Possible Rod knock issue?
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Teching In
Joined: Oct 2012
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Possible Rod knock issue? Hey guys, got a couple questions here, ive been doing my searching and havent recieved an answer.
Got a frest 383 stroker shortblock that i just installed. Friend of mine had it built at a local reputable shop (about a year and half ago) and it sat in his garage saran wrapped up. I picked it up for a good deal, bolted everything onto it and dropped it in my c5.
Initial start went quite well, built oil pressure right away. I did find the oilpressure to be a little low (25psi at idle when warm). Time came to do some break in/tuning.
While doing some data logs just part throttle (10%-15% throttle), the car seemed to sound like a beast, everything was working great. Started logging and taking it up to about 2500rpm, and i noticed a knocking sound that was apparent above 2000rpm, and would stay knocking for about 10-15 seconds following when i let it idle down. At idle there is NO knock what so ever, valve train is very quiet. It is only apparent above 2000+ rpm, but does not do it if rpm are kept below that. It also only knocks when there is a little load on the car, it cant be replicated when in neutral. oil pressure at 2000-2500 is around that 32-35psi.
Car has new lifters, rocker arms, valve springs, valves, valve seats, everything.
Im puzzled, and dont want to risk doing any more damage, I dont have any vids of it, but it does somewhat sound like rod knock according to videos, i just thought it would be there all the time.
Let me know what your thoughts are.
Thanks alot
Got a frest 383 stroker shortblock that i just installed. Friend of mine had it built at a local reputable shop (about a year and half ago) and it sat in his garage saran wrapped up. I picked it up for a good deal, bolted everything onto it and dropped it in my c5.
Initial start went quite well, built oil pressure right away. I did find the oilpressure to be a little low (25psi at idle when warm). Time came to do some break in/tuning.
While doing some data logs just part throttle (10%-15% throttle), the car seemed to sound like a beast, everything was working great. Started logging and taking it up to about 2500rpm, and i noticed a knocking sound that was apparent above 2000rpm, and would stay knocking for about 10-15 seconds following when i let it idle down. At idle there is NO knock what so ever, valve train is very quiet. It is only apparent above 2000+ rpm, but does not do it if rpm are kept below that. It also only knocks when there is a little load on the car, it cant be replicated when in neutral. oil pressure at 2000-2500 is around that 32-35psi.
Car has new lifters, rocker arms, valve springs, valves, valve seats, everything.
Im puzzled, and dont want to risk doing any more damage, I dont have any vids of it, but it does somewhat sound like rod knock according to videos, i just thought it would be there all the time.
Let me know what your thoughts are.
Thanks alot
TECH Addict
Joined: Mar 2013
Posts: 2,628
Likes: 30
Kinda hard to diagnose something like this over the net but i'll tell you what you can try. Get it to knock , start unplugging injectors one at a time and see if it stops. At least you'll know what cylinder or some direction to go.
Also you should have more oil pressure IMO. Might want to just pull the engine back out and pull it apart then find all the issues. Its easier than trying to guess what's going on inside there.
One other thing without hearing it this is just a guess but a damaged oring on the pickup tube can cause all the things you describe.
Also you should have more oil pressure IMO. Might want to just pull the engine back out and pull it apart then find all the issues. Its easier than trying to guess what's going on inside there.
One other thing without hearing it this is just a guess but a damaged oring on the pickup tube can cause all the things you describe.
Last edited by RockinWs6; Apr 15, 2015 at 07:05 PM.
Your best bet would be to take the car to the shop that did the engine and let them hear it. Forged piston engines can rattle if too much timing as the piston to wall clearance coupled with the non-offset wristpin location will make noise. If it truly sounds like it's coming from under the engine then perhaps a thrust bearing that was not properly clearanced which is now scoring itself to death and sending shrapnel through the bearings. Worst case scenario.....
TECH Addict
Joined: Mar 2013
Posts: 2,628
Likes: 30
Another thing to look at is the engine oil, If it has serious trouble you'll see it in the oil. Coppery silvery oil etc. If it's a serious problem it won't last long. If its just some lifter or piston noise it will last a long time.
