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help required on my carb turbo dellortos


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Hi Guys help required does anyone live round the Sussex/ Surrey Kent way who knows about dellorto carburetors iv be told so many different things not sure what is the problem or correct. 

 

4 years ago I bought my carb turbo Stevens car with a rebuilt engine. And the guy told me he didn't know anything about the carbs just unbolted and 're bolted them back on after the rebuild, however I have had problems with over fueling and pops and bangs from day one.

Now sparky gave it a quick tune up and balanced the carbs and it ran better, however I have since discovered a cracked manifold and a hole in the exhaust but not before the MOT guy fiddled with it to pass emissions and never set it back. Now both been rectified but the carbs are now running worse! 

 

Recently someone told me that it's running too rich so I tuned it with an gas analyzer which was better but the poppping and jerking was still there, all jets have be cleaned and unblocked but still the popping is there. 

 

Someone last weeks said I had the o rings crushed on the carb connections to the engine so do I need them to slightly float? If so can someone come over and look to tell me what I'm loooking for and help me balance these carbs if thats also an issue.

 

Please Help Matt. 

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I think its 1-2mm gap each side of the ally spacer. Enough to squash and create a seal but not fix firmly otherwise the fuel froths up with vibrations from the engine.  the exact gap is in the service manual. I just used a feeler gauge to set it the same all round. Sjs do the o rings , not to expensive ( before the postage!!!) .

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I have a set of new O rings from SJ if you need some. I bought them for my Esprit before I discovered that mine doesn't have the original spacers but Misab plates instead. Hence they are going spare...

I could let you have them for what they cost me plus the postage (no doubt a lot less than Steve at SJ would charge you!)

My Dellortos need a tune too (getting some hesitation at low revs) but I've read up, bought a 4 way manometer and a colortune so I can have a bash myself.

I've had a couple of local ish (to Chichester) places recommended for tuning via the forum but prices mentioned of £200-300!

I'll have an educated tinker myself first as from what I've read it's not rocket science...

Have yours been balanced already and individual mixtures checked?

Not worth starting anything now...🍺

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Hi Matt

Hadnt realised your car had cracked manifold and holed exhaust - Replacing all that must have cost a fortune. Did you do it yourself?

 

Popping on overrun is a characteristic with carb turbo cars fitted with the SJ exhaust system including mine, just depends how bad it is. I am probably the last person to advise on fixing a car, with my current problems, but running a bit on the rich side is correct - what were the emission reading when you had it MOT'd.

 

You could try checking the timing and using a manometer to set the air flow and then checking the mixture. Our cars are set at 6 half turns out on the mixture screws and that is normally reasonably accurate. Last year I set mine on this but decided to ask Pete Musgrove at the Lotus Festival to set them up more accurately. He fiddled away for ages and when I got home I decided to check and guess what, all were 6 half turns out from closed. You could try closing yours, making a note of their current position and then turning out 6 half turns and if it is worse putting them back to your current setting.

I can help with strobe light and manometer. 

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I also have a car turbo, as Mike says they do pop on the overrun, and they should run slightly rich. I have a manometer to set the balance.

When I got my car they were not balanced correctly and were actually missing a small spring and o ring on the adjustment, this had just been screwed home by some monkey.

I set mine up no problem, and did a plug pull to check the colour on the plugs. I'm just about to rebuild them and the engine. There is loads of info on the web. It's not that hard to do if you take your time, you need a decent strobe light to set the timing correctly as well.

I have a PDFs somewhere about setting them up.

Amateurs built the Ark

Professionals built the Titanic

"I haven't ridden in cars pulled by cows before" "Bullocks, Mr.Belcher" "No, I haven't, honestly"

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Thanks red vtec I will have a look iv arranged to meet up with Mike and compaire issues lol. The popping I know you get on over run but I'm getting it when pulling up the lower side of the revs and at motorway crusing speed as the turbo sort of kicking in and out at 70mph on that sort of 2800 revs and 3100 revs . It's like it's being starved of fuel! Ahh bloody annoying! 

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  • 2 weeks later...

I think the rev range that you are stating is the switch from the idle jets to the main jets.

Amateurs built the Ark

Professionals built the Titanic

"I haven't ridden in cars pulled by cows before" "Bullocks, Mr.Belcher" "No, I haven't, honestly"

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How did the car perform Matt. The timing was spot on and we balanced the carbs - one needed considerable adjustment. We also noticed that one or more vacuum pipes were too big and not sealing properly.

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  • 1 month later...

Ok guys thanks for everything. Just thought I'd update you on things iv fixed the issue it was the over boost sensor, the actuator was set to over boost this in turn was tripping out the over boost sensor for a split second cutting the power to the spark so as it reignited the spark the extra fuel that was still In the car backfired out hence the popping and jerking in the car.

All sorted also on my tinkering day found a vacuum leak in the Y piece from the vac pump onto the hard plastic hose. So replaced this and some of the oversized silicon pipes which were not sealing ok. 

Now help is required again. Only on cold running before the car is warm do I find that going up any kind of hill the car is popping and appears to have no power what so ever. It seems to jerk like  kangaroo while trying to get up the hill. Any ideas or is this normal while it starts to warm up? 

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