302 swap or rebuild?

[billy]

swap or rebuild?
my 1981 ford 302 has the following symptoms,and my experienced mechanic buddies say it is piston slap.
starts and idles fine
at about 45-50 mph i get a tapping from the #4 cylinder that gets louder the faster i go.
i just dont trust this engine with god only knows how many miles on it.
keeping in mind that i am no sort of mechanic.
would it make more financial sense to simply buy a different engine and swap it out rather than jump in head first and try my hand at rebuilding a 31 year old engine with an unknown past?
and if a swap is the way to go.
just how difficult would it be?

 

[Tripper]

Before you do anything... I would check to make sure you don't have an exhaust leak. A leak can sound exactly like that! And if you don't have a leak... goin' over 50mph in it could cause serious damage if something comes loose. My buddy totally lunched a $25K blown 572 recently at highway speed when a lifter & rocker grenaded!

BoB

 

[eyesore]

If you decide to rebuild, I would run a compression check and check the mains first! Does it have a lot of gunk under the valve covers and valley?

ISore

 

[donsrods]

If you go the swap for another engine route, you will have to be a little careful. 1981 was a transition year for Ford on the 302 where they went from a 28 oz imbalance to a 50 oz imbalance. You will need to make sure which one you have so you don't put the wrong flexplate/flywheel or damper on it.

Don

 

[billy]

thank you all for the valuable advice.
i hate to say it but
with my spinal arthritis after completely screwing my back up moving furniture.
anything that gets done to this car.
i am not going to be able to do.
that means i am actually going to have to hire a mechanic.
i cant believe i just said that.

 

[zzrodder]

This may be a dumb question but here goes anyway... When you are traveling at 45-50 mph, how can you tell it's #4 cylinder? [S
If it is piston slap or some other noise, it should occur at the same rpm whatever the vehicle speed is...
Have you taken off a rocker cover to check for obvious problems? More likely a rod bearing than piston slap - if a piston is that loose in the bore the spark plug will probably tell you something due to increased oil consumption. Drain the oil and look for silver (metal) colors - that's a for sure sign of trouble.

 

[billy]

This may be a dumb question but here goes anyway... When you are traveling at 45-50 mph, how can you tell it's #4 cylinder? [S
If it is piston slap or some other noise, it should occur at the same rpm whatever the vehicle speed is...
Have you taken off a rocker cover to check for obvious problems? More likely a rod bearing than piston slap - if a piston is that loose in the bore the spark plug will probably tell you something due to increased oil consumption. Drain the oil and look for silver (metal) colors - that's a for sure sign of trouble.

while running i killed each cylinder in turn and when the noise stopped i knew which cylinder is the problem.

 

[hotrodbill]

Really it could be a number of things.

Could be a sticking valve guide, or an exhaust valve starting to burn.
Could simply be a lifter collapsing.
It could even be carbon buildup, causing that cylinder to detonate.

A 302 can be rebuilt pretty cheap,
and an engine from a junk yard stands a pretty good chance of being....junk.

I would do the previous suggestions first. Check the plugs and see what they look like. All the same color? All running equally rich/lean?

Let the engine set overnight, and drain some oil. Check the oil for metal. Hold it up in the sunlight (not shop lights, SUN light) and look for swirls of metalflake.

 

[Crossfire]

engine problem

I f the engine runs fine except for the one cylinder. Get yourself a "real mechanic" and have him check it out. As said ,could be lifter,valve spring,valve,even a wristpin or rod bearing. No need spending more money than you need to.

 

[billy]

rod bearing trashed intself and screwed up the cam as well.
when we opened up up we were amazed it ran.
so i just bought a replacement 302 from checker.
3 year unlimited mile warranty.
i am not and dont know any machinists so it was cheaper to just buy a new one.
i called in some favors so i am only out about $500 for a new engine installed

 

[earthman]

Nice. This will keep you cruisin' and smilin' for years to come.