Ok all the talk recently about the 165HP specials and gearboxes had me heading to my Capri books and I noticed that two of them say the same thing, that in Oct 71 Ford UK added D port heads, new cam profile, 38 Weber and a viscous fan coupling for a power increase of 10BHp, bringing it to 138Hp.  I cant help but wonder if its the cam and not the D ports that made most of the difference but in any case where does the figure of 165 Hp come from and, if its real, what else did they do to get it?

Simple answer is that the quoted 138hp is a net figure and the 165hp is gross horsepower.
My dport supplement quotes the gross horsepower at 157hp.
Thats still a bit shorter of the 165hp which appears on the yellow sticker in the engine bay of the australian ford uprated Dport cars.
The 157 hp is gross DIN, which is euro metric and the 165 hp is gross SAE and when converted the 157 rounds up to about 160 gross SAE.
Possibilities for the 5 hp discrepancy.
Carby settings for europe a little conservative to allow for emissions control that we in aus didnt have.
In 1972 conversion figuring was done by hand and produced inaccurate results as evidenced in the workshop manuals.
Finally there was "rounding up". Why round down when rounding up produces a better looking number?
 
So for ballpark numbers, 
Oval port = 128 net din.
D port     = 138 net din.
D port RS3100 = 148 net din.
 
As far as i can tell, looking into the actual engine and the dport spec supplement its a standard dport 722F apart from any specific carby tuning for australia.

That makes sense but what has me curious is that in both books they state an increase in power of only 10HP. So whether DIN, SAE, gross or net if the increase is only 10HP then the D port heads and new cam didn't really achieve much. 

Very interesting  ........... 
is it possible we're not comparing apples with apples due to different RON in variable fuels used here in Oz compared to UK?
Also. I was led to believe our Dizzies had more Advance Curve in our 165 HP than ones in UK ?
And can anyone tell me if it was ONLY Oz V6 that got fitted with extractors, because if they didn't in UK, this would also influence HP figures ?

Another way of increasing horsepower and/or not wasting fuel, I found as many others have, is eliminating cumbersome Fan Blades on cars that are very well behaved in keeping their "cool", which usually applies to all cars with a clean healthy C/System. Ever since putting my GTV6 back on the road, in ANY heat, even 40 degree days, I've never had a fan either oem or electric backup. As long as I'm doing 50kph, my temp gauge always remains in the 40-60% safe range, even with normal stops like simple traffic lights; perhaps the onerous "Springvale 6 ways" intersection might prove a challenge.
If delay seems likely, simply turn off the engine (some modern cars do this EVERY time you stop regardless of temperature! .... great for Starter Motor, Ring Gear & Battery sales!)

I think we are comparing apples with apples as both HP figures are quoted out of the UK.  So fuel, extractors, dizzy advance etc. would also apply to Aus oval ports so the relative difference in power would be about the same.
 
Part of the upgrade was a viscous fan coupling so that would have dealt with a reasonable amount of fan power consumption.
 
Jermey Waltons book also states that the D Port upgrades saw max torque drop from 193lb/ft  for oval port engine to 174, both at 3000rpm.

 
 
Jermey Waltons book also states that the D Port upgrades saw max torque drop from 193lb/ft  for oval port engine to 174, both at 3000rpm.



Factory manual and supplement figures.
Oval port= 176 lb ft net @ 3000 rpm.
D port    = 174 lb ft net @ 3000 rpm.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 





 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

As far as I know. Dport had different pistons to raise compression to acheive more. The oval port flywheel doesn't fit? ( Never tried) and should be matched to motor. Others here know more but that's a start. The Dport block can be made to go much better than any Oval port block. Thicker walls so +60 is a start point not end point regards piston size.

 
Does anybody know if Extractors on all Capri Mk1 V6 were fitted worldwide, or just Australia ?
 
thanks

I've been looking at some d-port heads for a few days and from what I can see there is little difference between them apart from the obvious port shape. They are still a high-swirl port. The port finish on the pair I have is poor/very daggy. I cannot see much to account for a loss of torque as per walton's book. Pistons are interchangeable - so no real issue there. Iron heron head will be likely to have greater heat issues for the amount of power produced.