Engine Running On

[Darren Groves]

So a year ago I fitted a rebuilt, slightly modded engine into my 13/60. Mods were:

 

·         Warmer cam (70/30 30/70)

·         Larger Valves (36.4mm inlet and 31.3mm exhaust)

·         Megajolt

·         Twin HS2 SU's (AAQ Needles & Stronger Springs)

·         Four Branch Exhaust Manifold

·         Duplex Timing Chain

·         Crank, Flywheel, Clutch Cover and Con Rods balanced.

 

So the end result has been a very smooth engine (at revs) with a little extra go than a standard 13/60 Herald, just what I hope for.

 

There have been 2 ongoing niggles though; one is an inability to get a smooth idle, not so worried about that for the minute.

 

The second niggle was that after a couple of months of driving the car would run on a little when switched off, the problem gradually got worse. Now I know why, there was a lot of carbon build up, which I thought was a little odd given I’d only done a 2000 miles or so since a rebuild.

 

I took the head off, cleaned everything up, put it back together and the problem was fixed, no more running on. Using a Gunson Colourtune & Gastester combined I set the mixture and at idle got a steady CO reading of 3.0%, all was well I thought. However after a couple of thousand miles the problem is slowly returning, so I can only assume it’s due to carbon build up again.

 

The car is used 4~5 days a week, some short journeys of around 2 miles, but regular 10~15 mile runs as well so should be getting nicely warmed up.

 

Ideally I need to get it on a rolling road to get the Megajolt & Needles set up properly, rather than the trial and error method I have been using up until now. But before I take the plunge and book a session, are there any suggestions as to why it’s getting choked up so quickly?

[AndyTV8]

Hi Darren, what plugs are you running? Could be worth trying slightly hotter ones and/or trying a different fuel...... Shell Vpower always seems to be popular, (i find Tesco 99 works well with mine - although mostly so i can run at the advance that i want without pinking rather tan getting a more complete burn)

....... Andy

[Darren Groves]

Hi Andy,

 

I'm using BPR6ES plugs. Not much choice in fuels down where I am, so generally using local garage with standard unleaded. I did use Esso Super Unleaded for a bit but made little difference to be honest. Closest Shell station is over 30 minutes away, so not much chance of using that on a regular basis.

[Pete Lewis]

Hi Darren, 

yes never run on 95ron fuel made for side valves and motor mowers when these cars were tops.

 

lmpy idle could be just the cam, or it possibly needs a faster idle speed to suit 

 

have you done a cam timing test its easy to fit the cam with the cam lobe tdc being off position and the cam timing error makes it lumpy.

 

does the cam need special /larger tappet clearances ??  

 

make sure no gasket of filter box is covering any of the carb face breathing ports

 

maybe up the plug spec  from  eg NGK BP6ES  to    7ES   or Champ N9Y to 7Y   

 

check the float heights ??

 

just som thoughts  Pete

[Pete Lewis]

Wow a !!!!   .....Just read your reply

  Please . never  ever use spark plugs with an R in the suffix these are for more modern cars with a much higher HT than our machines produce you will be getting a very weak spark at the electrode.   get them out fit some std   and see what happens 

Pete

[AndyTV8]

Hi Darren,

As Pete has mentioned, avoid resistive plugs.....  i'd try changing to a 7 ..... although i'd go for BP7E  (if you can find some )rather than the ES - the E has the small 'V' cut in the electrode.

 

....... Andy

[Darren Groves]

Cam supplier said cam shouldn't give a lumpy idle, they have used widely with no problems.

 

Cam timing done using dial gauge, timing wheel and piston stop so I am as confident as I can be it's correct.

 

Clearances were recommended at 10 & 11 thou.

 

Carb breather holes are clear and float height fine.

 

I'm running Megajolt which uses a Ford coil pack, so restitive plugs are actually recommended. I used standard plugs up to a few months ago it ran a little better after the swap.

 

Initially I used standard dizzy, coil and plugs and these issues were there.

 

I'll give the hotter plugs a try.

[Pete Lewis]

good stuff darren,  I should have remembered some of your mods but senior moments and all that.

 

trouble is its not easy to apply basics to a hybrid as the normals are not normal  ha !

 

  if you up the idle does she smooth out a bit ??

      to keep producing carbon deposits that affect running so easily is rather concerning ,   low octane fuel wont help at all, 

      any 97+ will be nearer the designed rate , some tesco even show as 100   , not used it .

 

           Pete 

[Dzmarc]

Darren

 

I had the same problem on my spit. Like they mentioned above try primuiem unleaded.

If not add some octane booster to normal unleaded. Should help no end.

 

Also (and I'm guessing you've already checked this) but check the timing is as per the book, may just have to dial it back a little.

 

Marc

[Darren Groves]

Pete,

 

Gett the revs up to about 1100 and it's nice and smooth.

 

Definite downside to non-standard is not knowing what should be right, but it's fun trying to get there.

 

My local garage won't stock anything other than standard unleaded, say there's no demand.

 

Marc,

 

Did run the car for about 2 months on Esso Super unleaded but made no appreciable difference though at that point the engine would have been pretty carboned up by then.

 

Did read on another forum a while back that octane boosters don't actually work, not sure how they knew.

 

Looks like a rolling road session is the way to go.

[Pete Lewis]

think there's a general thought that some addatives actually make things worse. especially a hole in the pocket ,   best  leave well alone  

 

              things may improve with time as many more modern cars are moving towards 97 to get the performance up and emmission down 

 

                     this could just be the plugs glowing , and the carbon is incidental to the short runs with some choke , needs a blast for some time to burn that off

 

                     Pete

[Darren Groves]

So one week on from fitting hotter plugs (BP7ES) and so far no running on an still using standard unleaded, so fingers crossed.

 

One thing I should have mentioned regarding the quick carbon build-up, when checking plugs they have always been a nice biscuity brown colour....

[thescrapman]

With NGK plugs, the lower the number the hotter the plug I think, so you need a 5 rather than a 7.

 

Cheers

 

Colin

[PeterH]

My Spit Mk 3, standard engine 1293cc no mods. Has run on since its rebuild 800 miles ago. I've just changed the head gasket (to cure an oil leak) and was suprised to see how much carbon had built up in that time. Carbs set up by ColourTune and plugs a good colour. Plugs are Denso W16EPR-U, as supplied by either Canley or Rimmer (forget which), fuel - generally Sainsbury standard Unleaded

 

Changing plugs may help run on, but surely won't affect carbon build up.

 

Peter

[Darren Groves]

With NGK plugs, the lower the number the hotter the plug I think, so you need a 5 rather than a 7.

 

Cheers

 

Colin

 

Thanks Colin, you are correct, this is from the NGK website:

 

 

My Spit Mk 3, standard engine 1293cc no mods. Has run on since its rebuild 800 miles ago. I've just changed the head gasket (to cure an oil leak) and was suprised to see how much carbon had built up in that time. Carbs set up by ColourTune and plugs a good colour. Plugs are Denso W16EPR-U, as supplied by either Canley or Rimmer (forget which), fuel - generally Sainsbury standard Unleaded

 

Changing plugs may help run on, but surely won't affect carbon build up.

 

Peter

 

Peter, too cooler plug will lead to carbon build-up, here's a short video. I initially done the same as you by using just a ColourTune and plug condition, even what seemed to be correct showed a CO2 reading of around 5.0% when using along side a Gunson Gastester. Mine is now running with a CO2 reading around 3.0%, so I think the ColorTune does give quite a wide range when it indicates it's at the correct mixture.

 

Darren

[PeterH]

Thanks Darren

I guess modern petrol mean the old recommendations no longer apply, so I will try a hotter plug.

 

Peter

[Darren Groves]

Could there be any connection between fuel level in the tank and running on?

 

The running on started coming back last night and again this morning as the fuel level dropped from around 1/3 to touching the red. Brimmed the tank with regular unleaded and hasn't done it since.

 

Might be just a coincidence and have never noted fuel level before when problem arose.

 

Any thoughts?

[Pete Lewis]

unless there is some fuel  tank height/float level  pump efficiency  affecting the running , but thats a long shot.

 

Pete

[Darren Groves]

Just a coincidence I guess, will see what happens as the tank empties.

 

I have some hotter (rather than the colder I fitted) plugs on the way, so this may help.

 

I am going to re-route the fuel pipe also, it currently runs round the back of the engine and goes pretty close to the exhaust manifold and heater pipes so may have some adverse effects.

[Pete Lewis]

as a thought if you use hose all the way round it wont conduct heat like bundy tube

did this on the Vit6 although never had any hot running troubles ever.

ever thought of running the fuel line under the sump in cool air ?? 

 

Pete

[Darren Groves]

As the car's coming off the road for some bodywork, I thought I'd take the opportunity to get the head off again to remove all the carbon deposits that is causing the engine to run on, as mentioned in my post from August. As you can see from the pictures below it's got pretty choked up in the 4k miles or so since I last took the head off.

 

 

 

 

 

 

So I know why my car runs on, but not really why I get carbon build up so quickly and to the extent I do, given that Gunson Colourtune & Gastester & Plug Colour always indicate mixture is good. I swapped to hotter plugs BPR5ES (Yes 'R' as I'm running Megajolt), but probably too late as the car was pretty choked up already, so to start I will use these from day 1 when all back together. I will also check the cam timing once again (3rd time), just to be 100% sure it's spot on.

 

One thing I didn't do when building the engine was check the compression ratio as my little brain couldn't work out how to calculate manually, however I have since found an online calculator to do all the hard stuff for me - http://www.summitracing.com/expertadviceandnews/calcsandtools/compression-calculator, so I got all the measurements I needed and it worked out at 8.72:1

 

 

So not far off the standard 8.5:1 it should be, so I'm assuming this is perfectly acceptable? Any thoughts?

 

I am planning a rolling road session when the car's back together to fine tune the Megajolt and see what needles I need for the SU's (currently AAR, but have been on AAQ for the most part). 

 

So any thoughts or ideas are welcomed as to the carbon build up?

 

Happy new year to all!

[Clive]

Sounds like teh CR is too low. Especially with a warmer cam fitted as they lower the dynamic CR. A mk3 spit would run a 9.1 (poss higher, working from memory here) and I would be looking for even higher than that (probably 9.75, but again that is off the top of my head). I ran 10:1 on my 1500 with no side effects, and that was with a dizzy. With megajolt you will be able to tweek the timing and have an easier time of it.

 

Another thought. Have you double checked that the MK sensor is correct set up? and what it thinks is TDC is actually TDC?? sure you have, but worth a thought.

[Darren Groves]

Thanks for the reply Clive.

 

All UK Spitfire's seem to be 9:1.

 

Sorry, more questions!

 

How do I get to know what the most suitable CR is for the engine? Also is there a way of calculating what needs skimming off the head to reach a target figure or will I just have to skim in stages and recalculate each time? What info will I need to calculate a dynamic CR?

 

Thanks again.

[Clive]

No idea really! I just use google and find what other have done and it worked!

Have a dig through some of the other triumph forums. I know a certain (flawed) genius reckoned a Toledo 1300 low compression head worked brilliantly with a 1500 and TR5 spec cam. I think that CR would head towards 9.8:1 or 10:1

 

All gets a bit of guesswork as the "tuning" experts who sell stuff often do not really know what they are up to. Peter Burgess is a lesser known (in triumph circles, unless you are into proper mods) but true expert on heads etc. Not sure if he is willing to offer advice though.

[Steve P]

Dont know who your cam supplier was or if it was the same people that did the head work,i`m surprised they wouldn`t have worked out the optimal compression to work with the cam..on my Vitesse i had it worked to give 10:1 with a TR5 cam.

 

You need to work out the chamber volume required to give the ratio you want, and then get it skimmed to give you the correct chamber volume.My Herald has a TLD 244r cam with a CR of 10.2:1.That was 33CC`s per chamber iirc.

 

By the way my Vitesse runs on with anything other than 99 octane in it.It showed 172bhp on the rolling road though,with a standard Vitesse dizzy with no advance.Thats the next thing to sort.

Steve