Engine tune-up? Where to start? So many questions... (long)

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JimK
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Engine tune-up? Where to start? So many questions... (long)

Postby JimK » Tue Aug 22, 2006 10:43 am

I took the Fiesta to work yesterday, and even though it's only claimed to have about 10bhp more than the Trav it was much, much faster. The Festa is 80kg heavier, too. This makes me think that the Trav's engine is not performing as well as it might.

I'm also wondering about a couple of little puffs of grey smoke from the exhaust I saw at the weekend. Happened when pulling away after idling, is that normal?

It pulls without stuttering, just not that hard. There's also a sort of boominess that develops around 60mph. How many revs at that speed, assuming a standard gearbox and diff? (I might have to get a rev counter - I've always thought of engine revs as an essential piece of information for the driver.)

Oil level is fine, and oil is clean.

I haven't worked out a full-tank mpg figure yet, but 120 miles at the weekend have eaten in the region of half a tank. That sound OK to me.

I think I need an experienced Minor owner to run it and see if it's doing normal stuff. Any volunteers? A few quid and a pub lunch for anybody willing to give me an afternoon's introduction to spannering a Minor?

There are so many variables involved that I haven't a chance of learning how they affect eachother any time soon, and it would be good to pick up a bag of tricks for dealing with any of the common scenarios. Until I've got that knowledge I'm going to be reluctant to do long trips to rallies and suchlike.
Jim - New Forest, the Wiltshire bit

Kevin
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Postby Kevin » Tue Aug 22, 2006 12:04 pm

John I didnt know that a Fiesta was heavier than a Traveller and 10bhp can make a difference when you only have 45 to start with.
I think I need an experienced Minor owner to run it and see if it's doing normal stuff. Any volunteers? A few quid and a pub lunch for anybody willing to give me an afternoon's introduction to spannering a Minor?
John I think the solution could be right under your nose for there is a well meaning helpful group very near to you that seem to meet almost weekly and are around 20 miles away :D

http://www.morrisminoroc.co.uk/index.ph ... &start=180
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Kevin
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JimK
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Postby JimK » Tue Aug 22, 2006 12:11 pm

Kelvin, my 1996 Mk4 Fiesta weighs about 930kg and has a claimed 73bhp from the 1242cc 16v, and the Trav is about 860kg and I thought 60-something horses from the 1275 Spridget engine.

I was planning to ask the SADMOGs on thursday...

Incidentally, why would I have stopped getting reply notifications? Do they time-out a while after your last post to that thread?
Jim - New Forest, the Wiltshire bit

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Postby Kevin » Tue Aug 22, 2006 12:51 pm

Jim many small things can take the edge of performance, plugs, timing, valve clearances, carb setup if these are out it will affect performance, one thing when I ran a Midget engine it always ran far better on NGK plugs than on Champions.
Yes the board does time out if you havent clicked the `remember me box`
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bmcecosse
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Postby bmcecosse » Tue Aug 22, 2006 1:24 pm

I suggest air filter is your first check - is it blocked/coated in oil that sort of thing. Take it off and take the car for a run - does it go any better? Then it's always worth getting a compression check done on the engine - to see the general condition. You should be looking for ~ 170 psi on all 4 bores with this test. Next up - ignition timing - and test if the vacuum advance unit is working. I set mine by advancing it until I hear some pinking under load - then back off again slightly. To check vacuum unit - you need to suck the little pipe while watching to see the base plate just under the top plate of the dizzy - it should move slightly. Obviously if when you suck there is no vacuum - you have a double whammy - no vacuum advance and air getting into the engine - because the vacuum diaphragm is bust!! After sorting all that lot - mixture setting - have a look at the plugs after a good hard run - if white then weak, black is rich, light brownish beige is just right! Your 1275 will only have about 60 bhp if it has the bigger carb and manifold fitted - if it has the smaller carb - or worse still the original Minor carb - fitted, then it will be seriously strangled.
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Postby chickenjohn » Tue Aug 22, 2006 1:38 pm

A good place to start would be a service kit and a manual telling you how to carry out the service. I just did a service on my Traveller and am pleased with the smoother running- I think the timing had drifted out a little. Either that or collar one of the Sadmog crowd and get them to have a look. Points gap is a good one to check.
Cheers John - all comments IMHO
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Postby dunketh » Tue Aug 22, 2006 1:54 pm

Kelvin, my 1996 Mk4 Fiesta weighs about 930kg and has a claimed 73bhp from the 1242cc 16v, and the Trav is about 860kg and I thought 60-something horses from the 1275 Spridget engine.
The Ford 1.25 ZS (73bhp) engine is excellent. The 0-60 time is quoted at around 11 seconds. Thats a second off the figures quoted on a 1600cc XR2 (90bhp).
Its just that technology is so much better.

However, I found my 4-door (1275 engine, std 1098 carb) felt gruntier to drive than my old mk4 Fiesta. In traffic it was much nicer. The fiesta needs to be rev'd hard to release its power, the 1275 A series doesn't.
What would Macgyver do..?
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Postby JimK » Tue Aug 22, 2006 2:07 pm

BMC: Thanks for those tips. Let's see:

The air filter is 300 miles old and pristine.
The airbox is the standard Minor, so is there a good chance that the carb is too? Here's the only photo I have to hand:
http://www.flickr.com/photos/25441688@N00/221963165/
I checked the points gap recently, as the car was running very badly. Set it to 17thou as it had closed up a bit.

chickenjohn: I certainly intend to collar most or all of the SADMOGs about it - they know more about these cars than is strictly healthy...
The service kits have the wrong oil filter, but I can get the other bits, you're right. I need to get the Haynes book and lean over the car while reading it.

dunketh: The Zetec engine is indeed very good, I quite like its revvy nature. I find it perfectly OK in traffic, mostly because I'm almost always above 2k revs, where I can react quickly. Above 3.5k it really takes off...
On a twisty road it's a blast.
Jim - New Forest, the Wiltshire bit

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Postby chickenjohn » Tue Aug 22, 2006 2:53 pm

without comparing directly to my car- that does look like a standard carb. Just a thought- have you topped up the oil in the dashpot recently? One thing that has cause my car some lack of power in the past is leaking manifold gasket and or breather system causing it to run too lean all the time.
cheers
John
Other than that, I don;t know much about modified cars set ups.

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Postby JimK » Tue Aug 22, 2006 2:58 pm

chickenjohn wrote:Just a thought- have you topped up the oil in the dashpot recently?
No, I haven't. Any thin oil do? My dad said he used to use 3-in1, and I've got some 5W suspension fork oil somewhere.

Too lean might be right - I moved the airbox cover to let some fresher air in and it stuttered a little. What does the dashpot and its oil actually do?
Jim - New Forest, the Wiltshire bit

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Postby Packedup » Tue Aug 22, 2006 3:10 pm

It's an HS4 by teh looks of things - So not standard Minor! Probably about right for the engine really, though will struggle a bit at the top end.

I've tried various oils in the dashpot, from ATF to 20/50 - And I find anything thinner than 10/40 causes the piston to rise too quickly and results in it leaning out. Certainly not had any joy with 3 in one when I've tried it!

I wonder if you've got the right spring and needle for the engine? The carb spring limits the speed and lift of the piston, and the needle meters the correct amount of fuel. If the carb isn't originally off that engine then it might not be set up quite right.

But points (gap and condition), plugs (ditto), leads, cap, arm and mixture would be worth double checking before going any further IMO.
[url=http://www.rottingheaps.me.uk/index.php]Ooh, it's all gone purple. But otherwise all that changes is the date...[/url]
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Postby Kevin » Tue Aug 22, 2006 3:14 pm

It damps the piston action, you can buy the correct oil but most people find 3 in 1, sewing machine oil or even engine oil is OK and you only need to top it up to the shoulder inside not the top.
It does look like a standard carb if you take the air filter of can you measure the carb throat opening this will tell you its size 1 1/4" standard or possibly 1 1/2" as the manifold doesnt look standard and may be a mini one with the larger carb but still enables the standard exhaust to be retained.
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chickenjohn
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Postby chickenjohn » Tue Aug 22, 2006 3:22 pm

The oil in the dashpot acts together with the plunger as a damper, it stops the piston in the carb opening too quickly when the throttle is opened. I have used 3 in 1 and sometimes engine oil-

You really need to take systematic approach to solving the running problem. Make sure you have a good spark (ignition), and its at the right time (timing) then look at the fuelling (mixture etc).

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Postby Packedup » Tue Aug 22, 2006 3:23 pm

HS2 carbs have vertically opposed mountings, HS4 have diagonal - That one in the pic is most definately the latter!

Also the servo take off on the manifold says it's not Minor, and the shape follows into the carb body properly, so I'd say it's an HS4. It's not an HS6 as as far as I know they have 4 mounting holes, as do HIF carbs.

If that's a Minor filter box then it's been adapted. Which looks likely due to the plate between it and the carb, and the breather pipe inlet almost fouling the dashpot (which certainly looks way too wide to be HS2).
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Postby JimK » Tue Aug 22, 2006 3:23 pm

Seems like it's an HS4 then. Will it say that somewhere on it?

I have loads of 10/40 oil around - will heavier oil slow down the throttle response? Or will it just be rich for a bit longer while the piston reacts?

So I have some things to try:
I'll see if I can work out the timing
check the plugs
distributor condition

<MrBurns>Eeeexcellent</MrBurns>
Last edited by JimK on Tue Aug 22, 2006 3:28 pm, edited 1 time in total.
Jim - New Forest, the Wiltshire bit

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Postby Kevin » Tue Aug 22, 2006 3:24 pm

A 1275cc Midget manual wont go amis as thats the engine you have fitted.
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Axolotl
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Postby Axolotl » Tue Aug 22, 2006 3:28 pm

The fuel / air mixture in the inlet manifold is contolled by a tapered needle attached to a piston inside the round silver cylinder on top of the carburettor. The needle sits in a hole that supplies fuel into the airstream flowing through the carburettor past the throttle butterfly valve into the inlet manifold.

The further up the cylinder the piston moves, the further out the hole the needle comes and the more fuel can get out past the needle. Also, more air can get into the inlet manifold, depending on the position of the throttle butterfly valve.

The position of the piston in the cylinder is controlled by engine inlet manifold vacuum through the throttle on one side (tending to raise it), and a spring on the other (tending to close it). The dashpot is there to damp the movement of the main piston in the carburettor cylinder.

It is a hollow tube in the top of the main piston, filled with oil, and a smaller fixed piston (on the end of the rod that the black plastic cap is attached to) sits in it and is a close fit so that the oil is forced past the dashpot piston when the main carburettor piston rises or falls. That irons out any rapid fluctuations up or down, and smoothes out any change in the fuel / air mixture.

No oil there wouldn't result in lack of power necessarily, just lumpy or jerky performance as you accelerate or decelerate. It is possible that no oil over a long period could cause the main piston to sieze on the dashpot piston, or bind before it gets to the top of its travel. That would then reduce performance, but things would have to be pretty bad to get to that stage.

Fork oil should be o.k. The book suggests a 20W general lubricating oil, same as for the shock absorbers. Don't use a multigrade engine oil, as that is too thick and will give sluggish acceleration. 3 in 1 will do at a pinch, but is probably a bit too thin.

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Postby Axolotl » Tue Aug 22, 2006 3:31 pm

I'm going to have to learn to type faster. :-?

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Postby JimK » Tue Aug 22, 2006 3:35 pm

<snip useful Carb 101>
Axolotl wrote:Fork oil should be o.k. The book suggests a 20W general lubricating oil, same as for the shock absorbers. Don't use a multigrade engine oil, as that is too thick and will give sluggish acceleration. 3 in 1 will do at a pinch, but is probably a bit too thin.
My fork oil is 5W - it's very light, and from what you say it's too light. (It's for my mountain bike :-))

And you're not the only one who needs to type faster...

Since it's starting to look like the engine, gearbox and all the ancillaries came as a lump, I might well get the Midget manual. I didn't want to get the manual at first in case it turned out that it was a bitsa and I needed about 5 books :-)
Jim - New Forest, the Wiltshire bit

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Postby Axolotl » Tue Aug 22, 2006 3:43 pm

They didn't have mountain bikes when I was alive. (And bikes certainly didn't have suspension). I was think more of big motor bike fork oil. Sorry.


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