18 replies to this topic

[Danyul1275]

Afternoon peoples,

 

So currently I'm having a problem where under load going up hill I'm losing power and having to chug up hills.

I've owned the car for about 3 months and prior to getting it hadn't been on the road for 5 years so details about the engine are a bit of a mystery.

What I know about the engine is that it is running a HS4 carb which has been rebuilt and pancake filter fitted, water heated manifold, lcb big bore exhaust, powerspark electronic ignition, sports coil, fresh leads and fresh plugs.

I've set the timing with a timing light but had to advance it more than the recommended 4 degrees in the haynes manual as it was running very flat, also the carb mixture has been set with a colortune kit.

 

On the flat and slight inclines the power feels perfect but on steep hills I'm losing power in both 4th and 3rd to the point where I am having to nurse it up in 2nd.

 

Any suggestions on what could be causing it?

 

Thanks in advance

[Wim Fournier]

Symptoms of a weak mixture. Reading your story, you did everything to get good behaviour. So, ther eis something else wrong. First comes to mind that there could be an air leak in the intake track. As soon as you floor the throttle full vacuum from the down going pistons is in the intake manual. When the connection between the intake manifold and the engine head is not tight, there is false air sucked in -without fuel-. Or between the carburettor and the intake manifold false air is sucked in.

Do you have oil in the damper neck so that the piston in the damper bowl is rising with restrain?

Maybe you do good by feeling with your finger in the carburettor mouth if the piston is going up and down with no more restain than from the oil in the damper.

An other point is; is the vacuum bellows on the ignition tower tight (not leaking). Take the vacuum line off, put in your mouth and suck. You should see that the ignition is turning to 'early' beneeth the distributor cap. 

 

Tell us what you find out, please.

[carbon]

I had very similar problems with 998 unit in a clubman estate. Would get half way up a long hill then die...

 

Turned out the previous owner had replaced fuel filler with non-vented type. A 3mm hole fixed it, and it went great after that.

[gazza01]

I'd get the timing up to 10 degrees with the pipe taken off the advance and blocked up while settting it . Get rid of the pancake too, they are dreadful for airflow compared to a cone. Maybe Stick a cone filter on. Then with more air going in from the cone you can up the fuel to match. HS4's can have a problem with the wax stat cutting down the fuel once the engine warms up. You can take the wax stat out and replace it with a 1 pence piece. Or better still stick a hif 38 on instead. Make sure you inspect the plugs for colour and gap size too. Colortune could be the problem as the perfect blue flame only indicates the state of tune at tick over. Much above that and the clortune just isn't accurate enough to be a good way to tune for the progression of actually driving under load. Many people find they work better if you go past the blue flame and just start going into the yellow, it's only for ballpark tuning as far as I'm concerned.

Wind the nut out on the carb with it running and if you hear the revs pick up and the engine sounds happier, stop there. If it drives better check the plugs after it's been driving for a good while and check the plug colour, to indicate where your at mixture wise. Good luck.

As you will know though, there is nothing like having the car rolling road tuned. But take that wax stat out and also fit a cone filter too before spending on the RR

[Danyul1275]

Cheers Gazza, the carb is pre waxstat so don't think that's the problem, think I'll refit my cone filter tomorrow and have another go at setting the mixture, I ended up with the advance at 10 degrees to stop it feeling flat, I'll see how that goes tomorrow.
Replaced the oil in the dash pot this morning and I can't find any air leaks

[Ethel]

Could be ignition, fuel or even engine wear.

 

Compression test for the latter.

 

Check ignition advance against specs up through the rev range.

 

Use the choke to investigate the fuel mix, but it won't help air leaks or a blocked filter.

[gazza82]

Weak fuel pump?

[Danyul1275]

Could be ignition, fuel or even engine wear.
 
Compression test for the latter.
 
Check ignition advance against specs up through the rev range.
 
Use the choke to investigate the fuel mix, but it won't help air leaks or a blocked filter.

Thanks Ethel, what sort of psi should I be looking for to be healthy?

[Danyul1275]

Good news guys!
Changed the air filter back to a cone filter and set the mixture again and it would appear it is cured!!
Took it up the same hill again this morning and showed it who was boss! Pulled brilliantly with not a splutter in sight.
Just need to turn my tick over down slightly and she should be right as rain

Thanks for the help, it's good to know you guys are here to help

Edited by Danyul1275, 25 September 2016 - 10:40 AM.

[tiger99]

Is this a City E or HLE with the 2.95 final drive ratio? If so, the performance may be almost normal, just slightly off tune. The 2.95 helps immensely with high speed cruising and fuel economy but is not that great at climbing hills. If modding one of these I would be looking for a cam, head etc that would improve low down torque, not the high end, which is fine as it is.

[Ethel]

So as not to leave bits of the topic hanging...

 

There is no fixed "good" figure for a compression test, apart from the engine, the starter and battery will also effect results. The main thing is that all cylinders give a similar reading, a spoonful of oil through the p[lug hole can show up worn rings if it improves readings. I'd hope to see more than 100psi from a serviceable engine though.

[Danyul1275]

Tiger I'm unsure as the log book just states it's a city so the final drive is unknown to me.

Thanks for the info Ethel, I'll keep that in mind if I get anymore problems. I've had it for a good drive today and all seems well again, will hopefully last me till the winter when I'll have time to fit the 1275 I've got for it

[tiger99]

You should check your final drive ratio anyway, because you need to know it for ordering certain spares, and because it affects the performance when making comparisons as in this thread. You can find out without any major dismantling.

 

Jack up one front wheel and support the car securely. Put it in top gear, engine off. Spark plugs out will make it a lot easier. Make a mark on the crankshaft pulley, the timing mark will do if a bit of white paint is added to make it clearer. Wind the engine clockwise, its usual direction of rotation, till the mark lines up with the pointer. Now make a mark on the wheel that lines up with some feature on the bodywork.

 

Turn the engine by the fan belt or ratchet on the pulley nut, until the wheel has made exactly 1 complete turn. Multiply the number of turns of the engine by 2 to allow for the action of the diff, and the answer is your final drive ratio. For better accuracy, use 10 turns of the wheel and multiply the engine turns by 5.

[Dusky]

Why would you ever need to know the final drive to order spares?
 

[tiger99]

Speedo drive gears for instance. These do fail and need replacing. And there are various combinations of bits.  Also if you need a new final drive gear and pinion.

 

But mostly, as I suggested, so that you can see if the performance you are getting is reasonable.