My 87 needs a couple valve guides replaced. The car has 83,000 miles on it which leads to the inevitable question. Rebuild the heads or the entire motor? I'd like to pull the motor and rebuild it myself, just for the experience. Has anyone taken this project on?

 

You haven't really given enough information to make a sound decision.
Is this a car that can be down for awhile.
do you have some where to work on the car.
do you have tools to work on the car
is this old hat-do you have a knowledgeable friend if not.
do you have piles of money sitting around that you're constantly tripping over.
what goals are you striving for

personally if it was me i would fix the heads or take the opportunity to upgrade them and leave the engine in the car unless you need/want to go inside of it.

 

your engine has many miles left on it, when I replaced my 170,000 mile old 350 with a new 383 the bearings and bores on the old 350 were as new.

I replaced the engine as the rings were no longer sealing well with boost. I am sure she would have done many more miles naturally aspirated.

the old saying if it aint broke and running right don't fix it.
Unless you want more power and/or have a great bank balance

 

Before assuming that "a couple guides need to be replaced", it could be that only the valve seals need to be replaced; bad seals could easily be mistaken for worn guides; try replacing the seals first, and since the valve springs have to come off, replace them with new. Follow up with a good tune up.

BUT, a valve job would not be unheard of at 83,000 miles and assuming good oil pressure, at 83,000 miles, the lower end (pistons, rings, rods, bearings and crank) should be fine for many, many. miles to come

So do all the stuff that can be done with the engine in the car

pull heads, do valve job, don't reuse the valve springs, get new; replace rocker arms with roller tip design

pull lifters one at a time , DO NOT let them get mixed up, inspect bases for damage, excessive wear; if any are bad, plan on replacing cam and lifters (time for a hotter cam?)

pull timing chain cover; replace the stock timing chain (link and pin design), which has udoubtably a fair amount of slop in it with a new chain; double true roller preferred; new crank seal ; repair sleeve on the balancer if needed

ignition tune up including new plugs, plug wires, cap and rotor;

inspect distributor drive gear for wear; replace and shim as needed; or maybe, just replace the old disrtibutor with new

replace water pump (just good insurance)

all this can be done without dropping the pan, IF you install the timing chain cover WITHOUT the crank seal and install the crank seal after the timing chain cover is bolted to the front of the block

It is possible (and not that hard ) to drop the pan with the engine in the car; if you do , at a minimum, you can install a new oil pump, and new pan gasket.

If you do have the pan off and want to do more lower end work without pulling the engine, I would also replace the rear main bearing since it is also the thrust bearing (which wears from clutch engagements; automatic cars put little if any load on this bearing); you may also want to install new rod and crank bearings (this also lets you inspect the crank and rod journals for wear or damage).

unfortunately to replace the one piece rear oil seal on 86 and later engines, the engine, or trans has to be pulled.

Do all this, CLEAN EVERYTHING, and your 83,000 mile engine should be good for another 83,000 miles. Or more.

good luck

 

IMO,If you are going to have the top end off, I would go ahead and freshen up the bottom end. Rings, bearing, vat, freeze plugs, and oil pump. Shouldn't cost more than 500.00 if you do the labor for good parts.

 

If you are getting blue smoke on startup I agree with just replacing valve seals, springs & keepers.

If doing the work yourself you will have plenty of "fun" too keep you busy for a while...

BTW, I bought my prior '88 with 97k miles on the clock in 2000, did some minor bolt-on mods, drag raced it heavily every season for 9yrs before the #8 cam lobe went a little flat at >200k miles.

 

Unless you've got oil consumption problems and compression issues, or low oil pressure, 83k is still pretty young to be needing an overhaul.

You say a "couple" valve guides, and by your own admission you are inexperienced with engine rebuilds (SBCs). So, I'm just curious: Is that just a general statement, or do you know specifically you need guides? How do you determine you have a guide problem?

Unless GM started installing guides in SBCs that I don't know about, the SBC guides are honed into the cast iron heads. If they get sloppy, then they can be opened up and bronze guides pressed in and honed out to spec. OR, the guides can be knurled (which I never liked) in lieu of bronze guides.

Do you have the heads off yet??

P.

 

Great replies from everyone. It sounds like upper engine work is the general concensus. Valve seals were replaced as the assumed initial cause the 2nd year I owned the car. That was a waste of $500. Subsequently I have had a leak-down test performed that indicates an upper cylinder problem in two cylinders. To have the heads repaired and replaced where I am is about a $1800 job versus about $3000 to put in a rebuilt motor. I have access to just about every tool know to mankind (my buddy works for a rent-all shop) and my car sits in the garage as we have snow for five months of the year. I think I can do the R&R on the heads and have them redone for about $900.

I have owned this car for 11 years (second owner). Yes it puffs blue smoke when you start it up and it does use some oil. The mechanic I trust feels this is oil getting by the guides. The oil pressure is still 60 PSI on the highway and it runs smooth and starts every time. Based on everyone's comments this engine is still pretty strong. Thanks