Fuel Grade?

[WKPoor]

CJ- Thanks for the advise, I'll check it out.
George- Below is a copy of what I sent John. Apparently there are some misconseptions about fuel and octane. I thought you guys might trip up on that. Also todays fuels are fomulated different like alcohol and emission related additives. The AvGas is the good old stuff. Its very possible my bowl level is still wrong however I was fouling plugs when the bowl level was 1/2" lower than it is now. As I stated earlier as the outside temp has gone down it compounded my problem. Here we are at near 0degree temps and the Avgas has completely solved my problem. Something else nobody has hit on yet is the lack of lead in the fuel today. The Avgas has lead and lots of it. More than pump gas ever had. Lead boosts octane even above the rating. 80Octane leaded fuel probably performed better than 87 unleaded today. Let me know what you think. Bill
Quote:
Octane vs. Compression vs. Timing

The December, 2001 issue of Hot Rod magazine featured a very informative and interesting article concerning fuel octane levels and their effect on total timing and power production of high-performance engines.


But most of all, we discovered that our presumption that higher-octane fuels burn slower than lower-octane fuels (and therefore require more ignition lead) is largely incorrect. There are too many other fuel-formulation issues at work to assign a general rule about octane. Race fuel tends to have a more powerful formulation than pump gas, regardless of octane rating, because it is denser and can release more power and heat. (Note that we made the best power with 114 octane with the least ignition lead, indicating it had the fastest burn time.) California pump gas is blended with methyl tertiarybutyl ether (MTBE), alcohol, and other ingrediaents damaging to performance

John, here is the link to where I got this info.
http://www.diabolicalperformance.com/hotrodoctane.html
I've learned much lately about this. This article stresses that todays fuels may not follow age old rules. Also sometimes ( I'm guilty of this too ) what we've always thought about an issue may actually be very different

[cowboy]

Wow what a eye opener. Just had to read that article and see where they were coming from. Definitly gives a person something to think about. Just laped my valves so I belive when I put her back together I will run a tank of av-gas through to coat the valve and seat with lead eaventhough others haven't had a problem with it. Somone said somthing about indexing the spark plugs. for those who may not heard of it it is to give flame path a clear shot th the center combustion chamber without hitting the back of the electrode giving you smother and more controled power.

[moe1942]

To compound matters, todays engines and gas are made to burn leaner and cleaner and the computer is constantly changing the timing to achieve that lean, clean burn. The refiners aren't concerned about antique engines.

Using gas with an octane rating higher than engine needs, only wastes money.

I'd love to have access to 115/145 for my Hartley Get out the way!!!!!

[Eugene]

One more thought. If I had to bet a nickel on this problem I'd bet something inside the carburators is not set or adjusted correctly - missing small gasket - etc..

Short long story. Bought a Bobcat 610 skid steer real cheap. Ran poorly, loaded up with carbon. Turned out someone had put the gasket between the carburator bowl and top on upside down - blocking one of the vent holes. Turned the gasket over - runs great.

[rick 48 cub]

Wow - this forum has already paid for itself.

I hopefully re-attach my rebuilt magneto soon. How do I adjust the timing and what is the proper timing for a 48 cub ? (i.e. should I hook up to #1 cyl, should I check the advance at different rpm, does the engine need to be hot, etc.)

Thanks, Rick

[WKPoor]

Hey Guys- I went to Luker Carl's site and I surely intend to do that method to check bowl level. However It struck me that since the H carb has an adjustable main jet, I'm figuring I really can run lean. I had previously adjusted both needles as lean as possible prior to changing fuel types.The Cub carb has a fixed main therefore bowl level would be critical. You can actually kill the H engine with the main jet adjustment. So I'm still ruling out rich mixture at least for now. Just adding another log on the fire.

[Jim Becker]

The December, 2001 issue of Hot Rod magazine featured a very informative and interesting article concerning fuel octane levels and their effect on total timing and power production of high-performance engines.

Read the article. Reminds me why I quit reading Hot Rod several decades ago. Their little experiment was pretty heavy with uncontroled variables. Most interesting would be to have seen actual octane test results on the various home brewed fuels they were using.

[WKPoor]

Jim- I'll admit that one could shoot holes in the findings, however that was just one report describing the effects of compression and timing against different fuel types. If I learned anything it was that any given engine running any given fuel type will have a certain flame speed that require some optimul spark timing. Just maybe I got lucky and the flame speed of the AvGas combined with the pressure and fixed spark timing are a match. Whatever the reason the results were dramatic, dramatic enough to really get my attention to the fact that fuel grade may be very important to overall engine performance much more than I originally thought. When I first put this engine together with the help of Wheeler Rittinger ( some may know the name) we only ran it on 116Octane till I brought it home and got cheep. Thats when my trouble started and I didn't want to believe this old tractor engine needed such an expensive diet. The old guy knows more than I realize and I realize it more everyday.

[cjpenny89]

WKPOOR
like I siad above in my post the problem I had is on our 1944 H. It had to much fuel no matter how far you set the main jet those jets were designed for a certian fuel level in the bowl. The adjustment screws have certain limits to them and if you already have to much fuel the main jet can only help you to a certain point. If they would work the way you are suggesting don't you think that they would tell you it doesn't matter where to set you float level as long as when the bowl was full the needle and seat wre closed?
I work in the the machine design feild and I hear that kind of stuff all the time but in all reality if you do not use it as it was designed things just don't work. The engineers would not have spent the time figuring this out and setting limits on things if it really didn't matter.
just my thoughts and opinions since I am not a carb designer or manufactor what you are saying could be right but with most of my experiences when people try stuff with our products other then what they were intented for or how tell them to set them up is when things don't work. Like I siad on my "H" carb no matter what I did to the adjustment screws it would only help some and never fixed the problem untill I set the correct fuel height as suggested in Carls web page and since then no more fouled plugs so I hope that is the only problem and there is no others.
Good luck and let us know what you find out.
Chad

[danovercash]

How do you use a vacuum guage to time an engine? I have a vacuum guage, but no timing light. Which is better?

[John *.?-!.* cub owner]

I adjusted the timing for maximum vaccum when I used to use one. I personally beleive the timing light to be more accurate.

I usually run middle grade unleaded fuel in my cubs (both working tractors), and it seems to reduce fouling. Plugs seem to last a year or two longer with it than with lowest grade.

[George Willer]

I had previously adjusted both needles as lean as possible prior to changing fuel types.The Cub carb has a fixed main therefore bowl level would be critical. You can actually kill the H engine with the main jet adjustment. So I'm still ruling out rich mixture at least for now. Just adding another log on the fire.

Bill,

I finally went to the hot-rod site and read the discussion. I don't find much helpful there. Those guys are working on an entirely different problem than a low compression tractor. Our old Cubs can't really benefit from octane above the 80 octane they were built for. The closest we can come now is 87 octane. HIGHER OCTANE WILL NOT INCREASE THE POWER OR RUNNING QUALITIES OF A CUB.

Is it possible you are adjusting the air adjustment backward and making the idle mixture too rich instead of too lean? As you may or may not know, the idle screw is an air control and screwing it in makes the mixture richer. Your plug fouling indicates running a too rich mixture.

The only control for idle mixture on a Cub in good condition is float level, of course. Lowering the fuel level will cause the idle mixture to be leaner.

After we get your tractor running well without fouling the plugs will be the time to get it in racing tune.

George Willer

[WKPoor]

Ok Guys I need to go back and clearify a few items here.
1- the octane isn't as much an issue as the fact that the fuel I'm using doesn't have alcohol are any other emission additives and it has lead which should be a good thing.
2-The Cub may indeed just be overfueled but the H is now a very high compression engine. It may indeed be benifitting from the increased octane. Everything I've read suggests that above 10:1 compression pump gas will marginal.
3-The H carb could still be running rich, however I stated in an earlier post that the bowl level this past summer was 1/2" lower and it was fouling terrible then too. I understand perfectly well that the idle circuit is controlled with an air bleed. The bowl level would have a direct effect on mixture. But an adjustable main could compensate for main fuel delivery. Nevertheless, the very first thing I did was rebuild an already rebuilt carb this past summer paying strict attention to the float position. I notice the rebuilder had the float set way way low. So low I wondered how it could run. I set it up per the book just like every time before. After I was done and reinstalled, the valves could be adjusted more like they should. With a low bowl level I had the needles backed way out. It would be hard for me to believe that Bowl level is the problem knowing that 1/2" lower fuel in the bowl was still fowling plugs.
4-Now we come to where I'm at, simply changing fuel grade perfectly cleaned up the plugs. I've given my theory. Whats yours?

[moe1942]

A vacuum gauge will give a more accurate idea of what's happening in the cylinder. The object is to obtain the greatest volumetric efficiency and I believe the vacuum gauge method of timing is better in that respect.

Another advantage, and the reason I like it for timing the Cub, is you have the gauge on the same side as the distributor. Makes timing much easier.

[WKPoor]

What if the veturi is wrong size for my engine? That is about the only thing that I didn't check when I rebuilt the carb. I don't have reference material for the Supers or 300 so that did get over looked. I just talked to Wheeler and he said he has a couple of tractors (meaning H's and M's ) that will only run on 100+ octane fuel also. He mentioned that the lead is what he is after and I don't know where you can buy low octane leaded fuel. I might try and mix some of the good stuff with pump gas to see what that does but for now the AvGas is the right price if you know what I mean. Sumped fuel