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Author Topic: Valve to piston clearance  (Read 898 times)
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andyps
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« on: 14 July, 2021, 08:35:46 PM »

How much clearance is there between the valves and pistons? I'm asking because I've just replaced my head gasket and had 20 thou skimmed off the head. I lapped in the valves and having reassembled everything cranked the engine over a couple of times by hand and checked the compressions, all of which were OK and similar. I've not managed to get the engine started so this evening checked the compression again and other than cylinder 4 they are all low. I'm worried that valves may have met pistons but don't know if this is possible.

I'm planning to get an inspection camera/endoscope so I can see inside the cylinders and hopefully might spot anything, but would be useful to know if there might have been internal contact with the amount that was skimmed off the head.
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davidwheeler
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« Reply #1 on: 14 July, 2021, 09:11:28 PM »

I don't know for sure but I am sure 20thou will not close up the gap unless the timing is a long way out.    It is more likely to be a bit of grot in the way?   Double check the timing and turn the engine over a few times before trying again with the compressometer.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
lancialulu
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« Reply #2 on: 14 July, 2021, 09:14:32 PM »

Cold compression test is not very accurate.
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Its not the winning but taking part! or is it taking apart?
1955 Aurelia B12
1967 Fulvia 1.3HFR
1972 Fulvia 1600HF
1972 Fulvia 1600HF
1972 1600 Fulvia Sport
1988 Delta 1.6GTi
1998 Zeta
andyps
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« Reply #3 on: 14 July, 2021, 11:01:58 PM »

Thanks for the replies - I'm hoping it is something in the way that I can somehow remove. Timing is all very close to what it was before I removed the head, all the marks I made on cam sprockets, chain etc. line up just as they were before dismantling so should be OK. I didn't think it would be an issue, but obviously concerned with it not working now.

Difficult to do anything other than a cold test when the engine won't start!
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lancialulu
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« Reply #4 on: 15 July, 2021, 06:17:33 AM »

Thanks for the replies - I'm hoping it is something in the way that I can somehow remove. Timing is all very close to what it was before I removed the head, all the marks I made on cam sprockets, chain etc. line up just as they were before dismantling so should be OK. I didn't think it would be an issue, but obviously concerned with it not working now.

Difficult to do anything other than a cold test when the engine won't start!

How do you know if the chain has not moved wrt the crank shaft. Best to go through and t8me the cams properly. The Lancia book method is reliable but you need  to know what Lancia cams are fitted as this determines the thickness of the TDC slipper gauge (1.0, 1.8, or 2.2mm from memory).
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Its not the winning but taking part! or is it taking apart?
1955 Aurelia B12
1967 Fulvia 1.3HFR
1972 Fulvia 1600HF
1972 Fulvia 1600HF
1972 1600 Fulvia Sport
1988 Delta 1.6GTi
1998 Zeta
andyps
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Posts: 277


« Reply #5 on: 15 July, 2021, 06:44:57 AM »

Thanks for the replies - I'm hoping it is something in the way that I can somehow remove. Timing is all very close to what it was before I removed the head, all the marks I made on cam sprockets, chain etc. line up just as they were before dismantling so should be OK. I didn't think it would be an issue, but obviously concerned with it not working now.

Difficult to do anything other than a cold test when the engine won't start!

How do you know if the chain has not moved wrt the crank shaft. Best to go through and t8me the cams properly. The Lancia book method is reliable but you need  to know what Lancia cams are fitted as this determines the thickness of the TDC slipper gauge (1.0, 1.8, or 2.2mm from memory).

Before taking the head off I hand cranked the engine to get the removable cam chain link between the sprockets, put markings on the crank pulley and block near it to show the position, I put marks on the cam sprockets and chain and the cams themselves in relation to their bearing housings, I marked the direction of the rotor arm to be able to put it back in correctly. I also zip-tied the chain to both of the cam sprockets. The marks are still visible and all line up in the same way they did before disassembly which gives me reasonable confidence that the chain hasn't moved in relation to the crank - I had someone help me by holding some tension in the chain whilst removing and refitting the head, keeping it tied tight whilst the head was removed.
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davidwheeler
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« Reply #6 on: 15 July, 2021, 07:16:37 PM »

Put a timing disc on the crank pulley (I have one glued on) and check the timing of the valves from first principles, ie. valves open/close at so many degrees from TDC.  You find TDC by putting a rod down the plug hole and feeling when the piston is at the top then place the disc on appropriately.  Cannot tell you timing off hand   https://forum.viva-lancia.com/viewtopic.php?t=1403509  is one version from a quick Google search or somebody on here must know!    I think it will depemd on the engine but all you need to know is if a valve opens at the proper time to re-assure yourself that it is right.
If that is correct and the engine still will not start you need to do the usual checks for petrol and sparks!   Sometimes, a pull down the road and a bump start does the trick.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
andyps
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« Reply #7 on: 16 July, 2021, 09:06:19 AM »

I got the car started last night fortunately. The issue had become fouled plugs - the plugs that were in were relatively new but must have got fuel soaked. Apparently the insulator in plugs is no longer coated so they soak up fuel and stop working, and modern fuels coat the surfaces so they can't work properly if they haven't fired well. Not sure why it didn't start initially but at least it runs. I've got a valve rocker or two a little loose, it sounds very tappety - should be an easy fix.

I checked the compressions when it had run and they are fine.
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Richard Fridd
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« Reply #8 on: 16 July, 2021, 09:41:55 AM »

What a relief! Interesting regarding insulators soaking up fuel. How quickly can this happen, as fouled plugs have been mentioned as problems in several cases just recently. Hotter plugs and 'triple spark' plugs being one suggested  solution. Correct mixture a better solution? At least the valves are closing. Richard
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Richard Nevison Fridd                                                                      Happy Lancia, Happy Life
Jaydub
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« Reply #9 on: 16 July, 2021, 04:43:34 PM »

Try using ESSO Synergy +, it`s 99 Octane and contains no Ethanol apparently even though it says E5 on the pump. Sounds good for older cars as well as moderns.
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1600 HF. S2.
davidwheeler
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« Reply #10 on: 18 July, 2021, 09:33:15 AM »

You need 99 octane anyway of course...  Tesco and Sainsbury have high octane fuel that suits my 1600 Sport perhaps a little cheaper (especially with a 6p off coupon!)
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
andyps
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« Reply #11 on: 19 July, 2021, 11:53:02 AM »

What a relief! Interesting regarding insulators soaking up fuel. How quickly can this happen, as fouled plugs have been mentioned as problems in several cases just recently. Hotter plugs and 'triple spark' plugs being one suggested  solution. Correct mixture a better solution? At least the valves are closing. Richard

It was a relief when it started!

I have been given a solution to the fouled pug scenario (by the Green Spark Plug Company) which is to spray them with over cleaner, leave it as recommended on the can, wash thoroughly with water and leave to dry. Apparently they should then work. I've not tried it yet but if it works it means I have a couple of spare sets of plugs!
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