Engine Rattling

[DoubleL]

Wonder if you guys have any input here. My truck has started rattling pretty bad. It is especially noticable under load. This is a rattle up higher not a low rod knock sound. It seems louder than a valve adjustment need. I am wondering about two things. I changed the oil a few months back and didn't notice if it had Zinc in it. I have just recently found out my 292 needs this for lubrication. I also have an old HEI distributor and I noticed it is a little rusty inside and I am suspicious of the timing being set right. I am going to get a zinc supplement and have already bought a new HEI unit to install. I recently rewired the truck and converted to gauges. I just got the part to connect my oil pressure gauge so I can check that out too. I guess i just want to know if I'm on the right track here and if there is anything else you all would check.

[spacedebris]

My experience with a knock/rattle under load is 3 fold. They all sounded to same to my ears but had different causes.

1. on my Grand Marquis the knock was caused by high octane. I always heard it was caused by low octane but I always ran the 93 in it. When I dropped to 91 the knock went away.

2. in my dodge d100 (1970) it was lack of lubrication. I started using a "lead" additive and the knock went away.

3. In my VW it just needed a valve job.

Now to my ears it always sounded the same to me, but then my hearing has never been the same after my career in driving big rigs. All that time around loud diesel engines took its toll.

I would just go trial and error. try the zinc, and see what happens. Since you have the HEI already give it a shot. It sounds like you are on the right track.

[turbostar]

From what you describe,it sounds like it may be pinging(pre-ignition). This could occur from too much ignition advance. You might try retarding the timing slightly to see if it goes away.

[harpo1313]

vacuum advance working? pop the cap off ,suck on the hose leading to it and see if its moving.

[61_FL_Apache]

I would adjust timing if needed and try some 93.

[DoubleL]

Thanks for all the input guys. I will be checking all this out. I probably wont get to it for a few days (working sucks) but I'll let you know what I find.

[DoubleL]

Finally got around to putting in the new distributor and it fired right up so I must have put it in right I am getting a timing light tomorrow to get it set. Is the timing supposed to be advanced or retarded? Also, the vacuum advance was totally rusted and not functioning. I'll be anxious to get it timed tomorrow and start driving it again.

[PoDuck]

I guess that the sound went away.

I had a really loud noise coming from my top end once, and I couldn't figure out what it was at first. Come to find out, it was a loose rocker. The bolt on it decided to stop locking. It was hitting the top of the valve cover.