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Adventures in dirt track racing...roundy roundy...

I fought pull bar settings all year. I had to drop to a softer progressive spring 600/1200 versus the 700/2000 that was in it. I also had to lower the mounting on top of the diff to soften the power application with my lower HP. With the stiff spring and high angle the power hit immediately and just broke the tires loose as soon as I was on the throttle. Not bad on tacky tracks but terrible on slick.

The urethane puck you can see is the brake side dampening on the pull bar. There are a lot of pull bar options, full puck style, enclosed puck, spring/puck, spring/spring, spring/beville, etc...
 
I did what i could to simulate the car in a dynamic state. Full droop on LR, i put a ratchet strap on the RR but still couldnt get it sucked down.
This is "on the Bars" and on the chain.

Rear
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You can see the LF is off the ground. 10 years ago everyone was three wheeling with the LF about 18" off the ground all the way around the track. Times change, I dont like three wheeling I try to keep the LF as low as possible so the brake still works. On a slick track I run the brake bias all the way to the front so having the LF on the ground helps.

Obviously this isnt a true pic since the pull bar isnt in play but you can get the idea of how the car turns. The left side wheelbase shortens under load for rear steer. With my set up the Wheel base shrinks about 3". I like a tighter car. I can lengthen the chain and get the wheelbase to shorten up to about 6".

Rear wheels are 3" backspace LR and 4" RR. I also shuffle around wheel spacers on the rear. Spacer on the left side tightens the car, Spacer on the RR loosens the car.
 
Front under "load" 600lb RF spring, 650 LF spring. This is a tight set up. Neutral/loose would be equal weight springs, full loose is heavier RF 650, 600)
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On the banking it really runs on the bump stop the whole time.

You can kind of see the rear steer in this pic
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LR at full droop

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Some more rear suspension pics with no wheels. Full droop both sides.
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I really dont mess with the upper 4 bar on the LR. I keep it and the brake floater bar parallel. Lower 4 bar does get adjusted. Higher on the bracket is loose, lower is tighter.
You can also adjust the 4 bar lengths. Neutral is with the birdcage indexed at 0 degrees. I run 2 degrees to tighten entry.

RR is upper and bar lengths are adjusted the most.
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I keep the lower 4 bar parallel with the ground under load, the upper is changed constantly. Higher is looser, lower is tighter. I also adjust bar lengths. Longer is loose, shorter is tight. As little as a 1/16" adjustment is noticeable.

A lot of guys get really deep into bar angles but I dont. There are damn near infinite adjustments and you can really get buried in numbers. I find a base line and then adjust for feel and how I want the car to drive based on track conditions. Set it once you get to the track and check it out. Change after qualifying and change after heat race, trying to anticipate the track changes the entire time. Temp, humidity, car count, classes running, track prep during the week, it all plays a factor.

J-bar--Lower on the pinion is tigher, higher is loose. Frame side is more about side bite. Higher on frame=more side bite. One track we run is a paper clip, long straights and tight turns, I run it lower on frame and higher on the pinion. One track you are turning right the whole lap. I run more split, super low on pinion and really high on frame.
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I can get some good late model pics too if anyone is interested.
They run a lift bar. Think antisquat with a short anti wrap bar on a leaf spring suspension.
Lift bar hard mounts to top and bottom of quick change, its parallel to the ground. Then there is a chain and shock at the front of the lift bar up to the chassis. They actually run 6 shocks, 2 LR, one lift bar then one on each corner.
 
Engine pic.. Its just a basic SBC. its a 036 GM block. Promax aftermarket Vortec heads. Stainless roller rockers.
3.750 stroke light weight forged 4340 crank. H beam rods, balanced rotating assembly. Stock 4.000 bore so total cubic inches are 377. We have to run flat top pistons and cylinder pressure had to be 175psi or lower. 11.2:1 compression, GM single plane intake, and a "stock" Holley 4412 2 barrel. Distributor is a MSD pro billet and its locked out. Cam is a 2 barrel grind Isky.
Champ 8 quart pan, Edlebrock Victor CT water pump. Nothing fancy but dead nuts reliable. I am down on HP compared to the guys running the $12k crate killers, but its super driveable and smooth.
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Its just like wheeling or dirtbikes, or anything with wheels. You are always chasing set up.
There was one damn race last year in dads car when I hit the "UNICORN" set up. The car was perfect for track conditions that night. I got wiped out under caution by a lapper.

What is perfect? WFO the entire time, light steering input and just use a little brake to turn the car. Literally driving with one hand (could have been two fingers), flat on the floor, not on the cushion, light brake on corner entry and thats it. A set up like that is a high, always chasing it.

The top 10 at most tracks are all pretty much equal in the straights. I guess its like pavement its all about the corner and rolling it smooth, the earlier on the gas sets you apart. The race is won or lost in the corners. The big difference is how fast the track changes, you can hit a good line for 2 laps and the next lap its gone. You are ALWAYS hunting for moisture and trying different lines.

Dads car liked to turn left a little. Kind of tight.
My car likes the ass end hanging out and way on the loose side, totally different driving style. When its neutral/tight its slow as shit. I had one heat race this year that the set up was great. I out ran the fastest guy at that track by a straight. PInned on the high side, but still not the unicorn. :confused: I led 7.75 laps, went in too deep on last lap and he got by me at the flag :laughing: My wife still asks if my throat is sore from choking so bad. :lmao:

I am hoping for some good test and tunes this spring. I will get pics of the track and we can talk about how bad I am at reading a track and how its going to change.
 
Does this stuff same pretty much the same year to year? Or do you find you have to change things on the chassis to keep up?
 
Thank you for sharing all of this. That rear set up is intriguer. How much does that "stock" 4412 probably flow? The 2v classes always amaze me
 
JohnnyJ said:
Does this stuff same pretty much the same year to year? Or do you find you have to change things on the chassis to keep up?
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If you want to win you have to change/upgrade. The guy I got my car from buys a new one every two seasons.
Dads chassis was a 2010, but it had updates in 17 to change geometry. It was a solid top 10 car most nights.

Id say you can run up front consistently with updates every two seasons and a new chassis every 5-6 depending on industry changes. .

Are the differences significant? Probably not but when the top 3-4 qualify within .010 sec week in and week out you have to keep good parts on them.

There is a major difference in 2019-20 top chassis versus say a 14-15 chassis. Top builders are now setting jigs and fabbing the chassis in a dynamic state. The front clip is welded on at an angle.
Hell most of them are a true super late cage and rear clip chassis with a AFCO chevelle clip on the front. It will be a few more year before something truely innovative comes along.

Not much different than rock buggies. Stuff stagnates for a few years then boom some beautiful genius rolls something from left field out of the shop.
 
I don't get the rear suspension. I'm trying to wrap my head around what is going on there. You say its a 4 bar system, but I think I'm counting like 6 links, not including the panhard? I get what the pull rod and upper shock off the top of the diff do, but why are there multiple upper links on each side? What is a birdcage exactly? I'm guessing it allows the axle to twist in the mounts and not 4 link bind?

Kevin
 
Levigarrett76 said:
Thank you for sharing all of this. That rear set up is intriguer. How much does that "stock" 4412 probably flow? The 2v classes always amaze me
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a Stock 4412 is rated at 500cfm. Mine is likely closer to 625cfm.
Hell you can get aerosol 2 barrels that flow like 890cfm now.
 
Ghetto Fab. said:
I don't get the rear suspension. I'm trying to wrap my head around what is going on there. You say its a 4 bar system, but I think I'm counting like 6 links, not including the panhard? I get what the pull rod and upper shock off the top of the diff do, but why are there multiple upper links on each side? What is a birdcage exactly? I'm guessing it allows the axle to twist in the mounts and not 4 link bind?

Kevin
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There are really only 4 suspension bars then the panhard. The extra link on the LR is for the brake floater. The LR caliper mounts on a bearing housing and rotates independent of the axle housing.
You are correct about the Birdcage. Its just the 4 bar mounts but the upper/lower mounts are welded to a tube with bearings inside. Eliminates all bind. You can freely spin the cage with the bars/shocks disconnected. Actually after 4-5 races, you unbolt everything and spin the cage several times to keep the bearings from flat spotting.

My cages are double shear but they do make single shear as well. Something I find weird is the Bird cages on a super late. 900+HP, the axle tubes are aluminum, the birdcages are aluminum and they are ALL SINGLE SHEAR.
 
The shock in front of the axle is just he LR shock. The horizontal shock at the top of the housing is just to dampen the load/unload of the pull bar.
The coil spring is on a spring slider, its not a coilover shock setup. Its just a telescopic spring carrier to eliminate coil bind. There is no dampening, its just a shaft on bronze bushings that takes grease.
It also makes preload and ride height adjustments extremely easy since its a fine threaded body.
 
YJ4Rox said:
Engine pic.. Its just a basic SBC. its a 036 GM block. Promax aftermarket Vortec heads. Stainless roller rockers.
3.750 stroke light weight forged 4340 crank. H beam rods, balanced rotating assembly. Stock 4.000 bore so total cubic inches are 377. We have to run flat top pistons and cylinder pressure had to be 175psi or lower. 11.2:1 compression, GM single plane intake, and a "stock" Holley 4412 2 barrel. Distributor is a MSD pro billet and its locked out. Cam is a 2 barrel grind Isky.
Champ 8 quart pan, Edlebrock Victor CT water pump. Nothing fancy but dead nuts reliable. I am down on HP compared to the guys running the $12k crate killers, but its super driveable and smooth.
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So what kind of horsepower are you making? What do the other guys you speak of motors making?
 
MoparMan said:
So what kind of horsepower are you making? What do the other guys you speak of motors making?
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I'd guess about 425-450hp with what he is using for parts.

The "stock" Holley 4412 carb makes alot of difference when the engine rules are restricted. I know of racers that pay in excess of 2k dollars for those Holley 2 barrel carbs. Circle track engine guys buy pallets of those carbs from Holley and then flow bench test them all after doing the usual tricks. The one(s) that flows the most without the venturis being modified are the most expensive carbs in the lot. Proce goes down from there. The rest of the tricks are how they drill out the air bleed holes in the metering block ect. When your running a 2bbl carb on a race engine every extra cfm the carb can flow vs the next guy is worth gold.
 
MoparMan said:
So what kind of horsepower are you making? What do the other guys you speak of motors making?
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Haven’t had it on a dyno but my engine builder says conservative number should be 475ish.
the Mullins Crate killers are advertised at 525.
 
Ive always been really fascinated how folks squeeze 500+ hp out of smaller cfm like 5-600 in these class engines. What kind of vacuum do these engines pull at WOT?

Then you see dyno tests like engine masters does with the xp holleys on fairly mild small blocks. I guess its all in the build. Im also guessing slapping a 7-800cfm carb on there would increase the hp quite a bit?
 
Levigarrett76 said:
Ive always been really fascinated how folks squeeze 500+ hp out of smaller cfm like 5-600 in these class engines. What kind of vacuum do these engines pull at WOT?

Then you see dyno tests like engine masters does with the xp holleys on fairly mild small blocks. I guess its all in the build. Im also guessing slapping a 7-800cfm carb on there would increase the hp quite a bit?
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Yes sir its all about flow rates. I have three different two barrels depending on what track we are running and what they tech. My favorite is a Jim Evans racing with a billet metering block and lots of work. I can only get by with it at one track though.

The crate killer motors arent legal since they have extensive head and intake porting but most tracks wont tear down a motor post race to tech it. Technically we arent even suppose to gasket match.

My heads have very minor work to keep them legal.
 
I was wondering the same thing ghetto. I had to head scratch a bit but I think it is so that under acceleration you are not trying to control axle wrap and suspension input on the same mount. When under acceleration with a traditional four link the bottom bar is pushing on the chassis and the top bar is pulling on the chassis. Controlling axle housing rotation with adjustable mounts separate from the Axle location mounts gives a whole Nother realm of tuning. Separate every force into another spot
 
My uncle was telling me some guys up north are now building their own "crate" motors. They will buy all the seperate parts from GM and then have them massaged before assembling and sealing the engine.
 
SLOWPOKE693 said:
My uncle was telling me some guys up north are now building their own "crate" motors. They will buy all the seperate parts from GM and then have them massaged before assembling and sealing the engine.
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Yep lots of "sealed" GM 602's running around here in the mid ohio valley with stroker cranks and who knows what else.
Some tracks let our class run a "sealed" 602 crate with a 4 barrel and they get a 100lb weight break because they are only 300ish hp.
My bud that we pit with has close to 40 wins in three seasons, our engines are very similar. He started on the pole of the feature one night, crate car on the out side pole and I started 4th.
That "stock 602 crate" gapped the hell out of us on the start and the next restart.

most people say if you arent cheating your arent gonna win. :lmao:
 
Excellent Thread, Been a huge dirt track fan for years and have always tried to wrap my head around the suspension and setup. Thanks for taking the time to post all of this, cant wait to see the off-season rebuild and updates. :smokin::smokin::grinpimp::grinpimp:
 
YJ4Rox said:
Yep lots of "sealed" GM 602's running around here in the mid ohio valley with stroker cranks and who knows what else.
Some tracks let our class run a "sealed" 602 crate with a 4 barrel and they get a 100lb weight break because they are only 300ish hp.
My bud that we pit with has close to 40 wins in three seasons, our engines are very similar. He started on the pole of the feature one night, crate car on the out side pole and I started 4th.
That "stock 602 crate" gapped the hell out of us on the start and the next restart.

most people say if you arent cheating your arent gonna win. :lmao:
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We may or may not have had a "355" that was bored .030 on one cylinder (for compression/cylinder volume tests) and .060 on the other seven. The heads may or may not have been accidentally exposed to an acid bath that somehow enlarged the ports either. And I really hated when our engine guy would accidentally put the heads in the mill angled and make us have to mill the "stock" Edelbrock intake to match.

Its only cheating if you get caught.... Right? :lmao:

I won't even get into the hidden weight slider boxes and the fire extinguishers filled with lead that may or may not have been in our open show cars. :laughing:
 
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Love the thread, keep it going. Interesting to hear your take on the crate motors and crate killers. Out here with it seems like the crate motors made everyone better drivers. My dads buddy ran an open motor for as long as he could stand it and finally put in a crate motor this year. Had to completely change his driving style which he's still struggling with.

We ran saturday night in Petaluma. Track was incredible, moisture came up as the night went on and the track was killer for the feature. We struggled a little with a lean fuel issue due to building this motor with Esslinger's latest cylinder head that apparently flows quite a bit better than the last one we ran. Still ended up 5th which wasn't too bad. Haven't raced with my dad in about a year and damn it was a good time

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mjlogan88 said:
Love the thread, keep it going. Interesting to hear your take on the crate motors and crate killers. Out here with it seems like the crate motors made everyone better drivers. My dads buddy ran an open motor for as long as he could stand it and finally put in a crate motor this year. Had to completely change his driving style which he's still struggling with.

We ran saturday night in Petaluma. Track was incredible, moisture came up as the night went on and the track was killer for the feature. We struggled a little with a lean fuel issue due to building this motor with Esslinger's latest cylinder head that apparently flows quite a bit better than the last one we ran. Still ended up 5th which wasn't too bad. Haven't raced with my dad in about a year and damn it was a good time

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Awesome man!

I like the crates, honestly I wish they would make it a crate class, but with the GM604 or CT525 but im in the minority. Shoot i would be ok with the 602 and 4BBL.
On dry slick nights a crate car can win at our tracks and does quite a bit, if its tacky the lack of HP cant keep up though. There are some long time racers that have dropped down to our class and run crates, they are usually in the top 5 regardless of track conditions.

The people with big motors and cant drive worth a shit tear up a LOT of equipment. :lmao:
 
I was out to my buddies shop last night. They have three steel block late models.
His youngest son is putting together a new to him chassis. The one he ran this year was ready to be retired. 13y/o and putting it together by himself.

I grabbed a pic of the lift bar, its not complete but you guys can see how it works as opposed to the pull bar.
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