9” dilemma

[Hipopinto]

Hey all

I’m at another cross road with my 9” for my pinto!

I’m building a 3.25” tube rear with a support gusset

My plan is to use Calvert mono leafs and CalTrac bars

I’m upgrading to 35 or possibly even 40 spline axles

I would like to run a class called “true street” this is a class where you run two passes then do a 20-30 mile cruise, take 15 min to cool down and run another pass!

So my question is as follows: do I put in a Detroit locker or a full spool?

I’m leaning towards a locker as I have one in my galaxie and I love it but how will it perform on the race track and what should I expect?

I don’t want to add something that may hurt performance or even cause an accident

Thanks guys
Dave

[thatdarncat]

I think Jay Brown ran Drag Week each time with a Detroit Locker ( other than the Ford GT year ) without any issues, hopefully he comments. I ran Drag Week 2015 with the full spool I’ve had in my car for years, but I also didn’t want to buy a Detroit Locker just for one event. I know there are some others that run a full spool on Drag Week. I’ve seen comments from some people over the years that really don’t like the sound or feel of a Detroit Locker, it’s probably just one of those things a person needs to try and see if they like it, and it sounds like you already have experience. I’ll add, I was swapping to street tires with a fairly narrow tread pattern, doing the street drives with much wider tires or stickier tires would likely stress a spool and the axles more.

[gt350hr]

   Locker over a spool anyday unless it's a manual trans , then a spool in a pure drag race car. You can get a 35 spline locker , not a 40. 35 should be plenty.

[Falcon67]

Something to keep in mind, having raced with both for money and not so much for fun - especially at the power level required to be competitive in something like True Street.

A locker is fine for the street and street/strip. It has to be respected because under power it's typically going to lock up and the car will go where ever it's pointed at the moment. Thats on the street with dry tires. 

In the burnout box, maybe not so much.  Unless you get an good even burnout with the same amount of water under the tires, there is a chance that you'll approach the line with it partially locked, or even unlocked if one tire spins more than the other.  Typically those classes don't allow burnouts across the line, so you'll burn then stage.  If the ass end isn't locked, your nose may go one way or the other as opposed to straight. 

Spool removes any such guesswork.  If you nose into the wall or run over the tree, it's because you broke an axle.  Good axles will not have any problems with the spool and slicks or DRs.  So what if it chirps in some corners, those drives are not some sort of road race.  Usually a big gentle loop close to the track.  I've been known to drive my car on cruise night - methanol, locker, 4.56, 4500 stall, Hoosier DRs, etc.  Don't think anything about it.

If you run a nice powered street car and go to the Test-N-Tune for fun, run a locker.  If you're in competition to get there first, run a spool.

[Hipopinto]

So if the locker is not locked it can be a real mess!

Looks like a spool is likely the best bet

I have no idea if I can be competitive in true street this current combo will likely be mid 12 second or possibly into the high 11 second range with the nitrous

With The new engine I’m shooting for 650-700 at the wheels so that will change everything but again it may still be no where near enough to be a real competitor!

Either way a crash is not a good idea

Dave

[cjshaker]

I'll throw in my experience with the DL on a street/strip deal. I've been through 2 Drag Week deals with this setup.
'69 Mustang, 497 hp 427, 4spd, 4.30 gears, Detroit Locker, 28" MT ET Streets.
Only one time did I have an issue with it not locking properly. That was when I had to make a tight turn onto the burnout area. The car didn't dart either direction, but it did push slightly to the left going down the track. Not enough that I had to back off though.

That was during my 2nd Drag Week, and Alan Casida suggested that, after straightening the car up when pulling out, that I back up a few feet, then pull straight into the burnout box. That worked and the car hooked fine and went straight. Ran 2 more runs after that at the same track, doing the same thing, and never had the issue again. Otherwise, I've never had an issue with it locking at any track. That was running 11.70s at 115 at the time.

[Falcon67]

That would be the key, making sure you roll in straight and that the rear teeth engage.  The experience with my DL is that it works "pretty much most of the time."  I race for $$$ and the time it doesn't work or throws the 60' off will be one of the money rounds LOL.  I ran mine hard for about half a season before putting the spool back in.

Would need also to know more about the True Street rule requirements because there are a bunch.  Around here, you'd need to be mid to high 5s in the 1/8 to hold your own in "True Street".  A 5.8 is around a 9 second 1/4 mile run.  That's about 800 HP at the tire in a 3000lb car.  This may not be the same rule set you're running against.  Rotating weight reduction in racing is 4~5 times better at freeing power than static weight reduction, which is where you get into gun drilled 40 spline axles, relieved rear gear sets, super light bead lock wheels and such.  A locker is way, way heavier than a spool, hence a power eater.  Drag week I can see it.  20~30 mile survivor cruise, not so much.  Spend that money on the cooling system to keep the car and converter/trans temp in line and get the heat out in that 15 minute "mandatory closed hood" timeout.  From most of the rules I've seen, that is another important deviation from Drag Week type racing - once you stage for first qualifying pass, that hood stays shut.  You can add ice to an inter cooler and put in fuel, nothing else.  There is also the occasional race here where you unload and run, period.  No test passes.

You can still win rounds at slower ET, you just have to kill 'em on the tree and stay in the groove LOL. 

Sample I found at NMRA:
COOLDOWN PERIOD/RETURN PROCEDURES
After the vehicles return from the road tour, they will return directly to the designated staging
lanes for the cool-down period. They may not change tires. The cool-down period will typically
last between 15 and 45 minutes. During this cool down period only, entrants may:
1. Adjust tire pressure (add or remove tire pressure),
2. Install fresh nitrous bottles
3. Install ice in their intercooler (only if located in trunk, rear hatch or rear seat area).
Anything not listed above is prohibited.
A strict CLOSED HOOD policy will be in effect until a competitor has completed his or her three
back to back passes. No re-fueling allowed once car leaves on cruise. Engines must remain
turned off during entire cool-down period. External cooling of engine by any means (cold water,
outdoor fans, etc.) prohibited. Any engine changes, repairs, or adjustments (changing rocker
arms, carburetor adjustments, etc.) prohibited. Changing of tires prohibited. No external
charging of battery / batteries permitted.

[gt350hr]

   "I" run heavy "engagement springs" to keep mine from unlocking too easily. Back in the '70s we used to do the "back up procedure" after a burnout , but the heavier springs solved that issue. It is "best" to have equal tire diameter and tire pressure with locker OR a spool to prevent "rear steer".

[BattlestarGalactic]

I've got 30 yrs on my 35 spline spool in my '69 F100.   I tore up too many T/L back in the day and I hated lockers because of the "what if it isn't locked" scenario.   Totally street driven, 29x12.5 tires on it and 4" front runners.  Ya, it doesn't go around highway ramps very well, but I've lived with it for 3 decades.  I don't parallel park it either with manual steering!  It's a hot rod, I put up with "hot rod" issues.