Running issue help spark plug gap spec -NGKBR7EIX - 1969 S

[bazz55]

Hi guys

need some help, my 1969 911s has picked up rough running issue. At the moment we are trying to work our way through what it could be. I have changed the spark plugs, HT leads, coil, rotor arm, points and its still running rough. I was just checking the plug gap and its large to what the spec says in the haynes manual of 0.014in/0.35mm - the actual ngk plugs come gapped from the factory at Gap: .031" (0.8mm)


Currently I am running NGK-BR7EIX. I have ran these before with no issues however the plugs have always fouled. Could it be I never set the plug gap properly hence why the plugs are fouling and causing an issue?

I have checked on here in the search option and have found people setting plug gaps at all different settings? Can anyone help with recommended plug gap please? At the moment the car sounds as if its not running on all cylinders and has picked up a backfire issue - could it be the gap is too large and the spark is not igniting the fuel properly?

many thanks in advance Bazz

[mycar]

The manual says .014" or 0.35mm.

Are you running carburetors or fuel injection ?

[bazz55]

Hi Mycar

Apologies, more information would have been helpful

I am running weber 40ida carbs

Thats the gap I have listed in the manual however expected the plugs to come correctly gapped. If this is the case I need to reduce the current gap a fair amount

thanks Bazz

[mycar]

If you're running carbs then the miss maybe a blocked jet ?

[bazz55]

Maybe thats the next one to look at. With the spark plug gap I didn't know if its recommended that different plugs have different gaps as they are rated differently?

Does anyone have a pic of which are the idle jets on a set of webers as all the diagrams i can find on the web don't exactly show which they are. I have read that blocked idle jets can cause this sort of running issue.

thanks Bazz

[mycar]

This thread will help you locate the jets

www.ddk-online.com/phpBB2/viewtopic.php?f=1&t=55284&

[bazz55]

can't seem to get the link to work?

[mycar]

Click it again and say abracadabra.

[bazz55]

Thats exactly what I needed, fantastic thank you!!

[bazz55]

Hi Mycar

Any recommendations for sources of rebuild kits for webers? I have found a full premium rebuild kit on eurocarb for around £80 which seems to have everything I should need. I have pulled out the idle jets and cleaned them I also cleaned the gausing out in the inlet pipes comin into the carb. A good bit of debris was in there. When I tightend the bolt after It was seeping fuel as the card gasket has perished . Probably worth taking them off and giving them a check over and a clean

Cheers bazz

[mycar]

I don't really have a recommendation for Weber parts, I used Pelican in the States which can be a bit expensive depending on what the pound's doing and Webcon here in the UK. Webcon were good for jets but didn't have gaskets for these carbs.

If the kit from Eurocarb has everything you need then that's probably your best bet. Check out what Pelican offers and compare.

Before you whip the carbs off, pull the jets and blow them through with a can of carb cleaner or compressed air if you have a compressor. The main jets are just tubes and it's easy to look down them but the idle jets are very fine and a magnifying glass or loupe comes in handy for peering at them.

When you're happy the jets are clear, go for a run and see you've cured the problem.