Spitfire 1500 runs like a bag of nails until it's warm

[Will Orum]

Hi all,

I'm at a loss for what to do to fix my car. I've had a series of issues with my electronic ignition, resulting in me going back to points, once back on points, the car ran great.. For a bit. Ever since then (Just over a month ago) I've had issues. The first issue presented itself as a sudden loss of power when accelerating, after checking over the ignition, swapping the coil, and checking the carb balance and tune, I realised it was a vacuum leak. I sprayed WD40 around the manifold while the engine was running (Bit silly, I know, but I didn't burst into flames!), the engine didn't seem to change after spraying, at least not at idle. When I started driving, it was obvious it had fixed it temporarily. I then tightened the manifold nuts. All was good, so I thought.

 

This leads me on to the second issue, which is really just an evolution of the first. The car ran fine for about 10 miles after tightening the manifold. Then, one morning I went to start it, and got the video attached. Some further investigation revealed that the car ran absolutely fine after it warmed up, but warming it up when its running that badly and stalling as much as it does isn't easy. This lead me to basically conduct all the tests I'd done before. Attached pictures show some of the findings. (I used a boroscope to take photos of the top of the pistons. The plugs look rich but these photos weren't taken after a plug chop so they're sootier than they should be).  I tried swapping to a new coil, testing spark plugs outside the engine, re-checking the mixture, all to no avail. The spark did look a bit orange and danced around the electrode a bit, but I was looking in broad daylight, and a brand new plug was firing similarly, though less orange and less dancing. My final deduction was that it was another vacuum leak, maybe I hadn't tightened the bottom nuts up enough as they're a pig to get to. I have taken the inlet and exhaust manifolds off, expecting to find an obvious sign of a leak but I found nothing. I don't have pictures at the moment but the gasket looks fine, at least on the inlet ports. After putting a rule across the inlet manifold and the head, I noticed a slight gap in the middle of the head and basically no gaps on the manifold. Without the pictures it's hard to diagnose, but the gasket and sealing faces showed no signs of leaking.

 

That leads me to where I am now. Scratching my head. Anyone able to shed some light on this situation?

 

Will

[Pete Lewis]

as a 1500 is it still on waxstat jets ????  a known nightmare

as you have been messing with the carbs have you disturbed the fuel hoses   as refitting will make rubber slivers 

these can block jam up the float needle valve .

there is an easy fix to waxstats  will use 2 x 2  1p pieces .

dont use plugs with an R in the suffix.

soot after choke will take a Loooong time to burn off the plugs .

what air filters do you have ., makes sure the filters gaskets are not obstructing the carb vents .

more to follow as you give us more clues 

Pete

 

[Will Orum]

Ditching the waxstat jets was one of the first things I did after buying the car! Definitely don't need the problems they can cause.

I haven't had any overflowing of the float chambers so I think I got away with that one. I did initially think the issue could be fuel related as I ran out of fuel not long before everything went wrong (Embarrassing, I know). I thought maybe a load of sediment had been sucked up, and this was supported by the engine working ok after running for a bit. I have somewhat ruled out fuel quality though, as the fuel filter is pretty clean, and the float chambers had minimal sediment in them (I hadn't cleaned them in nearly 3K miles), and the car was back to spluttering when I next tried to start it.

Im using the NGK N12Y plugs from James Paddock (gapped to 0.63mm), I'm fairly sure they're genuine but a point I didn't mention before was that I when I encountered the first issue, the supposed vacuum leak, I changed the plugs to a brand new set, which fixed the problem for maybe a dozen miles. Out of curiosity, whats the issue with the 'R' suffix plugs?

The cold start issue came about after reinstalling the air filters (Generic 1500 HS4 filters found on Paddock) I've mostly ignored that as being a factor, but I could well have installed one of the gaskets upside down. What kind of symptoms would blocking the carb vents give, could that explain the difference in piston surface, or am I chasing a red herring with fact that piston 4 looks different to the others?

[Stratton Jimmer]

I'm just wondering if you still have a manifold leak which manifests itself when the engine is cold but seals itself up once everything is hot and expanded. I have HS4 carbs on my GT6 and use cheap pancake filters without any problems. 

[Pete Lewis]

i dont think your running headache is anything to do with the base engine its all to do with ancillaries 

R is resistive theres a good few you tube examples testing the reduction in HT 

fine on a 35kv modern but not good in our lower 22kv HT 

so its been clear to me that missfires are caused by corking up the HT    some use them and have no problem 

so its stick to simples not go chasing red herrings 

blocking the intake vents can cause chaos

there are some awful dizzy condensers about  best get one from distributor doctor 

Reconditioned Lucas distributors, rebuilt Lucas distributors, recurved Lucas distributors from Distributor Doctor

does delco parts too   have a read about rotor and condensers 

Pete

[chrishawley]

Tricky one. All runs well when warm but cold runninng very problematic. Is that correct?

Can't say I have a firm idea as to cause but here's a couple of thoughts about possible investigations:

• Remove air filters with gaskets. Then start engine. Any difference?

• With air filters still removed scrutinise the cold-start linkages. All intact and not deformed hopefully. With choke cable being operated check that both jets are being pulled down equally and that the action on the butterflys is equal. Cold start/running requires much enrichment so for large movement of the jets the butterfly movement should be pretty minimal.

• Check carb pistons free moving and dash pots have adequate oil.

• Examine breather hose from rocker cover to carbs. Splits or cracks may not be easy to see but as a test the relevant ports can be blanked off just temporarily to see of that has any effect.

On HS8 carbs a ruse to investigate cold start/cold running problems is to wind down the jets by several flats to (what would be) a very over-rich condition for warm running. A 'postive' result to this test is then indicative of insufficient enrichment from the cold start mechanism. Not sure it's quite the same wit HS4s (e.g. Spitfire) but could be a possibility to try. But subject to starting off in a known good position for warm running.

• Then there's a lead-removal test. If the engine can be persuaded to cold idle at all then remove  plug leads in order,  just one off  at a time. If removal of a given lead does not worsen the running or cause stall then it points to a problem related to that cylinder of pair of cylinders.

I'd concur with Pete that this is more likely about ancillary factors rather than a major engine issue.

 

[alan.gilbert_6384]

Hi I had a very similar problem, I found the solution for me was thus.

 First check that the choke works in the following way, when fully in jets are fully up and that the idle speed is correct when warm.

 Second check that the first quarter travel of the choke only increases the idle speed.

 Third, clean the spark plugs thoroughly.  

Next is the permanent fix, when cold, fully open choke then turn over, as soon as she starts push it back in to the point where it only increases the idle speed.  

The starting procedure is what was fouling up my plugs I had the coke out far too long this lead to the fouling of the spark plugs which made it run rough and only went away when burt off, and as said on this post it take a long time to get them to run right.

[Pete Lewis]

agree the choke not returning the jet to its adjusting nut after use is a very common SU problem

some need a few mm cutting off the jet tube as these can make return sticky .

a quick prod with a finger after returning the choke will soon show if the jet has stuck in a enriched position 

Pete

[Will Orum]

Hi All,

So I spent most of the day working on the car (apologies for such a late response, I've only just got on my computer). I Reassembled everything, making sure to clean the mating surfaces, fixed an exhaust leak that came from the joint between the downpipe and the headers. All of this culminated in the car starting nearly instantly and initially showing no issues at all. I read some responses before starting, and followed Alans advice to push the choke in as soon as possible. The car sputtered a bit but nowhere near as badly as before. I've attached some videos of it running, bare in mind I only got the camera out when it was playing up, which didn't last much longer than each video. 

The car then warmed up and smoothed out, as expected. I went for a little drive and struggled to get out of the driveway. I got about 50m down the street before it started misfiring like crazy so I turned around, stalled a couple times, and eventually got back home. As the driveway is on a slope, I used it to test the car again, and it was better.  I deemed it drivable and figured the plugs may be fouled up so I gave it an italian tune up. Car felt absolutely perfect, no issues whatsoever after coming back out the drive.

I wonder if maybe I'm having the same issue Alan had, I'm yet to start the engine again but it seems that cleaning the spark plugs the italian way has helped. 

I think I also ought to point out that I'm 21 and I despite this being my first car, I have never dealt with classics before. Could it be that I'm just expecting too much from the car? Is it normal for the idle to waver on occasion, especially when it 1 celcius outside? My dad built himself a Dutton Phaeton S2 when he was 17, he seems to think I baby my car which might be part of my problem.

 

I will have to try to start the car after work tomorrow. Hopefully it stays fixed but thats unlikely.  I probably won't be able to do much until the weekend but I will check out everything mentioned here. I have had the jet return issue, I usually combat it by pushing the choke in fairly fast. Removing material from the jet sleeve seems like a pretty good permanant solution for that, though. I currently don't have any spare dizzy internals so I will take a look at dizzy doctor. 

 

I have had a pretty thorough look at the carbs, and despite a bit of surface rust on the linkages, all looks fine. 

 

The steam coming off the engine is a WD-40, spilled coolant, and solvent cleaner mix. It stopped after a couple minutes!

Edited January 14 by Will Orum

[Pete Lewis]

well spark plugs are the life and soul  but sooted can lead to plug failure 

here is a link to some thoughts on modern plugs dont suit carb /choke operation as well as they used to

once the ceramic is "contaminated" by poor fueling you seem its not cleanable lots of alternatives but 

the lack of glaze does seem to plague us , less choke /drive it quick is the best solution 

any back fires point to a dodgy condenser ( but if electronics are installed you wont have one) 

 

Edited January 15 by Pete Lewis

[alan.gilbert_6384]

Hi good to hear your having fun 🤩 this video is also worth a watch

 

[Will Orum]

That post you linked is really useful. I had a little look on their website and called them up. Bloke I spoke to was really helpful and gave me an even deeper insight. 

As for my car, I started it up, making sure to put the choke in asap and all was good, car drove like a dream!

It seems that the issue was more knowledge and skill based than mechanical. I can't rule out that the reseat of the manifolds didn't help, but I think I had the same issue as you, Alan. That video you linked is also really helpful. Simple stuff but not necessarily something you'd think about. I'll definitely watch it again before I next start the car!

Can't say it's a definite fix yet as I don't really want to be driving on the gritty roads but thank you everbody for your input. It's been tremendously helpful, and even if it wasn't the issue, I now know more what to look for in these head scratcher situations!

 

Will

[Wagger]

Wait until the weather wams up and the grit and salt is gone. I have one plug that keeps fouling on my six pot and am trying to find original glazed plugs. I can echo the responses that you have had like do not use resistive plugs.

Unlike modern cars, ours do run smoothly until warmed up. No clever engine management systems. Modern fuel is not the same as it was when they were new either.

It is all part of the 'Fun''

You are brave to take this on so young. You will learn a great deal from it.

[Pete Lewis]

Will,  chasing your tail is all part of the "fun" 

classics can and do run really well ,as good as when they  were new  but getting there can be a 

long slow route of unravelling previous concoctions  of poor meddling .

it can take a season to get to know your car and its traits 

you will get straight answers on this forum , never follow daft ideas from the pub of FB 

unless you want to chase myths !!!

have fun   it will all come together 

Pete

[DanMi]

Don't forget that our cars are at least 45 years old with technology far older. A modern car is adjusting the timing and fuel mixture many times every second, so will idle far more consistently than our cars did the day they left the showroom. They can be set up to run well but it takes time a modern does it for you.