Top end noise?

JustJoshin · Oct 31, 2010

Hi all, new to this fine site and to mustangs. I just acquired an 88 vert LX with a V8, 5 lug, 5 spd swap. The previous owner said it had a bad main bearing and said it was knocking. Upon getting it home and firing it up, it sounds a lot more like a top end issue to me. I popped off the valve covers, and nothing looked too out of the ordinary. Dropped the oil and it was clean, no metal or shavings.

It runs well, but breaks up at higher RPM under load. I haven't hooked up a mechanical oil psi gauge yet, but the dash gauge reads in the normal and about a 1/4 of the way up the gauge at idle.

Any ideas? I have another 302 available if this one is toast, but if it is something simple such as lifters, I would like to fix it and drive the car while I build the motor for my lightning (supercharged 5sp 94). So far it seems like it will be a fun car! I have always wanted a mustang but always had the need for a truck.

http://www.youtube.com/watch?v=QZlIh_JftqM heres the link to a video of it running

Any insight would be great!

Thanks!

2000xp8 · Oct 31, 2010

Does sound like it's on the top half.
Also sounds like you may have a header leak.

Does the car have roller rockers on it?
A cam in it?
Could all ad up to bad valve springs with a cam and lousy rocker adjustment or wrong length pushrods.
Any mods to the car?

bmo37 · Oct 31, 2010

Hard to tell could be a spun bearing, bad lifter, rockers that aren't adjusted right, oiling issues leading to valvetrain noise. Crappy thing is they all sound similar so its hard to go by sound. You have the right idea I would start with the simple things, hook up a vacuum gauge check the idle reading (around 17-22) is normal, rev the engine (open to closed throttle) and you should get a vacuum drop followed by an increase than back to idle.

If everything else checks out, I would check that your getting oil in your valve covers, pull the filler cap and watch when the engine is runing to see if the rockers look like they are being oiled. If they are I would go and check that the rockers are properly adjusted. While your adjusting the rockers you check for anything obvious like excessive gap or broken springs, if the adjustment pans out than I would tend to think the original owners bad bearing theory is more plausable.

JustJoshin · Oct 31, 2010

Well the previous owner claims it has a "mild" cam in it but who knows. The noise sounds like its coming from the middle of the motor to valve covers. Definitely sounds like its on the upper half of the motor. It resembles the sound of one of those noise maker party favors that you spin around and produce an incredibly annoying noise.

Besides that it has an electric fan, ud pulleys, and an exhaust. I believe its stock besides that.

Negative on roller rockers, but i believe it has roller lifters. I tried to pull a few out but they would only budge about a 1/4 inch before catching on something.

How would you tell if its a bad spring? Nothing looked too out of the ordinary.

Now if it were a spun bearing and the crank isn't toast, can you just slap some new bearings in there?

I am starting to think it might be easier to just toss a new used motor in there....

2000xp8 · Oct 31, 2010

JustJoshin said:
Well the previous owner claims it has a "mild" cam in it but who knows. The noise sounds like its coming from the middle of the motor to valve covers. Definitely sounds like its on the upper half of the motor. It resembles the sound of one of those noise maker party favors that you spin around and produce an incredibly annoying noise.

Besides that it has an electric fan, ud pulleys, and an exhaust. I believe its stock besides that.

Negative on roller rockers, but i believe it has roller lifters. I tried to pull a few out but they would only budge about a 1/4 inch before catching on something.

How would you tell if its a bad spring? Nothing looked too out of the ordinary.

Now if it were a spun bearing and the crank isn't toast, can you just slap some new bearings in there?

I am starting to think it might be easier to just toss a new used motor in there....

Even a mild cam will make short work of stock valve springs. That could explain the high end miss. Does it feel like you are hitting the rev limiter, but you really aren't?

Bearings aren't worth the trouble.

I've had bad bearings, none made any sounds like that up top, in fact other than burning oil and low oil pressure everything was fine.

Lifters are rarely bad.

Used engines are probably the way to go if something is truly wrong with the bottom end.
Look for an explorer 5.0.

JustJoshin · Nov 1, 2010

Another quick noob question, if the rockers are secured with a bolt, they are pedestal mount correct? And are they adjustable? Or just torqued to a certain spec? (thought i read 26ft lbs somewhere)

thanks for the replies so far, very informative

bmo37 · Nov 1, 2010

Pedestals (which it sounds like you have) are torqued to spec and usually need to be shimmed to be adjusted right. If shimming doesn't work you might need to change to longer or shorter pushrods too (invest in a pushrod length checker). I don't remember the torque setting but though it was around 18ftlbs or so but don't quote me. If you have stud mounts its all by feel with the pushrod movement and you do about 1/2 a turn than lock down the poly locks.

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