I have a 67 BB 400 hp tri power, at low rpm say from 1200- 2700 rpm i have this raddle, its when your under power just giving it gas, under heavy load you cant hear it, or just reving the motor. i pulled the oil pan to take a look & changed the rod bearings - no help i cant tell if it is piston slap or not. timing is good as is gas. how about a lifter? it seems louder when cold, but never goes away. The engine seems to run fine, any one have any thoughts? Thanks in advance
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Re: engine raddle Help!
Jeff,
Sounds like I have the very same problem with a 66 427/390. How's your oil pressure? Mine is very good. Mine does it on acceleration and also a little when idling, but only when idling with the car in gear (auto). I've had it to the shop, and he went over it with a mechanic's stethoscope and can't isolate it either. I thought it might be pinging, so I ran a tank of 50/50 93 octane and 110 racing gas. It seemed to help, but did not eliminate completely. -
Re: engine raddle Help!
Hey Jeff -
Did you check the clearance of the rod bearings? Just installing new bearings won't help if there is too much slop. You can check the clearance without pulling the engine using Plastigage. I would also check the crankshaft main bearings and journals while I was in the neighborhood. There was an article in the April 2003 issue of Corvette Fever magazine about my 1963 engine rebuild. Check it out and see if the symptoms I had leading to my rebuild are similar to the ones you're experiencing.Comment
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Re: engine raddle Help!
Rod bearings would normally have more of a deep knocking sound than a rattle, it sounds more like a preignition or ping issue. I agree that if you had gone to the trouble to replace the lower rod bearings, a plastiguage check is in order, adn checking with a precision micrometer on the rod journals for uniform diameter and concentricity. Some times piston slap can exhibit itself at lower rpms as a knocking, usually that is a symptom of a forged piston, and usually that goes away after warm unless the clearance is excessive..CraigComment
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Re: engine raddle Help!
Do you have forged pistons? They raddle a little when warm and a lot when cold. Nothing to worry about it's normal.Comment
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