Pure Stock Drag Racing tips & tricks - Page 6

**YENKO DEUCE REGISTRY** · #51 01-10-2003, 01:33 AM

Hmmmmmm [img]/ubbthreads/images/icons/grin.gif[/img]

So, what tire pressure do you start with in the rear's and front's? I thought the rears got 15-18, and the fronts got 40 psi??

What about a blocked power valve in the secondary of the Holley's? Is that as beneficial as I'm being told? Before I had my Holley 'concoursed', I had a block in the sec's, and the car would really come-on at about 2500 rpm - but I couldn't keep the tires under it. I later read in the Holley book that this scenario is caused by a lag in the fuel delivery, and although it feels cool, it's not the best way to set up the carb. So, I've not re-installed the block, it's not breaking the tires loose, but it takes longer to get the same seat-of-the-pants power.

I won't know what this thing will do for sure until Spring, then I will have a chance to take it out and test a few things. Even if I don't make it to one of the Pure Stock events, I'll get it to my local track.

So, Casey, I just might pull up next to you in the other lane one of these years [img]/ubbthreads/images/icons/grin.gif[/img]

Chevy454 · #52 01-10-2003, 03:38 AM

You shouldn't have any trouble hazing the tires, so I advise AGAINST running that low of pressure in your rear tires! I would hate to see you put that thing in the ditch this early into it's restored life!

I think the general rule of thumb (on repro bias-plys) is to start around 40 and work up. Our Camaro runs 46psi on all 4 corners, but this is dependant on the car/tires...but it should get you in the neighborhood. Lay a set of black marks and make sure they are each nice and evenly dark all the way across. Adjust the pressure according to what you find.

My first year I tried lowering the rears to ~20psi...I almost took out the Christmas tree and both guardrails[img]/ubbthreads/images/icons/crazy.gif[/img]!

RonNova396L34 · #53 01-10-2003, 03:48 AM

Marlin,
I remember a friend who owned a Belvedere(sp) Mopar ran a low air pressure like that in his rear tires with the same almost devastating results! He said it was quite the scary ride down the track. Next time I see my friend Steve (The guy I talked about in the NNN article) I'll ask him if he has any tips for you since he raced Novas for years. Even stuck a 427 in his 70 at one time.
Ron

**YENKO DEUCE REGISTRY** · #54 01-10-2003, 11:43 AM

I'm not sure that I understand how the lower rear tire pressure would cause the car to launch 'crooked'?? I thought the tire would 'flatten out' a little bit as it absorbed the initial 'shock' and thereby give a little better launch because you could hit the tires with a higher RPM?? Remember, this is completely new to me!

Casey Marks · #55 01-10-2003, 01:29 PM

Similar to Rob....

I run 48 psi in the front, and 44 psi in the rear. I've found that is where I get the most consistent contact patch for the tire in the rear.

If you put in the 32 psi recommended pressure, and do a quick blip in your driveway (OK - I do them in my driveway ......) anyway - - - you'll most likely find that you will see the outside edges of the tread making the darkest contact, and the inside 4 inches or so of the tread will be a simple *wisp* of black. As you air up the tire, the distance of the dark patch should get closer and closer, until you have a nice flat contact patch across the entire tread width of the tire. If you look at a Polyglas, there really is quite a bit of rubber that makes contact - as long as it ALL is making contact. Also, it seems to be fairly agreed upon by the Pure Stock guys that the more *seasoned* tires actually get BETTER traction with use. READ: DO LOTSA BURNOUTS to season them !!!! [img]/ubbthreads/images/icons/smirk.gif[/img]

Chevy454 · #56 01-10-2003, 04:47 PM

Marlin:

It wasn't that it "launched crooked", but the wheelspin got pretty bad...I pedaled it for a ways down the track, but when I got back into it, mayhem ensued! Luckily I can't leave off the converter anyway, so I was leaving pretty much from an idle, but it still spun it sideways HARD. It was probably a good run to WATCH, but made for a terrible ET/MPH!

**YENKO DEUCE REGISTRY** · #57 01-10-2003, 05:08 PM

I seee....

**Salvatore** · #58 01-10-2003, 10:12 PM

Marlin, A bias tire reacts different than a radial. (obviously) When air pressure is low it causes the bias tire (also Radial) to react like it is flat. You feel like you are getting a flat tire and the car vears all over the road. You need to do a burn out and see how the tire is planting itself. Look at the marks and see if you have a full tire width on the ground. If not, add or subtract air till you like your burn out marks. If the tire pressure is too low you could possibly spin your tire in its rim. It is trial and error, but we have faith in you. Just don't be upset if the car doesn't get out of the mid 14 teens set up like that. I can see day 2 is just around the corner! Ha-Ha Sam

**SmallHurst** · #59 01-23-2003, 12:43 AM

Casey,
It seems that I am chasing you around. Maybe I can keep you from getting in trouble (not). I was needing to talk with you about a driveshaft loop. Can you reply to me here or send me an e-mail. To everyone else, Hi! [img]/ubbthreads/images/icons/grin.gif[/img]

retengw31 · #60 02-18-2003, 02:58 PM

Neat forum..... Good to be back amongst GM people.

Casey's loop works well on my Ramrod, but lots of vibration to the floorboard. One that mounts between the trans mount and the trans is junk, it throws your dive train angle wayy off and reduces the clearance between the driveshaft and the floorboard to the point that we had to cut away the top 180 degrees to clear. At that point it was no better than the H pipe. We snapped a driveshaft first year at PS drags at the top end. Also took out the bellhousing. Scary.

Love this smiley: [img]/ubbthreads/images/graemlins/

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