So we are prepping out our 62 Dart for endurance racing with NASA. I'll have a few smaller events for shaking things down. There is a very specific power/weight ratio system used for classing with a modification based points system that bumps you up and down in the classing with a maximum tire allowed for each class. The penalties are based off of what they call a BTM (Base Model Trim) which is basically the stripper, bare bones model of the year make model you are driving. So for this case, 62 Dodge Dart 225 3 speed manual /3 speed auto 8.75 open rear 2.73 gears.

We need to make 175-185 rwhp.
my current setup is pretty stout and I have a lower compression (9.0)ported head with over sized valves and a higher compression (10.5) ported head with larger valves sitting on the shelf(needed 100 octane to run without detonation). Currently a super six setup and clifford headers are on the car with the bigger comp cam. Current setup makes 137rwhp.
Cars have to have valid dyno sheets for tech and a dyno is on site at all races for protesting purposes.
I have an Offy on the shelf ready to go and am thinking about ditching the cam. Was thinking of calling Racer Brown and getting a Hyperpak repo cam.
Anyone got a better suggestion? I' rather restrict it down than come up short.

It's odd they would think a 3 speed manual would get tied to a 2.7x rear gearing... which is not typically what would be stock for manual Mopar at all....(typically it could be 2.94 to 3.55 depending on car and year)

Your formula for a large car like that will be something like this:

use the 10.5:1 head and combination... need a cam similar to Erson 280/270 or OCG 346 or 791... dial the cam for centerline around 102-104 to get the most torque to throw the weight. Ditch the offy it will not breathe, you will want a clifford shorty.... at the track you will need to run a 500 cfm edelbrock min... and you will also need a custom distributor curve to get the best performance out of it.

This will get you in the 190+ range...

If an automatic you will want a stall convertor... if possible a set of 3.55's over the stock gearing will help move the big car....

There is always more if you do more compression, but you will be running higher octane and the carb size will have detrimental effects on MPG at that point....

Sounds like a fun race to work within.

I don't think the Offy intake is all that bad, but the Clifford is better at high speeds. Road racing requires a lot of mid-range torque so the lap times may or may not improve with the Clifford. If you're using a 3-speed trans I would lean towards the Offy as the shift recovery RPM will be lower. Use a close ratio 4-speed if you can.

You will need more cam duration and lift than the Comp cam as DI says. Longer duration, later intake valve closing really, will drop the dynamic compression ratio. You will want to raise the compression as the intake valve closes later.

Once you get the tires, brakes and suspension working you're going to have oil control problems. Lou has done the most development here that I'm aware of. When my road racing '66 Dart threw a rod due to oil starvation I ditched the /6. You have more room for oil pan modifications in your B-body than I had and you'll need to add volume and trap doors for oil control.

3.91 gears are probably a good place to start unless the track is open and fast enough to use 3.55s. Tight tracks may dictate 4.10 or numerically higher.

I had clutch trouble road racing. If I were to do it again I would go right to a 4-puck metallic disc.

Good luck!

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Joshua

Thanks for asking. Sounds like a ball. Good info there from DI and Josh. I would like more info about the car, current engine, and requirements before I make recommendations.

Are you saying you are required to use 2.73 gears and a 3spd? What tires will you use? What is your desired RPM range?

225s like plenty of cam and quite far advanced due to the oversquare design and valve sizes relative to cyl displacement. Forget Comp unless you are bound by advertizing needs or something. Hpak cam will be a bit too small if you want to run pump gas w/10.5:1. I would not run anything smaller than an Oregon 346. Run the 10.5:1 head for sure.

The Holley 500 2bbl might be my choice for this application. You can make that power, tuning is a snap, and that carb is used on a million racing apps (circle track...) and is good for acceleration. We run this on our LeMons Valiant racecar.

Yes, oil control will be critical and I can help with that.

More to come...

Lou

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Home of Slant6-powered fun machines since 1988

"So we are prepping out our 62 Dart for endurance racing with NASA."

You aren't running a fever, are you?

A 62 Dart, one of ugliest modern era Mopars, with a slant on a road course? Really? Ok, I'm impressed.

I would think you will hit a brick wall or a point of diminishing returns in engine mods in this application with the slant, would think spending equal or more efforts on chassis/wheel/weight/aero would find more impressive gains after the basics are covered on the motor.

Well good luck. Can you run E-85?

FWIW, I have more then a handful of 62 darts, I'm on this site mainly because I recently added a 62 Lancer with a slant to my collection, as it is IMO really a baby Dart

Based on RWHP numbers, the flatest power curve under the limits is your best target?

I have run combinations similar to what you are talking about with good results. To make sure you have at least 185 RWHP I think I would try your best flowing head, get the compression to 10:1 by milling or using a thicker gasket, use the Offy manifold and an adapter to a 500 Holley 2 barrel, Clifford shorty headers, and a Racer Brown St14 cam with 106 degree lobe separation. You do not need to go all out to get that kind of HP and you want to preserve as much low end as possible, especially if you have to use that 3 speed trans. If the 500 makes too much power you could move down to a 350 Holley. I presume that rules try to equalize the power to weight ratio of various cars. Lou and Josh are right that oil control is very important. I believe Lou has posted the pan modifications he makes on this site.

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If you didn't drive it there, it's not a street car.

Just to be clear we are talking a 62 Dart, not a Lancer, because I have seen little if any factory road racing back in the day with slant in that car. And for discussion sake, A 62 dart is considered a Pre "b" body, as they weren't using the label "B body" until 63?, although structural it fits the bill as later "b"'s. Best thing, its one of the lightest "B" bodies ever built.

What is the penalty of going with a 4 speed manual, seems with a lower HP motor, rpm limited a 4 spd manual would be a big plus vs a 3spd auto.

And using a 2.76 rear, might a smaller lower profile say 14" be a better choice, lower gearing and lower COG, less MOI. Not sure which brake you are considering, but an 11" will not fit a 14", if a 15" lowest profile possible, the 60 stuff is tall. Can you have brake ducts?

Alum DS, Lighten Ring gear, Alum FW, Alum Carrier (pricey and only in a 742) composite leafs legal? Shorten front leaf segment and move rear axle forward inches?

If you read the factory brochure on that page Dart with the 225 is advertised as getting a 3.31:1 Axle Ratio.... the Lancer gets a 3.23 for the 225 and 3.55 for the 170.... 3.31 wouldn't be bad for a "B" body with a direct 3rd gear... that's my final ratio in the Hpak duster in OD with 4.56's....it moves 3300 lbs with 230+ rwhp just fine....

Thanks for the discussion and details.

Exner Geek has got it with the engine recommendations. I would probably keep your 10.5:1 comp and run a somewhat bigger cam, but that's me.

The ST-14 would be a good choice and it is almost identical to the Oregon 346 (send stock core to regrind). Yes, 106 LSA is the ticket. Regrinding a stock cam and using a known good oil pump and drive gear is a key to longevity of the oil pump gear. For either of those, install it at 99-101 deg and not a degree over 101. I am serious about this. No joke. Yes you are reading this correctly. This will give you the widest powerband and best overall HP, and your peak HP will be close to as high as you can get. For 10.5:1 and pump gas, I would go a bit bigger on the cam and then you can use a restrictor or retard timing a bit or whatever to drop HP at will. I can recommend a cam if you like.

Here are some pics of modded oilpans:

https://www.flickr.com/photos/16910097@ ... 6194152763

The top half of the pics are my fully custom 66 Valiant/Dart pan - 0.8" drop, big side kickout. The bottom half of the pics are my later version for 64 Valiant, but based on an Aspen/Volare pan, also 0.8" drop, and using a cheap kickout bought from Speedway. Saves a lot of time and effort and works well. Can discuss more. This has run in our LeMons Valiant racer.

Happy to discuss more,

Lou

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Home of Slant6-powered fun machines since 1988

jcc-
7 point penalty for swapping the trans.

And 14 may be nice, but I honestly haven't looked at performance tires in that range. We will be running a 200-300 tw tire to minimize our points loss. Most likely we will be on a short 15 to lower the car; however we may have a tire deal and then we may just have to work with what is cheap or free.

I'll have to look but modification of the wheel base can also incur a pretty good penalty if we go over 4 inches. And since we've already changed the spring rate and swapped leafs; I believe we can go to a fiber spring which we may do. We're set with 1.1 bars up front and 130in/lbs springs rear but I have a feeling we will be up to 1.24's front and 225ish rear when we get to that point of tuning.

DusrterIdiot-
I'm seeing that too. 3.31 for the manuals and 2.94 for the PB904. Good to know if we put a 3 speed in we can change the rear gear ratio quite a bit. But same thing; rear gear change is a 7 point penalty.

Dart 270-
Bench racing can be fun. I have a good core cam on the shelf but I think I'm going to call Racer Brown and try out one of these ST-14 cams. I've got a great freeway on ramp by my house that is good for acceleration testing, so shy of the dyno; we can get some concrete data after swapping stuff. Before the end of August I need to finish out the engine mods and rebuild the rear.

I'm on board with your Powerband idea; average hp and torque in our powerband will be the key to a potent package.

Thanks for the oil pan pics, should give me a good jumping off point. And since I'm a fabricator at a racecar shop, I'm thinking we can whip something up pretty nice
Is the tube on the side for a dipstick or catch can return?

Tube on side is oil return for turbo (future).

Lou

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Home of Slant6-powered fun machines since 1988

I like this project, when/where do you first expect to be on track or testing?

I'm going through the rules and it looks like you're dealing with a lot of reclassification points under:

8.3 Up-Classing System (TTC-TTF only)
Modifications and Point Assessments:
If a car accrues 20 or more points it will be bumped up in Class. There is no limit—a car with a
high level of modifications might move up several Classes.
20 thru 39 points - Up ONE Class
40 thru 59 points - Up TWO Classes
60 thru 79 points - Up THREE Classes
80 thru 99 points - Up FOUR Classes
100 thru 119 points - Up FIVE Classes

Under engine alone I count:

Carburetor, 2
Intake manifold, 2
Camshaft, 6
Valve size change, 6
Compression ratio, 6 if kept to 10.4
Exhaust, 5

That's 27 points which appears to bump you one class. A poly head 318 at 230 gross hp looks much better from a rules standpoint.

I see more points for suspension and brakes.

Shocks, 3
Front springs, 2
Sway bar(s), 2
Control arms, 4
Brakes, 2

Another 13 points and that gets you to 40 points which is a 2nd class bump.

I read the following as allowing alternate rear axle ratios.

I. NO-POINTS MODIFICATIONS:
d. Drivetrain
4) Final drive ratio modification

Am I off base here? It truly looks like modifying the engine to get a reasonable amount of power is not a good way to stay in class.

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Joshua

October 29 at Sears Point will be our first Enduro event. I have an event at Thunderhill in mid August I'm lightly shooting for, but if I don't make that date I have 2 other cars that need testing too. I believe next event after that is early September at Sears Point.

As is and with these planned mods we are at 61 points. I'm trying to find 2 to shave off to make it to D, which would put us in the slowest class for the Enduro series.

And if you read under transmission, you'll see the point penalties for swapping trans or rear gear changes. But now that you mention that, I wonder if I read/interpreted that wrong. If we can change rear gear and tune for top speed track to track that would be great.