71 Fast Back Recommissioning

[JackReddick]

Right, bit of an update -

She now idles nicely and revs freely. Probably needs the carbs setting up 100% but i’ll get a friend to come check them.

Decided i’s try and take her for a little spin, once in gear there is zero power, nor will the revs pick up. Had to stay in first gear to move it. I’m guessing the clutch is probably stuck/sticking? It slips/jolts a bit trying to lift off, then you can basically on drive it on tick over

[broady_6]

What is the timing now set too? In my experience its better to time to the distributors map rather than the engine code. So if you've got a light, id go with hose off and pluged at 7.5BTDC dynamically, idle is 800-900rpm roughly. Then try reving the engine to 3000rpm with the hose on. You should get some where around 30 degrees advance. after 3000rpm it shouldn't advance any more than this.

The penny has just dropped and ive had problems with two engines using this aftermarket vacumm 009. both of which were then thrown at a wall and a real distributor was fitted.

When I followed the advance of these after market ones as the revs increased, it would jump all over the place, advancing and retarding randomly over the rev range. Cheap Chinese crap.

[937carrera]

I doubt if it's the clutch slipping. Easy way to check put it in 4th, give it some revs and then let the clutch out slowly. If it stalls, clutch is OK, if not then it's knackered.

What you are describing is symptomatic of either:

Brakes jammed on - can you push the car by hand
Lack of fuel - you need very little fuel for idle, and blips of the throttle can come from the fuel in the bowls

So, back to previous advice. Take the pipe off the tank and make sure it still flows well. Then block off the tank and make sure the filter to tank pipe is clear by blowing through it. Both ways.

[JackReddick]

What is the timing now set too? In my experience its better to time to the distributors map rather than the engine code. So if you've got a light, id go with hose off and pluged at 7.5BTDC dynamically, idle is 800-900rpm roughly. Then try reving the engine to 3000rpm with the hose on. You should get some where around 30 degrees advance. after 3000rpm it shouldn't advance any more than this.

The penny has just dropped and ive had problems with two engines using this aftermarket vacumm 009. both of which were then thrown at a wall and a real distributor was fitted.

When I followed the advance of these after market ones as the revs increased, it would jump all over the place, advancing and retarding randomly over the rev range. Cheap Chinese crap.

So i’ve just checked the timing with the light, i’ve been trying to set it to 7.5 (far left mark of the three grouped ones right?) well - i’ve noticed it keeps fluctuating between the three of them, not sure if this is to be expected?

With the hose back on and given a rev, it revs to what i assume is the 30ish amount, then drops back to bouncing between the three marks when the accelerator is let off

[broady_6]

Sounds like we are looking for a series of small faults then. Poor fueling and sporadic timing. Im just about to pop my carb off and see why is under fueling. But my engine was sounds very similar to yours in the video. But not as aggressive. but as soon as you applied some throttle it would "chug" like yours

[937carrera]

Oh gawd, is it a 009 dizzy. Looks pretty works s4!te. I didn't look before and having looked now I am none the wiser.

Virtually "any" normal engine needs to see 28-32 degrees of advance at full advance, when my cars are on the rolling road the vac pipes are always left on, no need to take them off, and indeed that linked article makes clear there's no vac advance on full throttle so it won't make a difference either way.

If you are seeing 30ish on full advance then the timing is set fine, at least as a starting point.

The bouncing about on idle is because the idle isn't smooth, varying engine speeds produce different vacuum so different timing.

Leave the ignition alone now (unless you can put an old proper dizzy on) and go back to the fuel side

(4 minutes late again)

[937carrera]

... but thinking about it more, shouldn't you be seeing the timing bounce around on TDC if the vac pipes are back on.

I would try moving the timing again when the engine is running

( I must be having a good day, diagnosing your running problem Broady before you even asked the question and solving an auto gearbox starter problem over on the T25 forum when I know nothing about them. Now about to start some car shuffling of my own)

[JackReddick]

Oh gawd, is it a 009 dizzy. Looks pretty works s4!te. I didn't look before and having looked now I am none the wiser.

Virtually "any" normal engine needs to see 28-32 degrees of advance at full advance, when my cars are on the rolling road the vac pipes are always left on, no need to take them off, and indeed that linked article makes clear there's no vac advance on full throttle so it won't make a difference either way.

If you are seeing 30ish on full advance then the timing is set fine, at least as a starting point.

The bouncing about on idle is because the idle isn't smooth, varying engine speeds produce different vacuum so different timing.

Leave the ignition alone now (unless you can put an old proper dizzy on) and go back to the fuel side

(4 minutes late again)

I’m having second thoughts about my fuel system now they’ve run a hard copper pipe through the floor pan alongside the tunnel inside the cabin, is this correct?
Starting to doubt everything they’ve done previously now...

[937carrera]

I don't know about the type 3 but the type 4 has a steel pipe that runs in the tunnel. Mine rusted and leaked so I cut it out and replaced with copper, there's a thread on that somewhere.

I would not be happy with a fuel pipe in the passenger compartment, it's banned in motorsport for obvious reasons, but you'll need someone else to confirm where it should be running.

What diameter is the pipe, if it's about 8mm OD then that should be wide enough to let the fuel flow, which is your probable problem at the moment.

[broady_6]

Thats the brake pipe nor the fuel. The fuel line run through the tunnel.

I would ignore everything done by the previous owner. You have no idea what they really did, nor to what standard. It only waste your time trusting them. Always go from basics and assure your self that you have seen the thing do what its supposed to do.

My issue seems to be a knackered accelerator pump. No obviously holes in the diaphragm. But its not giving me a squirt when I open the throttle. Is yours still giving a good jet of fuel? Could be that they have given up after standing for years then suddenly being forced to move.

Im certain the problem is with you carb now as one side runs well and the other doesnt

[937carrera]

Im certain the problem is with you carb now as one side runs well and the other doesnt

I thought that, but he had no power at all when he drove it

[broady_6]

Im certain the problem is with you carb now as one side runs well and the other doesnt

I thought that, but he had no power at all when he drove it

Lots of changes at once, id have that carb off, confirm is operation and then do a fundamental set up of the whole engine

[JackReddick]

More progress chaps-

After all your helpful comments, i went and checked the fuel lines from the tank. There was a slight kink in the hose from the tank so i’ve rectified that. I also took out the right side carb and gave that a clean.
I then took it for another test spin - this time there was power in first, then i found in second if i pumped the pedal down, let off, then pumped again each time i’s get a surge of power.

I think next step is to get a friend in to get the carbs setup and double check my timing etc, but it’s definitely progressing

On another note - the clutch is bloody awful and basically on or off and just lurches

[937carrera]

Another thing to check.

Tappets. I know you have done them. But.

There was another guy I helped on the T25 forum who was setting his tappets using the wrong timing mark. Maybe you didn't use TDC ??

When the engine is properly cold I would go through them again, making sure they are all set at 6 thou / .15mm.

Start with number 1, make sure the engine is at TDC and then go round in firing order 1-4-3-2, using TDC every time. It's a longer way of doing it, but fewer mistakes made

One piece of advice I was given by a very good tech. If it was running OK, and now it isn't, then it's something you have done. Go away and recheck your work until you find what you messed up.

[JackReddick]

Another thing to check.

Tappets. I know you have done them. But.

There was another guy I helped on the T25 forum who was setting his tappets using the wrong timing mark. Maybe you didn't use TDC ??

When the engine is properly cold I would go through them again, making sure they are all set at 6 thou / .15mm.

Start with number 1, make sure the engine is at TDC and then go round in firing order 1-4-3-2, using TDC every time. It's a longer way of doing it, but fewer mistakes made

One piece of advice I was given by a very good tech. If it was running OK, and now it isn't, then it's something you have done. Go away and recheck your work until you find what you messed up.

Am i right that TDC is the seperate mark far left? That was what i was doing it off for balve clearances, i may well check them again.

My issue with it is when i bought it it only idled for a bit, so i don’t really have a “known good base” to start from as it hasn’t run 100% since before i bought it, and it had sat for 30 odd years so i’m expecting it to be a lot of ifs, buts and maybes.

As it stands now, this is the happiest it’s been since i bought it. It ticks over nicely, and keeps running, whereas before i even touched it it would just stall out after 30 seconds of idling so we’re definitely progressing.

[937carrera]

Am i right that TDC is the seperate mark far left? That was what i was doing it off for balve clearances, i may well check them again.

Yep, that's correct, but check again. I have a T25 with no power and I'm pretty convinced that it's a tappet / valve problem. Hydraulic so much more complicated. The engine is way down the list of priorities though.

When I recomissioned my 412 it had been stood for the best part of 20 years. Ran like a dog. The problem was balance pipes and carbs, but you've rebuilt your carbs so they "should" be OK

Have you / can you do a compression check ?

[broady_6]

Were they rebuilt with new gaskets ect? Or just stripped and cleaned?

[JackReddick]

Were they rebuilt with new gaskets ect? Or just stripped and cleaned?

New gaskets

[broady_6]

So you could be looking at something like this, especially with your car having stood for a lot of years. And I dont expect it was inhibited properly. Fuel is corrosive to the carb castings. I have removed this from my car.



Now I knew this was there, but I didnt know (I still havent been able to understand why) this corrosion was detrimental to the pumps operation. Both ports are clear and the ball valve is moving freely. Ive ultrasonically cleaned another body with a much better looking pump.



I then swapped all the parts over from one to the other, so I am using the same jets, same diaphragm, top, float ect. I want to change as few parts as possible to isolate the issue. So its essentially the same carb apart from the lower half of the casting its self.

I primed it with petrol and the pump operated perfectly a dozen times on the bench.

Back on the car and it runs much better. Still not at 100% but a little bit of set up work should sort it out. The engine even sounds smoother and is happy to bimble along at 60mph.

You could be facing a similar issue?

[937carrera]

I decided to scratch my head a bit on the accelerator pump problem, so first of all I needed to understand how they work.

Have you seen this, handy pdf for Solex carbs

http://oacdp.org/solex.html#q25

I'm still scratching my head as to why a roughened surface would cause a difference in the quantity of fuel (or atomisation) pushed through the injector tube. Could the control rod length have changed through the reassembly process.

I don't think old leaded fuel attacks the carbs, that's what they were designed for, but ethanol within fuel can attack non anodised aluminium

[broady_6]

No wishing to hijack this mans thread. Ill get this posted in my own thread soon. But the rod length hasn't changed. I tried pinning it at different lengths before i dismantled the original carb and it made no difference.

The link looks interesting. Ill have a proper read this week.

[sparkywig]

I decided to scratch my head a bit on the accelerator pump problem, so first of all I needed to understand how they work.

Have you seen this, handy pdf for Solex carbs

http://oacdp.org/solex.html#q25

I'm still scratching my head as to why a roughened surface would cause a difference in the quantity of fuel (or atomisation) pushed through the injector tube. Could the control rod length have changed through the reassembly process.

I don't think old leaded fuel attacks the carbs, that's what they were designed for, but ethanol within fuel can attack non anodised aluminium

Ethanol in fuel absorbs water and therefore will cause running issues if not regularly replaced, and will also corrode any ferrous metals in contact.

[broady_6]

Every days a school day. I didnt know ethanol is hydroscopic. Does that also apply to bio-ethanol?

[sparkywig]

Yes, bio-ethanol is worse apparently.
When I take the bus to Europe it runs awful, pops and bangs due to the higher ethanol content in Euro fuel.

[937carrera]

OK, so I need to step in: (sorry to the OP for going off topic)

Ethanol is hygroscopic, once the solution limit is reached the water separates out
There is no difference between ethanol and bio-ethanol, they are the same C2H5OH hydrocarbon, if you like vodka it's 200% proof alcohol, the bio bit is there if the feedstock is organic
Ethanol can attack aluminium in engines, and seals made from incompatible materials
Blend rates for ethanol are governed by EU directive, E10 is coming to the UK, already in Germany, France Belgium and Netherlands
Up to E10 ish the oxygenate within the ethanol results in a higher octane value and a "cleaner burn" reducing emissions without reducing power even though the energy content of ethanol is lower than gasoline. At higher blend rates the lower energy density of ethanol results in increased fuel consumption
Tesco Momentum is one fuel that has higher octane because of the ethanol content

Your bus shouldn't be popping & banging etc due to E10 compared to the E5 in the UK, but you will be better off (well the vehicle will be) buying a branded fuel rather than supermarket fuel due to the better additive packages.