X Flow progression mis- firing

[ian.hoper]

Hi Each

After a lot of help from all you kind technophobes on Blat Chat the old 1600 XF Webbers(40s) working now and runs a lot better but it is noticable that as you go up through the gears it misses a beat or two . Ok on full throttle and when driven from cold ? No popping and banging .Has got Lumenition egnition but through the old Ford Motor Co top lead distributor cap set up.

Any more helpfull tips ? Got a set of new Magnecore leads to fit but not plucked up courage top tackle that job yet . For your info I fitted the spare Unleaded head last winter and all the problems stemmed from that time .

First I overtightend the missabs then i over loosend the front pair but that seems sorted now .Found out by running the engine and pressing up and down on the carbs.back two no difference but front pair showed the problem up as then ran sweetly .

before that it had the leaded standard head big valves etc.

Thanks in advance .

 

 

Ian Hoper

[ashaughnessy]

As you're not getting any replies on this, perhaps you could detail what it is you've changed since it last ran well?

I could imagine it being the advance curve or the carburettor setup. If you've made significant changes to the engine then either or both of these may need setting up properly on a rolling road.

Anthony

[DW]

Do you have a coil for the ignition? When I replaced mine it resolved my problems with loss of power at certain revs.

 

David

1700XF: click here

[ian.hoper]

Anthony and David

Thanks for the questions ,had a problem two years ago and seemed to be valves not seating on back two cylinders Compression was down. Have a spare engine I got from Andy Couchman some time ago and had the head converted to lead free.

So decided to fit it . hung all back together and had it rolling roaded but never ran as well as befor after that .

They did fit a new coil at the rolling road session and said compression ok . Not been back as chap closed down and in hospital I was told .

So dificult to do any work under the carbs as you all know and think I now have it running better than ever but anoyed a the between gears missing .

Spoils the thrill of driving it around town .

any tips much appreciated .

Bought a Compession tester but baulked at trying it as it said disconect the coil?

Everytime I play with those bits it seems to cause another problem so use the adage if its not broke dont mess with it .

Probably I need to get it all to Steve Parker one day to properly sort .

frustrating as for seven years ran like a sewing machine despite Goodwood track days etc..As you appreciate I am not a mechanic but do like to have a go .

 

 

 

 

 

 

 

Ian Hoper

[ashaughnessy]

So you've changed the cylinder head on your engine by replacing the original cylinder head with a head from another engine, which you had modified by converting to unleaded?

 

Is your symptom a mis-fire or a flatspot? Where in the rev range is it? What did the rolling road operator do to sort this out? Did he do anything about the carburettor setup (chokes, jets, etc) ? I'm wondering if the problem is a flat spot due to poor carb setup, which would be quite likely if the new cylinder head has different characteristics from the old. How sure can you be that the new cylinder head is identical to the old one (apart from the unleaded conversion)?

 

You could probably try one of those home-tune guys who come round with a big computerised engine analyser and check all your ignition and emissions, etc. That would tell you if you have an obvious problem, like a broken coil. Otherwise you might need to get it on the rolling road again, with a competent operator who knows how to setup the carbs and timing, and get it set up properly.

 

Other obvious easy first checks you could do yourself are to check the static ignition timing, check the inside of the distributor for obvious problems (corrosion on the contacts, etc), check the valve clearances, plug gaps and condition, etc.

 

Edit - I've just noticed in your original question you said the original head had big valves. Does the new head have the same big valves? This difference would probably cause less than perfect running if you don't change the fuelling to match. Depends on your accurate diagnosis of whether you've got a misfire or a flat spot which might make either ignition or fuelling more or less suspect.

 

Anthony

 

Edited by - ashaughnessy on 10 Aug 2006 17:13:45

[DW]

Hi Ian

 

If you want to do a compression test then as you say you need to disconnect the coil - just pull the big lead out that connects into the center of the top of the coil....this stops the plugs sparking when you're doing the test so the engine won't start ❗ Take out each spark in turn, fitting the compressor. Turn the engine over using the ignition - suggest you count something like 6 turns on each cylinder so you get an comparable test for each cylinder.

 

Push the lead back onto the coil when you're finished.

 

David

1700XF: click here

[ian.hoper]

Hi David

Thanks for that given me the courage and I will have a go tomorrow with the test, Saturday,

will report results .

Liked the car pic have to learn how to do that .Know a chap in Essex with loads of X Flow engines and bits very reasonable if you want something .

ie lightend fly wheel @ £30

best wishes

Ian

 

Ian Hoper

[DaveMorris]

Don't forget when doing the comp test to have the throttle open.

If not you'll not get any air into the cylinder and have a heart attack when you look at the pressure

 

Dave