Joined: Aug 2017 Posts: 425 Threads: 30
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Location: Wellington, NZ
My engine assembly proceeds. I got the flywheel bolted on tonight (torqued to 150 ftlbs) so did a first test fit of the block. Studs are all in place and the block is loosely bolted down on a silicone gasket made from baking sheet. With the head (a Ruby one) just sitting on the studs and no head gasket in place it seems the valves hit the head. With a copper gasket there, but nothing torqued down, they clear. That doesn't seem like much clearance to me. How much clearance should there be? I haven't set the valve clearances at all yet of course. Just wound them up to lightly touch as a quick test. Is the only way to tell to have everything torqued down and adjusted?
Of course I don't know how much has been skimmed from the head in the past.
Another question is with the copper head gasket. Does the side with the copper flange wrapped around go to the top of the bottom?
I haven't done the rods and pistons yet but that will be next to check how far they come up the bores. Is it wise to do a test assembly without rings to measure that first?
Simon
Joined: Mar 2015 Posts: 5,442 Threads: 231
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I always place the head on top of the block without a gasket and turn the engine I’ve whilst holding it down with my hand, if I feel it lift I know there is contact and take appropriate action in the head.
I use wet white paint on top of the valves to indicate the touch point/s where metal should be removed.
If you have no touch without a gasket fitted, you will be fine once everything is assembled.
Joined: Aug 2017 Posts: 425 Threads: 30
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Location: Wellington, NZ
24-07-2018, 09:03 PM
(This post was last modified: 24-07-2018, 09:04 PM by jansens.)
I measured 33.7mm this morning in a very quick check before work but will measure it properly tonight. Ian reminded me we've fitted bigger valves and I had opened up and equalised the chambers ages ago but this is the first time I have had the engine together enough to actually try the valves on the cam. It seems to be hitting in one place only as far as I can tell but I will mark it up tonight to make sure. Shouldn't be hard to fix I think. With the head just sitting loose it only lifts up a fraction so the contact seems slight.
Simon
Joined: Aug 2017 Posts: 425 Threads: 30
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Location: Wellington, NZ
OK, I was able to blue up and work out where the interference was with the valves. I was going to try plasticine but I couldn't get any and in the toy shop I asked in first the guy didn't know what it was! I have some engineers marking blue so I used that. I just needed to grind the corners of the chambers a bit more square. I checked all the volumes matched and that there is no interference with no head gasket so that's all good now.
The issue now is twice a rotation there is a clicking noise. It took me a while to track down where it was coming from but it's from the cam and crank gears. I have plenty of backlash, perhaps too much because what is actually happening is at certain points in the rotation the cam gear jumps forwards fractionally. As it goes off one tooth and starts to engage the next. You can actually see it happening. Nothing is tight and the sound isn't there with the block off so I imagine it's to do with the pressure of the valves and springs on the cam shaft as it rotates.
Is this what is meant by noisy with gears that don't mesh well? I imagine in a running engine it would make quite a racket!
So do I have to find a better meshing set of gears?
Joined: Mar 2015 Posts: 5,442 Threads: 231
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How much backlash do you have Simon?
Joined: Feb 2018 Posts: 80 Threads: 15
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Hi Simon,
Looks like others have your critical issue well in hand, but with respect to the gasket the rolled edge goes toward the head. The way I think about it is to consider where the pressure is being produced i.e., in the combustion chamber, and keep any edges or joins (potential weaknesses) as far away from that as possible. Good luck with the build.
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End float on the camshaft is as important as the mesh. Both need to be right.
I select gears so tha tI can just feel backlash.
End float I think should be 0.002".
When I got my car there was more than 0.025" endfloat and conversation in the car at 30mph was impossible.
Huge difference with endfloat corrected.
Jim
Joined: Aug 2017 Posts: 967 Threads: 117
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Location: Melton Mowbray.
I draw your attention to the latest edition ( 2018C ) of the Austin Seven Clubs' Association Magazine which Clubs are in the process of receiving.
In it there is an excellent article by Peter Lawson on camshaft set up and fitting. Required reading!
Joined: Aug 2017 Posts: 425 Threads: 30
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Location: Wellington, NZ
Hi Steve, thanks for that tip. Will remember that! Very useful.
Endfloat is correct I think. I did the lapping trick until I got it to the correct figure when tight. I'll see if I can measure it in the engine now with the dial gauge to check though.
Looks like I'll be home today with a cold so I will see if I can film what's happening and show the amount of backlash later on when it's light.
There is definitely a lot of backlash but what worried me more is it seems inconsistent all the way around. More in some places than others.
A pain to have to take all that apart again but much easier to get it right now with the engine half assembled on the bench than in the car!
Simon
