No problem.

The magazine articles on Widmer's take of NASCAR are interesting reads too. Worked with some interesting builders... although they may not remember it.

WRT the F111,
I can only speculate on the dynamics of bird meets windscreen at those kinds of speeds. A small bird would be bad enough but watch out for those geese.

-Mindgame

 

Zero_to_69:

Let me know if you want any info on fuel motors-I have worked on a couple race-winning teams in the last couple years, and I should be able to answer most of your questions!

 

What kind of specifics are you looking for? I don't remember the exact #'s, but the cam specs are: Advertized duration in the 298-305 range, and lift in the high .500's. Every team has it's own grind, but the "stock" grind is a 298/298, high .500 lift. Now a days, teams are even going with 3 different ginds on 1 cam! The front 2 holes are 1 grind, the next 2 are another, and the back 4 are different still.

 

Spill your guts! Anything you are able to tell me/us would be cool.

.500 lift at the lobe huh? I know one of the teams was using a 1.7 rocker!

What is the purpose of having three unique grinds on the cam?

I've read that the valve timing is ground to align itself with the
crankshaft once the torsion and heat get to the motor.

Does that have anything to do with it?

 

Sorry, the lift is at the valve. Most teams run the 1.7 rocker, but some run a 1.6 on different holes. The reason they change the cam timing is because of the new setback blower manifolds. With the manifolds, it allows the teams to go with the same piston heights throughout the engine, and that balances the rotating assembly a lot better. The front holes still get a little more boost, so they retard the cam timing and run a lower lift at times as well. The engines are a lot happier during and after a run, mainly because the shortblock is balanced better, and they are getting better airflow distribution which in turn evens up the horsepower produced by each individual cylinder.

Some cool facts:
Fuel pressure: ~550psi at 8000
Oil Pressure: ~250-300psi at the step
Boost Pressure: ~30-35 at the step, 40-48 at 8000 (depending on overdrive)
Static CR (piston height): ~7.5 (varies team by team, track by track, and sometimes even run by run)
They also vary head gasket thickness run by run.

There's a lot more, that's just someting to get you started!

 

What kind of quench are they using for piston top to bottom of head clearance? How about timing numbers?

 

I'm not sure on the quench #'s, but it is pretty small. Usually the piston comes out of the deck about 100-120 thousandths, and they normally run anywhere from .060-.095" head gaskets. Naturally, the piston fits up in the giant ~160cc chambers.

For timing, the mags are typically set at 58-60 degrees and they run what is called a 6 shooter, normally 3 of them at a time (to actually make it a 18 shooter), which works kinda like a 3-step. They have pills that range anywhere from 1* to 25*. They can then put whichever pill they want in the 6 shooter, than at a set incrament, that amount of timing will be pulled from the engine. This is how they control the power output going down the track. Usually they will pull a bunch of timing at launch and then slowly add it back in and by mid-track it sees all the timing in the mags, then towards the top end they pull some out to keep from hazing the tires through the traps.

 

Please keep in mind all the numbers I give are general #'s, as I don't remember the exact ones, nor would teams want me giving out the exact ones anyway!

 

I question the .500 lift at the valve. As you sure that's not lobe lift?

 

I'd be surprised to see anything less than .700 at the valve.

A mild street cam is damn near .5" lift

 

No, it's somewhere in the mid-300's lift at the lobe. When I first started, I thought the lift would be much greater, but it really isn't.

 

uea but you have to keep the profile in mind...a street cam will have a "peak" at the top of the lobe, but these motors launch the lifter off the base almost straight off and the "peak" of the lobe is like a half circle

 

Well, not really. These engines have more than 500#s of seat pressure CLOSED, and upwards of 1000 open. While the lobe is more round over the nose than any cam I have ever seen, the lifter rarely leaves the surface of the cam.

 

I'm having a tough time imagining why those motors would have such a tiny lift. Why the need for 500# on the seat if they turn only 8k and run a chamshaft similar to the one in my street car? I get by with 130# on the seat. Also if you're saying their compression ratio is 7.5:1, how big a dish would they have if the piston is .1 -.12 out of the hole (which, incidentally, is a HUGE margin of error)? Also how does a piston that's .200 out of the hole miss the head with a .095 head gasket?

I could see the need for low lift if the thing turned 15krpm, but they dont. I've got a buddy that runs a match race fuel car. I'll call him and see what info he has about these things. I know they use big team's throw away stuff and I've seen and worked on some of their parts. Nothing looks at all exotic in their motors, but again they are match cars so it's a different thing altogether. It seems to me that there aren't any secrets in making 6,000 hp: Add 1 part nitro plus 1 part air under pressure and get it to light!

 

There is no dish in the piston. It is a flattop design with a big valve relief for the intake. Like I said before, the CC's are so big that the piston actually travels up into the chamber. Here is a good picture of that: http://www.delworsham.com/2002/gainesville/kevin.jpg
That is one reason for the low lift- any more and the valve would hit the piston. Also, the margin of error you point out is not an error at all. Teams stagger the piston heights throughout the engine. Some teams now run the same heights in all 8 holes now because of the setback blower, but they still might vary it run-by-run, depending on how the car ran. The guys that still run the conventional blower setup run the front 2-4 holes up to .060 lower than the rest, due to the air being forced forward by the way the rotors twist in the blower.

You are right, there really isn't anything exotic in a fuel motor, but often times the way they are set up defies conventional thinking. There are reasons for everything they do. Teams are constantly thinking of and testing new ideas that might give them an edge. That is what racing is all about.