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Northstar (pre-'99) Engine knock


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My first topic, I just received another present from GM, an engine knock. It sounds like its from the upper part (valvetrain)of the engine. It just happened, so I haven't investegated it to much yet. Luckely ??? it started when I was only a block from home, so it only ran for 30 sec./1min. or so. It didn't happen gradually, but instantly. I was at the end of a 30 min. drive (highway)and had WOT 'd it before the knock accured, but that was a few mins. before the knock accured. I don't think it's piston slap or bearing noise. Has anybody had a knock in a Northstar that isn't piston slap? If so, is it hopefully something simple "lol" like a collapsed lifter,broken link on a chain(if possible)etc. I love these cars, but with Head gasket problems,power steering failures,oil leaks ( which I've all had with two Caddy's )I'd like one problem that I could repair myself besides brakes,bulbs,batterys,and bugs.

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Carbon rap is not uncommon, particularly with cars that are mainly driven around town and those that are driven mostly on short trips where much of the time the engine isn't fully warmed up. If you run regular gas instead of premium that can make a carbon rap more likely. If you did a WOT some may have loosened and a piece may have stuck in the squish area. If so, it will decrease quickly, going away with a hot engine, in a couple of days.

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Carbon rap is also known as cold carbon rap because it shows up at start up and usually goes away after 30 -60 seconds. Anything dislodged would have made noise immediately and quickly been discharged out the exhaust valve. If this developed after a :30 min. drive, I doubt that it is carbon rap. I have heard of a few engines developing an upper end lifter noise. I think it was a bad cam, but can't swear to it. Get a stethoscope and listen to the cam covers. If the noise (usually a tick more than a knock) is coming from there, then you will probably have to pull the cam covers (not an easy task).

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First post huh?

We have seen Northstars blow a rod through the engine idling at a gas pump

We have seen Northstars knock and blow a rod during a WOT

We have seen them go 300K miles

Fill us in

How many miles on this car

How many owners

How was the oil pressure?

Which car the 98 or 97

How has the car been maintained

Did it have a case half leak?

How high was the RPM when you did the WOT? redline?

This is not a gift from GM, this is part an parcel of owning an old vehicle, you will need repairs on any older vehicle of the same sophistocation

If you are at all mechanically inclined these engines can be worked on

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