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Author Topic: Superformance A/C Cobra  (Read 1677 times)
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robert campbell
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« on: April 12, 2017, 12:11:16 PM »

Look at what wandered into Rob’s shop!  This is a Superformance A/C Cobra that is built in South Africa.  Superformance is the premier builder of A/C Cobra kits IMO and the car is pretty faithful to the dimensions of the original.  They are so nice that Carroll Shelby has allowed them to be licensed under the Shelby name.  Not sure what that means, but they reek of quality.  The come as a complete wired, painted, and assembled rolling chassis with new owner to provide the engine and transmission only.  I have known of this company for many years.  Below is a link to their site and the tour of the “factory” page will support the reason for the quality.

http://www.superformance.com/default.aspx

This car is powered by an older Ford Crate 351 Windsor stroked to 392 cubic inches.  Backed by a TKO 5 speed it is a nice package.  This is kinda why it ended up in my shop.  It was shipped to the Hampton’s in New York and a local facility installed the engine and tranny and got it on the road.  The new owner purchased it with about 1,500k miles on it and lives near my shop.

The new owner complained of it being a bit sluggish, hard starting, and running rich.  Top of the carb was black and sooty on both the primary’s and secondary’s.   I baselined the settings on the carb, vacuum signal, and timing.  Fortunately, it is similar to my new 351 stroked to 460 Crate Motor in Val’s car.  The timing marks are etched into a chrome damper and very hard to see.  And there are many grids around it for different types of tuning or valve adjustment.  Short story long (hey its rob) the initial installer had completely missed the timing marks or the original owner or someone in New York moved it.  The engine was set at about 5 degrees BTDC.  The MSD dizzy was set up with the proper short curve for the centrifugal advance at around 15 degrees total at about 3,000 rpm.  The engine at 3,000 rpm or all in struggled to reach 20 degrees of total advance.  What any easy fix.  Spun her forward to 14 degrees and then to 18 degrees initial and now have around 34 degrees total just like my motor.  Whoooo boy did I wake up a beast!!  I took this car for a short drive and it is a lethal weapon.  It is rated at 450 HP which is very close to what the original 427 A/C Cobra was rated at.

The original installer also improperly installed the dual return spring mechanism and the Superformance top cabin throttle assembly was miss-adjusted.  This caused the carb to not completely shut when hot.  Someone prior to the new owner had even installed a “cheesy” bracket under the dash and installed a spring to try and assist in closing the throttle to hot idle rpm via the gas pedal.  A simple adjustment coupled with the properly installed return spring setup cured all of this.  Hate to say it but the initial installer was not very talented in the setup of the engine.

Dialed in his electric choke and this car starts first time and runs like a top now!  Owner is very happy with his new car!!  It is a hoot to drive but a bit awkward with the left of center pedal location under the dash.  They need some getting used to

Rob










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car 26-JD
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« Reply #1 on: April 12, 2017, 02:35:56 PM »

Nice work unleashing this restricted animal.

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« Reply #2 on: April 12, 2017, 07:11:12 PM »

Glad you enjoyed working on it and driving it.  They are definitely a HOOT to drive!  I had a Superformance a couple years ago and really liked it.  It had "only" a 402 Roush, but it did make about 425 horsepower and was awesome on the street.  I have another one (10th Anniversary edition) arriving next week and it has a 500+ cubic inch big block with EFI that dynoed at over 715 Horsepower.  Now that is going to be a handful.

Here's a photo of my SPF street car I used to own.


« Last Edit: April 12, 2017, 07:15:00 PM by ITHERTZ » Logged

robert campbell
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« Reply #3 on: April 12, 2017, 09:04:29 PM »

715 HP!!  Holy $hi%!!!!  A handful is a huge understatement!  I would call it a lethal weapon!!

Of note the total in the centrifugal advance on the car I worked on was 18 degrees, not 15 degrees.  That is the minimum they can be shortened to.  I said around 15, but it was a bit more!

Rob

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mygt350
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« Reply #4 on: April 13, 2017, 07:02:05 PM »

Rob
Is 18 mechanical optimum for this caliber engine or is there a better target?
Martin284

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Martin
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robert campbell
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« Reply #5 on: April 13, 2017, 09:44:19 PM »

I can speak for my 460 CI 351 Windsor based Ford Crate motor.  They recommend 34 degrees total which allows for 16 degrees initial with 18 degrees in the centrifugal advance.  In my experience with all domestic V8 engines they thrive on lots of initial advance and around 36 degrees of total.  This includes basically stock engines and high performance ones.  Certainly, there may be exceptions, but even with stock engines I shorten the vacuum advance to allow for more initial advance.  Better throttle response, more power, less heat, and better mileage.  There is a great article in "Hot Rod to the Rescue" in hot rod on the stands now that supports these thoughts.

I would run the motor that I tuned at basically the same standards as above for best performance.  You may be able to move the initial advance to 18 or even 20 degrees based on weight of the car, and gear ratios.  The lighter the car and the lower the rear end ration can accept even more advance.  But 18 degrees of total centrifugal advance is IMO the best starting point. Now how quick it comes in is also based on the car weight and the ratios in the rear end.  As I commented, I like prefer example D or E in the MSD chart below.  My car loves it and there is zero pinging and great performance.  Lethal performance!!

 https://static.summitracing.com/global/images/instructions/msd-8464.pdf

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