I was just wondering what everybody thinks of putting new or rebuilt heads on an engine with 80,000 miles on it?

I have heard don't do it because the bottom end will fall out

Is this true? I am in the process of replacing an old tired 302 and only have so much money to spend, and can get a 302 with 80,000 miles on it for cheap but I don't enough to rebuild the whole motor so I was thinking just the top end? heads, lifters/push rods, and cam

Your thoughts?

 

My thoughts....if the 80,000 mile engine is still in a vehicle, get a compression tester ($20+/- anywhere). Take all the spark plugs out, disconnect the coil wire, and screw tester into each plug hole and crank the engine around 6-7 times and see what psi you get, number the cylinders and recorde each reading. If all the numbers are about the same and healthy, then call it good and leave it alone. If you just wanna add a better set of heads in search of more power, then connect a mechanical oil psi gauge to the engine ($20 or less anywhere), actually you might wanna do this anyway. If it builds and maintains a decent oil pressure over an extended period of driving and idle, then I would say the main/cam bearings are in good shape and slapping some performance heads on it might not be a bad idea. The oil psi when the engine is hot is fine if its around 20-30 psi at idle, you should be able to bring the engine to 2000 rpms and the psi jump to 40 psi or better.

If you do a compression test and one cylinder is a lot lower than the others, then have someone do a leak down test on that cylinder to identify the source. If its in the heads then replace'em, if it's the rings replace'em and personally I would leave the heads alone...but thats me.

If the shortblock is sound then slap the heads on it...it won't fall apart unless you persuade it with a heavy foot or poor installation but that goes with any engine new or old.

IMO, if your willing to go as far as replacing the cam and heads, then about the only thing left is to have the bores bored and the crank turned and you've completely rebuilt the engine..well might need to resize the rods. Maybe you can get in touch with a local machinist/ engine builder that isn't out to screw you over and see what he/she charges to check the block/ internals....you might be able to get away with new rings and bearings to have an engine that performs like new. Who knows?

To add more confusion, how much are these heads you plan to install..$3-400? How much is the initial cost of the 80,000 mile engine? Save a little more and you could get a complete longblock at your local autoparts store for $1000 +/-.

Good luck

 

Thanks for the reply,

I see your point(s), the problem is I am up north and everybody is out to screw someone up here! I can get the used engine for $900Cdn. (long block from parts store = 2,500 Cdn and a complete rebuild of my block = $3,500) What I was planning on doing, was putting in a gasket kit while the engine was out. I talked to Ford and they can sell me the complete gasket set (metal gaskets) including the head gaskets for $200 Cdn (This is actually cheaper than just the pan and valve cover gaskets). So I figured that while it was out I would change all the gaskets and get a valve job done and throw in a mild cam, I wasn't thinking radical high compression heads or anything, but a local shop mechanic who used to work for Ford up here said that it was never a good idea to re-build heads on a used engine because the increased sealing of the upper end will cause the bottom to fail. He said all or nothing (but he is the guy that would be doing the work...).

I guess my biggest concern is should I bother replacing the head gaskets? and is it ok to just replace the cam and lifters without rebuilding?

EDIT: the block in question has 155psi comp and 40 psi oil

Thanks again

 

With 155psi & 40# psi oil there isn't anything wrong with your motor. Unless it's burning oil, in that case new heads would make it use more oil.

 

No this is the motor that I am looking to buy, the block in my truck is absolutely shot - no oil psi and sounds like a diesel!! with more smoke coming from the dipstick tube than the tailpipe!

I was just thinking that while any engine is out of a vehicle wouldn't it be smart to replace all the gaskets? what I am wondering about though is whether or not to replace the head gaskets, and if I decided to replace the head gaskets, then wouldn't it be smart to have a valve grind and perhaps re-condition the heads? and of course while the engine is out I was going to replace the timing chain and waterpump, and would like to put in a mild cam. I am an accountant not an engine builder!! so I don't know these things, I just enjoy working on 'em!

 

I dunno, with the compresson psi you posted and the oil psi you posted, given it doesn't burn oil and it shouldn't with those numbers I wouldn't think. I wouldn't hesistate to slap a cam in it....you can change the timing chain when you do it. Performance wise I don't think your gonna gain anything by reconditioning your heads. From what I can tell, the main bearings on these sbf engines generally wear out before anything else and it really depends on how its driven and your luck. There is an old saying "if it ain't broke don't fix it". Haha. My vote leave it be and put the cam in. Only advice I have is go with a comp cam, give'em a call and they will recommend a cam that fits your needs...have always heard positive comments from those who use them, as well as, custom cam grinders. Its your engine and in reality I don't believe there is a wrong answer either way, Good luck with whatever you decide and keep us updated on your experience, later