V8 Tickover troubles

[vonkeyvong]

I am having trouble getting my engine to idle at a low enough speed.

The car has electronic ignition which I did not install so not sure how you set it up or if it is set corectly (do you need to set the dwell angle?).

The carbs are ballanced, the low idle stop screws are backed off as far as they will go, the ignition timing is set to 3deg BTDC and the carb dampers are fully topped up.

Fuel wise I am using Tesco Momentum 99oct with octane booster and lead replacement aditive.

With all the above settings I cant get it to drop below 800rpm indicated on my strobe light tachometer.

Any help much apreciated.

Matt.

 

[cooper1203]

hi, is the choke cable too tight???? might be a silly suggestion but popped into my head so thought it was worth sharing
coop

 

[vonkeyvong]

hi, is the choke cable too tight???? might be a silly suggestion but popped into my head so thought it was worth sharing
coop

Hi Coop,

Not a silly sugestion but no, it is not too tight.

Matt.

 

[vonkeyvong]

Spoke to a local mechanic who sugested setting the timing to 28deg BTDC @ 3000rpm with the vacuum advance conected. Does this sound right?

I gave it a go but found no improvement.

Matt.

 

[harveyp6]

the low idle stop screws are backed off as far as they will go,

If you can't reduce the idle speed if you continue to unscrew the idle screws, then it's likely that the fast idle screws are incorrectly set and they're holding the idle speed up.

[edit] If it doesn't turn out to be that, then check for an air leak on the induction side.

You don't need to check the dwell with electronic ignition fitted.

 

[vonkeyvong]

the low idle stop screws are backed off as far as they will go,

If you can't reduce the idle speed if you continue to unscrew the idle screws, then it's likely that the fast idle screws are incorrectly set and they're holding the idle speed up.

[edit] If it doesn't turn out to be that, then check for an air leak on the induction side.

You don't need to check the dwell with electronic ignition fitted.

Ahh, fast idle screws, now you have me intreagued!! I am off to check it out....

Matt.

 

[vonkeyvong]

Fast idle screws are well clear and not interfering with the throttle levers in any way.

Matt.

 

[harveyp6]

Fast idle screws are well clear and not interfering with the throttle levers in any way.

If that's the case, and there's definitely nothing in the mechanical linkage causing the high idle speed then I'd start looking for an air leak.

 

[vonkeyvong]

Fast idle screws are well clear and not interfering with the throttle levers in any way.

If that's the case, and there's definitely nothing in the mechanical linkage causing the high idle speed then I'd start looking for an air leak.

Oh well, I guess tomorrow will involve some time spent checking there are no loose nuts or bolts on the carbs and manifold.

On the plus side setting the timing to TDC has made it pull a lot better, but I think I will need to do some more experimentation though.

I have also spent some time tweaking the kick down cable and the gear changes are a lot smoother now and right about where they should be.

Matt.

 

[cooper1203]

hi I seem to remember someone telling me once to spray wd40 around the intake manifold etc as it will draw it in and identify where the leak is
many thanks
coop

 

[ghce]

How are you getting your timing figures? I find it often best to set timing by ear rather than relying on the timing marks.

Graeme

 

[vonkeyvong]

How are you getting your timing figures? I find it often best to set timing by ear rather than relying on the timing marks.

Graeme

Hi Graeme,

I am using a strobe light and setting it at tickover.

Matt.

 

[symes]

Why add additive to 99 octain ? no point is there ? the 3500s I work on run fine on straight unleaded -as far as i can tell anyway--if you had 11-2 compression ratio like mine then could understand additive and timing is TDC or 6 deg BDC maybe a degree either--cant remember exact figure

 

[ghce]

How are you getting your timing figures? I find it often best to set timing by ear rather than relying on the timing marks.

Graeme

Hi Graeme,

I am using a strobe light and setting it at tickover.

Matt.

The reason I cited this is that the factory timing gear was notoriously inaccurate.

Graeme

 

[rockdemon]

Just turn the dizzy till the idle speed is highest and back it off a touch. Then use the strobe to get yourself a personalized figure for next time

 

[vonkeyvong]

Just turn the dizzy till the idle speed is highest and back it off a touch. Then use the strobe to get yourself a personalized figure for next time

Hi,

If I did that tickover would be about 1500rpm.

Matt.

 

[vonkeyvong]

Why add additive to 99 octain ? no point is there ? the 3500s I work on run fine on straight unleaded -as far as i can tell anyway--if you had 11-2 compression ratio like mine then could understand additive and timing is TDC or 6 deg BDC maybe a degree either--cant remember exact figure

I am using Castrol Valvemaster Plus. Main reason is for protection to the valves and fuel system and secondary reason is for the slight octane boost it gives. As it is only slightly more expensive than Castrol Valvemaster I figured it cant do any harm.

Matt.

 

[quattro]

Just turn the dizzy till the idle speed is highest and back it off a touch. Then use the strobe to get yourself a personalized figure for next time

Hi,

If I did that tickover would be about 1500rpm.

Matt.

You need to get the timing sorted first. If it ticks over at 1,500 rpm on optimum timing, then set it there and then turn the tickover down with the adjustments on the carbs.

Might be a good idea to drop the additives as well, it will run perfectly well with the Tesco 99

Richard

 

[symes]

Just turn the dizzy till the idle speed is highest and back it off a touch. Then use the strobe to get yourself a personalized figure for next time

Hi,

If I did that tickover would be about 1500rpm.

Matt.

You need to get the timing sorted first. If it ticks over at 1,500 rpm on optimum timing, then set it there and then turn the tickover down with the adjustments on the carbs.

Might be a good idea to drop the additives as well, it will run perfectly well with the Tesco 99

Richard

as I said drop additives :wink:

 

[vonkeyvong]

Just turn the dizzy till the idle speed is highest and back it off a touch. Then use the strobe to get yourself a personalized figure for next time

Hi,

If I did that tickover would be about 1500rpm.

Matt.

You need to get the timing sorted first. If it ticks over at 1,500 rpm on optimum timing, then set it there and then turn the tickover down with the adjustments on the carbs.

Might be a good idea to drop the additives as well, it will run perfectly well with the Tesco 99

Richard

Hi Richard,

As I stated earlir in the thread the idle is set to minimum (basicaly the stop screws arent actualy touching anything). Unless of course there are some other adjusting screws I dont know about. Fast idle is corectly set aswell and not touching anything when the choke is pushed in.

I also checked the setting of the main jets today and found that on one of the carbs there is not full adjustment, this isnt a major problem as I managed to set them both equal with a depth vernier but I will need to strip that particulsr carb to see what is wrong. It looks like the previous owner didnt know about this so both carbs had different settings on the main jets. Resetting them has helped a little.

I also sprayed all around the carb and manifold gaskets with WD40 while the engine was running and found no drop in RPM so dont think there is an air leak.

Must say I am realy scratching my head now.

Matt.