Author Topic: Is my engine dead?  (Read 836 times)

Offline bigben5054

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Is my engine dead?
« on: October 08, 2018, 10:08:58 AM »
Hey all.  Bought a 79 K20 2 weeks ago.  Has a 350 SBC and 4-speed manual.  Previous owner told me they put new gaskets in the motor.  I thought that was odd.  Who pulls a motor apart just to do gaskets?  It has a Holley carb and Flamethrower HEI.  Anyway, first issue is with starting.  It would start to crank, then make this horrible grinding noise and it almost looked like it spun the engine back the opposite direction for a second.  It would do this quite a bit, but every so often it would crank normal and start right up.  Once running, it seemed to idle fine, but had zero throttle response.  Hit the gas and it would just bog down.  However, if you very gradually increased throttle and got the RPMs up, then snapped the throttle, it had pretty good response.  I thought the issue was timing, so I set the timing yesterday.  I set it about 10 degrees advanced.  It wasn't that far off to begin with.  However this did not fix the problem.  I also noticed that the big red power cord going to the starter had been laying up against a header pipe, melted, and grounded out.  At the time I saw it, it was not actually touching the header pipe, but pretty close.  Assuming this is why the battery kept draining on me.

I also noticed, after having run it a while, that the passenger side exhaust seemed to be spitting more water than it should, and actually you could see a little bit of steam (like in winter time, except its not cold here).  After a while, the garage windows near that exhaust pipe actually starting steaming over.  As if all that wasn't enough, I took a squirt bottle and shot a stream of water on each of the header pipes right by the head.  All would evaporate within seconds, except cylinders 2 & 3, which took noticeably longer (and I conclude were not firing).  I would think the steam and the misfire might be related on the passenger side bank (blown head gasket, cracked head, cracked block?), but not the driver's side.  Thinking I just need to pull it and go through it at this point?  Or could it be as simple as a blown head gasket?  I appreciate any input on where to start here.     

Offline Rapid Roy

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Re: Is my engine dead?
« Reply #1 on: October 08, 2018, 11:17:40 AM »
Welcome.
1974 Cheyenne 10 LWB 350/TH350/AC/4 BBL Quadrajet

Offline JohnnyPopper

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Re: Is my engine dead?
« Reply #2 on: October 08, 2018, 01:41:55 PM »
Welcome.

Do a compression test first. Remember to keep the throttle wide open while cranking.


Offline Captkaos

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Re: Is my engine dead?
« Reply #3 on: October 08, 2018, 05:57:56 PM »
Water is the expected output of a good running motor.  which side is putting out more?
What do the plugs look like?
I wouldn't question a refresh if everything else looked ok and it was leaking..
I would check the plugs and as above do a compression test.

Offline bigben5054

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Re: Is my engine dead?
« Reply #4 on: October 12, 2018, 10:38:57 PM »
Seems like passenger side is the steamy one.  Plugs looked pretty sooty.  Couple were oily.  Compression test as follows:
#1 - 120
#2 - 120
#3 - 0
#4 - 120
#5 - 120
#6 - 120
#7 - 120
#8 - 140

Obviously, #3 is a problem.  Any thoughts on most likely culprit?  This is a real bummer. 

Online VileZambonie

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Re: Is my engine dead?
« Reply #5 on: October 13, 2018, 07:25:18 AM »
Pop the valve cover off and look for a bent pushrod or rocker issue, or maybe a wiped cam lobe, etc. If you have have access to a cylinder leak down gauge, put #3 on TDCC and see what the percentage of leakage is and where it is escaping.
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Offline bigben5054

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Re: Is my engine dead?
« Reply #6 on: October 13, 2018, 12:10:05 PM »
Pulled the valve cover and looked things over.  Everything looks good - but I did not remove the rocker arms and pull the pushrods yet.  I bought one of those valve holder hoses that lets you pump air into the cylinder from a compressor.  I turned the engine by hand until I was sure #3 was at TDC.  Put about 15 pounds of air into it.  No noise from tailpipe, nothing from dipstick tube, but air was absolutely coming up through carb.  So I've got it narrowed down to the intake valve on #3.  I'll check the rocker arms and pushrods before I pull the head, but looking like I'll need to pull that head and check out what's going on.  At least I dont have to pull the whole motor...yet...*knocks on wood*

Online VileZambonie

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Re: Is my engine dead?
« Reply #7 on: October 14, 2018, 08:11:00 AM »
Are you sure you're on tdc compression? Both rocker arms are up? If so, back off the nut on the intake rocker are and see if it makes a difference. Just count the # of turns you loosen it so you can put it back.
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Offline bigben5054

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Re: Is my engine dead?
« Reply #8 on: October 14, 2018, 04:04:15 PM »
Well, too late.  I pulled the driver's side head last night.  Based on the photo, I guess it wasn't TDC, but I watched the valves very closely while turning it by hand and I'm certain they were both closed.  Great.  So now I can't be sure it was the intake valve?  At least I know its not a hole in the piston.  And it it were piston rings, I would have gotten some compression on the test, not 0, right?  Ugh.

Anyway, pistons look ok and considering how much cleaner #3 is compared to the others, I'd say this problem has been going on a while.  The valves look pretty nasty, its hard to tell from just looking at them whether the valve isn't closing all the way.  That gunk all over the intake valve is hard as a rock.  Wonder what caused this?  Anyway, think I'll pull the other side head and take them both in to a shop for reconditioning.

I just hope I dont go through all this just to find out the problem is actually in the short block someplace.

Online VileZambonie

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Re: Is my engine dead?
« Reply #9 on: October 14, 2018, 06:38:11 PM »
Put the spark plug back in and prop the head so it's relatively level. Fill the combustion chamber with ATF and let it sit. See if any ATF leaks past the valves or combustion chamber.
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Offline bigben5054

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Re: Is my engine dead?
« Reply #10 on: October 14, 2018, 07:12:47 PM »
Good suggestion; thank you.  I don’t have any ATF.  Would engine oil work just the same or is there something special about ATF?

Offline bigben5054

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Re: Is my engine dead?
« Reply #11 on: October 14, 2018, 08:41:47 PM »
Yeah, I'd say the intake valve is the culprit.  Still curious as to what causes this mess.  Thanks for the help. 

Offline JohnnyPopper

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Re: Is my engine dead?
« Reply #12 on: October 15, 2018, 02:11:18 PM »
Kind of odd, usually the exhaust valve goes... From your pics I can't see any scoring in the cylinder that might indicate broken rings.

Been some years since I tore down a motor, your pics are inspiring. Think a rebuild is in my future!  ;D

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Re: Is my engine dead?
« Reply #13 on: October 15, 2018, 02:40:14 PM »
5w30 is fine. Pop the valves out, decarbonize it and inspect.
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Offline JohnnyPopper

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Miles
« Reply #14 on: October 15, 2018, 09:06:04 PM »
Do you know approximate miles on engine?