4/7/03

Ed. Note:  Wady Hamam or Pro Mod Wad as he is known in the sport as drag racing's main nitrous Guru. He has been involved in nitrous oxide injection almost from its inception especially with the Pro Mod division.. He is originally from the Buffalo, New York area and has been involved in all types of racing from flat track motorcycles to fuel dragsters. In his wasted youth he even raced a fuel funny car powered by a blown and injected small block Ford! He and his brother campaigned a front motored Top Fuel dragster and lost a race against Don Garlits at the now closed Niagara Falls Dragway. His advice about nitrous problems is highly sought after but he is hard to get to. He has agreed to answer one question every couple of weeks for Drag Racing Online readers. Email your questions to: promodwad@racingnetsource.com, and he will answer the question he finds most intriguing. (Original caricature Pete Millar)

QUESTION 1

Hi. Has anyone come up with a jetting chart for propane? Or at least an approximate? I would like to use propane in a dry manifold application, and I have concerns with fuel puddling if I were to use gas. Getting to a fuel source is almost impossible, so using propane as the fuel would work out great, but I am clueless when it comes to the jetting.

Thanks you for your help.

X-NOS engineer...
Matthew T. Rondeau

Matt,

Your question is a little confusing as far as dry manifold application, but let me tell you what I know about propane.

First: Propane has many, many BTU's and does make lots of power in an internal combustion engine.

Second: Propane is stored in its container at high pressure (around 400psi) and when introduced into an engine as the fuel source it must pass through a regulator to drop it down to a usable pressure.

The people I know of that have used it with nitrous as the fuel have had to use a high-pressure solenoid (a nitrous solenoid will work) and send it into the engine via a plate system or multiple nozzles in order to work out the jetting map. The reason for that is that because of the high pressure, the fuel or propane jet size is much smaller than the nitrous -- much like the higher pressure EFI systems.

As an example, if you were to jet a plate system for 175 HP with a .073 nitrous jet and .082 fuel jet for gasoline, in a propane system that fuel jet would be down around a .050 jet due to the pressure that the propane will be flowing at.

No one that I know of has ever put the actual jetting map in print and that is why it is good to work with a good technical staff at the company whose system you are using. They have probably worked with someone that has used propane.

If you are planning on using propane as the main fuel in the engine and want to use nitrous as the power adder, then the nitrous jet will end up being slightly larger for a horsepower level than normally selected in a gasoline engine.

Is this all as clear as MUD? Hope I have shed a bit of light on your question with this answer and thanks for writing.

Wady

QUESTION 2

I have a 427 small block Chevy with 14.5 compression. I was blowing the head gasket between #6 and #8 cylinders, all 3 times same place. I'm not O-ringed and was not told I had to be. I sprayed 250 horsepower with NOS two-stage plate. I was told either the plate was bad or the retard box was not set right. I bought a new system by a different company that is custom made and flowed on my intake. It's a plate system.

In your professional opinion, what do you think it could have been?

Hope you can help. Thanks.
Mark

Mark,

Not knowing all the parameters of your 427 or if it was even built for nitrous use, let me try to give you a sensible answer. First off any engine that will be sprayed with 250 or more nitrous HP should be O-ringed for safety, due to the amount of cylinder pressure that will be created by the nitrous.

What you write is that you were or still are using a 2-stage plate system and, yes, that can cause a problem if the plate is not spot on or the timing does not retard when the second stage is activated. Sometimes in a multiple stage system if a jet size is not exact bad things will happen when the sizes are stacked or ganged up because the system flows more than expected and damage occurs.

Because some companies do mass produce their jets, the tolerance from jet to jet will vary and can create what you experienced between cylinders 6 and 8. Hopefully, you did not get some aluminum ashtrays also and it was just a gasket.

You did the smart thing by flowing the new system to your manifold; many times this will stop problems before they start. If you or the company flow the jet sizes to double check, you then can be comfortable that you are getting what you expected and not damage.

Wady

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