The 'E' Type Forum

Hello,
Searched the forum couldn't find a similar subject.
I'm after a bit of advice please, my car started missing when accelerating and giving a slight backfire. I have had the car to a garage that I use who has checked the carbs, timing, fuel etc. Everything is spot on, the same as he set it up last year and afterwards it ran like a dream up until now.
He seems to think that it may be a sticky valve or worn valve or valve seat. First question is I'm wondering has anyone else experienced this? What was the outcome? and what would a rough cost be to refurb the cylinder head?
The other dilemma is that he checked the compression in each cylinder and all were very similar however they had a lower compression that expected. I'm just wondering if it is just a case of a head refurb and valve inserts or its an engine out and full engine refurb.

You have a S2...the head studs are long and go right through the water jacket of the block....its not uncommon for these studs to snap when trying to remove them.....so it isn't just a guaranteed "lets just pull the head off"....you need to be aware of possible consequences of going down this route....does your garage specialise in classic Jags....I would be looking at electrics very thoroughly first.
Clean and re crimp or solder all the low tension connections and try a new coil, dizzy cap and rotor arm from the distributor Doctor.....Steve

Not sure how much I’d worry about the compression if they are roughly the same and it ran well before. My compression was lower than “normal” after a head refurb and it went like a train. I’d check much more as per previous post before going the head off route.

I did you do your compression test when the engine was hot or cold? Does the car smoke? Squirt some oil down the bores and test again. If there's an improvement it could mean some wear on rings or bores but if it's not significant leave well alone.

You need to do a leak down test.

Having said that, I tend to agree with Steve that your problem is electrical. One at a time I would be replacing points if fitted, cap, leads, plug caps if fitted, condenser, coil etc

Hi,
I had a similar problem on my 3.8, tried absolutely everything, fuel pump, distributor (123), plugs were about a month old so did not try those. Took it to a specialist garage, and they tried everything I did - compression test etc. It turned out to be a dodgy spark plug, even though they were new and from a reputable supplier. The plugs were NGK. Upon research there seems to be quite a lot of fake NGK plugs about. So I would say check the plugs. If it is backfiring it sounds electrical. I hope you find this helpful.

What electrical system do you have? Standard dizzie, 123, or standard but with electronic points? (Like Pertronix)
I ask because I had a missing engine under accleration at higher revs, despite all electrical components being new. I had Pertronix - type points. I had standard plug leads which interfere with Pertronix, powerspark etc, and was told to change them for Silicone leads which don't build up a field - problem instantly solved.

Morning,
Thanks for all the feedback, the car has a 123 dizzy which was fitted last year, I've replaced the leads with a set from Martin Robey, however they are not silicon, that said they haven't made a difference. Interesting comment about the spark plugs, fingers crossed I will try that today. The garage I use said that it was backfiring through the inlet and exhaust port. I was speaking to a friend the other day and he came up with a great idea of using a small camera to have a look at the valve seats. He also thought that it may be a broken valve spring does anyone have any experience or thoughts on this.

I’d double double check the timing of the 123. First check the timing pointer is correctly indicating TDC, then I’d use a timing light to check both static and the advance curve. It sounds like the timing might be quite wildly advanced. On S1s this is a pain in the neck as the timing pointer and the marks on the damper are under the car. Dunno if this was improved on the S2.

Hello
Unfortunately no its still on the bottom of the engine, however I do have my new lift now which will make things a lot easier.

Many Thanks

Paul.

Similar problem to me and after a number of discussions, it came up that the compression while even, was low in all cylinders. Local e-type club expert suggested changing plugs from 6E to 5E and problem solved. Try that as a first and relatively cheap option before dismantling head.

As an update, I still had some misfiring issues with the 5E plugs so I bought some Brisk N17YC plugs on advice from some club guru's and these have made a remarkable difference - no misfiring whatsoever, very smooth and other members have reported some power increase.

Also, I'm looking forward to the Ashes series here this Christmas/New Year...

Hello OzDave,
First of all I'm not mentioning the ashes other than to say congratulations on your slender win!!!! I was advised to fit the 6E plugs from 5E. I've still got a slight misfire which currently still trying to solve. I found that the alternator was sending 15-16 volts to the 123 distributor which it doesn't like apparently. So I've changed the alternator and the module (cant remember what this is called). I've now changed the coil to a RED DOT coil, I have been advised by the 123 company to remove the ballast which SNG recommended to fit and installed a 12v spike filter. Haven't had a chance to try yet as our roads are either wet or covered in salt.

Dunno if this is internet rubbish or truth. I’ve recently heard that there are counterfeit NGK plugs offered via your favourite on line sales platforms.

That story has been around for a few years now. Whilst there are undoubtably fakes around I'm more dubious that the major suppliers have been taken in, in any significant way.

There are videos out there comparing fakes with originals and in the ones I've seen the fakes are pretty obvious with errors on the packaging or the plug itself.

If you've bought your NGK plug from a reputable volume supplier I think it's unlikely but not impossible you've got a fake. Compared to the problems I've had with other brands over the years, I still use NGK across all my cars.

Hi Henda, out of curiosity, what are your cylinder compression numbers?

And when you changed from 5E to 6E plugs, did that make a difference on its own or did you make other changes at the same time?

The reason I ask is my comps are about 100-110 across all 6 cylinders and the 6E's that were in the carare better for higher compression. When i changed to some secondhand 5E's, that made a huge difference and when i bought brand new Brisk 5E's, the problem disappeared - I made no other change.

Also, we'll live off the narrow Ashes win for a while yet...

Hello OzDave,

Just seen your reply now, when I checked them dry they ranged from 135 up to 142, wet roughly getting another 30 or so per cylinder. Unfortunately we have the great British weather to contend with so still haven't been out in the car yet. If it doesn't work not sure where to go next, possibly to buy some matches!!!