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  #61  
Old 13-07-2015, 03:30 PM
SKiddell SKiddell is offline
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A bent valve can be very subtle, and it’s very rare that only one valve gets bent as often many cycles take place until its noticed, sometime the “bend” is only a couple of thou and will partial seal on the seat due to the spring pressure flexing the head almost back into place, sometimes this doesn’t cause issue for a while……..until the valve head has seated half a million times, then metal fatigue takes place and the valve head falls off onto the piston top and then all hell breaks loose.

The "problem" with a compression test is that if for example you had a slightly bent valve in each chamber then you would still get a relatively The leak down test will give both a direct measure of how well the cylinder/chamber holds pressure plus an audible indication of any leakage path.

Do the test with the piston at TDC on the compression stroke of number 1 cylinder when the valves are closed (cam lobes at 10 to 2), you will need to lock the crank with something as the air pressure (through spark plug hole on the piston crown) will tend to rotate the crank due to the pressure on the piston crown. Once checked rotate so that number 2 is on the compression stroke and repeat until done.

When you apply pressure get a short length of pipe, open the butterflies of the carbs and listen at each carb mouth, if all is ok then you will need to do the same with the exhaust, separate it at a suitable joint and listen for a tell-tale hiss, if you pass these tests then you’ve been very lucky.

As with any testing like this ensure the engine cannot inadvertantly start up.

Best of luck, hopefully all is well plus at the end you have learnt some valuable skills to boot.

Last edited by SKiddell; 13-07-2015 at 03:40 PM..
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  #62  
Old 29-07-2015, 11:09 AM
zedhed zedhed is offline
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I've had a number of questions about this thread, so

here's a post to clarify and answer some

Yes, Z Farm installed my engine under contract as described.

Yes, they retarded valve timing by one tooth and approx 1.5 tick marks as per the images posted here previously. I'm advised 1 sprocket link is 18 degrees, and 1 tick mark on sprocket, is 4 degrees, so total would be 24 degrees retarded.

From engine manual:
Camshaft:
Duration 290
Max Valve lift: .495 (12.6mm)
Lobe Center: Exhaust 106 (IN: 104)
Valve Timing
@ 0.50” lift: IN: 18 BTDC, 46 ABDT (should probably say ABDC?), 50 Before Bottom DC, EX: 14 ATDC.
(I think Inlet should be fully open 104 deg after TDC, Exhaust fully opens 108 deg BTDC maybe somone can comment on this info)

Ive been asked if anyone consulted me or attempted to contact me about anything before changing valve timing on my engine. Answer is no.

I've been asked whether Z Farm had the cam info. Yes, they most definitely had the cam information including, duration lift, opening and closing angles, because I emailed the engine manual which includes this info from Datsun Spirit to them on the 3rd of March. When I mentioned the strange behaviour of the engine to Datsun Spirit Eiji asked me to check the valve timing which is when I discovered it was retarded. When I mentioned this to the engine builder he became very concerned and told me to revert it back to where it was. Luckily he had photos of the build for me to refer to.

When I made adjustments back to the way the engine builder had it in the first place, the engine immediately fired up, whereas with their setup (when I received the car), it took several attempts to start the engine, which cut-out regularly even whilst driving.

So when I explained this on the forum, helpful club members suggested I check for valve damage. So I'm now taking the car to an independent garage with a leak-down tester, and will post results here. I don't think the valves are bent because the pistons have indentations for the valves in the tops. You can seem them in my gallery.

I think it's premature to assume the valves are bent and I prefer to give the benefit of doubt until I know for sure.

If anyone can put me in touch someone independent who can examine the head/valves for an opinion, I'd sure appreciate it. Just PM me or recommend someone you are personally satisfied with and trust preferably near to East Anglia.

Finally just want to say thanks for helping out a newbie like me - big learning experience - credit to the club to have such good support and info from you guys on here.

Cheers for now, will update with news shortly, Nick
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  #63  
Old 29-07-2015, 05:34 PM
MikeB MikeB is offline
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Nick

I feel I need you to clarify exactly who altered the cam timing. In post #48 you said it was not Z Farm but a local tuner. Above you say it was Z Farm. Please give a precise and full answer, so we can be sure who you mean altered the cam setting.

With regards to your cam timing, you really do need to get this checked using a lift gauge on Nr1 inlet valve and a protractor on the front pulley with TDC properly identified. Setting the wheel how you think Eiji had it set is not the way to do it. There are plenty of books telling how to measure the point of max lift, or I can drop you a PM on my preferred method. Any apparently small variance in the setting up of the cam can have a huge effect on performance.

Did Eiji run the engine before delivery?
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  #64  
Old 29-07-2015, 06:16 PM
franky franky is offline
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I guess before you were just trying to protect yourself? Was it you who was having trouble with a new mallory dizzy there?
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  #65  
Old 29-07-2015, 06:34 PM
MikeB MikeB is offline
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Franky

Who are you asking?
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  #66  
Old 29-07-2015, 06:44 PM
franky franky is offline
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Quote:
Originally Posted by MikeB View Post
Franky

Who are you asking?
The OP, zedhed
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  #67  
Old 29-07-2015, 07:52 PM
zedhed zedhed is offline
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Hi Franky, I'm not in the business of protecting anyone so not sure what you mean. If you mean me, then you will find I need no protection - but you probably don't know me. I just tell it like it is which is the responsible thing to do. Yes I forgot about the Mallory - but they swapped the original dizzy back in, and that's what I'm running now. It runs fine.

MikeB thanks for this - yes I'd appreciate that PM. Eiji took pictures of the engine with protractor installed, and a close-up of the sprocket setting at TDC, so we think my adjustment is within a degree or two (see previous images), because the engine runs fine - but I would still appreciate your guidance, this is a learning experience for me. No Datsun Spirit didn't break in the engine - I sure regret not asking them to though

As clarified previously by another poster further up, Z Farm were contracted to install the engine and get running for me to break in, so the tuner isn't relevant to this discussion - as far as I'm concerned my contract is with Z Farm and no-one else. However the tuner confirmed they didn't get the engine information because they asked me for it. Actually this isn't a big deal - mistakes happen but communication helps them not happen, eh? To assume I will ever know the decision making process which lead to these changes is naive.

I did the compression test today - here are the results using two gauges...

Cheap Chinese guage about £30 tested from C6 to C1 in psi*

C6 125
C5 112
C4 125
C3 135
C2 115
C1 115

Mac tools guage made in USA tested from C1 to C6 in psi*

C6 185
C5 198
C4 195
C3 205
C2 205
C1 210

* 5x compression strokes till needle wouldn't move any more. Not sure if battery power drain affects it.
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  #68  
Old 29-07-2015, 08:27 PM
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smileyinside smileyinside is offline
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Yes battery drain does affect it. I had a charger on mine set to "boost" while doing it and it made a huge difference.
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  #69  
Old 29-07-2015, 09:20 PM
franky franky is offline
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To clear up, you're saying the Z farm altered the timing which may have caused an issue? Or your tuner did?
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  #70  
Old 29-07-2015, 09:31 PM
SKiddell SKiddell is offline
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Did you get the leak down test done ?

Quote:
I don't think the valves are bent because the pistons have indentations for the valves in the tops
Flawed logic I'm afraid, 25 degrees of error could result in many mm of lift depending on the part of the lobe engaging the cam finger.... valve pockets are not very deep (2/3mm at best)
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  #71  
Old 29-07-2015, 09:50 PM
zedhed zedhed is offline
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Quote:
Originally Posted by franky View Post
To clear up, you're saying the Z farm altered the timing which may have caused an issue? Or your tuner did?

I'm saying that the Z Farm employed a tuner to alter the timing without checking with me or the engine builder first.

Got it now Franky? Let me know if not and I'll clarify again for ya.
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  #72  
Old 29-07-2015, 09:52 PM
zedhed zedhed is offline
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Quote:
Originally Posted by SKiddell View Post
Did you get the leak down test done ?

Flawed logic I'm afraid, 25 degrees of error could result in many mm of lift depending on the part of the lobe engaging the cam finger.... valve pockets are not very deep (2/3mm at best)
not yet - ran out of time - and yes that's what I'm afraid of - but I'm ever the optimist...

when you say error I'm assuming both retard and advance are equally risky?
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  #73  
Old 29-07-2015, 09:54 PM
zedhed zedhed is offline
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I'm going to a local garage for the leakdown test either this week or next week... In the meantime I'll get some more pics up.
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  #74  
Old 29-07-2015, 09:59 PM
franky franky is offline
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Quote:
Originally Posted by zedhed View Post
I'm saying that the Z Farm employed a tuner to alter the timing without checking with me or the engine builder first.

Got it now Franky? Let me know if not and I'll clarify again for ya.
Now it makes sense, I don't think i'm the only one who couldn't work it out
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  #75  
Old 29-07-2015, 10:39 PM
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SeanDezart SeanDezart is offline
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Quote:
Originally Posted by franky View Post
Now it makes sense, I don't think i'm the only one who couldn't work it out
Yep, wasn't clear enough especially given the potentiel seriousness of the situation.
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