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#1 |
Registered User
Join Date: Jan 2006
Location: Dallas
Posts: 504
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Engine knock
This is not truck related but engine related and you guys are some guru's so I hope it is ok to ask this question...
Last night I went over to my friend's house who has an all original 70 Nova with a 307, and it ran perfect when he parked it FIVE years ago... I was planning on buying the car. I changed the oil, put in a new battery, primed the engine oil before starting it, but when I started it, it knocks pretty bad from deep down in the middle somewhere and blows gray smoke. ![]()
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_______________ Thomas '78 Silverado '74 Monte Carlo '47 Teardrop Trailer East Texas Classics Local Club |
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#2 |
Account Suspended
Join Date: Aug 2007
Location: Austin, Tx
Posts: 81
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Re: Engine knock
Do you have an oil pressure guage on the car? It sounds like low oil pressure. I have seen purpose built primers, but I have a priming tool I made out of an old distributor. I took the shaft out, cut the top out where the cap mounts, then cut the top of the shaft down so that it fits in a 3/8" drill. I have used this to prime new engines and cars that have sat for long periods. I hook a mechanical oil pressure guage to the enginge, spin the oil pump with a drill, turn the engine over, then repeat.
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#3 |
Registered User
Join Date: Aug 2007
Location: reno
Posts: 397
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Re: Engine knock
It sounds to me like a lifter issue. I have noticed that small block chevy's in particular do not like to sit. If it was a rod knock or a main knock it would probably still run half way ok, but if the lifters are bad the valves are not working correctly causing a bad miss. I have had several used engines in various vehicles and have had that problem many times. I would suggest pulling the valve covers and making sure the valves are all moving.
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#4 |
Account Suspended
Join Date: Aug 2007
Location: Austin, Tx
Posts: 81
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Re: Engine knock
Good point on the lifters. They usually do not knock, though. If there is a miss, there is a pretty good chance one is stuck. It sounds ghetto, but I have solved this issue before adding some kerosene to the oil, running the car for a while, then changing the oil. A deep knock sounds like lack of oip pressure or a bad bearing, though.
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#5 |
Registered User
Join Date: Jan 2006
Location: Dallas
Posts: 504
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Re: Engine knock
No oil pressure gauge
![]() It doesn't sound like a lifter "tap", like I have heard in the past, more like a knock, I don't know if lifters can make that kind of sound. (I can swap engines in my sleep, I just never tore deep into one before). When I first start it, it will run smooth (sometimes knock sometimes not) and about 1 min later, it will be knocking and missing pretty bad, but it will idle by itself. I've heard and seen people drop some tranny fluid in the carb to blow it out, then change the oil, but that would just clean the valves and cylinders right? I'll pull the valve covers and see what I get. Any other ideas for me to try are very welcome!
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_______________ Thomas '78 Silverado '74 Monte Carlo '47 Teardrop Trailer East Texas Classics Local Club |
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