backing down blower motor

[noslin]

before starting do you back down ALL blower motors or only blower with nitro?    do you just do one complete cycle from example cylinder one , cycle back to cylinder one?

ty
dean

[Draw 3D]

I run a blown SBC alky motor and don't back it down.

[msundstrom]

It is a nitro thing, I'm injected BBC nitro and pull the plugs after a pass, crank it over for 10 seconds, check the valves then crank it over for 5 seconds and put the plugs back in, I believe the process is different for a Hemi. I have seen the results of not clearing them, I don't want my equipment broken and more importantly no one hurt.

[noslin]

thank you, let me add to the question.  if in the lanes, you start the motor (alky) and then have to turn off due to oil down or ?.  when you go to restart while in the lanes is it critical then?   not from the aspect of with running nitro and blowing up the motor such as could occur if nitro motor wasnt backed down, but for ease of restart on blown alky motor?   

i seen a few guys backing down alky blown motor (i think) while watching some of the runs at MM

ty
dean

[Paul New]

With a hemi you can back the engine down and the left over fuel in the engine will flow out the exhaust pipe. If you have a wedge headed engine than this exercise is futile unless you remove the spark plugs. Now remember I am one of those kind of guys who say stuff and it's just my opinion take it with a grain of salt.

[Frontenginedragsters]

Paul New, Your right.
The idea is to turn the engine backward to push left over fuel out the exhaust valve into the header.
Any engine other than a HEMI does not have the exhaust valve and port pointing down for liquid to free flow.
Spark plug removal and spinning free will blow it out of that hole.
Nitro requires large volumes of fuel and often times uses down port nozzles.
These nozzles have check balls and springs to prevent fuel flow at idle.
Never assume that Nitro is not leaking down when the engine is not running.
Backing it down will prevent disaster if fuel is in the cylinder.
Nitro is just like dynamite or diesel fuel. It needs to be compressed to light.
I've been involved with Nitro cars for many years.
I have seen first hand what happens when an engine is turned over to start and it was assumed the cylinders were clear.
Its very volatile and can be deadly when not treated carefully.

Matt

[BK]

If you are talking about an injected motor on alcohol. Its best to kill the engine with the fuel shut off and then the ignition. That way you don't have as much fuel above the nozzles to leak out into the cylinders.

[noslin]

awesome, thanks everyone
dean

[wideopen231]

Firm believer in pulling fuel shutoff before clicking the mag . One bent BBC 7/16 steel rod made me that way. I see lots of guys not doing so , but its their motor . Even with blown alky I have never backed a motor down and never had problem.Made hundreds of runs . The TA/D crew I am working with back it down every time its fired  .Hey can't see that it can hurt anything.