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Author: Subject: Continuing SC Zetec saga
ChrisL

posted on 20/6/20 at 09:17 AM Reply With Quote
Continuing SC Zetec saga

So where are we, we'll I switched to a smaller pulley and seem to be make 8-9 psi which is better than 12!
My current issue are:
1. The engine seems to bind when hot, only if I stop and re-start, it's like the battery is a bit flat. Not sure if this is just normally running in or indicates a problem?

2. Little bit of smoke from the breather, this could be because I'm running 10w40 running in oil or it's fooked

3. It sounds like a bag 'o' nails under load, I'm thinking either fooked or timing?


Smoke:

bag 'o' nails (TM)

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number-1

posted on 20/6/20 at 11:03 AM Reply With Quote
What size injectors are you running? Mine had 440cc fitted

It sounds like its missing under load in the 2nd video. Are the plugs the ones that came with the engine? Pop a HT lead off and check there is no water between the plugs.

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perksy

posted on 20/6/20 at 11:41 AM Reply With Quote
Definitely sounds like its missing under load

Tried new plugs?

Has a compression test been carried out and what ECU are you using?

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ChrisL

posted on 20/6/20 at 12:13 PM Reply With Quote
I rebuilt the engine so it is still running in. Plugs could do with renewing as Iíve had them a few years. No compression test yet and itís running on a Microsquirt ecu which Iím trying to tune
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big_wasa

posted on 20/6/20 at 04:39 PM Reply With Quote
Zetec's are notorious for being hard to start when hot on the old Sierra starter motors.

The oem zetec starter is a gear deduction starter unlike the old sierra one.

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ChrisL

posted on 21/6/20 at 10:27 AM Reply With Quote
Looks like I'll be getting my spanners out again, compression test results on a warm engine with WOT (in PSI):

1: 10
2: 100
3: 25
4: 100

So it's a 2 cylinder ATM, which explains why it sounds like it's misfiring!
I need to work out if it's the head or the pistons. I replaced all of the piston rings (checked they were correctly aligned at 120 degrees t each other) and the exhaust valves.
I think I'm going to take the head off, align all the pistons to the same height pour 50 ccs of oil in the and check every hour or so, unless anyone's got any better ideas, probably do the same test on the head....

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perksy

posted on 21/6/20 at 11:43 AM Reply With Quote
Those are all low, so something is well amiss sadly

Leakdown test in the way forward but have You tried pouring some oil in the bores and then re-testing the compressions?

[Edited on 21/6/20 by perksy]

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ChrisL

posted on 21/6/20 at 01:14 PM Reply With Quote
Wet test results, 10cc oil in the bores:

1. 10
2. 125
3. 50
4. 190

So my thinking, given the limited mileage (about 50 miles under load) I think the rings are still to properly bed in and no. 4 is probably ok. No. 2 has a slight leak on the head, and nos. 1 and 3 aren't really trying, so I'm going to get some new inlet valves whip the head off regrind the inlets and check for sealing and see where I am at that point.

Sound like a plan?

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rusty nuts

posted on 21/6/20 at 02:08 PM Reply With Quote
Did you check and adjust the valve clearances when the engine was rebuilt? Tight valve clearances will cause your problems. I would check before stripping the engine
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ChrisL

posted on 22/6/20 at 08:15 AM Reply With Quote
Good call, yes checked the clearances, no. 1 was tight. I've been advised to run the compression test with the cams off, so thwart will tell me if it lifter/cam related
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rusty nuts

posted on 22/6/20 at 10:49 AM Reply With Quote
Carrying out a compression test with the cams removed will not achieve anything, if the inlet valve is closed how is it going to allow air in to be compressed? A cylinder leakage test on the other hand will work as the air is supplied via the spark hole
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ChrisL

posted on 4/7/20 at 02:57 PM Reply With Quote
So the results with the cams off:
1. 100
2. 95
3. 25
4. 95

All cam off tests were run with the cylinder starting in bottom dead centre, as the inlet valves wouldn't be opening so I needed to start with a known amount of air to pressurise. I ran no. 3 twice to make sure it wasn't an error.

I think what this is telling me is no.1 the shims are too big preventing the valves from closing properly. No.3 is the pain as I don't know if this is a valve seating issue or piston rings not sealing.

I've decided to send the head off to re cut the valves seats...

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rusty nuts

posted on 4/7/20 at 06:17 PM Reply With Quote
Like I said in my last post a cylinder leakage test is what you need
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obfripper

posted on 4/7/20 at 06:47 PM Reply With Quote
When i rebuilt my blacktop (had done 80k in donor car + 20k in my car), the valve guides on all the exhaust valves were worn beyond spec, i had them replaced while the head was being ported.

I didn't have any sealing issues at the time, but have repaired quite a few vw engines where the seat wears oval due to valve guide wear allowing the valve to wobble as it closes, you may have the same issue.

Dave

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ChrisL

posted on 5/7/20 at 12:35 PM Reply With Quote
I'd thought I'd get away with not getting them cut, to be fair on 3 of them I would have but for how long?
I don't have access to an air line so trying to run a leak down test is a non starter, although if I'm still down on pressure on no.3 then I might have to...

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ChrisL

posted on 28/7/20 at 01:18 PM Reply With Quote
Status update:

Had the valves re-cut and replaced the inlet valves, so now all new valves, lapped the valves and shined to spec. N0.3 Still 25 PSI. Took the piston out and no.3 has collapsed. So what's going wrong? I should be down around 9 PSI and I've not seen a consistant max boost higher than 9, timing should be conservative enough, see below? I'm now thinking forged pistons and I think rods too as I'm not sure you can split them on blacktops?


Description
Description

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big_wasa

posted on 28/7/20 at 02:30 PM Reply With Quote
A Fully forged Zetec is a lot of pennies for just 9psi.
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