i have got a question about interpeting the rule of 9 method for use with chain driven 4 cyl pushrod engines. (when 8 is fully open check & adjust 1 etc).
the biggest difficulty i have is determining when 8 is "fully open".what i ended up doing was turning the crank to get 8 to its full open (fully depressed) and then rock the crank a bit in both directions, this should result in valve 8 moving a bit up in one direction and a bit down in the opposite. then i would know it is at the right place (fully open).
my question is, on chain driven pushrod engines, does valve timing get screwed up if you turn the engine backwards to rock the valves, due to the slack in the chain?
No. The rule of 9 is just a guide. When no 8 is open, it just means no 1 valve follower is on the 'heel' of the camshaft, or on the root diameter of the cam, this extends for at least 180 degrees of the cam circumference, which means adjusting the tappet clearance, with the follower anywhere on that 180 degree leeway is OK. Hope you understood that. It's not too easy to explain.:-) Mike.
No. There's only one camshaft, so any play in the timing chain isn't going to affect individual valves.
Only thing to consider is does the Rule of 9 apply? It only works for uniflow or crossflow ported heads (ie. each valve has it's own inlet port) If it's siamese ported (some valves share an inlet port), the valves have to be done on the rock.
Unless off course it's a ford transit, which despite having a crossflow head, has to be done using ford's valve sequence.
I think what he means is that when you turn the engine one way then go back a bit the backlash in the chain stops the camshaft turning. So the crank has moved but the camshaft hasn't. And does that matter? Probably not, but even so, if you press the chain tight with your finger then there won't be any backlash.
Rule of 9 ( or 13 if it's a six cyl engine) works for any engine with 'standard porting' ie starting off with one exhaust, then two inlet, two exhaust etc to the end, finishing off with one exhaust.
If you use rule of 9(13) on anon standard ported engine, you find that after about 15-20 mins running, one or more valves take up all the play and lose compression, causing misfiring and the loss of power that you would expect.
We used to get that with the old Commer lorries in the army.
I don't know where you got that from, but it isn't true. Porting makes little difference. On a 4 cyl engine, if either valve is open on No 4, the valves on No 1 will be fully closed, and vice versa. The same applies to No's 2 and 3. With 6 cyls, it's pairs 1 and 6, 2 and 5, 3 and 4. I,e whichever cyl has a valve open, the valves will be fully closed on the one it's paired with. That principle can be used to set the tappets on almost any engine.
I don't see how it's possible for 'one or more valves take up all the play' That doesn't make any sense at all. Mike.
Nonsense. There are only two crank possibilities for a 4 cylinder inline engine. 1-2-4-3 and 1-3-4-2. Both operate on the rule of nine for valve clearance. How the ports are arranged makes not a scrap of difference.
Why do the simple things have to be so complicated? I've been thinking about this all weekend now. I'll admit that I got the adjustment methods above, the wrong way around, but valve adjustment is something I rarely do now, since ford started fitting hydraulic tappets. (I know they've went back to adjustable tappets on some off their petrols, but they're a rare sight)
Ideally when you check the clearnace, you want the cam follower to be on the back off the cam lobe. Now on a cyl head with crossflow/uniflow porting (ie. inlet are all odd numbers/outlet are all even numbers or vice versa), in order for valve 1 (say an inlet) to be on the back off the cam, the inlet valve on cylinder 4 has to be fully open. Now the inlet valve on cyl 4 is valve number 7, so rule off 9 doesn't work. But due to the sufficient valve lead/lag/overlap designed into the camshaft, if you keep turning the engine, until valves 1 and 2 are both evenly open, valves 7 and 8 will both be closed and be as near the back off the cam lobes to make very little difference to valve clearance, hence using On The Rock. Although if you wanted to be 100% accurate, you would work out the valve pairs and ensure the cam follower is on the back off the cam.
Now with a cylinder head with Simaese porting, where the centre two valves share a port (normally exhaust), then the next 4 ports out from the centre, share ports and so on, like the diagram below
1 2 3 4 5 6 7 8 E I I E E I I E Using the same method as above, in order to get valve 1 on the back off the cam, you need the corresponding exhaust valve on cyl 4 to be fully open, which in this case is valve 8, and when you repeat it for each valve, rule off 9 works. But it should also be noted, that On The Rock would still work, but would be marginally slightly less acurate.
As for the transit 2.5DI, don't ask me how, but ford managed to complicate things with it. From memory, the the valve pairs are 2&3, 5&8, 1&4, and 6&7 (I've got this written in my toolbox somewhere). When one pair are on the rock, you adjust the corresponding pair. If you adjust the valves using any other method, the engine will sound like a bag off nails.
And another note, there is only 1 crank configuration for an inline 4 cylinder engine (well there are other possibilities, but they wouldn't be very well balanced), but there's 2 possible firing sequences ;-)
Less accurate? Seems to me you're just bogging yourself down with technicalities that are completely irrelevant. An individual cam on a camshaft, is basically a diameter with a lobe. The diameter is concentric with the camshaft journals. For a large proportion of the cams rotation, (at least 180 degrees to keep the figure easy) the clearance between the cam follower, and cam is constant. Therefore it follows that a tappet may be adjusted accurately as long as it's follower is anywhere on that 180 degree of concentric diameter. To put it another way. You could say there are 4 stages in a valves action. Starting to open, fully open, just closing, and fully closed. As long as the follower is nowhere near the first 3, the tappet may may be adjusted. The rule of 9 for a 4, or 13 for a 6 cyl engine, IMO is simply a guide. For anyone who understands the mechanics of the interaction between the camshaft and valves it can be ignored. Mike.
Oh, but it is. On some engines the order is not EIIEEIIE, but IEIEIEIE etc.
Yes it does. If you have No 1 valve (exhaust) fully open on a standard-ported engine, valve No 9 is also an exhaust valve. However if the engine is non-standard ported, No 9 is an inlet valve.
Now Exhaust valves are traditionally designed with a greater clearance (when cold) than inlet valves, typically .008in for inlet, and .012 or .018in for exhaust valves. When the engine warms up however, the exhaust valve, being subject to more heat, closes the clearance more, so that when the engine is at fuill operating temp, the clearances will be the same, or very nearly. In fact an old hand's trick is to set all valves to .002in clearance when hot.
Now, if you set the valves to the wrong clearances, one or more exhaust valves will have the lesser clearance recommended for inlet valves. When the engine warms up, the clearance is insufficient, and the valve does not fully close.
This happens to Commer lorries, believe me.I was that soldier.
So how can that possibly cause 'one or more valves to take up all the play' after 15-20 mins running?
You mean No 8. Not No 9, but no matter.
All of which has nothing to do with 'one or more valves take up all the play'.
I know what your driving at. My mistake was to assume that anyone taking part in a discussion about adjusting tappets, would take it as read, that exhaust valves should be set to the correct exhaust valve clearance, and inlet valves to the correct inlet valve clearance, regardless of the actual port configuration. Just because No1 is an inlet, the rule of 9 doesn't mean you adjust No 8 as an inlet, if it's an exhaust valve, which is what you seem to be putting forward as a possibility. To anyone who knows the difference between an exhaust and an inlet valve, porting doesn't matter.
Only if idiots are allowed to set the tappets. Mike.
I explained that already. They close up due to thermal expansion. If the clearance is insufficient, the valve does not close correctly.
You mean You're, not your, but no matter.
My mistake was to assume that anyone taking
Point is that people were then used to standard configurations, and an unfamiliar one could lead to mistakes. You use the term " anyone who knows the difference between an exhaust and an inlet valve" as if they weren't identical to someone looking at them. Don't forget when the tappets are being adjusted, the head is on and the valve heads can't be seen.
I'm glad to see you don't go in for sweeping generalisations. The old adage " The man who never made a mistake never made anything" is still true, although I was naturally feeling a bit less charitable towards the person who made the mistake when I had to put it right on the hard shoulder of an autobahn in November in freezing driving rain, but that's another matter entirely.
There is an element of cross-purposes here. For the purposes I have used the term "standard porting" which is technically correct, but perhaps it would be more helpful to use "valve order", ie EIIEEIIE or alternatively EIEIEIEI. A port is where a valve sits in the head to close the inlet or exhaust tract. The fact that these tracts may be siamesed further downstream is of no consequence. One valve, one port. For this purpose there is no such thing as a siamesed port, it's tracts which are siamesed.
The firing order is also irrelevant for this purpose. No 1 is still paired with No 4, it is the order of the valves in the head which makes a difference. I just checked an old tuning book for some examples and found the following -
Old ford (kent) engine - EIIEEIIE - standard
1297 OHV engine - EIEIEIEI - non-standard
1297 HCS engine - EIEIIEIE - non-standard but different again.
To simplify - Rule of 9 can be used for an engine with standard valve order. This means that when No 1 valve(E) is fully open, No 8 valve (also E) is fully closed ie the cam follower is on the back of the lobe and the clearance will be at it's maximum.
If the engine were a non-standard valve order, then No 8 would (could) be an inlet, which means that the follower would be at or very close to the start (or end) of it's lift, which would mean that clearance was not at it's maximum. Adjusting the clearance at this point will mean that the clearance is excessive, giving rise to increased valve gear noise, failure of the valve to fully open, poor cylinder charging and therefore impaired performance. This is of course another valid reason why rule of 9 should not be used.
What should be used instead is the rule " Like valves in paired cylinders are opposite". This ensures that whether or not the valves are in the standard order, having an exhaust valve fully open will ensure that the valve being adjusted is fully closed. This rule can of course be used instead of rule of 9, or in deed any other rule, at least for a simple engine which is what I was referring to.
It has to be admitted that rule of 9 is now outdated for general purposes, having been bypassed by various developments. I have deliberately not even mentioned multi-valve set-ups, DOHC, V or flat engines,radial engines or any others.
The Kent engine is the OHV engine introduced in 1959 in the Anglia and has always been 1-2-4-3. The Valencia was the basically identical FWD version of this introduced in the Fiesta in 1976 and this was also 1-2-4-3. I still remember this well from some 20 years ago after cocking the plug lead order up on a friend's Fiesta after I serviced it for the first time after which it resolutely declined to start until I figured it out the next morning.
The HCS came out in 1988 and finally the Endura-E in 1995 which I think was the three bearing crank engine but I wouldn't want to be definitive as neither are engines I've been involved with. AFAIK both of these were
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