Quote:
Originally Posted by Jack Ferris
Help me out understanding the rules in "Pure Stock". As far as the engine goes I get that. What about the rest of the car? What about the high dollar automatic transmissions that NHRA Stock and Super Stock use? or the high dollar slider clutches? Are they allowed in pure stock? What about gear ratios in the diff? These cars are purpose built for the class right? Along with suspension mods, weight relocation and whatever makes these cars about as far from "stock' as one could get. So, is this class basically based on a factory engine, but any other chassis/drivetrain mod is allowed?Im not trying to be a wise guy. Just want to know more about the class.
|
Quote:
Originally Posted by Formulabruce
Great post, you are 100% correct. Even "factory" engines are not so factory.
"supposed to be stock suspension..."
I watched a stock 71 Cuda AAR with disc brakes , get brakes gone, all impact bars, GONE, and lots of lightening, when done, you couldnt tell... same treatment went into a "ZL-1" Camaro
So its back to "stock appearing" in my book
Also a Trans Am was never meant to drag race....makes me sick seeing them on the drag strip, and looks dumb too
|
The rules haven't changed since I've done it. We are talking pure stock here....
As far as the engines go,,,they are as stock as one could expect after 50 years. The rules allow 1 mojor change and that's compression ratio. That's for obvious reasons. After 40-50 years of use these engines have been rebuilt 2 and sometimes 3 times or more. They need bored, decked, milled, etc... All of which will increase the compression ratio, you just can't help that. So the rules implement a .070 overbore maximum and a 1.5 compression bump over the "advertised" compression. Since rules dictate all casting numbers must match the HP and model claimed, you can't use aftermarket blocks.
Heads are as cast, no port work allowed of "ANY" kind, same goes for intake and exhaust manifolds. All have to be factory correct for the HP and model claimed. They aren't worried about date codes.
Carb is also the same way, and chokes must be present and functional. Cam and valvetrain also have to be stock per HP and model claimed. They only allow 130 lbs. seat pressure on the springs which is stockish, this keeps people from spinning these engines higher than a stock engine would normally go and making more power.
So for all intensive purposes these engines are as stock as one can be, and believe me this stuff is checked, they will perform complete tear downs for certification, they check bores and strokes, camshafts etc.. to make sure everything is on the up and up for your model and HP claimed..So everyone is on an even playing field.
As far as suspensions, no trick springs or fancy shocks allowed, sway bars must be attached and functional. No traction bars allowed etc....
A couple things they will allow are "no hop" bars on coil spring cars, and they allow clamping the leaf springs on a leaf spring car,,,,,that's it.
Now you can tweak things like pinion angle. Another trick that I employed was to shim the front sway bar frame bushings so they didn't "crush" the bar. This allows the front end to move more freely. Most guys now just hone out the bushings so there is no "crush". Technically legal because the bar is still hooked up and functional. Some will go as far as to employ a similar tactic to the control arm bushings.
Another simple trick I did on the front suspension (and it's not really a trick) is that I ran, and still run, oil filled shocks on front because they move more freely than a gas filled shock. These simple mods are all in an attempt to hook those little bias ply tires.
These simple and basic tricks got me 1.8 60 foot times on stock rubber. Others have gone even quicker nowadays.
There are no trick transmissions allowed, no lightweight parts allowed in the engine or transmission. They do allow rearend gear changes of your choice since most cars came optional with just about anything anyway.
No fuel system upgrades of any kind, it must all be stock.
As far as lightening goes, it's not allowed at all in pure stock. One of the reasons why people will choose an advantageous platform for racing this class to begin with. You may see things like heater and radio delete, just like cars were back in the day, but you won't see door bars cut or lightweight suspension pieces. Low option, small package cars that are already lightweight are the best ones to start with.
Formulabruce seeing brakes gone (or more likely lightweight brake package), door bars gone, was most likely a F.A.S.T. series car. Completely different. They appear stock and parked right next to a pure stock class racer you wouldn't be able to tell them apart, but the rules are different in F.A.S.T.
Engine rules just as above but they allow stroker cranks (has to be stock block though) They allow all the porting you want, but again has to be stock cast parts. They also lighten as much as they want, making most pieces and brackets out of aluminum (once painted you can't tell) and swiss cheesing anything out of sight. Radios and gauges may appear intact and functional but on the back side all guts are removed, it's out of sight.
Overall the F.A.S.T. cars must appear as the day they rolled off the assembly line, but anything out of sight is fair game. There are literally dozens of tricks in the F.A.S.T. class that would take a book to list here, but I've typed enough.