Camshaft timing when the sprockets are ONE tooth off from straight up.

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PRH said:
The “classic” timing set mistake, which I have witnessed several times, is to put the crank key straight up and line that up with the dot on the top gear.
This puts the cam advanced 2-1/2 teeth on a BBM with a double roller chain.
Most times this results in 8 bent intake valves.
But some engines actually have enough physical room to run without damage occurring.

Had a customer who was working on a 455 Olds.
Very low power, 200psi on the compression tester, no spark knock.
I told him it was likely cam timing way off.
They didn’t want to tear it down and look so they spent a summer with it being a dog while they messed around with timing, carbs, etc.
They finally pulled it apart…….and it had the “classic” mistake.

Put the timing set on correctly, way more power everywhere.
Lost a bunch of cranking pressure.
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I had the unfortunate opportunity to learn from this very mistake in the past. This is what I have displayed in my garage to remind me to never take short cuts, measure twice, don’t get frustrated, walk away if you have too, make it right! Expensive lesson for sure!

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kiwigtx said:
How much for the steering wheel? :p
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This is not a sales ad.
Maybe you need a review of the rules ?






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HA!
I wanted to give credence to the question. I wasn't just laying in bed trying to come up with new topics to clog up the forum....THIS actually did happen. The episode of Engine Masters reminded me of this. Since their numbers with their cam advanced dropped off so much, it got me thinking. My results matched theirs.
Cheers.
 
mygasser said:
the chain has to have stretched a lot to jump teeth, if it's not stretched ie correct tension it can't jump. now installed a tooth out? that's entirely possible, lol.
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That is not true "back in the day" when they used those DAMNED alloy sprocket hubs with nylon teeth. I can still remember we replaced a sprocket on my buddies Chev 350, then later he did some other work to the engine (don't remember what) and the sprocket, with less than 40K on it had worn nearly to the aluminum in places. I have seen FEW chains jumped with all metal sprockets. Most were because of these damned nylon ones.
 
I find myself wanting to call them gears but that dang Rick Ehrenberg wrote that gears mesh with other gears, sprockets are driven by chains.
He was a stickler for Mopar specific terminology.
Spindles? Nah...the factory called them Knuckles.
Drive shaft? No....Propeller shaft.
Clutch fan? No...Thermal drive fan.
There are others.
Posi = Sure Grip.
Z-bar = Torque Shaft.
Emergency brake = Parking Brake.

Can you recall any of the others?
 
I just remembered another one.
EVERYone I know calls them "Head Bolts".
Not him. He calls them screws because according to him, a bolt is retained by a nut, not just threads cut into a casting.
Bell housing screws?
Door hinge screws?
Intake manifold screws? Doesn't that all sound really weird?
 
Kern Dog said:
I find myself wanting to call them gears but that dang Rick Ehrenberg wrote that gears mesh with other gears, sprockets are driven by chains.
He was a stickler for Mopar specific terminology.
Spindles? Nah...the factory called them Knuckles.
Drive shaft? No....Propeller shaft.
Clutch fan? No...Thermal drive fan.
There are others.
Posi = Sure Grip.
Z-bar = Torque Shaft.
Emergency brake = Parking Brake.

Can you recall any of the others?
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Call them head bolts, and consider the block as just a big nut
 
screws have the thread cut/rolled right up to the head, bolts have an unthreaded section between the head and the thread. so they are head 'bolts'. you never see them fully threaded as that would cost the factory more money/time.
 
THAT is an excellent explanation.
Ehrenberg also uses the term "Cap Screws".
Maybe he is just being facetious there?
 
Kern Dog said:
THAT is an excellent explanation.
Ehrenberg also uses the term "Cap Screws".
Maybe he is just being facetious there?
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He probably said "cap screws" instead the longer mouthful "socket head cap screws".

BTW, socket head cap screws don't necessarily have the threads run all the way to the head. Also BTW, good design practice is to NOT have threads extend through the shear plane.
 
DeltaV said:
He probably said "cap screws" instead the longer mouthful "socket head cap screws".

BTW, socket head cap screws don't necessarily have the threads run all the way to the head. Also BTW, good design practice is to NOT have threads extend through the shear plane.
Click to expand...
You could distinguish screws from bolts...
screws: internally driven
bolts: externally driven
 
We call bolts with a part plain shank as bolts - or 'shank bolts'.
Fully threaded bolts are called 'set screws'.

Allen/Hex head socket screws are called 'cap screws'
 
I have the distinction of always landing on my feet. Sometimes after the landing, I fall to the side or back to standing up.
The only time I ever got hurt enough to go to a hospital was last year after the roof fall.
I am a pretty lucky guy for the most part.
 
Inertia said:
It'll push a straight section of stiff chain straight UP, - till it finally flops over, - a tooth over from where it should be .
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So that's how it happens!!! I've taken 318s apart and found the chains like that, but never knew why.
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On another note;
Many years ago, mid 70s, my BIL called me up, (he knew I worked on cars) and said his 71 Demon 318, (plastic toothed gear) wouldn't start, at 20(or so) below.
So I just figured he needed a boost. Not so.
After plugging in the block heater for several hours, charging the battery, and restoring the ignition timing; this 318 eventually fired up, but needed even more idle-timing; but it wouldn't stay running unless the throttle was wide open, and then, the rpm was like 500. I soon found out, that the cam-timing was out.
Popping the cover, sure enough, the chain had jumped over several torn-off nylon teeth. I counted the teeth, but in the nearly 50 intervening years I have forgotten. I have a number in my head, but it seems impossible.
It had ran normal the night before.
In this case, the cam was severely retarded, so I just always thought that it had happened at start-up of the frozen engine.
Several years later, I inherited that car. I fixed it up and started "renting it out" to my little brother and his friends. Made some good coin on it, back in the day.
 
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