Jump to content

How Many Horses? - Free Beer


Recommended Posts

After nearly a year away being fettled, the Cobra is nearly finished and had a small road test at the weekend (it is a long way from here so the weather was not a problem). On Friday it goes to  Northampton Motorsports for a tune and dyno run. This car has a 427 cu in engine fitted (7 litre) and the engine was originally a 400 cu in which in factory tune produced 185bhp. It has been bored and stroked to 427 cu in and allegedly has forged pistons and a performance camshaft, but never has been dyno tested.

I estimated (judging from performance compared to my Saabs, the weight estimated at 1100kg etc that it was producing around 260bhp since I have had it. BUT during the fettling many faults were discovered, including a broken distributor clamp, the wrong firing order and set up with number 1 cylinder on the wrong bank! Good job you can trust specialists :-) 

So, the question is, how many horses will it produce on the rollers on Friday? Nearest to the actual peak recorded will receive a free pint at the next AS meet we are both at, or can be collected from here at any time! I really have no more to go on than what is above but will put up my guess before Friday lunch time when it goes on the dyno.

Guesses below please!

IMG_0265.thumb.JPG.b3ca996ff403e715f1d9aff2702dddf3.JPG

IMG_0267.thumb.JPG.bb23ef0d6c0a9a4b528995a03366d0f0.JPG

Link to post
Share on other sites

273 BHP at 5400 RPM

295Nm at 3123 RPM 

And a red line at 6501 (that is don't take it above 6510 because it wasn't built by Honda. 

Also we need to know when the rolling road was last calibrated. 

Link to post
Share on other sites

348bhp (calculated @ flywheel) at 5500rpm and loads of torque across a wide range, max 370Nm.

That's only about 50bhp/litre at the flywheel, same as a totally standard Pinto in a Cortina.

Original mid 1970s 400ci 6.6  Firebirds, etc were strangled to fuck but took to tuning well.  IIRC the Smokey & The Bandit Trans Am was a 185bhp 6.6 litre ,  - that's 28bhp/litre.   (Often through a 3-speed slushbox too).

Whatever the figures turn out to be, in a 1100kg car it'll be 'adequate'  :-)

Link to post
Share on other sites
1 hour ago, New POD said:

273 BHP at 5400 RPM

295Nm at 3123 RPM 

And a red line at 6501 (that is don't take it above 6510 because it wasn't built by Honda. 

Also we need to know when the rolling road was last calibrated. 

I'm assuming at fly wheel. 

Link to post
Share on other sites

Is it a 3-sp auto?

Am not sure how 'at the wheels' readings are converted to 'flywheel' estimations.  There must be some margin for error with the calculations, based on tester's experience and the condition / efficiency of the box.

Link to post
Share on other sites
23 minutes ago, captain_70s said:

A typo surely?

No, lazy detroit penny pinching, alaruming smog nonsense that was very silly and increased fuel consumption and a soupcon of insurance loadings for big horsepower meant the 1970s were the decade that power was forgotten in the US. IIRC at one point there were 5 litre small blocks available that put out something like 120 nags, makes the 90bhp V8 in the stage one landrover look like a NASCAR entry.

My guess is 427* on the basis that 1 dobbin per cube is about as much as is readily achievable while remaining civilised on the road with analogue things like dizzies and carbs.

 

*I reserve the right to retrospectively claim I meant SAE, DIN or some other made-up standard that allows me to win.

Link to post
Share on other sites

As far as I know, it will be at the wheels. It is fitted with a manual 5 speed Tremec box, and my mechanic has suggested a self imposed rev limit of 5500 due to the large amount of reciprocating mass!

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...