Problem, the second Vee dub i Own which is 74 Bettle(Barbie Girl) has had a major engine rejuvivation with Brand new Single port heads fitted to the big bore Kit (1916).

Problem is sometimes developing pre ignition , Timing has been checked and is spot on. Stopped the pre ignition as turned down the idle screw but after a while say 200klm started to get slight pre ignition.

thinking about the problem have thought about changing the jetting on the 3.1 carby or sourcing another carby .

or
secondly
putting in a new distributor as the old one might have ware in the shaft and thus the timing could be retarded from time to time due to movement.

any advise will be greatly appreciated

Are you referring to pinging (detonation) or auto-ignition where the engine runs on after you switch it off?
L8tr
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i am referrring to auto ignition that is the motor continues to fire after the key is switched off.

would ur engine not be very undercarbed with a 31pict?

is this not what was run on the 1300s and the such? small carbie.

i have one on my 1600 single port and almost feel that its choking at its 316ccs smaller than your 1916.

could be getting very hot. check u arent running very lean.

also try running PULP if u are running ULP

There is a recent thread on this topic.
There are a variety of strategies to deal with this irritating condition.

Deiseling is caused by local hot spots withing the combustion chamber, igniting the fuel after the ignition is switched off. This might be a chunk of coke (carbon) glowing away or a very sharp burr in the metal somewhere and so-on causing it. Perhaps spark plugs of too hot a range.....perhaps.

I have heard some pretty good and some downright preposterous "cures" for this annoyance.
Just dont get sucked into altering the freakin ignition timing. For christs sake, the friggin ignition is switched off! You could remove the bloody distributer altogether and the engine will continue to happily diesel away!

The different fuel Ie: PULP or SUPER PULP one seems to hold some water, guys reporting success after a time.
A solenoid valve that vents under the carby when the ignition is off is another one that works well. 1600 Ford Escorts had this valve. It just leans off the mixture and bypasses the carb altogether so no fuel makes it into the cylinders.
It worked extremely well for me with a very high compression 1600 atmo Capri engine years ago.

Some later carbs have an idle fuel shutoff solenoid which blocks the idle fuel circuit and prevents fuel getting into the engine after shutoff. These work well and are fitted to a variety of cars and carbs. Ive seen them on different kraut engines.

Another strategy is to run the engine at a high idle and dribble water down the carb. The suddenly steaming water is supposed to blast the carbon deposits away.
There must be some credibility to this as witness the tops of pistons on a water cooled engine after prolonged running with a buggered head gasket....all nice and clean around the leak site.
Watch out haw fast you pour in the water tho. The fire will go out pretty quickly!

Good luck M8
L8tr
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My Austin Healey used to run on, - I knew the reasons, being a highly modified motor I built,
I simply got into the habit of turning ignition of while in 1st gear, & letting out clutch gently at same time

THANKS FOR THE ADVISE, WILL CONSIDER MY OPITIONS BUT PULP WILL BE THE FIRST

How was the timing checked at idle or at full advance eg. 3000rpm with a strobe,Mick.

Before i put in a pointless dissy i was adjusting my points once a month,and i never forgot because it started to knock at the same street on my way home,sounded like marbles dropping on plywood,probaly not your problem but i just like to vent now and then :P.Oh yeah whats your compression like now and did u rejet your carb idle jet or main jet,Mick.:thumb

Geez u guys are stirring my brain archives!

Yes! The Ford Escort dump valve works a treat.

Yes! I used one on a heavily modified Austin Healy Sprite Mk3A that had compression of 240psi that used to startle a few MGB's but would never switch off except with top gear engaged & the clutch pedal up until I put a dump valve in the intake mainfold.

[ Edited on 18-2-2006 by geodon ]

Speaking of healy's

I raced for a cobber of mine a "Spridget", front half an Austin Healy sprite Mk1 and the other half a MG midget joined together.

This thing was a work of backyard art with a solid mounted "B" series engin blown out to 2 litres, 12:1 flat top pistons, valves that almost overlapped and a cam that was copied from an 800 Hp Sprintcar Chev, 45mm Weber, Cortina 'box, Escort diff with a Falcon LSD shoehorned in and Commodore rear brakes. Front end was stock wishbones, Gemini quick rack, vented brakes and inboard mounted shocks.
It had the most delicious set of hand (sand) bent extractors/merged collector with a 3" dump running thru the firewall, 3'14" straight thru muffler mounted where the seat used to be and exiting thru the passenger door.
Awesome sound!
Amazing car that was built on a shoestring by a Sprintcar preparer as a personal project down here.
Thing is it NEVER ran on even on pump fuel!!! Go figure?
L8tr
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1916 with single port heads:alien why would you bother?