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Spitfire MK3........spitting!!!


MSZ
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Hi everyone. I have been a member of the TSSC for about seven years but never used the forum as I have pretty much managed to solve problems that have ever crept up with my Spitfire. I am the second owner of the Spitfire. After restoring it six years ago, I took my partner on a road trip doing the N500 route in Scotland and returning home to Kent via the Lake District - very satisfied at an achievement. The car didn't miss a beat!! Mechanically, the car was sound, engine, gearbox, axle etc etc. The carburetors were overhauled and distributor replaced with an electronic distributor with mechanical tachometer. There was always a minor back fire at high revs, but apart from that it was sound. The car was in the garage for six months since the trip and last week I decided to start it and take it for a run. I always start it and let it warm up to operating temperature then off I went. It misfired on (attempted) acceleration and was a real pig..................it sounded rough as old boots. Back to my garage tools were out, timing checked, carbs checked (adjusted and re balanced). On revving the engine at my garage, a backfire would blow through the rear carburetor and the engine feels like its holding back?. I even did a compression test which more or less matched my original figures when I first tuned it all those many years ago. Readings were Cylinder 1-135, 2-135, 3-145, 4-110 psi. I always had a slight suspicion at cylinder 4 because of a minor oil weep at the back of the cylinder head and engine block mating surfaces - head gasket?. My question is  - that with the same compression readings before (when all was well - apart from minor back fire) and now after, it must point to something else. Granted the head gasket maybe gone and the trip progressed that - but there is no oil in the water/radiator? Regarding the carburetors, I only overhauled them using Rimmer Bros kit. Somebody suggested that the carburetor connecting rod bushes may need doing as its impossible to tune the carburetors correctly........this, perhaps could be true as there is some lateral play in the connecting rod? Checking the plugs they all appear sooty - rich mixture, in turn minor lifting of the carburetor piston, the idle remains the same for both carburetors - I assume this is correct?.

I want to avoid taking the head off (although I can see this might have to be done to replace the head gasket and check valves) making sure I have covered all other avenues first. I wonder if there is an experienced classic car tuner in the Kent area that I could contact re tuning the carburetors?

Any way, any advise or comments would be very helpful in trying to solve the issue.

Thanking you all in advance

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back fire and misfires is looking towards condenser  but you have an electronic dizzy   ...who's unit is it

most electronics do not need a condenser  but>>>>>>if it has  

if it has a orange wire be suspect 

suggest you buy one from    http://www.distributordoctor.com/distributor_condensers.htm

do you have spark plugs with an R in its suffix       note there s a post about all the comments on these  but i find they are troublesome 

stick to straight BP6ES      not  BPR   if  you have NGKs 

on you compression test  did   you have the throttles  OPEN  ???

Pete

 

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Pete, I cant remember who's unit it was......trying to find some paperwork. there are no markings on the actual distributor to identify it, will look tomorrow.

The distributor has a vacuum take off and mechanical tachometer but with electronic bits inside replacing the condenser and points.

I note your comments re spark plugs and will check these.

Not sure I understand "throttles open" ? On doing the test, I removed all spark plugs and connected the gauge to each cylinder and allowed 5/6 turns of the engine.

Thanks 

Mike

 

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7 minutes ago, MSZ said:

Not sure I understand "throttles open" ? On doing the test, I removed all spark plugs and connected the gauge to each cylinder and allowed 5/6 turns of the engine.

To get the most representative and consistent compression measurements, you want to minimise any restriction to getting air in, hence you do the test as you describe but with the accelerator on the floor - throttles wide open. I don't usually find it makes very much difference but that's the "book" method.

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14 minutes ago, NonMember said:

To get the most representative and consistent compression measurements, you want to minimise any restriction to getting air in, hence you do the test as you describe but with the accelerator on the floor - throttles wide open. I don't usually find it makes very much difference but that's the "book" method.

Ahh right.........thanks for that.......gotta be done right!

Will try again tomorrow

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59 minutes ago, Pete Lewis said:

back fire and misfires is looking towards condenser  but you have an electronic dizzy   ...who's unit is it

most electronics do not need a condenser  but>>>>>>if it has  

if it has a orange wire be suspect 

suggest you buy one from    http://www.distributordoctor.com/distributor_condensers.htm

do you have spark plugs with an R in its suffix       note there s a post about all the comments on these  but i find they are troublesome 

stick to straight BP6ES      not  BPR   if  you have NGKs 

on you compression test  did   you have the throttles  OPEN  ???

Pete

 

Pete,

Finally found it.......Powerspark Delco type Electronic Distributor.

I think ill check all connections at coil as well and get in touch with Powerspark Ignition and see if there have been any known problems with these.

Mike

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power spark   not without some problems compared to higher end units  

like all things  can be good but can also have hic ups 

there are mixed reviews about problems 

 

yes if the throttle is closed it restricts the ease of air getting in ,  a low result may be down to poor throttle balancing and one carb idle is shut more than the other

does the carbs have waxstats on the su jet holders ??? like this  If so they need the 2 x1penny mod to remove the wax capsule   these  can cause chaos

Classic Mini Hs4 Su Carburettor Waxstat Jet Assembly

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Pete,

I will contact Power Spark and ask their advice.

Don't have Waxstat luckily!!

I note your point about throttle closing re compression test.

All things to look into.

Again thanks

Mike

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If the car has sat in the garage for 6 months it could be as simple as stale fuel, which can make it run very badly, mine ran like a bag of nails until I burnt off some of the old fuel and topped up with fresh after lockdown (engine had only done 1500 miles since full rebuild). If the oil leak is from the rear nearside of the head, below the oil gallery plug, it is probably a very common and not worrying fault

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 oil leaks if its from the rear N/S its common as this is the dribble feed to the rockers  

a retorque of the head nuts   may help ....   always check the rocker cover sealing 

head gaskets rarely give oil in water or water in oil  

what you do get is combustion high pressures into the water  jacket   and if left the low coolant pressure drops a little inthe cylinder and 

you get a misfire when starting up on one cyl due to the water content 

 

please  check the tappet clearances all 0.010"   cold 

Pete

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When I rebuilt my daughters Spit Mk2 engine around 18 years ago (need a refresh) it had that horrible leak at the rear N/.S of the head to block ie the rocker oil feed.

I was bu**gered if I was going to remove the head to fix this little dribble so I made a nappie that fitted over the top of the bell housing to block joint area, which I regularly replaced/cleaned, here is our then club magazine editors response when he saw it, think you'll find it amusing. 

Spit Oil Leak Bodge -Fix.jpg

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I wish mine WAS a dribble. It's not from the rear of the rocker, nor the head area - all bone dry, but the rear of the sump is soaking as is the underside of the car. This is after ten minutes idling to get up to operating temperature:

FC11572F-E0EC-4E98-AF67-C2D467550EBE_1_105_c.jpg.2d96e710cb0a0c4458a275f643ec86e3.jpg

I've just changed the oil, so now it's a golden yellow pool and not black, but still happening...

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Thanks for all the advice above.

I did the compression again with butterflies open and got readings 135, 137, 137, 115 starting from the radiator end (front of engine, so marginal differences in reading. I am waiting till Monday to contact www.simonbbc.com who are Powerspark Ignition in Bromsgrove to see if there are issues with the module etc. Although i have read that Powerspark do recommend using non copper cored HT leads, but I think this is more for better performance as opposed to developing faults. Spark plugs are Champion N9YC.

I cant find anywhere whether the ignition timing needs to be altered if electronic ignition is fitted, again i will seek guidance from them.

The carbs are set up perfectly I believe. The car starts without problems and once at operating temperature it idles without any misfiring. When increasing revs gradually to 3-4000rpm there is no misfire, only a misfire occurs from idle if I blip the accelerator rapidly and sharply. Also there is faint white smoke puffing through the front carburetor when there is a misfire after I blip the accelerator pedal rapidly on and off.

Mike

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Not sure if you have posted this elsewhere, as I replied to an almost identical post earlier...

anyway, yesterday I helped a mate who had a misfire on his stag. New lucas coil, bit better but still happening. Fitted an electrnic ignition module, no change. Checked fuel system, new filter etc, still there. I suggested trying my (27 year old) lucas coil. Instant fix. The new one was poorly made and getting VERY hot. Easy fix, but people assume new parts work, e=when the reality is many are poor quality.

Likewise the "new" distributers. The only one I have come across was so bad out of the box (would not rev above 3k) the original was refitted. Not sure what happened as that was before covid, and not seen the chap since. 

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10 minutes ago, clive said:

Not sure if you have posted this elsewhere, as I replied to an almost identical post earlier...

anyway, yesterday I helped a mate who had a misfire on his stag. New lucas coil, bit better but still happening. Fitted an electrnic ignition module, no change. Checked fuel system, new filter etc, still there. I suggested trying my (27 year old) lucas coil. Instant fix. The new one was poorly made and getting VERY hot. Easy fix, but people assume new parts work, e=when the reality is many are poor quality.

Likewise the "new" distributers. The only one I have come across was so bad out of the box (would not rev above 3k) the original was refitted. Not sure what happened as that was before covid, and not seen the chap since. 

Thanks for that Clive, I have only posted this thread. Yes, I believe you may have a point re new parts and quality, I do have an old coil, so I may dig that out and try with that. The distributer I bought and fitted 2019 together with a new coil.

..................now where did I put it? Mike

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2 hours ago, MSZ said:

I cant find anywhere whether the ignition timing needs to be altered if electronic ignition is fitted

No, the ignition timing is governed by the burn rate of the mixture in the cylinder, which is independent of any electronics used to drive the coil that produces the HT that causes the spark that starts the burn. However, as Pete will often point out, changing from points to EI nearly always messes up the timing so it needs to be re-set. I recently fitted an EI distributor to my Spitfire (I'm keeping the old one, complete with fitting clamp, for an easy swap if I have problems), beginning by setting it in the same position as the points one. I had to rotate it by 45 degrees (that's 90 degrees of crank advance) to get to the right position.

That said, the correct ignition timing depends, as I said, on the burn rate, which depends on the fuel. The book figure may not actually be optimal for any of our cars on modern petrol.

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1 hour ago, NonMember said:

I cant find anywhere whether the ignition timing needs to be altered i

you wont  but it as rob says needs to be  close to as per the book which is the basic static  setting , there is no way of knowing if the component parts of either dizzy mimic

each other  as most often they are wildly different  so just retime the ignition and see what that does for you 

Pete

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1 hour ago, NonMember said:

I had to rotate it by 45 degrees (that's 90 degrees of crank advance)

I wonder - and wild off the top of head theory here - if the cam that operates the points uses the point of the operating cam on standard points, but the electronic magnets use the flats? If you think of the four corners of the cam, as each one rotates it pushes open the points so that's the milestone by which the timing is set / adjusted. The collar that you put over the cam for electronic ignition is very thin at those corners, but is thicker across the flats, maybe more suitable for placement of the operating magnets? So: is the electronic ignition triggered by a different part of the rotation? Just a possibly wild thought... :.

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yes and the position of the pick up on the base plate also contributes to the variance 

it all changes the trigger point on mechanical points and the electronic rotor compared to what you removed 

any replacement must be retimed as a matter of course 

electronics or any dizzy change is only fit and forget if you reset /check the basics as a first job

Pete

 

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Have you checked the Powerspark , same as Accuspark unit . Check the magnet is not too close to the electronic unit and the bottom of the rotor arm is not clipping the electronic unit . A giveaway is black dust particles when you remove the dissy cap . Lastly check the rotor arm has no fractures 

Paul

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Of the number of times I've offered the benefit of my advice about this sort of problem at a distance I've been wrong 50% of the time. But here goes anyway!

My guess would be that the issue is on the ignition side rather than carburation or internal condition of engine. Or, to be more precise, it's aspect I'd investigate first.

Assuming one still has the original distributor a way to proceed would be to substitute the Powerspark unit with the original one with its own points, condensor, cap and leads (such as are to hand and in fair condition) and leave the vacuum blanked off at both ends. Outcome will be a) improved = diagnosis is the Powerspark unit, b) No change = diagnosis is not the PS unit, c) worse/differently worse  = no useful info.

And of course, swapping between points and EI and vice verse necessitates re-timing.

If 'a' that would be no surprise to me because I've had two EI units fail in under 100 miles: One because it was spiked off a superboost battery charger and one because it just failed.

If 'b' then i) multimeter check that with engine running there is a 'clean and stable' 12v to coil (I'm assuming your system is unballasted). If suspect, coil can be hot-wired off the battery for further checks) ii) check coil for approx 3 ohms across primary winding (if 1.5 ohms it's the wrong coil) and between primary and secondary windings many megaohms (varies by coil but lets say 10).

Another exploratory investigation is to get a new, correctly gapped, sparkplug and connect directly to coil and touch down to engine block. Cranking should then give a good spark at twice engine rpm. Repeat with each plug lead which should then give spark at half engine rpm. Rather hard to describe what a 'good' spark looks like compared to a 'feeble' one so that's a matter of judgement. But any variance between the 'coil' spark and the 'individual plug' spark narrows down the area of enquiry a bit.

Without trying to cover everything in one post some other experiences I've had with this sort of thing are.

• Triumphs: Air leaks in breather pipes, no oil in dashpots, air leaks at inlet manifold, wrong needles or jets

• Mini: Unpredictable misfire: Compression test seemed reasonable(ish) (15% variation) but valves, guides, seats all severely deteriorated

• VW T2; Misfire, poor pick up. On strobe timing could be seen to be 'dancing' and flitting around all over the place. Extreme wear in distributor drive gear and distributor shaft.

I have the premonition that everything I've mentioned above is wrong (!) but I hope it might stimulate some thoughts about how best you can proceed with further investigation.

 

 

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i have said before a guy at work who was a bit of a plague  told him to put ht lead in mouth and crank it over to see if theres a spark

next day had to get security to remove him from my office   so    ............   dont do it 

 

one thought to add

if you swapped to EI and did not  retime then if this is retarded  you may have cooked /overheated the spark plugs and they faulter

when under pressure 

pete

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30 minutes ago, chrishawley said:

Of the number of times I've offered the benefit of my advice about this sort of problem at a distance I've been wrong 50% of the time. But here goes anyway!

My guess would be that the issue is on the ignition side rather than carburation or internal condition of engine. Or, to be more precise, it's aspect I'd investigate first.

Assuming one still has the original distributor a way to proceed would be to substitute the Powerspark unit with the original one with its own points, condensor, cap and leads (such as are to hand and in fair condition) and leave the vacuum blanked off at both ends. Outcome will be a) improved = diagnosis is the Powerspark unit, b) No change = diagnosis is not the PS unit, c) worse/differently worse  = no useful info.

And of course, swapping between points and EI and vice verse necessitates re-timing.

If 'a' that would be no surprise to me because I've had two EI units fail in under 100 miles: One because it was spiked off a superboost battery charger and one because it just failed.

If 'b' then i) multimeter check that with engine running there is a 'clean and stable' 12v to coil (I'm assuming your system is unballasted). If suspect, coil can be hot-wired off the battery for further checks) ii) check coil for approx 3 ohms across primary winding (if 1.5 ohms it's the wrong coil) and between primary and secondary windings many megaohms (varies by coil but lets say 10).

Another exploratory investigation is to get a new, correctly gapped, sparkplug and connect directly to coil and touch down to engine block. Cranking should then give a good spark at twice engine rpm. Repeat with each plug lead which should then give spark at half engine rpm. Rather hard to describe what a 'good' spark looks like compared to a 'feeble' one so that's a matter of judgement. But any variance between the 'coil' spark and the 'individual plug' spark narrows down the area of enquiry a bit.

Without trying to cover everything in one post some other experiences I've had with this sort of thing are.

• Triumphs: Air leaks in breather pipes, no oil in dashpots, air leaks at inlet manifold, wrong needles or jets

• Mini: Unpredictable misfire: Compression test seemed reasonable(ish) (15% variation) but valves, guides, seats all severely deteriorated

• VW T2; Misfire, poor pick up. On strobe timing could be seen to be 'dancing' and flitting around all over the place. Extreme wear in distributor drive gear and distributor shaft.

I have the premonition that everything I've mentioned above is wrong (!) but I hope it might stimulate some thoughts about how best you can proceed with further investigation.

 

 

Very useful and interesting information  there, many thanks. The testing of the coil looks complicated to me, so I’m waiting for my mate to pop over so I can take his coil off and substitute it with mine to see if that is at fault.

I did initially start the car with a boost from the battery charger…….so interesting to see if that cooked the EI module in the distributor. 
The timing is spot on ………..I have checked dozens of times now as it’s got to a point where I keep doubting myself now LOL!!!

I think I’ll then proceed to replace spark plugs, ignition leads (copper-less core as recommended using with EI)……………then finally the module. I replaced the distributor because the original one had so much play in it………so that’s why I opted for the EI. As I mentioned before I had it all set up beautifully and did a 1200 mile round trip faultlessly, left it a few months and then the problems began!

If the problem still persists after replacing all electrical bits above, I’ll move onto to possible air leaks as suggested above……………classic cars- don’t you just love them 

 

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