1972 302 Engine Noise

[Subzero]

My truck I just bought has an engine noise that sounds kind of unnerving at idle. Abive idle it goes away but does increase slightly til is estimate 1000 rpm ( not tach in the truck as of yet). I changed the oil out today to 10-30 Rotella with a quart of Lucus Oil stabilizer. It didn't really do much different after that. I took a video before I changed the oil, it sounds better in person. I'm not planning to rebuild the engine for a few years atleast. https://www.youtube.com/watch?v=5Woy3q5mJSc . Anyone know what this sounds like to you?

[Canonman67]

It sounds like an exhaust leak to me, but I'm no expert. Have you checked you manifolds?

[Subzero]

Have not, I maybe thought that too, they look pretty crusty . But that's a relief to hear, my 360 had an exhaust leak but it sounded much different.

[tynall44]

its a rod knocking

[hazelnut]

The best tool you could use to find out where the noise is coming from is a piece of heater hose. Use a piece about 4' long and put one end on valve cover, oil pan, ect and you can listen to hear where the noise is coming from.

To be honest it doesn't sound like a exhaust leak. I would only run the motor to listen for the problem, Then you will know where you stand and can make your game plan.

Hopefully you will find it is something simple to fix.

[mulletmobile]

I am betting on rod knock. Same noise on a 70 shortbed I walked away from (that plus cab mounts that were fiberglassed in and a CV swap in the front with burnt through booger welded in re-inforcement plates). As soon as I told the kid to shut the motor off asap he said that was the same thing the guy before me said and he revved it up. I politely declined and ran. I vote for get ready to yank the motor.

I just finished an exhaust donut replacement on my 360 that solved most of my exhaust noise and it sounded nothing like that. Yours is to consistent for what an exhaust leak usually sounds like.

[Subzero]

Going to look at this tomorrow, if it's a rod knock I'll probably just let it go. How can I tell if it's a rod knock externally by just the sound? All rod knocks I've heard were terribly loud

[hazelnut]

The best tool you could use to find out where the noise is coming from is a piece of heater hose. Use a piece about 4' long and put one end on valve cover, oil pan, ect and you can listen to hear where the noise is coming from.

[Subzero]

Not good news to tell, the engine seems to have much of the noise coming from the low end. No noise at the fuel pump so if doubt it was that. I'm gonna say it's a bottom end problem of sorts, likely a rod knock like y'all said. I used a long pry bar and put it on both valve covers, block where the fuel pump is, timing cover, and lower block under the exhaust. Then I pulled individual spark plugs and couldn't really tell much of a difference with each one, did get a little zap from one . Really bums me as I just bought it and it's basically a 1 owner truck, not a spot of rust anywhere I've seen. Aside from selling the truck and taking what I get for it, what's the cheapest option to fix?

[Jacksdad]

Don't give up on this motor just yet - a rod knock that audible at idle should decrease or stop when the plug wire on that cylinder is pulled. And a bad rod bearing should get noisier with increasing RPMs - they don't typically quieten down as the load/engine speed increases. Now you've isolated it to the bottom of the motor, crawl under there and try to find the source. There's other stuff that can make a noise down there that hasn't been ruled out yet (loose harmonic balancer/pulleys, torque converter/flex plate).

This is a classic noisy rod bearing - https://youtu.be/qJEXuUGOGwM

[hazelnut]

I would call Johnson Mustang in Chesapeake and see what they get for a 302. I asked about a 390 a while back and it was $475, They would start it and let me hear it run before I bought it.

[Subzero]

Before I throw in the towel on this one, I'm going to take it up to the shop that does all my big work that I don't have the time or means to do. He knows much more than I do about them than I do. Why does the noise happen on start up for a few seconds then disappear until it's warmed up? My theory is that the cold thicker oil is covering it up, then when the oil is more fluid, it's less of a buffer for the lower end bearings. Upon cold start up there is no oil there as it drained away. I did notice some change of noise with the spark plugs, but I just don't have the experience with a issue like this to say more. I've bought a few things from Johnsons, they'll have what you need but definitely charge a good finders fee. Local Craigslist I haven't found anything that doesn't need a rebuild also. How hard is it to convert this to a FE 360 and C6?

[hazelnut]

The 302 could have a loose wrist pin. They sound a lot like a bearing knock.

To install a FE/C6 you need to change the engine perches, And put in the right driveshaft for it. I have the right driveshaft if you make the change to a FE.

I would go with a 390 before a 360. They are easier to find and if you get one that came out of a car it would have more compression and get better mileage and have a few more ponies.

360's are very low compression motors and have never got good gas mileage.

[Subzero]

Either way it must be torn down to fix? Due to low money for this and I still want to paint the truck, I might just rebuild the 302 in it, or locate a replacement. The C6 I find would probably need to be gone through and my little c4 is just fine right now . This truck is going to be an occasional daily driver but mostly a weekend ride. I don't plan to tow anything but I'll sure load up the bed with whatever I need to. By the end of today I hope to have an estimate started for the cost. I paid a pretty penny for this truck up front not two weeks ago in the hopes I could just clean up the engine and paint it, which really limits my overall cost to restore it now.

[DuckRyder]

There seems to be quite a bit of echo in the video... but that does sound a bit deep for an exhaust leak... based on symptoms wrist pin could be a definite candidate... should not be too hard to find a decent used 302, or if you are so inclined/equipped to do a rebuild on that one....