Fuel question for a T2X

[3rd Gen]

Going in to my 2nd season running my T2X Ive been running a mix 50/50 Can Am 2 super unleaded 110 octane with super unleaded at the pump with a 16:1 penzoil synthetic. I wanted to run it on 100LL from one of my local airports but no one will pump it unless its in to an airplane.Would like to know what I can run that wont harm the engine and if what I'm running is OK...Thanks Ed

[milkdud]

my airport pumped 100LL right into a can for me....

I would expect 93 would be just fine. I don't think those motors had any more compression than a 1500 high dome. I run straight 91 in my 1500 high dome and it runs pretty hard.

if your timing it up to 27 then I guess 91 or 93 would be a gamble. If your timing it 19-21 you would be fine IMO. I ran mine up to 23 on 91 on a light boat. But I kept a very close eye on it and went up slow.

Conrad

[JohnR]

This is a great site for finding AvGas locally.

https://www.airnav.com/fuel/local.html

Look for a local airport that has "SS" next to the price. Some places you can walk up, swipe your card, and fill your cans, sometimes going later in the evening is better as everyone is gone and no one is there to question you. The one close to here its $5 a gallon for 100LL (about 97 octane as rated for highway fuel) so its a pretty good deal compared to race fuel.

[baldad45]

I've been running a T2 for several years , initially I used avgas but that got harder to get so for the last couple years have used 91 non ethanal with a good octane booster without incident . Currently I have this engine apart to do the rings , no damage only problem was rings are gumming up from the high oil mix 20/1 to 25/1 .I turn this engine up over 7000 on a regular basis . Keeping the fuel system clean is the biggest problem , no ethanol , fuel filter and drain the entire fuel system for the winter or storage . Real pain to have to clean and calibrate the 6 carbs . I run timing close to factory, witch was 20-24*, good luck and lets see some videos . Glen

[milkdud]

Also, I think you get more power out of a motor using the least octane needed. Using super high octane in motors not designed to utilize it just lowers the output of the motor.

But since these motors don't exactly grow on trees anymore, I see good reason to put a little more in there to be safe.

When the 1500 came out in 1973 some of the early ones had 27 degrees timing stickers on them from the factory. That quickly changed to 23 I believe.

In the end I personally settled on 91 non-ethanol gas 23 degrees timing 32-1 oil and made some good speed runs with that set up. It would be fun to have a dyno and run 91 for a pull then put 100LL in for a pull to see if there is a change in output going to the higher octane.

Ill admit the 91 here is non-ethanol and our 93 is ethanol. If the 93 around here was non-ethanol, Id probably use it.

Conrad

[Galveston340]

This is a great site for finding AvGas locally.

https://www.airnav.com/fuel/local.html

Look for a local airport that has "SS" next to the price. Some places you can walk up, swipe your card, and fill your cans, sometimes going later in the evening is better as everyone is gone and no one is there to question you. The one close to here its $5 a gallon for 100LL (about 97 octane as rated for highway fuel) so its a pretty good deal compared to race fuel.

....WOW!! Thanks for the link JohnR. Found there are a ton of places around here where I can get some decent gas without having to drive halfway to New Orleans or west towards Austin to get away from the ethanol. Thanks again!!

[3rd Gen]

Thanks everyone for the feed back! Chasing the Can Am at $9.99 a gallon and not being able to pump the AV gas has been a little discouraging ! Love the engine and it is thirsty to say the least. Definetly going to change up what Im running for fuel and mix. I keep hearing about calibrating carbs ive got the butter flies in sync and set the low end idle am I missing something more than that? Don't want anything to go boom! I lost my belt last year and waiting on my new pulley set from the machine shop want every thing right for this season! I have a vacation in 2wks and I'm dying to run it! again my thanks Ed....will post vid's

[JWTjr.]

A lot of airports will give you that "we can't pump it unless it's into an aircraft" bunk, but there are no federal laws that prohibit selling avgas to a person without a plane to put it in. In some cases I've just given them a tail number to write in if they get jerky about it. That works.

[Mark75H]

Cylinder pressure is increased in these motors by exhaust tuning, not mechanical compression. Just because the mechanical compression ratio is the same, does not make the operating cylinder pressure the same.

16:1 is excessive oil ratio

[milkdud]

Cylinder pressure is increased in these motors by exhaust tuning, not mechanical compression. Just because the mechanical compression ratio is the same, does not make the operating cylinder pressure the same.

16:1 is excessive oil ratio

This does make sense. Never put much thought into this aspect.

[T2x]

Cylinder pressure is increased in these motors by exhaust tuning, not mechanical compression. Just because the mechanical compression ratio is the same, does not make the operating cylinder pressure the same.

16:1 is excessive oil ratio

We used to run about 20:1 with the T2x's but that was before the new 50:1 and 100:1 oils came out. I would think 30:1 would work today, especially if you are not racing flat out. Also be aware of what jets you are running in the carbureters. We used 3 seperate sets in these motors depending on temperature, humidity, etc, but I will be damned if I can remember any specifics , other than they were exactly.01 apart (.03 total range). We never had much in the way of altitude changes so that was not a factor, but it could be. My last T2x powerheads (single ring) turned about 7800 RPM's...(Modified one extensively and it turned 8600 but lunched in under a lap at speed)

[3rd Gen]

My Thanks to all!...I just got a call from the machine shop I can pick up the new timing gears today. The cost for the new set up wasn't as bad as I thought it would be it was $67.00 for 2 pulley's and 2 belts $160.00 to machine the pulley's to spec. Here's hoping for good results! After reading everyone's post I definetly have been running heavy on the oil and believe it or not in mass going to have to LOOK for none ethanol 91 oct Ed

[JohnR]

Remember, more oil leans out air/fuel ratio and lowers the octane of the fuel.

[2us70]

It seems to me that the older Mercury motors had much less appetite for octane. I turned my 44in 50s 6200rpm and ran double oil mix as well as a bit of timing advance on Amoco high test gas. Those motors lived just fine like that even running marathons with no adjustments. the 44s also responded to small jetting changes from winter to summer. My 49in 650 and my 850 were not so forgiving. You really had to watch timing and jetting or you would melt pistons. Avgas was of no value in the old 44s but it did seem to help when running extra oil in the later motors. In my opinion you have to pay close attention to how your plugs read, the appearance of your piston tops and checking the cylinders through the intake port covers.

[Mark75H]

Remember, more oil leans out air/fuel ratio and lowers the octane of the fuel.

Not significantly enough to be a concern. Work the math and you will see its just not there; this also supposes that the octane rating of the oil is lower than the gas; does not have to be the case

Same thing with a concern with oil viscostiy thru jets. Until you are using more oil than 20:1, there is essentially no flow change