madmax442

I have an NHRA Rulebook, although not on me currently. My question is, does anyone know at what ET or speed you have to change from fuel tank to fuel cell? I read what I believe my car falls under in the book (summit series) but to me it was vague! I currently have a fuel cell but am thinking of converting back to a tank. My car has gone 10.3-10.5 in its current form by the previous owner. The reason for the possible change would be for a in tank EFI setup for a new EFI 455 done by Mark Remmel (CutlassEFI)

Rallye469

I don't think (for a stock bodied car) you ever have to switch to a cell.
If you can get what you need done with a tank, do it.
I've seen sumped stock tanks in the 8's


-pete

madmax442

Thanks Rallye! That was my thought but I honestly couldn't remember! It would be nice to use a tank and have my trunk free to use as well!

Is that your car in the Avatar Rallye? If so what type of setup and times are you pulling? Looks like you're hooking and making lots of power!

Rallye469

Yep, that's my car. I drive it every chance I get.
BTR built 469, RR heads, pump gas, 3.90's & radials

I'm still using a stock tank.
I just had this one sumped and went with an electric pump.
Up until a month ago I was still using a mechanical pump.

-pete

madmax442

Very nice!!! Trying to get the funds together for a Mark Remmel 496 EFI engine to replace my BBC 502. I'll most likely switch to a modified in tank pump setup! How much power does your BTR engine make?

Rallye469

583hp/ 602 ftlbs

Olds torque is a beautiful thing.

madmax442

Great Numbers and Wicked Torque!

NHRA W-30

I don't believe there is a rule re: tank for bracket racing . I've seen some high 8 second cars at Summit Series races here in CA. w/ OEM gas tanks . Also some pretty fast super stockers around w/ OEM tanks. For running stock class , I prefer the OEM tank because it holds the weight down lower than a fuel cell thus a slight weight transfer advantage . I keep about a half tank full at all times and try to keep the weight the same every run.

madmax442

Thanks guys! The way I read it was that you had to have it between the frame rails or if it was in the car you had to have a bulkhead and it must be vented to the outside.

chadman

Actually having the weight higher will transfer (pitch rotate) faster. It's basic physics.

chadman

Pete, any particular reason you have the sump so far forward? Further back would be less likely to suck air.

Rallye469

Good question Chad. I asked that myself when I picked it up.

Yeah, honestly I wish the guy mounted it exactly where I told him instead of the easiest place...
But- I usually race with a full tank and that sump holds enough fuel so even with slosh, it shouldn't see any air.

-pete

69455

More info


Aeromotive makes a Stealth stock tank with pump installed.
Plenty of fuel and sumped.

NHRA W-30

I'm always open to better ideas that will help me w/ my stocker. Would love to have a brief phone chat w/ you and get some info re: weight relocation on my car without a fuel cell . Times change and this car is pretty old school, yet fairly quick on a national level . Car apart now for freshen-up and good time to entertain a new idea or two . If interested-- pass on your Phone # , I will call you at my own expense. Thanks

NHRA W-30

Sorry --That last post is directed to chadman . Having trouble as I'm an analog guy and poor w/ computer writing and chats--Thanks

Rallye469

Hey Chad, you might have to explain that too me as well.

If the center of the weight on either a tank or a cell is the same distance from the fulcrum(rear wheel) than I don't see how height can be a factor.

Assuming the tank and cell both weighed the same.

My analogy is this.
If you placed a weight on the top of a see saw on one end, and at the same distance from the fulcrum(pivot) on the bottom of a see saw at the other end...would the one on top weigh more?

***now granted, you should be able to put a cell a little further back than a tank, but all things being equal, I'm not sure height would have anything to do with it.
Why don't folks mount their cells as high as possible?
I cannot wrap my head around this.

chadman

OK, I will try to explain the best that I can. In order to transfer weight onto the back tires you need the weight of the car to pitch rotate around the center line of the rear axle. When the weight is in line vertically with the rear axle it has no influence on pitch rotation when forward motion is applied from that point (axle centerline). Now take that same weight and put it on a point on the same axis only higher vertically. Now when forward motion is initiated at the axle centerline that weight will want to move back and down until it reaches the same vertical point as the axle centerline.

Rallye469

Ok, so I get that something higher than the axle VS. something being level to the axle would indeed help once forward motion was gained...
But upon initial launch/hook, there really is no forward movement.
If we looked at radials (which are termed "dead hook" tires, right?) They can't wait for forward motion to work.
I always understood that traction comes more from the axle/control arm/angle "lifting" or borrowing weight from the front of the car(instant center), then adding it to from the back.

In my mind I think that upon launch- weight placed in a position further from the axle would make more of a difference than the degree that it is above the centerline.

On the other hand, to your point, I guess even if you lift the weight of a tank even 6", once forward motion is applied, it would mean something to traction.

-Pete

NHRA W-30

I kinda get the science and physics idea . Here's my problem-- Without chopping up trunk floor and without drilling holes in trunk floor to bolt in a weight bar , In a F/SA '70 W-30 I need to relocate 180 lbs. to the rear . NHRA mandates ballast be welded or permanently bolted to the frame or crossmember. { both low in car } Anyone have suggestions of a better way ? I've been using heavy wheels and a full 3" exaust system w/ mufflers { cutouts for headers } . Car has full OEM interior.

chadman

I assume you have down bars running into your trunk? If so you can use these to mount weight bars.


http://www.appliedracing.com/weight-mount.html


And here are the weight bars. These come with weld on tabs. Just omit those and use one pair of the above mounts per bar. This will allow you to move the ballast anywhere you would like.


http://www.appliedracing.com/adjusta...-unwelded.html

NHRA W-30

Thanks for the feedback. No, I do not have down bars that extend into trunk. Your recommendation is great if you run Super street or just bracket race . However that idea is strictly prohibited in the rulebook for Stock or Super Stock . Stock IS the hardest class to build a car for because there seems to be more things you can't do than things that are legal . Hence there are only a handful of Oldsmobiles still in Stock Eliminator these days . Last couple years none even showed up at the U.S. Nationals at Indy . Last years bump spot was .82 under index . Nearly 60 cars went home without qualifying for eliminations . The fastest '70 442 in the nation is about .70 under.

BlackGold

I hate to get picky, since you're doing an excellent job of convincing people that the higher the car's mass ("weight") is the more it will want to pitch rotate. But technically the point of rotation for a drag car is not the rear axle. It would be if the rear tires were clamped in a vice and not allowed to roll. But in reality the rear tires are free to roll on the ground and thus the contact patch is the actual point of rotation. This means that even the mass of the differential -- which is above the tire contact patch -- contributes to pitch rotation.

Having said all that, yes, a fuel cell in the trunk will help with rotation more than the stock-location fuel tank. This is the same reason that Gassers back in the day both lifted the body and raised the crank centerline. Fortunately, today we have better tires, better suspension geometry, and better track prep and can get decent traction without building a skyscraper.

chadman

Black gold you are correct. I apparently had a brain fart but as you said the principal is basically the same.

Dick Miller

Not trying to cause trouble here but you definitely need some suspension work.

wr1970

I agree with you Mr. Miller that drivers side is way to high.