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Old 07-19-2010, 10:10 AM
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cylinder #1 not firing

The number 1 cylinder in my chevy 350 is not working. I put new plugs, wires, cap and rotor, checked to make sure rocker nuts aren't too tight, i dont have a compression tester but when you crank it over with the starter and the plug out i can fell air coming out. The weird thing about it is that it was running fine a few days ago. I just rebuilt it and it has only run for about 20 minutes. Any suggestions for what to check? It seems like once i fix one thing, something else goes wrong, but thats my luck anyway.
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Old 07-19-2010, 10:22 AM
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if none of neither valves are bent, you will have to get a compression gauge and check it. or do a leak down test.

is that cylinder getting spark?
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Old 07-19-2010, 10:27 AM
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Maybe the spark died? Try removing a spark plug, leave the wire attached and ground the plug then crank the engine and see if you have spark.

Are you getting 12 volts at the distributor BAT terminal? Good luck.

BT
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Old 07-19-2010, 01:12 PM
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cylinder #1 not firing

swap wires on 1 and 2 cylinder , see if 2 miss'es .
swap at cap too .
you break the wire in plug boot ?
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Old 07-19-2010, 06:00 PM
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Thanks for the replies guys. It is getting spark but i think the exhaust valve is not closing all the way because i took the valve cover off and it looks like it's not coming up as high as the rest. What would cause it to bend? I had it running with this problem so i know the other cylinders are working fine. Also, if it is bent, i have a set of 305 heads from the old engine laying around; think i should swap them out until i can get the valve fixed? (if it really is bent)
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Old 07-19-2010, 06:15 PM
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Bent valve would be unusual, unless it seized in the guide first. Is an intake or exhaust? Is the pushrod for that valve moving up and down as much as the others?
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Old 07-19-2010, 06:57 PM
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Could you have over tightened the rocker and bottomed out the lifter? because if the spring is not retruning the the height of the other valves your rocker would be loose and rattling - right?
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Old 07-19-2010, 07:03 PM
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it's the exhaust valve. I took both the rockers for the number one cylinder and both for the #3 so i could compare them and it looks like the #1 cyl exhaust valve doesn't come up as high as the rest. And no, I didn't over tighten the rocker nuts.
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Old 07-19-2010, 08:59 PM
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any thoughts?
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Old 07-19-2010, 09:12 PM
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I remember on another forum some guy installed some headers on his truck well they didn't have the bung hole for the 02 sensor and he burnt the valves the story was he didn't know it was that and he messed up two new crate engines. Just sharing a story.
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Old 07-19-2010, 09:28 PM
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Quote:
Originally Posted by bigdog7373
it's the exhaust valve. I took both the rockers for the number one cylinder and both for the #3 so i could compare them and it looks like the #1 cyl exhaust valve doesn't come up as high as the rest. And no, I didn't over tighten the rocker nuts.
A simple compression test will show if the valve is open.

If the heads are fresh (new or newly reground seats), you can replace the exhaust valve w/a new valve- providing the guide is OK. I would lightly lap the new valve to the seat- others may disagree w/this and that's fine.

Just be sure the valve stem seals aren't sealing so good that the valve is sticking because of a lack of lubrication. Also be sure there's sufficient guide to stem clearance.
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Old 07-19-2010, 09:36 PM
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Quote:
Originally Posted by bigdog7373
any thoughts?
Cam is going flat.
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Old 07-20-2010, 02:41 AM
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Bingo! I bet thats it. There are so many problems with new cams getting wiped out these days. And if i understand correctly, you just rebuilt this engine so I assume it has a new cam. If its only run 20 minutes then it probably hasn't been broken in correctly.

I think there are certain motor oils that should be used during break in (Rotella T? And John Deere plus 50 i noticed is CJ4 rated as well, but i honestly think it is just Rotella rebottled.) There is also a special additive that i cant call the name of right off hand that should be used with a new cam.

Someone else please chime in and fill the gaps in my info...
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Old 07-20-2010, 03:01 AM
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I'll throw my hat in the ring and say, if the valve isn't bent...the hardened valve-seat might have came loose. Could be wedged back in crooked, keeping the valve from coming all the way up. Either way, you should do a compression check before going any further.
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Old 07-20-2010, 05:45 AM
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Quote:
Originally Posted by Torque454
Bingo! I bet thats it. There are so many problems with new cams getting wiped out these days. And if i understand correctly, you just rebuilt this engine so I assume it has a new cam. If its only run 20 minutes then it probably hasn't been broken in correctly.

I think there are certain motor oils that should be used during break in (Rotella T? And John Deere plus 50 i noticed is CJ4 rated as well, but i honestly think it is just Rotella rebottled.) There is also a special additive that i cant call the name of right off hand that should be used with a new cam.

Someone else please chime in and fill the gaps in my info...
I am surprised at all the problems with cams mentioned . I built engines and replaced cams in at least a dozen engines at a shop I worked at in '84-'85 . I always just coated the lobes with STP and ran the engine at 2500 rpm for 20 minutes ( no idle time ) and never lost a replacement cam . Just fired up my 350 yesterday with a new Sealed Power CS274 cam and used the old break in method . I hope it doesn't fail prematurely . BTW I have always used Valvoline . If the cam wasn't broken in properly , could have very well wiped a lobe .
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