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Discussion Starter · #1 ·
ok, what with the price of fuel these days, not to mention the ever growing pressure from the eco green lot, my question is just how fuel efficient can you make an old engine with modern technology ??

lets say you have just been out an bought a, lets say, 1970 camaro with a 454 and auto box in it, lucky you but blow me - your also fortunate enough to have a fairly big bundle of cash left over,

what mpg could you get it average using whatever modern techy stuff you wanted,
would it be poss to have 500 bhp and still have it averaging 20 + mpg by having some sort of in-car switchable injection/ ignition system which would give you a couple of hundred bhp for just tooling about and the full fat 500 odd bhp available at the flick of a switch for play time ??

using other components such as roller rockers/ lifters, free flowing exhausts etc would surely only improve the efficency but what else could/ would be do'able to turn a b/block car into a daily driver ??

:tup:
 

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John Sleath allegedly can tune an EFI 540 BBC to get 20mpg.
Obviously not at WOT.
You wouldn't need switchable states of tune, you'd set it up to be frugal at low throttle openings and balls-out at full throttle.
 

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Discussion Starter · #3 ·
John Sleath allegedly can tune an EFI 540 BBC to get 20mpg.
Obviously not at WOT.
You wouldn't need switchable states of tune, you'd set it up to be frugal at low throttle openings and balls-out at full throttle.
:shock: your kidding :eek:

maybe i should have asked for a theoretical 30 mpg :D
 

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Well you'd really need mappable fueling. Use a wideband gauge and have it run 14.7 on idle and cruise.

Some people lean them out to sort of 16:1 but you need strong ignition to ignite it
 

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I know it not a BBC, but my old 3.9 rover in my Cortina Returns 33/34mpg on a motorway run at around 70-80mph with little bits of insanity thrown in as well, Thats on Throttle bodies and Emerald managment,
BBC, its got to be down to gearing and weight, as well,
an old friend of mine stuck a 455 olds in his Mk2transit, straight out of a 60s ambulance, he used it for work in London, and was getting 23-4 mpg out of it, far better than the old pinto,
 

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Think you need to up that figure to 30mpg.

On a run I will get about 22mpg, mind you driving it 'properly' that drops down to well below 10.

BBC that dynoed out at 480ish, 830dp, DNE 4 + 1, 3.25 diff, 29" tall tyres in a fat old 56 Chevy bodyshell.

Mind you I would trade 10mpg for an extra 2 seconds........

P.
 

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I know it not a BBC, but my old 3.9 rover in my Cortina Returns 33/34mpg on a motorway run at around 70-80mph with little bits of insanity thrown in as well, ,
I'd LIKE to get anywhere near that from my A at the mo ( though the bottom end is very tired). Normally manage 33 on a run from the Pinto in the POS ( 3 speed auto , 4 speed makes the world of difference to them ).
 

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To get decent economy you'll need an overdrive gearbox, fuel injection and final drive gearing to keep the rpm down at cruising speed also a slippery shape like a 2nd gen Camaro would help.
From memory [a little hazy] Car Craft did a blown 355 sbc Chevelle with 2 goals- 400 hp and 25 mpg. They got higher hp but narrowly missed 25 mpg.They did say at the time that they would have had over 25 mpg if they had used the same engine in a smaller lighter car like a Nova or a Vette.
 

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My experience from Capris, is that EFI is the way to go.

Fitting an injected Pinto from a Sierra into my mk3 2.0S changed from 34MPg to 42. Went better, had proper throttle response and cost £150 to do. At 600 miles a week, that's well worth having!

The 2.8i special that I had was also typical. The K-jet is hopeless; it feels like the car has an elastic throttle cable. Couple that to the 2.8s lack of torque, and you wonder why they did away with the 3.0l. That car received a 2.9 from a Scorpio. Simple bolt in job, with about an hour's worth of exhaust mods. Suddenly, the car was a the 2.8i always promised but never acheived. It gives the best of both worlds; 3.0l grunt, with the revs of a 2.8. The car went from struggling to get 28 MPG on a run to AVERAGING that on my daily town commute. That whole job cost £211, and also gave the bonus of unleaded heads for a fraction of the cost of modifying the stock ones. Again, drivability and performance also increased.

Carbs are crap, and I don't want another one!

Nick
 

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To get decent economy you'll need an overdrive gearbox, fuel injection and final drive gearing to keep the rpm down at cruising speed also a slippery shape like a 2nd gen Camaro would help.
From memory [a little hazy] Car Craft did a blown 355 sbc Chevelle with 2 goals- 400 hp and 25 mpg. They got higher hp but narrowly missed 25 mpg.They did say at the time that they would have had over 25 mpg if they had used the same engine in a smaller lighter car like a Nova or a Vette.
Yeah; I remember that, Jeff Smiths car wasn't it? Built an efi 302 SBC with 6-speed manual trans. Given that US gallons are only 85% of imperial ones, he'd have done it comfortably over here!
 

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Take a look at current C6 Vettes for an idea re. good fuel economy - not quite 500 hp and not big block but 30 mpg is more or less there on cruise - step up to Z06 with 'big' small block and 505 hp and mid 20's are still feasible.
BTW my 528 hp 489 Chev build-up by John Sleath records 16 mpg on 70 mpg cruise with 4 speed, 3.08 rear end and 950 cfm double pumper - and yes 20mpg for me is achievable with mapped mpi - but the cost :eek: it would take years to recoup the expected £3K to £4K investment to have it done properly.:shake:
 
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