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1940 Buick series 70 camshaft


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I am restoring a 1940 Roadmaster sport coupe. I owned the car 40 yrs ago, sold it unfinished, bought it back 4 yrs ago. Nothing was done to the car in the interim. I had the motor completely rebuild 35yrs ago, new babbit bearings, everything was done. Put the motor in the car, started it, ran beautifully. Sold it unfinished a couple years later. It then sat for 20yrs, not sure if it was even turned over. I bought it back, it turned freely, I started and it ran ok, but had a miss. I have started it occasionally since then, but yesterday decided to try and find the miss. Zero compression on last cylinder by firewall. Took of valve cover, zero movement of either rocker. Valves are free, I can push them down they come right back up. My diagnosis is wiped camshaft lobe. Who might have this camshaft. It is the 320 cu. in. engine. How big of a job is it to change it?. I am a body and paint guy, hate mechanical work. 

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You can buy a cheap bore scope from Harbor freight store or online. It will allow you to look thru spark plug hole and possibly see the problem. If the cylinder head has to come off make sure you have help or a hoist. All the pushrods can be removed easily, except the one at the very back. When pulling that one it will hit the overhanging firewall. Cyl head must be pulled up part way then moved forward some with pushrod held carefully part way up to prevent it being bent while moving cyl head up and forward to remove. Good luck with repair! Machine shop can check head for flat. If it needs to be removed consider having .040-.060 milled off to pickup some compression. Massive amount of cast iron there and very low compression. Made to run on crappy early fuel available b4 WWII. Better fuels developed for airplanes during war allowed higher compression use after. Better mileage and more power. I have a 1940 320" parts engine if you need something lemme know.

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Thanks, probably going to need a good cam. Very frustrated with the car at this point. Body is ready for paint, I bought the paint, orginal color is Monterey Blue and Silver french gray. Entire interior is redone in correct material, most chrome is done, grill needs to be redone in my opinion. I thought the engine was fine, since I had everything done to it years ago. About ready to sell it and be done with it. I have other cars. This was a virtually rust free, dent free car when I got it 40yrs ago. Unfortunately, the person I sold it too, a friend, just let it sit in a building. He lost the hood, that cost 1500 to replace. Guess I will talk to my engine guy and maybe just pull the motor and let him check everything out. 

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You don't need to pull the engine to replace the cam.  Take the hood and radiator core off then disassemble the front of the engine to gain access to the end of the cam shaft.  Also pull the valve cover, rocker arm, push rods from the top of the engine and the lifters from the side of the engine.  Cams can be found easily, if you are having trouble finding a cam, shout back.

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On 9/28/2020 at 11:31 AM, kgreen said:

You don't need to pull the engine to replace the cam.  Take the hood and radiator core off then disassemble the front of the engine to gain access to the end of the cam shaft.  Also pull the valve cover, rocker arm, push rods from the top of the engine and the lifters from the side of the engine.  Cams can be found easily, if you are having trouble finding a cam, shout back.

Do you know if a cam from a 1938 320 is the same as a 1940. 

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14 hours ago, michealbernal said:

I wonder if the valve lifters may have seized in their boars.  Prior to going any deeper into this I would make sure the lifters are free.

Push rods are free, I need to check lifters. Since all sheet metal is off car, I will most likely pull engine.

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If the lifters are frozen, and the engine turns over, they would have to be stuck open and you would readily see that condition at the valves.  It's strange that both valves in a cylinder have the same problem.  Broken camshaft?? Hole in Piston??

 

Bob Engle

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4 minutes ago, Robert Engle said:

If the lifters are frozen, and the engine turns over, they would have to be stuck open and you would readily see that condition at the valves.  It's strange that both valves in a cylinder have the same problem.  Broken camshaft?? Hole in Piston??

 

Bob Engle

Who knows, will pull engine, take to my guy and let him figure it out. 

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