1800: Engine Tune Up

[andrew111]

I have been trying to tune the engine over the last couple of days, and am having poor results. I need some advice.


The problems I face are:- idle speed too high, lumpy acceleration, and engine running on when the key is turned off.


I have set the various settings as below and would appreciate confirmation if these are correct:

1965 P1800S - Engine is twin SU HS6's B18B engine. With valve inserts for Unleaded fuel. Re-bored with new pistons, and head cleaned up, new plugs , contacts, pumps etc. Car has just been restored so most parts are new or refurbished originals. Otherwise standard.

Valve Clearances - Cold .5mm on intake and exhaust (this sound too clattery to me - but that's what the manual recommends.)

Timing 18 degrees BTDC at 1500rpm.

Trying to set idle at about 900rpm -1000rpm - but with idle screws all out, am still getting about 12-1500rpm. (although this is variable!)

When adjusting the mixture am finding that it wants to be more rich - so that when I lift the air pots the revs don't fall away too much. But as a result of the richer mix, the idle speed goes even higher and I cannot adjust this down.

Am waiting for a Colortune kit to be delivered to check the mixture - but fear I might end up at a professional tuning firm. Can anyone recommend a firm in the Warks. area or nearby?

Would appreciate any advice you can give.

[JP 1800]

This sounds like you have an air leak and as such the mixture will be too lean. Are the carbs reconditioned and importantly were the spindle bushes re-done. Also do not over look the adjusting screw for the choke cams, there should be a small gap between the screw and the cam as the gap can close when the engine heats up leading on to higher hot idle. Lastly check that all the manifold bolts are tight it is not uncommon for some to be loose after a restoration.

I am facing similar issues and suspect that my bushes will need doing in the future as I have recently rebuilt my own carbs.

JP

[andrew111]

Hi JP

Thanks for the advice - I will try and spray WD40 around the shafts while the engine is running and see if this alters the revs.
Will report back.

[Steve121]

Had the same problem a few years back, for me it was the spindle bushes causing the leak, hence high idle. Now it idles nicely and can be killed if the idle screw is out fully. And no running on anymore.
There was just the slightest bit of play noticable in the spindles, that's all it takes!

[andrew111]

Just thought I'd let you know how I'm progressing.

The colortune arrived and was put to good use. I am getting a blue flame - showing the mixture is OK.

Found that the idle was too high due to the fast idle screw interfering - now that has been corrected can get down to about 1000rpm.- but still a bit lumpy at idle & acceleration is also a little lumpy.
On the advice of a carb repair shop I brushed neat petrol onto the spindles - and this does result in an increase in rpm. So probably the spindles are worn as you advise and letting in air.

Having adjusted balance, mixture and idle speed again I now find the engine a little smoother - and it on runs on only momentarily before cutting out on switch off. But again the acceleration is a little uneven.
Am not sure whether to live with it or go for a carb refurbish. Although the prices I am getting are not far off a new pair of carbs from Simon at Brookhouse.

Can anyone recommend a decent carb refurber?, or tuner.

thanks

[arcturus]

Burlens but a long wait
http://sucarb.co.uk/?SID=77qakcejosd...l1&___store=su
Give them a bell