True HP of the 1967 GT-40 427 engines?

[427LX]

I had read where the FE 427 used in the LeMans GT40's was a detuned NASCAR version putting out 485 HP for longevity.

I just read about the 1967 Shelby GT 500 Super Snake Mustang that Shelby built for a tire test had a single 4bbl Lemans 427 and claimed HP was 600. The Mustang is supposed to be auctioned at the upcoming Mecum Auction.

Now were they really getting 600 HP from the single 4bbl. 427 wedge back in 66-67? To me that sounds like 427 Cammer HP level which was the superior top end engine of the time.

The Super Snake was clocked at 170 MPH during the tire test...so they say.

[67428GT500]

No way they were getting 600 HP out of the Super Snake. The ford aluminum 427 heads are also not known for doing well in street service. It's why I sold the set I had. The figure I'd heard was 525 HP.
I don't think anyone questions the 170 MPH figure. It was clocked at the speedway.

[427LX]

No way they were getting 600 HP out of the Super Snake. The ford aluminum 427 heads are also not known for doing well in street service. It's why I sold the set I had. The figure I'd heard was 525 HP.
I don't think anyone questions the 170 MPH figure. It was clocked at the speedway.

525 HP sounds about right given the mechanical cam and induction setup used.

[FrozenMerc]

According to Leo Levine in his very complete history of Ford Racing ("The Dust and the Glory" - only available through SAE).  The engines gained 25 hp between dyno sessions before and after the race weekend.  Mostly due to friction loss and the "opening up" of tolerances.

[Tobbemek]

Pretty impressive what FORD went though to make sure the engine would last and bee competitive to win the LeMan race.
https://youtu.be/NxP__UPj7L8

[67428GT500]

You also forgot about the infamous "bundle of snakes". They were truly tuned equal length headers.  The heads where also aluminum and from the GT40 program.
I always wonder if they were changed for something without the chamber issues the OE heads were known for.

[RJP]

According to Leo Levine in his very complete history of Ford Racing ("The Dust and the Glory" - only available through SAE).  The engines gained 25 hp between dyno sessions before and after the race weekend.  Mostly due to friction loss and the "opening up" of tolerances.

I also have that book... a very good read for any die hard Ford freak. According to the book there were 12 engines sent to France for the race. The engineers did not label the engine crates with any specifics such as horsepower and torque. Management did not want the drivers, crews and crew chiefs fighting over the most powerful engines. As it turned out the engine that made the most hp [505hp] did not ever get uncrated and the lowest rated engine [468hp] was the engine in the McLaren/Amon car that won Le Mans. The winning engine gained 12 horsepower [480hp] when the were dynoed after the race. 

[WerbyFord]

SAE 670067 by A.O. Rominsky shows about 500hp for the 4v and 530hp for the 8v versions with IIRC the c4ae-b cam at 244-244-107 .525 .525 lift.
At about 12.5 CR IIRC.

[RJP]

SAE 670067 by A.O. Rominsky shows about 500hp for the 4v and 530hp for the 8v versions with IIRC the c4ae-b cam at 244-244-107 .525 .525 lift.
At about 12.5 CR IIRC.

Werby, The Le Mans engines were set up to run on crappy low octane French gas as according to the rules all competitors had to run from a single batch common source. Although I don't remember the exact octane rating IIRC it was in the neighborhood of 85-87 octane but there are too many unknown factors such as how the French rate their fuel's octane, contamination and the actual chemical make up of their fuel. Bottom line is that Ford engineers had to set up their engines for all the unknowns, as a results IIRC the static C/R was set at 9.6 to 1...Further research is needed to confirm this.

[TomP]

Apparently Ford learned that gas thing from the 64 and 65 attempts.

[WerbyFord]

RJP,
Looking at SAE670067 they don't list the CR. I guess I just assumed 12.5 CR for the dyno tests in that paper.

In "Ford Total Performance" Schorr pg123 quotes dyno tests for 1967, dual 652 Holleys, as
Torq 470 at 5000
Powr 500 at 6400
This is at 10.75 CR.
That CR sounds a little high, but I have the 289s racing over there at 10.6 CR so maybe it's close.
The Gonkulator fits that dyno test better at 10.0 CR but supports somewhere in that range.

Either way I think we have the power range pretty much here, now the actual CR is bothering me more than before though!

[gt350hr]

    The Super Snake engine was UNDER 500 hp.  A couple of factors were responsible for that.  The aluminum heads C5AE or C6FE versions ( not tunnel port) used LOW RISER valve sizes ( 2.090 and 1.660) not the 2.190 and 1.73 used in iron medium riser heads. This was done to keep the larger valve seats from falling out of the aluminum heads. Next was the cams . They used smaller cams as they weren't drag racing. They were also given a 6,200 MAXIMUM rpm redline despite over 7,000 rpm capability so they would last 24 hours. The compression was 10.75 as listed in the Experimental Engine Engineering build books. The technology wasn't there in '67 to build an endurance engine with 600 hp. The whole Idea of the "light weight" 427 was to provide more usable hp at the sma weight as an all iron 289. With the Magnesium intake , aluminum heads , aluminum (or magnesium ) water pump, and aluminum center harmonic balancer , they were close but with almost 100 more HP at 1,500 less rpm.
  It's amazing hoe the HP numbers have grown over the years.
      Randy