225 bhp 302 EFI vs 340 bhp 302 carburettor

[AC Ventura]

Hi guys,
   
   Re:225 bhp 302 EFI vs 340 bhp 302 carburettor
   
    I'm new to the club and am delighted to announce, new custodian of AK 1500. I guess I've been looking for a MK IV for the best part of 30 years and finally, finally I own one and I'm very impressed all round. It's clearly a proper car, already developed, very nicely made, well looked after and documented by the previous owner.
    It's a '93, pretty much standard on 16" rims and has the EFI motor, but with GT 40 heads. I'd like to know what difference these are supposed to make, as power is still quoted at 225 bhp on the factory data sheet. It has the later flat dash, that is not quite the Mk III retro upgrade, as it retains the Ford light cluster and (hmmm...) steering column.
    I bought the car for many reasons, but mainly as an alternative to our Austin Healey 3000 rally car, for gentler events with my wife and where something more civilised would be ideal.
    The first stop will be 15 " wheels and later on a 340bhp Ford Racing, motor upgrade. I would love to hear from anyone who performed this same upgrade or who runs a lightweight Mk IV. As fuel tank range is a vital factor on long distance rallies, I would like hear of any real world expereince, regarding how much the fuel consumption really dropped, compared to the original EFI motor?

[C9OBY]

Hi, and welcome to MKIV ownership, you have many years of fun and tinkering ahead of you!
   
   Firstly, 15-inch wheels are a great first step. They improve the feel of the car on the road, enable you to use Avon CR6ZZ tyres (superb), and look great on the car.
   
   Regarding engine output, I'd not rely too heavily on what the factory data sheet says as the same sheet was used by the factory irrespective of 302-block engine used, headers fitted, exhaust manifolds used etc. If you really want to know its current output, put it on a rolling road.  Just don't get your hopes up, as it may output less than 225!
   
   However, based on your intended use of the car (wife, long distance rallies, MPG), you may want to use it for 2-3 years before changing the engine. In my old MKIV and running the factory fitted engine I would get around 22mpg combined cycle on a trip across France and back and a little less around the Surrey countryside on weekends. Once I'd changed to a 347 stroker, consumption went down to around 15mpg on a lucky day and into single digits when pushed harder / Surrey weekend blasts.
   
   Decide what you want a faster engine for: Yes, it's louder and acceleration is quicker, but the aerodynamics of cobra's are not great hence there won't be much difference to usable top-end speed (plus your wife won't enjoy it!).
   
   By all means consider a new engine, but beware of it's impact to your pleasure in the car.  If your wife tires of the noise and you tire of an empty wallet each time you take it out, you'll become less inclined to do long distances and hence may actually spend less time in the car than if it's left 'as is'. Also, apart from the cost of the engine build itself, factor in another £6-7 for engine installation (it cost more than I was expecting).
   
   The one thing you've not mentioned is suspension.  Have you got front and/or rear anti-sway bars fitted? And have you had the overall suspension set-up look at? Getting the suspension etc tuned will deliver you a car that's far easier to drive, gives you more feedback, and actually allows you to go that bit faster using your existing engine. If you do have it done, do it on the wheels that you intend to use long term (i.e. don't set it up on 16" wheels and then fit 15" wheels, put the 15's on first). It will only cost you around £3-400 to do (assuming that you already have anti-sway bars) and is a very worthwhile investment.
   
   Overall, the MKIV is a superb car and you'll have tonnes of fun whatever you do.  Each car becomes as individual as its owner which is great, but take your time.  Get to know it 'as is' first as it will save you money in the longer term and make you happier.

[AC Ventura]

Hi C9OBY
   
   Thanks for the reply and kind welcome. I already know the car is here to stay.
   
   Clearly there seems to be no downside with the 15s apart from cost on top of an already significant outlay!
   
   Interestingly, motor-wise you're the second respondent(other was a PM) who has said don't rush in so fast...you might like the civilised EFI better than you think. Also are you sure 225bhp isn't enough? Truth is I don't know and both my other cars, a 911 and a Works type Austin Healey 3000, have more than this. I guess initially, most of us expect a Cobra to have explosive acceleration, tinged with a threat of uncontrollable road holding. In any case, clearly most of the extra power from the carb engine comes from extra fuel and on an 1800 mile road rally, the difference between say 18 and 11 mpg is significant cost and range wise. Would the std engine destroy my enjoyment of the event? Probably not so I will indeed persevere with what's already in there and see how it goes. In any case probably better to explore the cars handling with less, not too much grunt on tap.
    Luckily the car already has ARB's front a back. I can also see the ride height is somehow adjustable. I presume I'll have to alter it for the 15's and the Avons. I presume 225/60/15 and 275/55/15 CR6 is the correct sizes? Also does anyone know if the Trigo's 7.5 and 9.5's, come with correct backspacing for a Mk IV and did everyone have to bend their steering arms?

[wenzeh]

There is a topic from 2013 on 15" wheel conversion called: "15" wheels" which will give you a good insight in what is needed, and what to do with the steering arms, which will - in most cases - need bending, as every car is a bit different.  I know from at least one person, that the Trigo's he purchased did not work on his MKIV.  I had purchased rims (Compomotive) from Gerry Hawkridge and they fit fine.  The Avon's sizes you mention is what I got fitted as well.  They are great tires making the car very safe.  But somehow, the great performance of the tires made my engine ( carb 351) look poor and the car unspectacular to drive.  At the end, after 3 years, I did changed the engine.  Hope you enjor car and hope your planned customizations will lead to the car you want.  I was working now since 2007 on my MKIV and found, that the only way to finish this project was to start on a new car! :-) Hope you enjoy your car and your planned customizations will lead to the car you want.