Just wondering if anybody has heard of this.It's a 302 30 over flat top. Crank is turned 10, 10, under. All clearances seem good. Has excelent oil pressure. About 60 to 70 psi.Here is the problem, It seems to make a slight diesel noise. That is the best way I can describe it. It isn't near as loud as the actual diesel but it has that sound. It's not something that you can hear while in the cab but if I have the hood up and rev it I can hear it. Hope somebody has an idea because I have no idea at all what would cause this. I have rebuilt many engines Ford and Chevy and never heard of this. Thanks

 

The only thing the comes to mind would be maybe a really small exhaust leak. I can't think of anything else.

 

I checked that. I wish that would be all it is.

 

Thread moved to " 221, 260, 289, 5.0/302, 5.8/351W V8" tech forum. Should find more resources here for your question.

 

Just a suggestion...pull and plug the vacuum advance and try revving it again. I have one that has too much vacuum advance but it only acts up under a load.

 

I'll try that and see if it changes

 

my 87 with a 302 had a cracked exhaust manifold years ago, and it would sound just like a diesel. You couldnt even tell it was cracked until i pulled the first two bolts out and the whole manifold separated into two pieces. went to factory replacement headers and now instead of a diesel, it sounds like a well built 5 liter mustang!

 

one other thing, when i removed my smog pump i didnt plug the hose in the crossover tube...that kinda sounded like a diesel too....until i plugged it

 

I had a broken manifold but I put headers on it. While I had the engine out I plugged the smog holes on the back of the heads. I drove it today and it hasn't got any worse and hasn't blown up.

 

Say, aside from the sound, did it make your mpg or power go up?

 

well not at first cause it wasnt running 100 percent when i did it....after replacing some sensors though, i would guess it gave me 10 or 15 horse more than stock. a little more power and an awsome sound.

 

are you running roller rockers? ive heard they will make such a sound.

 

No they are just the standard rockers

 

you might pull the valve covers and see if they need readjusted

 

I just was under the truck and the sound is coming from the bottom. I can't tell if it from the oil pan or the flywheel area. I can't think that it would be the flywheel because it was fine before.