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MG MGB GT V8 Factory Originals Technical - Timimg question

Hello all,
I'm sure this question has been dealt with in the past, but I figured I'd ask it anyways.

How does one go about timimg the 3.9L Hotwire EFi engine?
Problem is, I can't get revs above 3000, and it's really hesitating to get up to 3! It's actually a dog on the road right now. So I'd figure I'd start with the timing. If this sounds familiar to anyone else, (especially those with the Hotwire EFi) I'd really appreciate some input.
Wally Jonker

Good to see you online again.. Hey have you tried Rover's North or TSI? I bet either of them could tell you right off if no-one here knows..

Is the engine pinging or just sluggish? If it is pinging, try "retarding" the timing, otherwise try advancing. have you checked vacum lines? Not sure if your distrib is vacumm advance, but if there is a vacumm leak it could also cause problems especially the higher the RPM..
Larry Embrey


The first check is the tune-resistor - if the kit has come off a catalysed Range Rover and you have an MG exhaust, you will need a different resistor - off the shelf from any Land-Rover agent.

After that it becomes plain sailing assuming the electrics are up to scratch and properly timed. With the revs at about 1000 - turn down the wick until the CO mixture is about 1% then block off the tube at the rear of the plenum chamber which connects the chamber to the intake housing - use a mole grip - turn down the revs to 550 - release the mole and let the CPU adjust the engine idle speed - this will be about 750 rpm. Finally check the CO mixture again.

I treated myself to a Land-Rover tune up at the end of the conversion - it was expensive but my reason was that there are so many new component which might not function properly - they check the whole nine yards on a computer - it's quick and accurate and so easy to change the dodgy bits.

Roger Parker advised that the engine would settle down when the system was run in and he was right. Apart from the howling fuel pump (you may have seen my moan a few days back) - touch wood - it works very well.

Come back if you need.

Roger Walker

Roger W,
Wally is a local friend and I know he has limited internet access, so I will throw a couple questions back at you I know he might have..

Wally has a custom installed 2.5" dual exhaust system, no Catalytic. Can you give him a PN or maybe vehicle for the tune resistor he needs? I know he has two O2 sensors one in each RV8 header, that he had to order in, is that what you are refering to?

By turn down the wick I am guessing to turn down the idle mixture screw? Where/how will he know when he reaches 1% CO mixture?
Larry Embrey

Thanks for the help so far. Larry is right about my limited internet access. And his questions are mine as well. And I was wondering what the proper setting was for the distributer? At what degree before or after top dead centre? (I assume it's before TDC) And I will look into the tune resistor
Wally Jonker

You should be able to buy a simple CO tester for under 50 bucks - we have them over here....

Wally / Larry

the right resistor is essential - they are coloured so if you tell me what colour you've got, I will let you know what you need.

Larry - sorry - 'wick' ex oil lamp translates fuel/air mixture controlled from the airflow meter and measured in percentage CO. Aim for 1% then adjust to suit your drive style.

The ignition should be at 5 degrees btdc with the advance tube disconnected and the engine at normal idle - HOWEVER your fuel is not necessarily the same as ours and again you may need to adjust.

David's advice is good although the sort of meter that costs $50 is not more than 0.5% accurate and may not read under 1% (the engine will work well at 0.5%).

Persevere - you are going to be pleased when its working as it should.

Roger Walker

Thanks for the help again. I don't know where the tune resistor is on the harness, so I can't tell you what colour it is.
Thanks again,
Wally Jonker

Wally - look somewhere close to the two fuses in the loom.
Larry I am going to be away from the net for the weekend but if you can get a message back by 1100 New York time, I may be able to catch you before -otherwise its Monday.

It might also be helpful if Wally could identify the loom itself by part number - or vehicle type and date.
There are other options which will also need to be explored - speed sensors - manual gearbox correction and heavy electrical load correction.

Roger Walker

This thread was discussed between 14/08/2001 and 17/08/2001

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