possible engine knock

[madvette74]

I dont believe I have any bearing issues, the car runs super sweet, but just recently I noticed when I first start the car it sounds like it detonates, I replaced the distributer cap that was badly cracked.. it started a few days after I had the new cap on.. I have a msd ignition, I got another brand cap, not sure if that has anything to do with it.. I have an msd ajustable timing control, sometimes when I retard it it will not make the sound when first started, doesn't always work though.. my oil pressure is fine. just dont know what causes this...

 

[AKRAY4PLAY]

check your mechanical advance under the cap. it may be rusted up and sticking.

 

[jdp6000]

If it goes away its not a bearing. I had a similar problem. Cause was my timing being off marginally. I think whats ever is causing it is timing related. The previous post is a good suggestion.

Jim

 

[madvette74]

YOU guys are not going to believe what it was......... well I changed my oil, about 2 weeks ago, I bought a case during the winter.. I noticed that my gear drifves were quiet, but my roller rockers got louder, and the sound at startup was what I believe to be the oil pump.. I wa sorting some stuff down my cellar and came across what was left of the case of oil.. sure enough it was 10-30..

I changed the oil yesterday to same brand castrol gtx 10-40.. the weird startup sound went away, my gear drives got louder (thats normal) my roller rockers hardley make any noise.... what I find real strange about this, is that the gear drives where very quiet, with the 10-30.... the 30 weight oil and 95 degree weather dont go together..

 

[goertz]

glad it wasn't bearings. the sign of bad bearins is low oil pressure when warm. if the bearings are shot, it will not under any circumstance build good oil pressure when warmed up, the clearances will be too large. when cold, it might pull good oil pressure, but after a short drive, you'll see a major drop. if oil pressure stays good at all temps, it's usually a sign of a strong bottom end.

also, depending on the engine build, if forged pistons were used, sometimes you hear a piston slap when cold, and it almost sounds like a knock. this is also very common in newer GM v-8's. there was a TSB a few years ago on the truck 454, that a knock on cold start up was totally normal, and there was no fix for it.

 

[madvette74]

yes, I have always had good oil pressure, I didn't go with a HIGH FLOW oil pump, just standard melling pump.. when cold startup it's at 80 when fully warmed close to 40..