Basic drivability tips

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   Hi All!

Questions frequently come up about problems with engine running attitudes.  I was visiting Tom Langdon's page, and he posted a really nice list of the 10 things he found most likely to affect driveability of the Chevy Stovebolt Six.

Since these same concepts apply to most engines of the era, I'm copying a version here, and have 'tailored' it slightly to suit Allis engines of the "B/C/CA" WC/WD/45/D17 flavors.  Feel free to add your own.

1. Check for vacuum leaks at the gasket between the manifold and head and also around the carb base.  Allis engines frequently 'burn through' gaskets at the cylinder head exhaust port junction.  Leaks here WILL affect scavenging, and cause the affected cylinder to run very lean.

2. Check idle vacuum at manifold– should be 15 – 20 inch Hg. and steady.  (This figure isn't specific for an Allis engine, but I suspect fairly accurate, and ANY STOCK engine should have steady vacuum at idle.)

3. Check for carb flooding or dripping. Dripping out the bottom of the carb IS a concern indicative of a stuck or improper float setting, saturated float, or a crack in the carb body.

4. Check ignition initial timing.  The basic rule here, is that if your indicated timing is DIFFERENT than what spec indicates, and the engine won't run right if you TRY to set it at correct timing, then you clearly have a problem elsewhere.

5. Check advance function.  Distributor-based ignitions have advance weights in the base, and the advance mechanisms can, and do wear.  As they wear, the weights can stick, or cause the mechanism to get lazy.  They can even have broken or disconnected springs.
6. If you have a distributor with points, check upper bushing wear by
 pushing the rotor “north to south” and then “east to west”.   Reason for this, is that any lateral play in the shaft will cause the contact point operation to be unstable... either opening too soon, too late, with insufficient or excess lift, bouncing contacts, and in all cases, unstable timing.  It will also cause rapid erosion of distributor cap and rotor contacts, and send erosion spoils around the inside of the cap, causing carbon-tracking.
7. Check individual cylinder power at idle by pulling each spark plug wire and note RPM loss for each cylinder.  Good way to localize manifold leak and valve problems.

8. Check cranking compression (with throttle open).  Should be equal.

9. Are all the rocker arms going up and down?  Check lash.
10. Check for internal crack or hole in intake manifold heat chamber.  I haven't found this in Allis engines, but it is possible, and VERY sneaky- you can have a crack between intake and exhaust side that stays closed up tight when cold, and once warm, the crack opens enough to leak... or vise-versa.

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DaveKamp Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Apr 2010 Location: LeClaire, Ia Points: 5754	Post Options Post Reply Quote DaveKamp Report Post Thanks(0) Quote Reply Topic: Basic drivability tips Posted: 14 Jan 2012 at 9:42am
	Hi All! Questions frequently come up about problems with engine running attitudes. I was visiting Tom Langdon's page, and he posted a really nice list of the 10 things he found most likely to affect driveability of the Chevy Stovebolt Six. Since these same concepts apply to most engines of the era, I'm copying a version here, and have 'tailored' it slightly to suit Allis engines of the "B/C/CA" WC/WD/45/D17 flavors. Feel free to add your own. 1. Check for vacuum leaks at the gasket between the manifold and head and also around the carb base. Allis engines frequently 'burn through' gaskets at the cylinder head exhaust port junction. Leaks here WILL affect scavenging, and cause the affected cylinder to run very lean. 2. Check idle vacuum at manifold– should be 15 – 20 inch Hg. and steady. (This figure isn't specific for an Allis engine, but I suspect fairly accurate, and ANY STOCK engine should have steady vacuum at idle.) 3. Check for carb flooding or dripping. Dripping out the bottom of the carb IS a concern indicative of a stuck or improper float setting, saturated float, or a crack in the carb body. 4. Check ignition initial timing. The basic rule here, is that if your indicated timing is DIFFERENT than what spec indicates, and the engine won't run right if you TRY to set it at correct timing, then you clearly have a problem elsewhere. 5. Check advance function. Distributor-based ignitions have advance weights in the base, and the advance mechanisms can, and do wear. As they wear, the weights can stick, or cause the mechanism to get lazy. They can even have broken or disconnected springs. 6. If you have a distributor with points, check upper bushing wear by pushing the rotor “north to south” and then “east to west”. Reason for this, is that any lateral play in the shaft will cause the contact point operation to be unstable... either opening too soon, too late, with insufficient or excess lift, bouncing contacts, and in all cases, unstable timing. It will also cause rapid erosion of distributor cap and rotor contacts, and send erosion spoils around the inside of the cap, causing carbon-tracking. 7. Check individual cylinder power at idle by pulling each spark plug wire and note RPM loss for each cylinder. Good way to localize manifold leak and valve problems. 8. Check cranking compression (with throttle open). Should be equal. 9. Are all the rocker arms going up and down? Check lash. 10. Check for internal crack or hole in intake manifold heat chamber. I haven't found this in Allis engines, but it is possible, and VERY sneaky- you can have a crack between intake and exhaust side that stays closed up tight when cold, and once warm, the crack opens enough to leak... or vise-versa.

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