what all needs to be done to make an engine last another 150,000 miles? The heads need to be rebuilt(burning oil, valve seals), but will I need to get new springs and valves? if everything looks okay, do I NEED new piston/rods/crank? If I can just get away with honing, and re-ringing with the short block, I'd be happy. What do I NEED to have replaced? I have brand new trans, tires, brakes, just need a freshened up engine. Thanks.
1987 L98 700r4, if it makes a difference.

Ryan

 

you only need to replace what needs replaced so you have to take it apart and measure everything, or you can go at it blindly and have it bored and buy a complete rotating assembly. one way cost a lot more than the other. most likely there are a lot of parts that will need replaced without checking either because of wera and age or because it's the right time to do it, valve springs and oil pumps would be on that list.

 

CF87,

Many of the answers to your questions cannot be answered until you open the engine and start measuring. 150,000 miles with mineral oil and typical maintenance is about the point where the piston rings are wearing quite thin. That may be the majority of your oil consumption, lack of compression, and loss of power/reliability. If you get into the engine before a ring breaks, you may be able to simply hone and refit new rings. Of course, you'll need all new gaskets, a new timing drive, a new oil pump, and possibly a few push rods, rockers, or other items you discover along the way. You might get lucky and not need any additional parts, but for the minimal cost of some items (like an oil pump) it almost isn't worth the risk. You're fortunate in that the 1987 model year was the first to have a roller-lifter camshaft design, so that cam wear may not be a serious problem.

At the same time, you'll want to check the crankshaft for wear and replace the bearing shells with the necessary size. If you're lucky, you can get by with only polishing the crank and new bearings. If you're not so lucky and have crank damage, you'll be grinding the crank or replacing it.

An inspection of the piston ring grooves and skirts for wear, and con rods/pins for damage will also be necessary. If you have been good about warming up your engine before loading and kept up on the required maintenance, you may get by with your old pistons and rods, reaming the ridge, honing the bores, and fitting new rings. If not, your measurements will tell you to replace them. Don't "fudge" it or try to argue with the measurements, since you'll be sorry later. At that point, if you need new pistons, the case should probably be bored to clean up any taperd wear and the next oversize piston should be used.

The heads will get the same treatment. Measure valve stems and guides for wear/clearance. Inspect the valve seats and faces. If you're lucky, you can clean the valves, lap them into the seats, and install new springs and retainers. I wouldn't advise using the old springs at all. Factory valve springs weren't even that good when they were new, and certainly won't be any better after aging - they aren't wine. And as a side benfit, you'll be able to get rid of those useless, heavy exhaust valve rotators with the new springs and retainers. A whole set of springs and lightweight retainers with locks doesn't have to cost any more than $70.00, and will be well worth it. For another $18 you can replace the stock pressed-in studs with screwed studs right in your own garage, or have the machinist do it for $75.00 or so.

The temptations will arise as well. "Should I replace the pistons with domes? Port the heads? Install larger valves? Change the cam? Install a gear timing drive?" You'll have to try to reason with that inner child and answer those questions yourself.

EDIT: Summunabich. Once again, I spent 15 minutes typing a response, adn Ed sums it all up in a paragraph - AND beats me to the "click".... I gotta get more terse.

 

How do you measure what I need to measure? I'm guessing just the rods need measured to check for stretch. Tape measure work? What would the crank look like if it needs to be more than just polished (other than a giant crack/gash/chip)? How to tell if pistons can be re-used? I understand they'll be quite blackened. All porting can be done between me and my dad, and I have an SLP cam with lifters, and a set of shorty headers. I was going to go for an all-forged internals, but now I need a reliable daily-driver. I need a car that'll stay together until I can get up on my feet (college student/going into the military), so I can resist the urges to buy domed forged pistons and aluminum heads...for now

 

you need 4-5 mike for pistons, dial bore gauge for piston bores and rods, 2-3 mike for the crank, precession straight edge to check flatness, might want a depth mike, feeler gauges, telescope gauges or inside mikes. if you don't know what you need there's a very good chance you ought to take it to a machine shop and let someone else do the checking

 

As others have mentioned you will first need to tear down the motor. At the bare minimum you will need a gasket set with rear main seal,rod and main bearings,oil pump,timing set,rings and i would suggest cam bearings. You will need to mic the rod and main journals as well as the bore to check for wear. I would just about bet the cylinders will need .030 to true them up and the crank will probably just need a polish if you have been good to your motor. Take the block to a good machine shop and have it cleaned and new cam bearings and plugs installed, they can mic the bore and the crank. Around here it costs around $150 to prep your block (bore and hone included) around $140 for a set of hypereutectic pistons hung on the rods and around $60-70 to turn the crank and much less to polish it. Have your heads cleaned, crack tested, resurfaced, valve guides and valves checked, valve job, new springs and seals.

Do it right the first time.

 

Lookey that..Vader spent 15 minutes of typing in detail, and left out an important item.

If you have any ring groove at all, you'll need to run a ridge reamer on the bores...it's a must, if you expect eny milage on the engine at all. What happens is while the bores wear a ridge, the ring does as well...

So imagine puttiong in a new ring with a minimal radius on the "edge" and running it up and down on a larger radius....the ring is hammering against this radius, and wears out in no time.

But everything else applies, mike it all to see what needs to be replaced...once you have the engine apart, no use skimping on parts. You don't have to spend mega-bucks for parts to have a long lasting daily driver,, but the labor is just the same.

Edited:

By the way, my comment to Vader was in jest.

 

Ah-HA! Gotcha! Obviously, I put you to sleep before you got to the part about the ridge reamer. It's buried in there somewhere.

You can do most of teh rough measurement with a decent 6" caliper. If it gets close enough to split hairs, you'll have to break out a mic to check down to the tenth.

 

Dang...musta been that 4th MGD last night