I need some advice

I have just put together a 250" BOS RED with an injected ( old style stack 2 & 5/8 Hilborn) 511" BBC on alky. I would like to run a percentage of nitro in 2011, but am concerned about scattering the engine, Engine details are: Chev OE 4 bolt truck block, Ross 14:5:1 slugs, steel rods ( I know they have to go ), Eagle sportsman crank, and a CompCams roller .782/.714 282/278. Trans is a 2 speed Glide w/5500 converter. Heads are Dart 360's completely fresh. Current ignition is MSD 7AL with a 3 step. I'm old skool so I'm gonna dump all the MSD stuff and go with a SuperMag IV... As far a fuel delivery goes, I can get all the nozzles changes etc., from Hilborn. If anybody would care to help me out here I sure would appreciate it. So.......with this normally aspirated OE truck block engine, am I safe to add some pop, and if so, what percentage would you recommend to keep me safe...and at that percentage, what kind of ET increment do you think I would see? Should I be changing the converter to a lower stall? Right now she's a 7:60 car on alky

 

Just with that CR you probably want to stay below the 25% mark, you really dont need to change your fuel tuneup much if you stay below 25% either.

 

Keep your methanol flow rate the same as you add nitro. For example, if you add 25% nitro, then up the total fuel rate by 25%. In this way you are using the methanol as the "primary" fuel and getting the extra kick from the nitro.

The nitro will add about 110-125 HP per GPM of nitro, not the total fuel. For example, with 8.0 GPM total fuel flow at 25% nitro, the nitro fuel flow is 2.0 GPM. So you could expect an extra 220-250 HP over straight methanol.

Patrick Hale
www.DragRacingPro.com

 

Much appreciated guys....What about the damage factor?....Will my OE truck block handle up to....but not more than 25%?

 

I dont know much about BBC blocks, but I know there are people in here that run them plenty hard.

About the torque converter question, nitro loves to make low rpm torque so stiffening up the converter is not a bad idea.

 

I run a 505 bbc n/a hillborn stack injected alky motor also, that is configured for a percentage.

As mentioned above your compression ratio is your limit to what you can do with how much percentage of nitro,...
Since you will be at such a low percent your 5500 converter will not play a factor to the
theory of nitro needs a load, you will not have enough in your system to require you to lower your converter stall. Your tuneup will still be alcohol, just on steroids.
What size nozzles you running Now ???,
Being too lean is always at the top of the Damage starter, melted piston, detonation, broken ring or ring gland, beating the bearing out.
Expect your motor to idle faster with a percentage from the very start,..richen barrel valve, put a larger main in too..expect your plugs to read lean, more in the main.



Vic

 

Answers to your question

Right now we're running Hilborn 24A nozzles with .120 pill centre range. Idle check set @ 18 lbs and hi-speed @ 45 lbs. Would I be correct when we get it running to start 3 steps fatter then read & lean?...

 

O ring & copper HG's

Sorry to be a dummy here but @ 25% pop, will I need to O ring the block and run copper HG's?...I just wanna do this once....the RIGHT way!

 

Yes that would be the way to start 3 STEPS,
On my alky tune I run a 120 main with H/S .070 cracking at 57lbs for a 2500 corrected altitude@ 84 temp, 45% humidity,. my system psi at 7400 is around 64 psi, as you tip the can the system pressure will increase too,..If you run a 120 and start out at with a 105 or 110, the psi will be greater and your HS will open sooner now too, so dont forget to stiffen up the HS to open at a higher pressure.
I too have Hillborn 24a`s , I am not o ringed,..it would be a safer way to
be if block and heads were O-ringed.


Vic

 

Thanks Vic

Much appreciated Vic.....That is precisely the info I needed. Is it opening day yet?..L0L

 

One final question

Right now I am using an MSD 7AL-2 and with the coil - puts out 2.2 amps at the plug. I don't know for sure, but I kinda think this is a bit light to adequtely burn the alky/nitro mix. I'm liking a SuperMag IV which puts out about 4.3 amps and with the rare earth magnets never needs re-charging. Any opinions?....

 

We ran 20% a few times NA injected, with a vertex mag and it did fine, now we use the same mag on a blown alky motor.

More power at the plug is going to be better, but with just 25% I dont thing you are going to see a problem.

 

Thanks very much for your advice

Much appreciated