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Help Me Build a Drag Race 225
https://slantsix.org/forum/viewtopic.php?t=35089		 Page 1 of 4
Author:  bobw [ Mon Apr 27, 2009 9:29 pm ]
Post subject:  Help Me Build a Drag Race 225
I am 90% done building a nostalgia (HAMB) dragster with a 225 and an OD 4 speed, probably using the first 3 gears. I'll work the bugs out this year with a stock engine with a home made intake with 2 1 bbl. Holleys. It should weigh around 1,400 lbs and will have a 3.70 gear initially.
This winter I want to build a race engine. Race gas is ok. It must have old style carbs and a stick shift. No power adders. Since slants are new to me I would appreciate it if the experienced among you could give me a "recipe" for a really strong engine. I'll port the head myself. I need advice on compression, pistons, rods, cam, valve selection, etc.
This will not be a budget build, but I want to go with tried and true hop up parts and techniques to create a powerful but reliable engine.
Your advice is appreciated.
Author:  Joshie225 [ Mon Apr 27, 2009 10:08 pm ]
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Get a real 4-speed if you can. Heck, if you're serious about this and you aren't too far away I'll sell you one. 3-speeds, including the A833OD, have huge RPM drops between gears and it really hurts acceleration. Don't overlook a good flywheel and clutch. The 10" slant clutch will explode around 6k RPM and the stock 9 1/4 probably won't hold up. Spec Clutch has 9.5" clutches listed for 273s which will fit the slant and Wilcap has steel and aluminum flywheels.

You'll need more than two 1 bbl Holley carbs. You'll also need numerically higher gears. I'd start around 4.30 or 4.56.

Look at the K1 connecting rod and Weisco piston deal. This will get the compression up, lighten the rotating and reciprocating assembly a bunch and help the rod to stroke ratio.

The slant wants a cam with more intake duration than exhaust. The split is usually around 6-8°. 225s like a narrow lobe centerline (104-106°) and advanced to around 102° intake centerline.

Use the board's search feature to read about oiling system mods, Engnbldr oversize valves, Erson Cams and/or Oregon Cam Grinding, clutches and flywheels, etc, etc, etc.
Author:  Charrlie_S [ Tue Apr 28, 2009 4:17 am ]
Post subject: 
Quote:

You'll also need numerically higher gears. I'd start around 4.30 or 4.56.

.
I'm not so sure about that, Josh. The HAMB dragsters must run "street tread" tires, I think, 6 inch wide max. 4.30 or 4,56, will probably blow the tires off the car.
Author:  terrylittlejohn [ Tue Apr 28, 2009 3:16 pm ]
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how light is this car going to be? i tried a 3spd with the low first gear (3.09) the transition between 1st and 2nd is to much, the car will launch hard then fall on her face in 2nd, if this is the only trans you have when racing it , leave in 2nd and shift up , with low rear gears it will work better. :wink:
Author:  wvenable [ Tue Apr 28, 2009 5:37 pm ]
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Is it a slingshot? Can we have pics? this is way cool! :D
Author:  Exner Geek [ Tue Apr 28, 2009 5:51 pm ]
Post subject: 
How fast do you need to go? I have always used the first three gears in the A833 OD with good results. You didn't say if 1400# is with or without the driver. At 1400# you could go 11 flat at 124MPH or 11.5 and 119MPH at 1600#. You need 10:1 compression, 240 degrees of duration at .050, a head that will flow about 180CFM on the intake, and carburetion equivalent to a 500CFM Holley 2 barrel. The McLeod 9 1/4 pressure plate seems to work well with a kevlar disc, especially if you can't use slicks. The final drive ratio depends on tire diameter. You could go even faster but this is a reliable combination that will give you a fun ride. Keep the RPMs under 5800 and it will last a long time.
Author:  bobw [ Tue Apr 28, 2009 7:27 pm ]
Post subject: 
Image
The rules require a 6" wide bias street tire. I know the 3.70 Auburn rear isn't optimal, but I had it laying around. When I complete the hot engine, I'll be gearing it accordingly. Is 10 to 1 a good number, or will more compression provide more HP in these engines? Thanks for the clutch and flywheel info. I haven't found a SFI clutch that fits the small slant bell housing, which is what I'm using. I built a scattershield to meet rules. I have built this chassis to meet NHRA's 10 second and slower, non-certified Altered requirements. Some of the SDRA cars, which are like the HAMB cars with the exceotion of carburation and auto trans, are running low 11's with (ahem) 302 Jimmy engines. I'll be losing quite a bit ot time shifting, because I'm old & slow. Do the Wiseco pistons and K1 rods make sense for this build? 3 Holley 1bbls? or 2 BBd's? or ???.
Author:  bobw [ Tue Apr 28, 2009 8:03 pm ]
Post subject: 
Image
Here's a better view of the intake/exhaust. The top plate is removable so I can replace it and use any number/kind of old school carbs. Looking for recommendations for the race engine. Thanks.
Author:  slantEdgar [ Tue Apr 28, 2009 10:46 pm ]
Post subject: 
Image
Author:  runvs_826 [ Tue Apr 28, 2009 11:08 pm ]
Post subject: 
Well from everything I've read about "old school" hopping up the inline sixes was two main things: carb and compression. I think that if you run race fuel you should really push the limit on compression, 10:1 will still run with premium at the local gas pump. The carb issue is up to you, but I would be considering two-two barrels in that configuration. Long runners should help a lot also....
I know exactly what Josh is talking about with the A833od, and would say get the standard one and run realistic gears ie 3.73, 3.90, 4.11 so forth. A three speed is just an automatic with lag time.
Author:  wvenable [ Wed Apr 29, 2009 3:38 am ]
Post subject: 
Sweet project!! Thanks for the visuals!
Author:  Exner Geek [ Wed Apr 29, 2009 5:02 am ]
Post subject: 
After I made a post here last night I got to thinking about your restrictive tire rule, and what its effect would be. The projected times I gave you were based on just adjusting the performance of my car for the difference in weight. I use a 225X50X15 BFG Drag radial that is 23.5" high and has an 8" tread. A 6" wide old style tire would be very tricky to launch and would probably be a half second slower with the same power available.

Usually racers find a tire that fits the rules but acts like a modern slick. I don't know if they have been able to do that in this class yet. A slant 6 definately has enough power to go that fast if you can hook it up. What kind of trap speed does a low 11 GMC turn?

Your car looks like a serious effort well thought out. Keep us posted on your progress. A Slant 6 should be very competitive in this type of racing.
Author:  bobw [ Thu Apr 30, 2009 6:38 pm ]
Post subject: 
Thanks to everyone who has provided information. It will be very helpful. I also recieved advice from Doc in response to a PM I sent. Thanks Doc. The record for a HA/GR car with 6" street tires and manual trans is about 12.20 @ 120mph. You can see that the tires and trans cost some e.t. because the MPH is pretty high. It is 302 Jimmy powered so I would guess it pulls real hard once it is rolling. It has been dyno'd at over 320hp.

Still in a quandry regarding carbs. Any recommendations? Keep in mind I have to use old style one or two barrels. Holley one bbls.?, BBD's, 2 or 3? Or??? I could even use Rochester Monojets or 2GC's. Any actual drag strip experience based advice would be appreciated.

How much total ignition advance do these engines like when buit to about 300Hp?
Author:  slantsixbob [ Thu Apr 30, 2009 7:07 pm ]
Post subject: 
a pipe for each exhaust :shock: :D :D :D :D
Author:  sandy in BC [ Thu Apr 30, 2009 7:11 pm ]
Post subject: 
Not to knock the cool look of individual stack headers......but headers with collectors would be much easier to tune and will make more power.

(If you are running nitromethane or mebbe alcohol please disregard)

With a car that light and small tires the 9.25 clutch with Mcleod disc should be fine. I have a 9.25 Mcleod Kevlar clutch in my street car and it is a great improvement over stock.

I would run a light 3 speed with 2nd and high only .

If performance is the goal ....the Holley 500 2 bbl
If Kool is the goal....as many tiny 1 bbls as you can synchronize.
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