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Crank gear 180 degrees outconfused smiley
Posted by: woodwalker ()
Date: November 17, 2018 08:00PM

Evening all. I assembled a motor for our 65 turbo vert following the instructions in the shop manual, Helts's book and the info I've gotten from this forum in regards to cam timing. The motor ran for 30 minutes at 2000 rpm for proper cam break in but didn't sound quite right. I shut it off but couldn't get it running again. Dropped the oil pan, checked again and sure enough cam is 180 off. Wtf. Dropped and dis-assembled motor and discovered that if crank gear key way is at 9 o'clock, #1 and #2 rod journals are at the bottom of the stroke, not at TDC. Pulled 2 cranks out of my stash and sure enough, key way is at 3 o'clock when #1 and #2 are at TDC. Anyone seen this before? I'll post pics tomorrow when my head is clearer.

Btw, there was absolutely no damage to the internals. Everything looks great which was a huge relief after all the time and money I've put into this.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Frank DuVal ()
Date: November 17, 2018 08:12PM

OK, so the engine started and ran. Cam might be out 180 degrees (of crankshaft rotation), but it turns twice as many revolutions as the crank, so every 180 degrees of crank the cam is back to "0" again.

It started and ran. If the cam out 180 was the issue, it would not have stated in the first place. Look for something else that caused it to not start again.

I can not explain the crank keyway being off 180 from the others in your stash.

They are all 8409 cranks?

Frank DuVal

Fredericksburg, VA

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Frank DuVal ()
Date: November 17, 2018 08:26PM

I forgot to add, since the Corvair distributor is driven off the crankshaft, the cam can be out 180 °, whereas on a cam driven engine, this would not work.

Frank DuVal

Fredericksburg, VA

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Vairismo ()
Date: November 17, 2018 08:36PM

Where is the suspect crank keyway when you have the 1 & 2 cylinders @ TDC? I'm not sure, but it seems to me like you may be reading this wrong.
9 o'clock keyway at BDC vs 3 o'clock keyway at TDC. Not the same comparison, or am I missing something?

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Re: Crank gear 180 degrees outconfused smiley
Posted by: davemotohead ()
Date: November 17, 2018 09:25PM

Proper timing the crank Key way is 9 O-clock and the Cam is at 6 O-Clock, Cylinders #1 and #2 are at TDC, BUT #2 is ready to fire not #1, and remember #1 & #2 are on the other end of the engine, when you pull the pan and rotate the crank to where #1 is ready to fire, the Timing mark on the cam will be at the split in the cases under the pan and the cam Key way will now be at 12 O-clock,and the Crank key way will be 9 O-Clock once again and both #1 & #2 will be top dead center again, Proper timing by the book sets Cyl #2 TDC ready to fire, NOT #1.

I am thinking that might have confused you, I doubt your other 2 cranks are at TDC with the Key way at 3 0-Clock, I think you might be tired and frustrated and not looking at things correctly, We all have those days When we get frustrated and can't think clearly, Happens to the best of us! if the cam timing was 180 out I do not think it would run at all, I am betting maybe if running points your dwell might have been off, What was the engine doing?





Email me at: Dave Motohead

1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca



Edited 1 time(s). Last edit at 11/17/2018 09:28PM by davemotohead.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Wagon Master ()
Date: November 18, 2018 05:14AM

I somewhat agree with Dave. Although on any 4 stroke engine, pick one, with the key ways and gears properly machined and installed, someones going to have to show me a cam installed exactly 180 degrees out.
Thought of another way, a crank only knows TDC of a given rod journal, happening once every revolution. There is no compression or exhaust stroke. The cam determines this.
On any given cylinder,
Valves are in position for 1 compression and 1 exhaust stroke every cam rotation. Valves are in position for 1 compression and 1 exhaust stroke every other crank rotation.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: woodwalker ()
Date: November 18, 2018 08:18AM



This is the best I can do for pics so grab a coffee, turn your screens and follow along. On the bottom pic, the crank on the left is a 66 140pg crank. on the right, the mutant 65 180 4spd crank. Keyway's are marked with red tape and are at the 9 o'clock position.

The top picture illustrates where the rod journals are. Mutant 180 crank has 1 and 2 at the bottom of the stroke while 66 140 crank is at TDC.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: woodwalker ()
Date: November 18, 2018 08:30AM



They are both 8409 cranks. I've also compared the 66 140pg crank to a 65 110pg crank and they are the same.

I see no evidence of any machining or repairs to the mutant 180 crank.

I've installed the mutant crank with the keyway in the 3 o'clock position and the cam timing checks out perfectly.

Yellow mark on the mutant crank is for proper flywheel installation.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: davemotohead ()
Date: November 18, 2018 08:41AM

Is the timing notch stamped on the seal ridge like most cranks? Hard to see the key ways in the pictures, I guess GM could have put the slot 180 out? Never seen that before in the 100's of engines I have built, if you degree the cam it should have been blatantly obvious something was wrong, I still don't see how the engine would run like that? I guess if it was 180 out #2 would now become #1 and you could set the distributor on #2 ready to fire and move the spark plug wires to match? More pictures please?

looking at your new picture, one crank end sticks out of the gear a lot more than the other one?





Email me at: Dave Motohead

1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca



Edited 2 time(s). Last edit at 11/18/2018 08:47AM by davemotohead.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Frank DuVal ()
Date: November 18, 2018 09:09AM

Quote
Frank
Cam might be out 180 degrees (of crankshaft rotation), but it turns twice as many revolutions as the crank, so every 180 degrees of crank the cam is back to "0" again.

What an idiot, well, at least a brain fart.sad smiley

Let me correct my statement. The cam turns 1/2 (NOT TWICE) the revolutions of the crankshaft. Big gear on cam, small gear on crank. So, every 180° of camshaft movement the crankshaft turns 360°, and is back to "0" again.

Frank DuVal

Fredericksburg, VA

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Re: Crank gear 180 degrees outconfused smiley
Posted by: MattNall ()
Date: November 18, 2018 10:35AM

I recent worked on an engine with the key 90 deg. out....





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Re: Crank gear 180 degrees outconfused smiley
Posted by: solo2r ()
Date: November 18, 2018 04:21PM

Sheared Key on Crank. You cant see the keyway on crank only the key in the cam . It is sheared. lucky that it ran at all!

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Re: Crank gear 180 degrees outconfused smiley
Posted by: woodwalker ()
Date: November 18, 2018 07:20PM

Evening, solo2r you nailed it. Gear appears to have sheared the key.

davemotohead; gear has moved towards the end of the crank. There is about an 1/8" gap between the gear and the main journal. Evidence of a sheared key also?

I'll be dropping it off at a machine shop this week to have the crank gear pressed off and checked. I'll post updates as they become available.

It would explain why it ran and then quit. Damn, did I get lucky and not have the motor grenade.

Thanks all for your thoughts and replies. They were all helpful and appreciated.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Wagon Master ()
Date: November 18, 2018 07:51PM

As long as you're not running a high lift cam, this is a clearance engine.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: solo2r ()
Date: November 18, 2018 08:21PM

I meant to say cant see the keyway in crankshaft, only the [sheared] key in the gear.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: solo2r ()
Date: November 18, 2018 08:22PM

Glad that You found it.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: davemotohead ()
Date: November 18, 2018 08:30PM

That was my next guess, the crank snout look suspicious.





Email me at: Dave Motohead

1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca

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Re: Crank gear 180 degrees outconfused smiley
Posted by: MattNall ()
Date: November 18, 2018 09:30PM

.

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Re: Crank gear 180 degrees outconfused smiley
Posted by: davemotohead ()
Date: November 18, 2018 09:33PM

What is amazing about this is it went 180 and stopped, I have seen them slip like that but never a full perfect 180.





Email me at: Dave Motohead

1960 4dr sedan caveman car
1961 Rampside (Chetside)
1962 Rampside (Barnside)
1962 Short Rampside (Shortside)
1962 Monza 700 Wagon
1963 Monza 900 coup (General Nader)

-----------------------------------
Rust Free Lancaster Ca

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Re: Crank gear 180 degrees outconfused smiley
Posted by: Kims65 ()
Date: November 19, 2018 06:11AM

Just curious and interested...

Did this key shear during the initial 30 minute run at steady 2000 rpm? If so, what would cause torque/load enough to shear a crank key under break-in conditions?


Is it more likely the key already sheared and the gear spun 360° (or close) on the crank before assembly followed by another 180° at the end of the run?

Glad you found the issue. Thanks for sharing...

John G.
'64 Greenbrier
Central PA

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