My car is a Mk2 1272cc MH square with DTMR (standard jets) and GK manifold.

Since fitting a far less restrictive exhaust (standard 4-1 manifold straight through to G40 back box) my car seems to be running a lot richer and I even thought the exhaust was blowing because it has seemed quite fumey in traffic. My breather is admittedly just pointing down into the bay so theres always been a bit of that.

So using various advice from before I leaned the carb out a bit. Drove home(about three miles) and the car actually felt better/ more responsive. The only thing though is my paranoia about it running hot. When the car has run up to temp it doesn't seem long before the fan kicks in. Probably not a bad thing but I have always thought that it could be running a bit colder?

My next purchase will probably be a new rad but will that help?

Do I look at changing jets? I can't afford to pay to get it on a rolling road and re-jetting thereafter..

I know Gaz on here was looking at jet options in the weber thread so if your about man what would be you or anyone elses thoughts? or simply more discussion on weber DTMR's or DTML's...

It's getting a balance of performance and efficiency that I'm aiming for. The petrol prices are creeping up so that doesn't help convince me I'm getting good mileage either.

Cheers Dunc.

Edited 7 October, 200916 yr by MacColl

Take a look at the spark plugs after a decent run, they should tell you if its running lean or rich.

Admittedly not very accurate but might be a good starting point

Yes, I've done that before and might check them out after a few miles on this leaner setting.

My neighbour mentioned these transparent spark plugs/basically a kit for indicating the fuel mixture that flash a certain colour as you adjust it. Worth having a go?

Yes, I've done that before and might check them out after a few miles on this leaner setting.

My neighbour mentioned these transparent spark plugs/basically a kit for indicating the fuel mixture that flash a certain colour as you adjust it. Worth having a go?

Yes Gunson Colortune's are great for idle setup.

Fine for midrange progression too. Push to 3000 rpm hard and see yellow followed by purple then blue.

If there's a long period of yellow you can up the pump jet for a quicker squirt of the same amount of fuel for example.

But they are plastic bodied so can't use them for high speed and no load on engine then anyway - unless you've got a rolling road (what about an inverted four wheel trailer) or you want to risk some lashup of digital camera and duct tape to use as you drive.

Other possibiities are Air Fuel Ratio meter and a lambda sensor in the exhuasts or all out like Innovate LM1 measuring gear.

Lean (bright blue flame) gives more power but it is dangerous when combined with Nos or Turbo or Supercharger.

If you are worried about heat fit colder plugs, I use Beru UX56. They are quad electrode at different heights so last ages and should ignite more fuel regardless of flame front during retarded ignition.

Edited 8 October, 200916 yr by dvderlm

Probably not a bad thing but I have always thought that it could be running a bit colder?

My next purchase will probably be a new rad but will that help?

Cheers Dunc.

The GK engine has a Passat sized radiator!

What about an oil cooler off an oilstat on the oil filter?

Lower thermostat temperature would open the circuit earlier as temperature rose, but engines like to be warm for efficient running.

I know an Opel Kadett tuner who bypassed all the heater piping completely in summer and fitted a higher temp thermostat switch

and a double electric fan on the rad.

Yeah I found the standard DMTR setup too rich at part throttle. I played about with it, used different emulsion tubes and air correctors in the first stage and so on, but ended up going back to the F22 because I never got around to getting a bigger pump jet, and now I'm doing away with the carb altogether in favour of fuel injection as I can't be bothered messing about with it anymore. I set my mixture using a lambda which I also used to set up the carb while driving about.

Cheers,

I think in the short term I'll just need to make gradual adjustments. I need some old skool dude with a rolling road who knows these carbs. Might go to that Retro cars in Edinburgh? Leaning it out a bit yesterday seems to have made a difference and no sign of things being any hotter.

I cleaned the jets yesterday and re-fitted the hot air pipe for winter. So what happens this morning driving to Uni, no idle! so a bit of roadside jet cleaning/blowing and it seems fine.

As for radiator I reckon a new one will probably help. Do I maybe get a G40/GT one? it will fit a mk2 won't it?

The other worthwhile investment would be a servicing kit for the weber (fast road do them I think) but time/money is always against me just now. I'll get some scene wheels on this car eventually lol.

Cheers,

I think in the short term I'll just need to make gradual adjustments. I need some old skool dude with a rolling road who knows these carbs. Might go to that Retro cars in Edinburgh? Leaning it out a bit yesterday seems to have made a difference and no sign of things being any hotter.

I wondered about the limits of lean.

Fiestas in the USA ran 60/100/F22/250 so there's headroom

http://www.triumphspitfire.com/jets.html#dfta

As for radiator I reckon a new one will probably help. Do I maybe get a G40/GT one? it will fit a mk2 won't it?

I reckon Eurocarparts Part Number: 203440611 is good for nz (GT or is that 3F?) and hk (Mk2).

433 X 299 X 22 mm

Reverse flushing is even cheaper

Edited 8 October, 200916 yr by dvderlm

if theres a huge price differance , mine seems super cool on the new std rad , maybe yours is blocked up

yeah a 430mm rad will be fine.