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Discussion Starter · #1 · (Edited)
CIH Cam and Ignition Timing

GTJIM said:
. . .

Timing the cam is one of Opels little endearing foibles! Even the Factory Service Manuals cam be misleading as the drawing of the engine is actually WRONG in some of them - nice huh! Fortunately the picture of the crankshaft keyway position and the text is correct. The keyway in the crankshaft MUST face upwards and #4 cylinder be at Top Dead Centre with the camshaft turned so that the valves for #4 cylinder are closed ( the cut outs in the cam for access to the head bolts will be in the correct position as this setting). Once the cam wheel is bolted on, with the dot lined up with the mark in the presssed sheet metal "shelf" that is bolted to the block beneath it, the motor must be rotated one complete revolution. This puts #1 cylinder at TDC with the valves shut and the motor is now in the postition to have the distributor installed and lined up for firing on #1 cylinder.

That is why Opels are usually timed 180 degrees out from where they are suposed to be - some twit in the design stages obviously put the cut outs on the camshaft in the wrong place and we have struggled to cope ever since!

HTH
To amplify what GTJIM said a bit, the 4-cylinder engine's #1 and #4 cylinders are "paired", as are the #2 and #3, so they are always at exactly the same position during their revolution, just "180 out" as far as ignition timing is concerned (one's firing at TDC, the other fires at TDC on the next crank revolution). The complete "cycle" of any "four stroke" engine requires TWO revolutions of the crank.

All engine "timing" is done in relation to crankshaft position. Almost ALL engines "share" cam timing and initial #1 cylinder ignition timing settings, the Opel CIH engine DOES NOT! Therein lies the confusion that sometimes baffles even experienced mechanics, at least initially. Some, who don't take the trouble to look at the valves, never get this.

Easiest way to remember CIH "timing" from scratch is to:

Set both crank key and cam dowel pin to 12 O'Clock position. This positions #1 and #4 pistons at TDC and also positions the cam to allow plug-side head bolt installation and torquing. The ignition "timing" is for the #4 cylinder however, NOT the #1 cylinder as in almost all other engines. Your choice, either leave it and time the ignition for the #4 cylinder or rotate crank ONE full revolution and time it for the #1 cylinder. Makes NO difference!!
 

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Hidebound

tekenaar said:
All engine "timing" is done in relation to crankshaft position. Almost ALL engines "share" initial ignition and cam timing settings, the Opel CIH engine DOES NOT! Therein lies the confusion that sometimes baffles even experienced mechanics, at least initially. Some, who don't take the trouble to look at the valves, never get this.

Easiest way to remember CIH "timing" from scratch is to:

Set both crank key and cam dowel pin to 12 O'Clock position. This positions #1 and #4 pistons at TDC and also positions the cam to allow plug-side head bolt installation and torquing. The ignition "timing" is for the #4 cylinder, NOT the #1 cylinder as in almost all other engines. Your choice, either leave it and time the ignition for the #4 cylinder or rotate crank ONE full revolution and time it for the #1 cylinder. Makes NO difference!!
Just shows how "hidebound" some of us are! It had not occured to me just to time the ignition for the motor on #4 cylinder instead of #1. That will save me having to rotate the motor one complete revolution - I now realise that a motor can have the ignition timing done on any cylinder ( as long as that is the cylinder which is suposed to be firing ) Thanks Otto
 

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Discussion Starter · #3 · (Edited)
Ignition timing . . .

GTJIM said:
Just shows how "hidebound" some of us are! It had not occured to me just to time the ignition for the motor on #4 cylinder instead of #1. That will save me having to rotate the motor one complete revolution - I now realise that a motor can have the ignition timing done on any cylinder ( as long as that is the cylinder which is suposed to be firing ) Thanks Otto
Correct. As long as the engine's firing order is maintained at the distributor cap, any engine can be timed at "the end of compression stroke" TDC of any cylinder. Of course it's always easiest to "time" any engine at the #1 cylinder or its mate because the TDC timing mark is already established for that pair.
 

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Timing marks are for #4?

Hmm....
I bought a manta in 2002 and almost immediately installed a pertronix and did a full tune up on it since I was about to move from GA to PA. After I had everything complete, I was going to check the timing and I couldn't even see the timing marks when I was triggering from the #1 cylinder. When I went to #4, it was dead on. Gene Smith was with me at the time, and we were thinking that someone had been into the engine at some point and had something 180 degrees out. Are you saying this was NOT the case, and that those timing marks were FOR timing the engine using #4? I never worried about it since the car ran great...just curious.

TK
 

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That doesn't make sense at all since #1 and #4 pistons are at TDC at the same time, as are #2 and #3 but #2 and #3 are 180 degrees opposite #1 and #4. So the timing marks should be lined up for #1 and #4 regardless of which plug wire is used at the triggering source for the timing light. Something there isn't quite right. JMTCW.
 

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First, the discussion above about #4 versus #1 is just related to cam timing. The cam timing marks line up when #4 piston is at TDC in the firing position (top of compression stroke). #1 piston is also at TDC, but it would be at the top of the exhaust stroke. The IGNITION timing on an Opel is no different than any other engine, in that the normal procedure is to adjust the ignition timing in relation to #1 cylinder.

Ron is right, the #4 plug fires at the same position (but 360 crank degrees later) as the #1 plug, so the flywheel timing mark will still work if you have the timing light pickup on the #4 plug wire.

Maybe the #1 plug wire was dead. Or you weren't getting a good signal from it to the timing light pickup.
 

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And because we sort of wandered off topic (which had been the valve job on RallyBob's head), I split these posts off into their own thread
 

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All the service books I have seen on the CIH engine show #1 cylinder next to the fan. The old German way of numbering cylinders the #1 is always next to the flywheel. If you set up the engine with that cylinder as #1 all the timing marks on the engine will be in alignment.
 
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