Fuel question for a T2X

**olboatman** · 04-23-2015, 08:55 PM

Originally Posted by 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

I would think that when adding more octane you could add some timing to increase hp output to some degree. Please correct me if I am wrong. Gary

**powerabout** · 04-23-2015, 09:05 PM

avgas doesnt make any power like race fuel does, just designed not to detonate
When you have the factory truck on the shore full of pistons you lower the octane down to just on detonation for max power
The harder you rev it the less timing you need

**milkdud** · 04-23-2015, 10:32 PM

Originally Posted by olboatman

I would think that when adding more octane you could add some timing to increase hp output to some degree. Please correct me if I am wrong. Gary

Good question Gary. I guess if you went past factory timing specs? possibly? but I don't know what that result would be?

**JohnR** · 04-24-2015, 01:08 PM

Good info. I'm not one who thinks changing ratio alone will be enough to do anything bad but just wanted to mention it.

John

**2us70** · 04-24-2015, 05:32 PM

One of the old school guys I learned from built 44in Mercury power heads to run in race cars. He told me he would add diesel fuel to the mix to gain power. He also said he broke a few parts doing that. I never had the nerve to try it in any of my motors.

**99fxst99** · 04-25-2015, 01:53 PM

In the days of in lines and early V6s I was told at the Merc race truck that the standard double oil.was excessive. The oil cut back the octane rating of the fuel and 1.5/1 was plenty. Also, my biggest favor for avgas was that it was consistent. You knew what you were getting and could tune to it.

**powerabout** · 04-25-2015, 02:06 PM

There is a test on the web somewhere done on a bike engine on a dyno where they kept adding oil and it was increasing the power down to about 16:1 then they said they didnt have any more needles as it was leaning it out
I guess that must have a whole lot to do with the combustion characteristics of the oil and how well the rings seal.

**3rd Gen** · 04-25-2015, 10:16 PM

Great Info!!!!

**olboatman** · 04-26-2015, 05:39 AM

Originally Posted by 99fxst99

In the days of in lines and early V6s I was told at the Merc race truck that the standard double oil.was excessive. The oil cut back the octane rating of the fuel and 1.5/1 was plenty. Also, my biggest favor for avgas was that it was consistent. You knew what you were getting and could tune to it.

99fxt99 Do you mean that they recommended 1.5 times the normal ratio of 50 to 1 (37.5 to 1) Thanks Gary

**3rd Gen** · 05-26-2015, 10:38 AM

Just installed New Pulley's last nigh going to put back on mid tonight looks good so far! getting it ready for the Romp...If it last the Romp it will be the way to go!....

**FMP** · 05-26-2015, 11:26 AM

Originally Posted by 3rd Gen

Just installed New Pulley's last nigh going to put back on mid tonight looks good so far! getting it ready for the Romp...If it last the Romp it will be the way to go!....

YOu really should show a few more pics of that MERC!