Hi,

I've got a rebuilt 302 motor that I'm running in an '85 F-150. The bottom end was put together by my machine shop. Everything is pretty much stock.

Before I got it started, I primed the oil pump with a drill. Then I had to turn it over a lot to get my fuel pump primed. It turns out that I had a bad fuel pump so the next day I replaced it. When I was turning it over then, I heard a few squaling or screeching sounds as it rotated. I pulled the dist and primed it again. The noise went away.

When I finally got it started it sounded fine. But then once it got warmed up I heard a "dud dud dud dud.." sound. It is pretty noticible and I feel a vibration in the truck. When I open the throttle, I hear the sound increase up until I hit about 1500 RPM. Then I can't hear it anymore. The engine sounds good all the way up until 4000 RPM.


I checked the plugs on the 302 and they were black and sooty... after about only 20 mins of idling. I adjusted my floats and idle needles but it ran the same. It is definately rich. The Holley carb has 59 jets in it. What size do you think should be in a Holley 600 4bbl carb on a 302?

When I crawl under the engine, the sound is louder and has more "hammer hitting concrete" do the sound.


When the engine first started (it was cold) I did not hear the noise at all. Then, as the engine warmed up I started to hear it.

I started pulling the spark plugs out and plugging them back in one by one.

When I got to the #3 spark plug, the sound went away. Put the plug back on and "dud dud dud dud..." take it off and it went away. Then I let the engine idle and gave it a little gas and the sound came back slightly and then went away.

So I think something is definately related to the #3 cylinder. I pulled the valve cover and everything was fine up there. I did a compression test and I got the same on all cylinders.... about 90-100 PSI on the first puff and then topping out at 150 PSI after about 5 puffs of the engine.

I drained the oil and checked it with a magnet (it was really black) and I didn't see any metal shavings. I pulled a few grit particles with the magnet, but nothing catastrophic looking.

So.... BEFORE I pull the motor back out and tear it down... anybody have any suggestions?

Does what I just described here sound like a bottom end issue?

If I pull the motor and everything looks OK on the bottom end, what would you do?

Thanks,
Sal

 

That screech you described at the second startup, could it have been a rod bearing failing?

did the machine shop plasti-gauge the main/rod bearing clearance's? They should have kept a record of the results.

Then there is the firing order. As I recall, the small block ford had a different firing order depending on the crank.

 

I bet the oil pressure looks funny, too. You have a rod knock. If it goes away on 3, it is cylinder 3.

Robbie