What's your mileage?

[jcramsey]

Originally Posted by Todd W. White

I get 16 mpg in town consistently. In a recent trip, I got 17.5 on the highway traveling 60 miles per hour, but that was with some contrary winds. The best I've done on the highway is 18.75

I find wind is my biggest hindrance to good mileage.

Mine is a 1965 C-10 with the following:

283 CID Engine
Holley 4360 Economaster 4-barrel Carb
ME Wagner Dual-flow PCV Valve with a custom designed catch can system
Headers
Dual exhaust with X-pipe
SM 420 Transmission
3.08 rear end
29" tires

Also, I use ethanol free gasoline exclusively. I also use AMSOIL synthetic oil and their oil and air filters.

How do you like the Economaster carb? I've got one sitting on the shelf waiting to be used on something. Sounds like a good setup with the 283 for sure!

[Todd W. White]

Well, it WAS running poorly - after the stock PCV valve failed (it never did work properly), my highway mileage dropped to 12, at BEST. However, I didn't know what the cause was until I began to track it down. In fact, it never ran "right" since the rebuild a year ago - only "OK", and I chocked it up to being an old 283, and not a modern engine like I could have purchased from one of the sellers today.

After eliminating all kinds of possibilities, I was about ready to either park it or sell it. My in-town mileage was down to 8-9 MPG, and I couldn't afford to drive it. A couple of local mechanics graciously advised me where to look, and the search narrowed to the fuel delivery system.

That resulted in a new fuel pump, fuel filter, and a removal of the carburetor to let the guy that does carb's check it. When I pulled it, I found oil inside the intake manifold and the base of the carburetor. As I traced back through to find the source of the oil, I came to the conclusion that it was the PCV valve. I replaced it with 3 or 4 new ones, all of which "the book" said were "correct".

No luck. Same problem.

So, off came the carb again and, this time, I took it to the guy for a rebuild. I had a genuine factory kit for it, and he rebuilt it. When I went to pick it up, we discussed how it looked inside. He said that there were several channels and passageways inside that had oily crud (my word) stopping them up. This crud hindered my carb from operating properly, thus affecting efficiency, and, therefore, gas mileage.

Once clean, though, I didn't want to subject it to the same problem that gunked it up in the first place, so I began to look for an answer as to why it got there to begin with, and how to stop it from happening again. Of course, oil in the fuel also dilutes the octane rating of the gasoline, so that affected my mileage as well.

During my search prior to discovering the oil in the intake, I was replacing the plugs, and noticed that the passenger's side plugs were somewhat oily, but not the driver's side. My mechanic friends and I have concluded that the valve stem seals on that side are leaking oil, hence the oil being sucked out so readily, due to that being the same side as the PCV valve, which is installed in the valve cover on that side.

I installed the carb, but didn't run it yet. I decided to do more research before running it and dirtying it up again.

What I found was interesting:

1. As I have said, engines that have been modified from the original design won't work properly with the PCV valve originally specified. They may work "ok", but not like the engineers designed them to.

2. Engines that have aged, or have "issues" (valve stem seal leaking, stopped up or partially stopped up breather caps, etc.), will also not be properly served by the stock, OEM-specified PCV valve, because the entire crankcase ventilation system has been compromised.

3. A "catch can" is a viable, and reliable, way to reduce the amount of contaminants that get sucked through the PCV valve, back into the intake, and, thus, back into the engine.

4. However, most commercially available catch cans are all hype and don't do anything but look pretty as they sit there in your engine compartment - they do not do what you think they're doing. In fact, most do nothing at all.

5. There are a gazillion designs for catch cans out there, and most of them are flawed, at best. Most are downright useless. However, this article explains a properly designed catch can, and is sound, from an engineering standpoint:

www.conceptualpolymer.com/Air_Oil%20SeparationBeyondBasics.pdf

6. Since there are only 1 or 2 units available that are designed in a manner that follows the article listed above, and even they aren't in full compliance with it, I set out to build my own, as can be seen here:

http://www.persh.org/Pickup/PVCseparator.html

It wasn't hard, and it wasn't expensive.

And it WORKS.

7. I installed it, setup the carb, and began driving, carefully monitoring performance and mileage.

8. The results were ASTOUNDING! Even without a PCV valve, and with leaking valve stem seals on the passenger's side, my mileage in town went UP from around 8-9 to FOURTEEN, and my highway mileage wen from 12 to SIXTEEN!

I didn't believe it was possible, but, over and over again, I documented it carefully, and the results were virtually identical with each tank.

9. However - I was still fighting the vacuum from the intake as it sucked oil and contaminants from the port where the PCV valve used to be and my catch can was hooked up. I was emptying the can daily, and knew that there had to be more that could be done, in addition to replacing those seals (which I will be doing here shortly).

10. SO - more research. I found others out there, particularly the NOVA guys, who had similar experiences, or knew those who had.

The answer to my problem seemed to lie in making sure that my engine "breathed" properly. As I pursued this line of research, I talked to several professional mechanics that I trust, and, somewhere along the line, I came to the conclusion that I needed to put a PCV valve back in the circuit, so as to let the correct amount of fresh air into the engine while venting out the correct amount of gases.

My natural inclination was to look for one that was adjustable in the field, under actual operating conditions. To my amazement, no one had heard of such a thing, much less did they think it was necessary.

But I was convinced it was necessary, but could not find anyone who had one available. That is, until I discovered the Dual-Flow PCV Valve from ME Wagner. The guys at Steve's Nova site had found it, and were raving over it.

I went to the website. I read their engineering data and explanations, even the patent online. I called them and asked a bunch of questions. I discussed it with professional mechanics.

My conclusion was that I should save up and get one, especially since it carries a 30-DAY MONEY BACK GUARANTEE: if I didn't like it, all I was out was the time and trouble, plus postage back to the manufacturer.

11. So, I saved up, ordered it, and installed it. I called them, asked a few questions, and then watched the video they have - which is excellent - and calibrated it accordingly.

I then went back out on the road and began testing again.

The results were impressive.

My in-town mileage went UP from around 14 to a very consistent 16, and my highway mileage went UP from 16 to a very consistent 18, although I have achieved 19 on one occasion thusfar.

Incidentally - my engine performs amazingly better: I have power I didn't know I had, mileage I always wished I had, and it even SOUNDS better!

Now, I have said all of that to say this -

While I have never said installing the new-style PCV valve was a cure-all: what have and am saying is that removing the contaminants from the inlet to the base of my carb and, thus, into my engine, has increased my gas mileage, and the Dual-Flow PCV Valve has played no small part in that increase.

I hope this helps to "clear-i-fy" the issue, as they say in Texas.

- Todd

[Todd W. White]

Originally Posted by jcramsey

How do you like the Economaster carb? I've got one sitting on the shelf waiting to be used on something. Sounds like a good setup with the 283 for sure!

Now that it's running properly, I like it. You just have to be sure it's set up and jetted for your engine, your locale, and your power train requirements.

While it's NOT a Quadrajet, and, therefore, doesn't peel rubber, it does what I want it to do - it gives me "enough" power when I need it, and delivers good gas mileage, which, at today's prices, I definitely need.

One thing, though - you MUST make your own base gasket for it! There are small channels in the base that must be covered with a gasket to pass the air through properly, and the "spreadbore" gasket available at the parts house leave some of those passageways uncovered.

[supercharged]

What's zero divided by infinity?

[66Submarine]

That's what I thought, Todd. Glad to hear that you got it figured out and it works for you, but I'm confident that if everything was right with the old setup it would have worked just fine like that, too. I'm sure the nicer PCV probably made tuning easier, but with an engine that is in good tune and without problems, the stock setup should work fine--hot-rod or modified engines included. The real problem was that it sounds like air bleeds were plugged in the carb, which certainly will make it run like crap and blow black smoke! And you also loose tons of power running rich like that, as you obviously already know now.

From the sound of your oil problem, I'd bet that you got a spray-can "rebuild"/re-ring job, or that someone messed something up a little when they rebuilt it, which is depressingly common. It probably also burns oil, doesn't it?

Although the stock PCV valve may not be absolutely optimal with a tired or modified engine, it certainly shouldn't cause problems like you had. All my old tired engines have no trouble like that, and my father used to do a lot of hot-rod and racing stuff and never had problems like that.

From my perspective, it sounds like you got a dud rebuild that loses oil, and some of that managed to plug air bleeds in the carb. With the carb plugged, different PCV valves obviously didn't help any. After fixing the carb, you removed the PCV in favor of the oil separator, which didn't work as well and sucked a lot of air/oil. If I'm thinking about it right, the oil separator line was just a giant vacuum leak at that point, right? Then, you finally added back the PCV, although it was the special one at that point.

My bet is that if you drop the factory PCV valve back in at this point, the engine will run just like it does now. Whether it will stay cleaner with the magick PCV valve or not I don't know, but if the engine wasn't "sick" you wouldn't have any trouble with it.

Thanks for the in-depth reply, too. People will make claims like that all too often and never explain the situation that caused them to make them in the first place, which just leads to confusion and misinformation.

Keep on truckin',
"Sub"

[Todd W. White]

Well, thank you for your reply, but my answer is, "not quite".

My rebuilder is a friend of mine. He has been a professional rebuilder for over 50 years. His firm is one of the largest and most well respected rebuilding companies in this part of the country. I have absolute confidence in his work. My engine does not burn oil. It never has, other than during the early break in period. I now have about 20,000 miles on the rebuild, and it still doesn't burn oil, in the classic sense of the term. What little that does make it to the plugs now will, I'm convinced, be eliminated as soon as we replace the valve stem seals.

I think the problems came, primarily, from a failed PCV valve. And, while the valve stem oil seals on the passenger side may have contributed to the problem, the failure of the stock PCV valve is, in my opinion, definitely the main cause of the problems with the carburetor, and resultant mileage issues.

You are not correct about the catch can. Without a PCV valve, and just the catch can, it performed far better than the stock PCV valve did before it failed. However, as I said, it was not enough. When I used it with a new stock PCV valve, my performance suffered, because the PCV valve didn't match my engine performance characteristics. When I put a brand new stock PCV valve in, bypassing the catch can, my performance also suffered, even though the carb had been cleaned and rebuilt. When I put the adjustable PCV valve in conjunction with the catch can, my performance improved dramatically. The new style PCV valve works well by itself, also. Therefore, I chose to keep the catch can and the modern PCV valve, even though I can return it and get my money back, because using the stock one alone with the corrected other measures, or the stock one with the catch can, just doesn't work as well as the combination I have now. Perhaps the catch can will be of far less use once the valve stem seals are replaced, but I think I will have to look at that once they're done.

At this point, I'm staying with what I have because it works for me. Proof of that is my latest guess Philip and mileage, which I did today. On the tank I just used, it was quite a bit of city driving, but also a very different use.

Yesterday, my 2001 Saturn blew a head gasket, and the water pump failed at the same time. My son had to drive my truck from my home to where we were stranded in Tulsa, which is about 25 miles. We worked on the Saturn, going back and forth to the parts house a couple of times, until we determined that it could not be fixed there. So, we hooked it up to the truck and towed at home (25 miles).

Today, I drove the truck quite a bit, all in our town, and in Tulsa, and then came home. After my son got off work, we hooked up the Saturn to the truck again, and towed it to his house, another 25 or so miles more. Keep in mind that during towing, the trailing car being towed has to be kept from running into the vehicle doing the towing. Therefore, my son had to ride his brake quite a bit, creating quite a bit of drag on my truck, and affecting the efficiency of my truck.

After we got it to his house, and put the Saturn in the garage, I drove back home, stopping on the way to fill up with no ethanol gas at my usual station.

Much to my surprise, my truck got 16.15 miles per gallon! I had plenty of power, no problems with the pulling the car, and am pleased with the mileage, even under such conditions.

Again, this tells me, that my system, as it is, works for me.

[66Submarine]

Well, what do you mean by "...it still doesn't burn oil, in the classic sense of the term..."? It burns oil or it doesn't. 20,000 easy miles is pretty much a brand new engine IMO; no excuse for any problems at that point. Oily plugs tells me that it kind of has to burn some oil, you know? Not to bad-mouth your guy or anything, but I'd be very unhappy with the results you have had so far, assuming I paid for a rebuilt engine. What does the leakdown tester say about it, BTW?

The truck my father is driving now has a super basic 350 shortblock with late-model vortec heads and flat-top pistons, with an Edelbrock 1406 AFB copy on a generic dual-plane intake--all of which is of course not a GM combo. Probably over 100,000 on it now, and the plugs are all beautiful, the exhaust is clean to the touch, it gets fantastic mileage, etc. That's what I expect, more or less. Oily plugs, etc. to me=shot-out super-high-mileage junkyard engine to putter around town with, not a new rebuild. My <$200 junkyard 250 six in the truck I'm driving right now very probably has over 100,000 on it and similarly performs flawlessly and runs very clean.

"You are not correct about the catch can..." I didn't question how well it ran like that, I just questioned how it wasn't essentially a giant vacuum leak. From what I saw, the only real restriction is whatever the media you stuffed it with provides (BTW, why use an abrasive cloth like scotch brite for filter media?). You say without the PCV it pulled a lot of extra oil, which reinforces my unrestricted vacuum leak theory.

"the PCV valve didn't match my engine performance characteristics" You keep saying this, but you haven't mentioned what makes your engine so special. What heads/intake/cam specs/compression, etc? The hot-rod small block is kind of the definitive "hot-rod" engine of the last few decades...

"...the failure of the stock PCV valve is, in my opinion, definitely the main cause of the problems with the carburetor, and resultant mileage issues..." That's kind of my point. Most of your problem was nothing to do with the PCV valve; it was from carburetor issues that you say resulted from it, and you actually say that the valve failed.

I still stand by my original statement that I can put a hot-rod 283 together in my yard and have it run just like it should with the normal PCV valve; it's not anything new that hasn't been done a million times before. Early SBC's didn't even have the PCV setup to begin with (road draft tube). The PCV is only meant to ventilate the crankcase--I don't even see the website of the people that want me to pay $130 for their PCV valve trying to claim anything different, or even implying it. Maybe your carburetor's factory tuning worked slightly better with the magick PCV valve, and maybe tuning would be easier--I could see that. But, I swear to God, I will cut the 283 I have up into little pieces with a plastic knife and eat it if I can't make it run like it should without that. The PCV is not there for economy or power. Notice that racing applications will use a vacuum pump dumping out into nowhere instead of a PCV system feeding back into the engine?

"Yesterday, my 2001 Saturn blew a head gasket, and the water pump failed at the same time." I think the water pump failure might have preceded the head gasket failure by a couple minutes...

[Todd W. White]

Thank you for the clarification.

[JBX66]

Got her running again and took her out for the first time on a long drive (36 miles) And averaged 7.6 mpg. I suspect a tune up is in order. I see most people with the 250s getting around 17+.

[66Submarine]

WOW! Must be an ungodly amount of black smoke coming out of the pipe to get that! I'd check for needle and seat issues (maybe excessive fuel pressure) and potentially plugged air bleeds, and also insure that the choke isn't stuck closed. I agree that when running well you should see something like 17MPG with a half ton like that.

[66Submarine]

Also check the timing and points of course, but I think if you are actually getting <8MPG that something is probably wrong with the carb. Must run horribly like that!

[JBX66]

Actually, no, it idles great and runs well. Today a friend of mine and I adjusted the timing to normal, from about 10 degrees advanced. No smoke, no major shaking (Ok, it's a 48 year old truck. It shakes. And rattles. And occasionally booms.), nothing. When I measured it I realized later I had the choke on a small amount. I'm not sure how much this would affect the readings, it was about 85-90% in. I'm also thinking I have might have a low geared rear, because my dad (who had a '69 with a 250) said that it revved higher at highway speeds. Oh, and as for the carb, I did a rebuild on that a few months back. Granted, I only found the directions for the rebuild after I finished and put the carb back on the manifold.

[AcampoDave]

JBX, could it be possible the true culprit is simply your odometer giving you a faulty calculation for your m.p.g?

[66Submarine]

Yeah, I like to at least check the odometer with map distances.

I'd guess you probably just had the choke closed further than you thought you did, though. Check it again and I bet it'll be a whole lot better.

You could possibly have a 4.11 rear instead of the 3.73 most of the came with, but you should still have got a lot better mileage than that (and it seems like 99.9% of the base-model trucks came with 3.73's IME). 8MPG is 454BBC mileage!

BTW, 10 degrees advanced (obviously with the vac advance plugged and the idle slow enough that the mech advance isn't out) is what I have mine set to IIRC (might be 12).

Also, it's super-easy to drop a column-mounted tach in to see what RPM you are running at any given time if you're curious (I always like having one).

[joedoh]

Originally Posted by Lugnutz65

I have talked to a lot of owners who want to improve their fuel economy.
The popular choices in no particular order are:
1. Keep the 3 speed and swap in a 3.08 rear differential
2. 700R4 AT with a 3.42 or 3.73 rear differential.
3. T5 5 speed MT with a 0.86 OD gear and a 3.42 rear differential
4. T5 5 speed MT with a 0.72 OD gear and a 3.73 rear differential
5. Tremec makes "bulletproof" 5 and 6 speeds but very $$$.
Fuel injection will help improve MPG as well.

Most importantly, match the rear differential with the transmission OD gear.

good advice. an overdrive cog is a way to drive at highway speeds and lower rpm. which means the simplest way to get better gas mileage is not included on your list and is actually free, and that is to slow down. since air resistance is exponentially growing as speed increases (its the velocity squared part of the drag equation), the torque required to overcome drag at a speed of 70 is much more than that of a speed of 50.

I know a lot of guys who miscalculate their mileage too. I rode next to a guy in a ford last weekend who looked as his gas gauge, said "sheeeeet man we got 270 miles outa that half tank, thats 30mpg wooooo!". We then got about 110 out of the second half tank. Thats 21mpg. thats also what his truck is said to get for highway mileage on fueleconomy.gov. I have a ford focus and its gas tank behaves the same, first half lasts forever then plummets to e. When I went to lunch I had a 1/4 tank, this was driving home.

[1963chevyc20]

I get about 14 mpg. 63 c20 283 with a 3 on the tree. Always drive with the tailgate down for improved mpg!

[AcampoDave]

Originally Posted by 1963chevyc20

I get about 14 mpg. 63 c20 283 with a 3 on the tree. Always drive with the tailgate down for improved mpg!

Mythbusters busted the tailgate myth.

[LostMy65]

Originally Posted by AcampoDave

Mythbusters busted the tailgate myth.

Yes, they also displayed the difference in a wind tunnel.
It was pretty cool.
The tailgate down actually creates more drag.