110 vs 140 crankshaft

[6T5VAIR]

Hello, I have inherited a project that I'm trying to figure a few things out about.

The motor seems to have started life as a 110. What I'm sure has been done is crank bearings, forged pistons, balanced internals, .30 over jugs, new valve seats, upgraded cam, 4-carb intake, tubular headers, electronic ignition.

What I can't find is evidence of an upgraded crankshaft being purchased.

So my question is, with those mods, should I be worried if the crankshaft is the original 110 crank as opposed to the hardened crank?

[davemotohead]

A turbo and 140 crank will have a ampersand stamp on the crank hub indicating its nitride coated, at this point I would not worry about this with your build and the crank you have will most likely be fine if its not cracked. Even the hardened cranks can break, I say run it!

[Dennis66]

And if the engine has been "rebuilt", the rebuild could have included turning the crank for undersized bearings, which eliminate the surface hardening. Dennis

[66vairguy]

Good comments. It is sometime suggested the 140HP/180HP "nitrided" crankshafts are stronger than the 95HP/110HP crankshafts. If they are it is trivial. Nitriding is treatment that hardens the surface ONLY. It is mainly an anti-wear treatment.

I have mic'd a number of nitrided crankshafts from engines with over 80,000 miles and ALL were still in specification. A basic journal polish and they were good to go.

Usually a NON-nitrided 110HP crankshaft has to be "turned" down due to uneven journal wear, unless it is low mileage, or the owner changed the oil regularly.

If you are not going to put a huge amount of mileage on the engine, then their is nothing wrong with a "turned" 110HP crankshaft. Just my

[6T5VAIR]

The engine had about 80k miles on it when parked in the 80's.

I was able to dig up the following also by the way from Clarks

Cam – C8800 New Otto Cam (non-turbo)
C7737 Cam Gear
Valves 6 C124R Turbo Exhaust Valves & 6 C3020 Intake Valves.
C8629 Otto Intake Guides (set of 6) and the C8628 Otto Exhaust Guides (set of 6).
C8619 Valve Springs & C8637 Valve Spring Shims.

Anyway sounds like I have nothing to worry about.

Thanks all

[66vairguy]

Looks like you got some good parts.

Keep in mind a few folks have noted the OTTO cams have had issues with the timing being off. I've never used the OTTO cams, BUT I always degree a cam. Keep in mind a few degrees off can be tolerated. If the timing is off enough so one tooth of the cam will correct it, then you can shift the cam gear one tooth to the crank gear. If you can't get both the exhaust and intake timing to agree to specification, then don't use the cam.

Many will say you can freeze the cam and heat the cam gear to get it on the cam. That may be true with the basic cast cam gears, but I found that DOES NOT work with the forged cam gears sold by California Corvair. Calif. Corvair has a fixture to keep the cam gear hot WHILE inserting the camshaft. Very slick. With the Clark's "Super Strong Cam Gear" I would suggest using a fixture (steel plate heated via rosebud torch) to keep the gear hot while inserting the camshaft.

If you "broach" the cam gear inserting the cam, then it WILL come loose. Just my

[6T5VAIR]

You are really talking over my head with this — super appreciative for thr care and detail though… help me understand what being off by a tooth does and how youncan deal with it without opening the motor again?

[Dennis66]

My first question would be: Has the engine been run? Is it installed and how far from being cranked up if it hasn't? On cams, gears, and timing. Yeah, there could have been some cams that were machined wrong. Yeah, if you are in the assembling stages and degree (this involves using a 360 degree marked disc and measuring when valves start to open and close - very technical, yet really kind of simple. If you were going this far when building the engine, you could index the cam to crank timing by one tooth to make up for differences. There are also offset cam keys. HOWEVER Corvair cam gears aren't so easily installed. During assembly, one could loosen the case bolts and move a tooth, but that would also require re-applying the sealer to the needed spots. Additionally, the Corvair cam and crank timing gears are a helical cut, so if a cam gear were improperly installed and it managed to slip forward on the camshaft after assembly and running, that could affect the cam to crank timing (I have an engine where this had happened). Some engines will run with the timing off by one tooth, they just don't run right.
Given the detailed list of things done and components, I would figure that they did the assembly right and everything should be okay. Dennis

[vairmech]

Good comments. It is sometime suggested the 140HP/180HP "nitrided" crankshafts are stronger than the 95HP/110HP crankshafts. If they are it is trivial. Nitriding is treatment that hardens the surface ONLY. It is mainly an anti-wear treatment.

SNIP ---

I have to add to this.
While the above is true that is NOT why GM put the nitriding on ONLY the 140-180 cranks. GM was not worried about wear, only during the warranty period.
The real reason is crank breakage, the nitriding hardens the surface stopping cracks from starting. It does not make the crank stronger and the cranks will still break but they take a beating first! Also the nitriding is only .005-,010" deep so if you grind one of these cranks you have effectively removed the nitriding and it becomes a standard non nitrided crank.

With all of that if you have a 140 engine and you only drive it like a normal car with the occasional blast a regular crank will work just fine.

One more thing, there was talk of cam timing but you have to look at the gear also. ALL of the aftermarket gears are marked wrong! The timing "0" is in the center of the tooth. GM did NOT put the gear timing mark in the center of the tooth! They put it to the left of the aftermarket "0" at the tooth root.
Others will go into how they use a straight edge and remark and, and, and. All of that is not needed.

This is a common aftermarket gear. look where the mark is. This mark will never line up!



This is a GM gear, look where this timing mark is. It's placed exactly where I said above, to the left of center in the root of the tooth and this mark will line up!

[66vairguy]

Ken makes some good points.

The "0" cam marking has been an issue for years. I've got an old GM camshaft gear that is marked incorrectly.

Once I installed a new repro crank gear, new repro cam gear, new camshaft. I sure DID degree the cam and it was O.K.

Bottom line --- the "O" is a general place marker. I draw a line on the cam gear that is centered and through the woodruff key slot. That will line up with the crankcase split line AND the mark on the crankshaft gear.

See pic of GM incorrectly stamped cam gear.

[Wittsend]

As a novice who only ever did this once I was concern. However, (as a means of checking) I also shifted the marks one tooth left and then one tooth right and it was VERY obvious that in one position I couldn't even see the mark and in the other I could barely see the very end. Thus, assuming the mark was "relatively" accurate I set it to 'the most visible position' rather than expecting it to be visually dead accurate. And likewise this also corresponded with the keyway right angle visual test.

I'm not disputing that degreeing the cam is the most accurate and offers the greatest assurance. I've done that myself on engines that have slip fit gears and multiple keyways cut in the gear. Unfortunately a lot of people don't have a spare gear machined to slip fit the cam, the dial indicator/base a degree wheel to measure with (much less access to offset keys if needed) and a heat source/press to install the gear. So, they have the 'one time' press fit gear preinstalled from the vendor. And at that point they are at the mercy of the marks being accurate - as possible.

Anyway, the point I'm making is that while there is some ambiguity in the marks being aligned dead accurate it is also obvious when they are shifted one tooth off in either direction they become more inaccurate and thus the correct position should be obvious.

[66vairguy]

As a novice who only ever did this once I was concern. However, (as a means of checking) I also shifted the marks one tooth left and then one tooth right and it was VERY obvious that in one position I couldn't even see the mark and in the other I could barely see the very end. Thus, assuming the mark was "relatively" accurate I set it to 'the most visible position' rather than expecting it to be visually dead accurate. And likewise this also corresponded with the keyway right angle visual test.

I'm not disputing that degreeing the cam is the most accurate and offers the greatest assurance. I've done that myself on engines that have slip fit gears and multiple keyways cut in the gear. Unfortunately a lot of people don't have a spare gear machined to slip fit the cam, the dial indicator/base a degree wheel to measure with (much less access to offset keys if needed) and a heat source/press to install the gear. So, they have the 'one time' press fit gear preinstalled from the vendor. And at that point they are at the mercy of the marks being accurate - as possible.

Anyway, the point I'm making is that while there is some ambiguity in the marks being aligned dead accurate it is also obvious when they are shifted one tooth off in either direction they become more inaccurate and thus the correct position should be obvious.

Good observation. Each cam gear "tooth" is about 7 degrees apart, but keep in mind the crankshaft has to turn TWO revolutions for each camshaft rotation, or about 14 degrees crankshaft when you use a degree wheel. That said davemotohead once built an engine were the new camshaft key was cut in the wrong position and he had to shift the cam TWO TEETH to get the cam timing correct via a degree wheel!! While doing a cam degree check is time consuming, it is MUCH EASHIER than taking an engine apart to fix a cam timing problem. Also you can verify the harmonic balancer marks. Yes sometimes that are off a few degrees. These little things add up to why some engines run better than others.

[vairmech]

See? That is what I am talking about!
Everyone make the big deal about drawing the lines and all this other stuff. Drawing the line through the center put the "0" in the center of the tooth! That's wrong! The GM gear that "66" posted is not the most correct but will line up with the crank timing mark and will get you to time the gear properly! Look at my GM gear, The mark is correct and will properly line up with the crank like below. When I remark the gear at the ROOT of the tooth it lines up perfectly. Any other mark placed somewhere else will not line up!

[joelsplace]

If the nitriding is .010" deep a .010" under crank would still have .005" of nitriding, wouldn't it? Of course if it is only .005" deep it would be gone.

[vairmech]

If the nitriding is .010" deep a .010" under crank would still have .005" of nitriding, wouldn't it? Of course if it is only .005" deep it would be gone.

Correct, but are you sure how deep it is?? All we know is what is called out in the blueprints and what the crank manufacturer wanted to do. If they were generous or forgot then the nitriding is deeper if they were cost conscious then it is probably only .005 deep!