another misfire

[scraggs]

The saga continues. The old girl has been neglected all her life and I'm trying to improve her health but she is not playing ball. Stripped engine honed bores, gapped and fitted new rings. Lapped in valves,etc. Carbs have all new gaskets,seals,and needle valves. Starts on first turn of the key hot or cold ( without choke) settles to tickover but sounds if there is a misfire. Rev engine slightly and misfire more pronounced. Replaced distributer cap, leads,and new ngk plugs. Also installed accuspark. The car did not have point when I got it but had remains of luminition ( rats had had most of it). Any pointers please. I know my way round engines and electrics but in this case I need a fresh brain. Thank you.

[wilf]

Compression check would be my own next step - have you done one yet?

[scraggs]

As yet, no. Turning over by hand or starter feels even on all cylinders and when listening to exhaust there is no popping etc or back firing which would show me from my experience, a valve problem. Ive checked resistance on plugs and leads and all looks ok,though maybe one could be breaking down. As I put it starts immediately and stops the same, no running on etc just stops so there must be loads of compression but if a gauge will show they are equal thats another question. I will do a compression check as soon as I can locate a gauge. Thanks Wilf for your reply..

[flying farmer]

You could try pulling off the plug leads one at a time until you have narrowed it down to the offending cylinder.

I had this problem a few years ago with one engine after a total rebuild, took months to find and turned out to be a sticking cam follower, would not show up on a compression check as the valve was closing at cranking revs. Ended up refitting a worn cam bucket on the problem inlet valve and cured it, after trying another new cam bucket that made no difference.

I can only assume the problem lay in the cylinder head cam bucket bore.

Neil

[73stagman]

Does it misfire just at idle or all through the rev range. I have an accuspark unit too and had a small misfire.... not regular either. Idle seemed to be ok but it very occasionally misfired when accelerating...I also have a stealth mappable advance system so played about with the fine details on that and along with using a gas analyser found that the mixture was quite a lot weak so tweaked the mixture up too. All misfiring has gone....

[4x4]

I'd managed to lose one blade off the chopper for the optical switch in the distributor on my Lumenition

[Stagsongas]

Along time back I had an RV8 in a Range Rover that did just that, took me ages and many £'s to renew everything I could think of, all to no avail. All compresssions were fine. I even fitted a camshaft as they are known for wearing off one lobe, but no joy.

Still, when you've done literally everything it rules out a lot of things and you can be more focussed. I found that the distributor shaft was slightly bent, moving away from the cap electrode for the offending cylinder just enough to make it misfire.

Good Luck

Steve

[scraggs]

Sorted. New coil and or rotor arm knackered. Changed both for new ones I had in stock and I now have a completely different engine. A v8 that fires on all 8. P's I have power spark fitted not accuspark. Thank you all for your input. Regards. Gwyn