A little nitro advice ?

[masracingtd1167]

Ready to try a little nitro next weekend and I have a few questions . It is injected alky and runs very well as it is but I would like a little more . My compression is 14.5 but I run a large cam 280 on the intake and 294 on the exhaust with a lobe center of 114 . I have figured out the dynamic compression and it is 10.78 . Normally run 34 degrees timing and an 86 main jet . It normally crosses at 9400 so I changed the rear gear from 4.86 to a 4.56 . I would like to start at 15 pecent ! I launch off a 2 step is this ok ? I plan on going richer by 10 percent is this ok ? I bought a hydrometer kit so I can mix the fuel the correct way . Any thoughts or suggestions ! Thanks Bill 

[dusterdave173]

Skydiver bob has been running 20% with no change from his right on alky tune--and flying I might add
Folks I talk with say that 10-15 % is fine no change at all --Bob is running I think maybe 40 degrees  have to ask him
Most alky tunes are fat side  Spud says small amounts you may actually need a tad leaner--Spuds Nitro section on his site is a GREAT start to your questions see it at FIE under Nitro notes

[denverflatheader]

Bill – happy to share my limited information from my slightly over stock mid-1960s injected Ford 300 six cylinder with 3.90 gears.  Compression ratio close to 11:1, cam not radical at .512 lift and int. 260 exh. 274 gross duration with lobe separation at 110 using 1.6 rocker ratio.  This engine has run at 3 different tracks in a 1450lb front engine dragster.  At Bradenton, my friend used it to secure his nhra competition license running 9.40-9.50s.  At Speedworld before they closed, it ran 10.00-10.10s and at Bandimere it runs 10.70-10.80s.  I looked up the 3 tracks and Bradenton is 19 feet, Speedworld was 1470’, and Bandimere is 5800’.  At our June Bandimere race, temperature was 95 degrees, humidity was 17 percent and the DA was 10,200’. 

At Bandimere I’ve run with both straight methanol and with 22 percent.  Straight methanol it runs 11.00-11.10.  With 22 percent it runs 3/10s quicker.  Timing was 34 degrees for both straight methanol and 22 percent.  Main jet with straight methanol was 110 and with 22 percent it ran best with a 95 main jet. 

Did install a high speed lean out but have not used, just bracket racing for fun.  The first thing you will notice with nitro is more engine torque off the line and after a pass, the cylinder head/combustion chamber runs much hotter over straight methanol.  Your decision to switch to 4.56 rear gear is a good one.  With more and more nitro, resulting in more torque, you will continue moving to lower gear ratios (4.10, 3.90, 3.55, etc.) numerically. 

With your 2 step launch and only 15 percent nitro, probably okay.  I’m guessing once you move closer to 50 percent nitro and above, could be issues.  After your run, and seeing your plugs, you will know right away if 10 percent richer tune was good decision.  Alan

p.s.  Agree too FIE website nitro notes excellent.

[wideopen231]

according to Spud you can go 30 or 35% w/o any tuneup change from tuned alky setup/Pretty sure he said 35%.  Now if your  of running automatic the extra TQ will add good amounts tall . According to FTI my combo should gain 700 rpm using spuds TQ calculator on his site for tq gain.

[Curly1]

I have 14.5 and it is too much compression to run over 5 or 6% safely from my experience. Now you can use Toluene and that will allow you to go up to maybe 10% but you are borderline hurting parts even then. Now with my old motor racing ha was 13.5 compression 20% was no problem the few times I tried it.
Now when I buy Nitro I get it in 2.5 Gallon can and I mix one gallon of Toluene with it then I cut the mix to 20% with alcohol and will cut it down from there to 2 or 3% what ever I need to run the number.

In my opinion if you are going to run that much compression Ii would not go over about 5% and up to 10% With Toluene. Now if you had 10 to one compression it would be a different story. IMHO.

[Curly1]

I just rechecked my compression and it may be as low as 13.85 and even that is still too much compression to run the over 5 or 6% Nitro safely. I had forgot I went from a .041 head gasket to .051 last time.  By the way my cam is 285-292 duration @ .050.
So if you plan on running Nitro keep the percentage low and use plenty of Toluene. Also I do not like to put as much heat in the motor when I run any Nitro, seems to help. Straight alcohol seems to run better as it gets hotter with Nitro detonates like crazy.  Hope this helps.

[JrFuel Hayden]

i know of a NE-1 Heritage and aNRA [7.60] car that runs a 355 SBC as much as 50% , when the engine is a little tiered

[JrFuel Hayden]

OPPS, I hit the wrong key, but the NE-1 team has won races and Champions runing mostly 20-25% with at least 13.5 compression, but I'll check and post when I double check.

Jon

[msundstrom]

Intake valve closing point is important in compression consideration. I add a quart of toluene to a 5 gallon mix of 30 to 45% but add it after I've got the % I want. The toluene has a specific gravity of .870 or so at 60 degrees and can skew the true % probably not an issue but??  Spud's Nitro Notes are a very good resource.
Mark S

[masracingtd1167]

Made some runs last weekend with a little nitro 12 percent and we were very careful with the tune up . Started out a little too rich and had to lean it down some . I had made some changes to the car and they were not the right thing to do . I put my tight converter in it . Changed the rear and lowered the shift chip from 9200 to 8400 . I should have left the converter and shift chip alone ! The motor is making more power and the plugs look great . It still ran a good MPH almost 183 but my first half is slow ! I changed the converter and we are going to Epping Sunday to try again ! I will post my results ! I think it should run 7.10 or better !