installed and says it solved all his problems, albiet for $3,000.

One more time, with a modified engine, it's almost impossible to sort out carb problems without the use of an O2 sensor and direct reading meter.

jack vines

[Ron Dame]

John and Jack: Thanks to both! Now, I know 6 cam specs and 8 cam specs ... well, as best as I can tell, there is no way to compare duration, etc..or it is beyond me. One more hint: though the cam card specs are at 0.012 and 0.14", I've loosened them to 0.018" and 0.020", which "I was told" would help low end torque and improve idle. Yeah, the vacuum is a bit low, but at 2400' elevation, it's not that low is it? I'll admit I let "the experts" figure out the cam. Maybe I need a stock or close to stock cam? I dunno, it's beyond me.

[jclary]

I know it must be a bit frustrating for you professional mechanics to converse with us backyard wrenchers, but may I beg your indulgence regarding oxygen sensors. For me, I understand that built-in oxygen sensors are used by modern computer-controlled systems to make adjustments in real-time regarding fuel/air mixture ratios and timing advance/retard. But, I have never used one as a diagnostic tool. Certainly not on one of our vintage engines.

Without an onboard computer connected to an oxygen sensor, how do you use an oxygen sensor on a vintage engine to adjust the cleanest (most efficient) burning of fuel? Is there some kind of handheld or portable sensor you can place in the exhaust to measure efficiency?

[Mike Van Veghten]

J -

You buy one of these - https://www.innovatemotorsports.com/..._D_BwE#digital

Or other brands that do the same thing.
Install the oxygen sensor that comes in the gauge kit into an exhaust pipe, connect the other end to the gauge per the instructions, and your off and running. Then you'll need to do a little studying (info should be in the gauge kit) on exactly what you will be looking for.

By the way, when you have an obvious "rich" condition, the answer will "not" be found in the ignition...unless the engine is misfiring badly..! Don't let anyone convince you otherwise.

Mike

[Jeffry Cassel]

Lot of over-thinking going on here. Is it really rich? An educated nose can tell you that, or lacking that, an electronic gizmo that measures % unburned hydrocarbons in the exhaust. I'd probably just find another carb., rebuild it (with cam would probably want a step up in jet size) and see if it makes a difference. Lots of places rebuild carbs; far fewer do it well. Altitude isn't high enough to make a difference. Jet size didn't change 'til 5,000'. For Pete's sake, don't do anything as dumb as aftermarket fuel injection. Expensive. Unreliable. Unoriginal. Put the Pertronix back; it can not be the problem.( Lapse rate in barometric pressure is about one inch of Hg per 1,000') KISS

[PackardV8]

I know it must be a bit frustrating for you professional mechanics to converse with us backyard wrenchers, but may I beg your indulgence regarding oxygen sensors. For me, I understand that built-in oxygen sensors are used by modern computer-controlled systems to make adjustments in real-time regarding fuel/air mixture ratios and timing advance/retard. But, I have never used one as a diagnostic tool. Certainly not on one of our vintage engines.

Without an onboard computer connected to an oxygen sensor, how do you use an oxygen sensor on a vintage engine to adjust the cleanest (most efficient) burning of fuel? Is there some kind of handheld or portable sensor you can place in the exhaust to measure efficiency?

Trying to tune a carburetor on a modified engine without a direct reading O2 sensor is akin to the analogy of looking for that black cat in a dark room and the cat may not actually be there.

What the O2 sensor does in real time is tell us the air/fuel ratio. At idle, it wants to be approximately 14:1. For best full power, somewhere around 12.5:1 and for best steady-state highway cruise, about 16:1.

Once the current A/F ratios are known, then it becomes tuning. The tuner must know what circuits and which jets serve each RPM range.

I have the Innovate system Mike mentions connected permanently to the Packard Caribbean V8 in my '55 E12. I'd never have been able to get that 2x4 system tuned without it. Even so, all eight throttle blades never seem to return to exactly the same idle position after a full-throttle run. The idle A/F is always slightly different, no matter how carefully it is adjusted.

I know 6 cam specs and 8 cam specs ... well, as best as I can tell, there is no way to compare duration,

It's not the number of cylinders, but the size of those cylinders The R3 cylinder is 30% larger than the 185". Even there, some R3 experts have told us they prefer the standard 276-degree cam to the optional 288-degree cam.

Also, the R3 has four large carburetor throats on a dual plane intake. The OHV6 intake is a single plane, which does not separate the overlap as well as a dual plane and there is only one tiny carb throat.

Since none of us has direct experience tuning an OHV 185" with this long cam, we don't know precisely where to start looking for our black cat.

jack vines

[Ron Dame]

Jack (and others) is maybe a return to a stock or close to stock cam profile perhaps a better choice? I'll admit, this cam is a lot wilder than I expected, but still, it's not that crazy. All I want is a good driving truck that has most of it's power in the lower RPMs. A 3.030" bore x 4.375" stroke will never rev well., so maybe the cam was not a great choice, even though a long time vendor chose the profile... but he is a drag racer, and I'm not!

[PackardV8]

Ron, if I weren't already a year behind taking on any new projects, this would be an ideal test bed for something I've always wanted to try on an engine just like yours:



an individual runner intake manifold mounting three of the smaller SU carburetors. This could work because IR manifolds don't allow the cam overlap to pollute other cylinders and thus can tame a longer cam duration.

jack vines

[jclary]

Well, Ron, after reading (and trying to comprehend) all the posts, I'm thinking it would be interesting to locate someone with a dyno so that you can do some true load testing on your engine and make adjustments from there. I suppose the first thing is to settle on a carburetor that is capable of supplying a consistent fuel/air ratio you can live with and then tinker with the timing. I wonder if you have a local tech school equipped with a dyno? It could be an interesting learning exercise for a class of young aspiring mechanics.