few questions

[Carl]

Yep, the pinto was a crossflow head. Pretty dire in the scheme of things though! IIRC the standard pintos and modified 1600s would tend to run on 40s and the modified 1800+s tend to run on 45s.

When it comes to engine tuning, in my eyes Dave Barker is a God. Although there's obviously no definate answer, having just had a read of his site he reckons that 40s are good for up to 150bhp on 33mm chokes. Any bigger than that and 45s would prove a better bet.

Looking at a Dellorto tuning guide I downloaded a while ago it gives a handy little graph which you can work out choke sizes from - max power at 6krpm on a 2000cc engine gives a choke size of 36mm - the max for a 40 bore carb, although it recommends 45s would be better. For max power at 5.5krpm it gives a choke size of ~33mm.

I'm sure there is scope to break 150 on your car James, no doubt, but you'll be pushing the carbs right to the max of their operating potential which probably isn't ideal. But if you can get it running right, and reliably then I'm sure you wont be complaining!!!

[foggyjames]

Sorry...I worded that badly...I meant Pinto OR a nasty non-crossflow thing

I think you're right Mr Bilbo - 45s are just 'bored out' 40s, with 48s having larger bodies. Didn't realise you run 45s...that would explain the significantly higher peak power!

Let's take a quick look at this graph...


What that shouts to me is that RPM plays a much larger role than you might think, with a '7000rpm tuned' B14 on sidedrafts ideally requiring larger chokes than my '5500rpm tuned' B200. If most of these sites are written for people with race tuned (7500+rpm) engines then they're maxing out 40s before they're much above 1300cc - in which case still trying to hang on to 40s at 2000cc is a big deal. However for 'fast road' use (~6500 and below), I think you can get away with 40s on a 2.0 motor.

I'd also dispute some of the maths. http://members.aol.com/dvandrews/webers.htm says "For example: a two litre engine giving its maximum power at 6000RPM will require a venturi size of 36mm". Where's my O RLY owl? Volvo's R-Sport tuning kit made peak power at 6k on 32mm chokes.

At the risk of sounding a bit like Stavros with his anti-forum-info rant, I'm worried that much of the (free) information out there may not be that accurate, or more to the point, people are assuming that because what they're saying is true for a Pinto (or whatever) that it's true for all engines of that displacement.

I'm probably being a bit of a pedant here, and I'm sure that I'd make more power on 45s....but my research so far has appeared to show that they're not essential in the way that you'd believe after reading most of the info out there (which I have, at one time or another...must...get...out...more...)

Bottom line is....I'll see how far I can get with the 40s. There are lots of little bits and bobs to be done which ought to free up power....but maybe my 40s will stop that potential being realised? Time will tell

cheers

James

[redline]

nothing wrong with fords 1600 crossflow as long as you remember to bore it out to 1760 cc
fit duplex timing chain
a stage 3 head ,
lighten and balance the flywheel,
fit a toughened crank ,con rods and anything else that moves
uprate the cam,
uprated oil pump and baffled sump
chuck on twin 40 webers
a full janspeed system ,
drop it back into your mk2 1600E cortina
and light up your rear wheels in second gear

Oh how I miss the 70's

[Carl]

Unfortunately tuning is not an exact science, so it's just a case of making the best out of what you've got. 150bhp isnt necesarily the limit for 40s, what I think most people are saying is that if you are aiming for 150bhp, then go with 45s. If you've already got 140bhp on 40s with some potential left in them (ie you've can still use bigger chokes James) then there's no reason why you cant go above that limit.

Refering back to Dave Barker again, he reckons if you want 179bhp at the top end of the rev range then 36mm chokes is what you'll need (although he recommends them in 45s). Bringing it down to your Solexs, he reckons 32mm chokes will give 141bhp. So the potential is definately there for more power.

[A M R]

hmm intriguing. well 45's it is for me as im going the track car route

[Bilbo]

tuned x/f's are nice but have a habbit of blowing up. one of my dads friends used to build pintos for ford and rich rallydrivers with 2.8 capri pistons etc . most people these days i think use rods etc from 1.6 deisels ? anyway enough of the "Fixed Or Repaired Daily" machines
Volvo's for the win

[foggyjames]

Husky also suggested that 36mm chokes in 40s wasn't a good setup...he said get some 34s (available to buy new, shockingly!), but beyond that, it's 45 o'clock. On the face of it, I agree I should be near 'the limit' on 40s, but on the face of it, I seem to be nowhere near. Maybe that's misleading?

We'll have to see...I'll take it as far as I can on 40s, and then go larger if I feel the need. The 'big' R-Sport kit (for the 16v engine) had 48s, so I've even got an option if I want to be all nerdy and OEM

cheers

James

[classicswede]

James,


seeing as you already have 40's I would stick with them for now. The 34mm ventrui should work well with the kind of set up you have now.

At the power levelsyou are at now the down side you will have is just in the way the power is made. In other wors as already pointed out is the flat lining at higher rpm. Unless you are looking for over around 175bhp ish for cost reasons I would stick with what you have.

If you starting an engine build and looking for that power then I would personaly recomend 48's (45's would do the job but you want some spare)

Engine performance is like drugs you just need more and more.



As said all engines repond differently and different mods will produce different power curves. Cards are not an exact science but experiance does hold a lot of weight.