Can't afford new truck. Should I replace engine?

[maul ratt]

I welcome the advice from those with automotive knowledge. I am the original owner of a 1994 Chevy Z-71 4x4 with over 350,000 miles. I take good care of the truck and want to keep it for sentimental reasons. The gas mileage is horrible now, like 10mpg and the engine idles and runs a little rough. The engine goes through about a quart of oil a week, yet it does not smoke.
The rest of the truck is in good shape and is great for hauling firewood in a trailer.

Should I get a decent used 5.7L engine or have something done to the original engine? I'm looking for "the best bang for the buck". I hoping for the truck to last another 3-4 years or so. Thanks for any help or advice out there.

 

[Richard_]

replacement would be the cheapest route , should be able to get a good long block for around $500.00 , plus with a replacement your down time is minimal , maybe 4-6 hours if you have the tools

 

[ShoerFast]

I welcome the advice from those with automotive knowledge. I am the original owner of a 1994 Chevy Z-71 4x4 with over 350,000 miles. I take good care of the truck and want to keep it for sentimental reasons. The gas mileage is horrible now, like 10mpg and the engine idles and runs a little rough. The engine goes through about a quart of oil a week, yet it does not smoke.
The rest of the truck is in good shape and is great for hauling firewood in a trailer.

Should I get a decent used 5.7L engine or have something done to the original engine? I'm looking for "the best bang for the buck". I hoping for the truck to last another 3-4 years or so. Thanks for any help or advice out there.

At 350K your going to have a lot of cylinder taper and bell-mouth in the valve-guides requiring inserts and oversized pistons requiring machining.

If you price out a long-block, it's my bet that it will be cheaper.

With that, I would have that puppy on an engine stand cleaning the crud of it!

 

[tjf85]

Go for it

I have a 1993 Z71 that I bought new and I have enjoyed this truck since new I put a new Jasper engine in the truck five years ago and have not regretted it one bit the truck is still in great shape everything still works AC cruise pwr windows radio everything we still pull our travel trailer any where on vacation with it.

 

[buildmyown]

This is kinda a tough question. A remand motor from Jasper is going to run you about $1700 + labor for install $500-$1000. A used motor from a junk yard can run you about $500-$1000 + Labor this is kinda a roll of the dice unless you can hear it run and do a compression test.

If its not burning the oil where is it going? Do you have leaks external or internal?

For the low fuel mileage the running rough and ideling rough have you done a good full tuneup plugs, wires, cap, rotor, pcv valve, fuel filter, air filter etc.. Have the fuel injectors been cleaned? Is the check engine light on if it is there is a major problem right there if not have it scanned to make sure there are no hidden codes or other problems and not by one of those cheap Autozone scanners bring it somewhere that can do a drivability test.

If it were me I would do a compression test, leak down test and check for blow by. If all those checked out good I would look into a set of remanufactured heads and maybe a camshaft lifters and pushrods along with a new timing chain set. Should be about a $1000-$1200 for parts and labor.

Now the tough question how is the transmission, transfer case, brake lines, fuel lines, front end parts.

 

[streeter]

I would first atleast pull the plugs and check them for oil fouling (crud build up). That will tell the health of the valve guides/seals and rings and you can check the gap, your truck should be @.040. Another common thing to check is the ignition coil, check and see if the plastic is discolored (grey) around the metal ring (coil is often ignored and causes missfire) aslo replace your thorttle body gasket as alot of times it sucks in and causes rough run and poor gas mileage.

I am sorry for rambling, check the basic...... plugs first! Then let us know how they look.

P.S. you can check for codes with a paper clip......connect the upper right connectors in the OBD1 connector and count the light flashes on the engine light on the dash.

 

[fletcher0780]

I welcome the advice from those with automotive knowledge. I am the original owner of a 1994 Chevy Z-71 4x4 with over 350,000 miles. I take good care of the truck and want to keep it for sentimental reasons. The gas mileage is horrible now, like 10mpg and the engine idles and runs a little rough. The engine goes through about a quart of oil a week, yet it does not smoke.
The rest of the truck is in good shape and is great for hauling firewood in a trailer.

Should I get a decent used 5.7L engine or have something done to the original engine? I'm looking for "the best bang for the buck". I hoping for the truck to last another 3-4 years or so. Thanks for any help or advice out there.

How does it run, any skips or odd noises? if it's not burning the oil, then you must have a hell of a leak. rear main seals are quite common with that many miles.
Before throwing in another engine I'd check yours out. How do your plugs look? What is the compression in each cylinder? How about a leak down test? Those TBI injectors can't be too pretty after that many miles, check the spray pattern, check for drips. How is your oil pressure?

If the compression and leak down check out OK, I'd fix the oil leak, probably change all the easy gaskets (valve cover, oil pan, timing cover, etc), replace the injectors or entire TBI unit if the old one is not giving a nice consistant pattern, do a complete tune-up with plugs, cap, wires, ignition module, everything that could affect performance (and stuff that would be used on a new engine anyway).

 

[cityevader]

I'll jump in with my 2 cents based on the title of your post first.

Old truck vs. new truck......I assume you own the truck outright and have no monthly payments...so if you buy a new truck, the payments, plus required full coverage insurance, will undoubtedly be over $600 a month.

A "new" engine or rebuilt or junkyard, could easily be $5000 if you don't do it yourself. ....but... that "huge chunk of change" is barely 8 months of payments on a new truck, and you'd still owe another 52 months before paying off the new one!!!

Clearly, continuing the lifespan of something you already own if much more advantageous than starting something now.....unless you've got one of those "posessed vehicles" that suck up a grand in repairs every other month until eternity.

As far as diagnosing whether or not you actually need a new engine...well, I won't go there....because if there is something simple causing everything (EXCEPT oil consumption which can only be base engine) than you don't need an engine, and online diagnosis is worse than over-the-phone-diagnosis, which is worse than driveway-diagnosis.

Ford/Lincoln/Mercury technician's advice.

 

[streeter]

As far as diagnosing whether or not you actually need a new engine...well, I won't go there....because if there is something simple causing everything (EXCEPT oil consumption which can only be base engine) than you don't need an engine, and online diagnosis is worse than over-the-phone-diagnosis, which is worse than driveway-diagnosis.

Ford/Lincoln/Mercury technician's advice.

Very true...25 years doing mechanical here

Practice the K.I.S.S. system first.....Keep It Simple Stupid, first, then make judgement from there.

 

[John D]

Very true...25 years doing mechanical here

Practice the K.I.S.S. system first.....Keep It Simple Stupid, first, then make judgement from there.

The basics first,id start with the PCV valve,is it clear,and working? beleive it or not ive seen trucks fixed by just replacing the pvc valve,and cleaning the passages in the TBI unit that are plugged up. Its got 350K on it,it is likely worn out,or close to it,but you'd be suprised how far those tbi 350s can go.Start with the simple stuff first,and go from there. As for replacing the engine, if it is determined that that is the course of action,I'd consider a GM crate engine,as well as a jasper,ive done a few of them,and they arent that expensive. BTW whoever said 5-6 hrs to swap an engine is wrong.A 350K truck will have 5-6 hrs just getting the exhaust mainfold off,exhaust studds extracted,accesorys,adapters/oil cooler and the intake off.The powersteering pump requires a special puller on that truck,but overall its straightforward and very basic design,very easy to work on.
Id definetley fix the truck if the bodys solid and rest of drivetrain strong.

 

[KsWoodsMan]

Seems like the vortec engines have a regulator inside the intake manifold. When it starts leaking it will flood one bank of cylinders with fuel.

If you take the top half of the intake off and one side ( with the regulator) is washed clean or even semi clean, you can be sure this is the cause of the rough idle and poor mileage. I dont recall the cost of the regulator but it is less than a rebuild and may solve some of the oil usage. The excess gas thins the oil allowing it to pass the seals and rings.

Hopefully this will help you keep the wood hauler going a little longer and stronger.

 

[maul ratt]

Clarification

Here's a little more clarification to the engine situation. The engine goes through oil however, it does not send a smoke screen behind me when I'm cruising down the road. I notice a little smoke maybe when I start it in the morning and cruise down the road for the first 1/4 mile. I also notice some dirty looking exhaust spots that are in my driveway from starting the truck.

I guess I'm burning some oil. In comparision to my first car, a 1977 Chrysler Cordoba, that thing smoked so bad that you would see the smoke cloud behind me as I cruised down the road. I always hoped that I wouldn't get stuck at a long light with that car.

I'll get under the hood tomorrow and pull the plugs. I brought it in for a full tune up a couple years ago, which was about 60,000 miles.

I just wonder how far I can go on the original engine? I've had a fair amount of other work done over the years replacing the transmission, transfer case, front end 4x4 work, etc. Hopefully just some improvement to the engine will get my by for awhile.

Thanks for the advice so far.

 

[jwfirebird]

seems like the cheapest thing to do if you dont work on it your self would be to find someone who does to look at whats wrong with your current engine. the oil is most likely leaking from the seals.

a good resource for trying to fix it your self is fullsizechevy.com

 

[husky455rancher]

payments are the devil!!! chevy engines are cheap you know what to do!

 

[John D]

Seems like the vortec engines have a regulator inside the intake manifold. When it starts leaking it will flood one bank of cylinders with fuel.

If you take the top half of the intake off and one side ( with the regulator) is washed clean or even semi clean, you can be sure this is the cause of the rough idle and poor mileage. I dont recall the cost of the regulator but it is less than a rebuild and may solve some of the oil usage. The excess gas thins the oil allowing it to pass the seals and rings.

Hopefully this will help you keep the wood hauler going a little longer and stronger.

The trucks a 94,it isnt a vortec .Its TBI,the regulator is in the throttle body.

Maul ratt, before you pull the plugs,pull the pvc valve out of the valve cover with it running,it should suck your fingertip right up against it,if it isnt sucking at all,you found a portion of your problem.With a plugged pcv system,you will burn oil,could pressuize your crankcase some,and it will not run correctly.It takes less time than pulling one plug.

 

[mattmc2003]

Its got over 300k miles....a tune up would be good, but hey...300k. If you have the money and like the truck, put in a new motor. And spend the money on tune up parts on the new motor. Cause at that mileage, its a ticking time bomb anyway. It could last ten more years, and maybe ten more minutes. About 1750 for longblock. 100 for plugs and wires and pcv. +gaskets and such. MAybe a new front seal in the trans. Prob motor mounts will need replacing too. You'll easily have 2500+ in the parts alone. And then the transmission is on its last leg too. So factor that into your decision also.

 

[BIG JAKE]

I would first atleast pull the plugs and check them for oil fouling (crud build up). That will tell the health of the valve guides/seals and rings and you can check the gap, your truck should be @.040. Another common thing to check is the ignition coil, check and see if the plastic is discolored (grey) around the metal ring (coil is often ignored and causes missfire) aslo replace your thorttle body gasket as alot of times it sucks in and causes rough run and poor gas mileage.

I am sorry for rambling, check the basic...... plugs first! Then let us know how they look.

P.S. you can check for codes with a paper clip......connect the upper right connectors in the OBD1 connector and count the light flashes on the engine light on the dash.

+1 streeters right. Pull the plugs first. If they're all tan that's perfect, assuming they've been in the truck a while. IF those are good then how's the antifreeze look? You're losing oil so if it's clean then oil's leaking out the pan, rear main, or valve covers. You can fix those but if rear main is leaking I wouldn't mess with the mileage you have and would slap in a crate motor. Check with GM on their target engine line. Very reasonable/good quality. Distributor and timing chain will be pretty sloppy too. Main thing is to see where your at then you can decide the best way to go. If your weak on troubleshooting tap into the knowledge of a friend and dive in. No better time to learn than now.
BTW I had a 78 blazer and was in a similar situation back in 1990. I put in a GM 350 4 bolt mains, Mallory Unilite distributor, Edelbrock intake and carb, wires etc. I ended up with reliable machine that ran a long time. It'd be alot cheaper if you do the work and pretty easy if you get a service manual. Good luck with your project!

 

[Stihl051master]

If you're mechanical, why not rebuild the engine yourself? Provided your block isn't too whipped out to be bored. I did one for a friend (a 94 in fact). I got hypereutectic pistons which were flat tops to bump the compression up a bit, installed a larger cam - pretty much the standard "RV" profile which is about one step up from stock, and put on headers with 3" duals and v-force mufflers, and of course got the crank turned and installed reman-ed heads, dbl roller timing chain, hv oil pump, etc. We also replaced the manifold temp sensor and oxygen sensors and some misc. other stuff like new plugs, wires, cap, rotor, hoses, belt, etc. Total investment for everything (including the exhaust) was under $1500 and I knew exactly what I had. The thing ran very well and had lots of power-way more than stock. It was very relaible until he sold it a couple years later to buy a brand new truck. We figured this route was better than a re-man long block b/c we knew exactly what we had and that everything was put together right. Plus, we had a more powerful engine.

If you didn't want to re-do it yourself, make sure to check prices on GM crate engines too. Long blocks are cheap, and last I checked they carried a 3 yr/50,000mi warranty.

Another option would be an upgrade to a Vortec engine, as there are thousands of these trucks out there, but you're taking a gamble buying used as was mentioned before.

Don't be intimidated on doing the work yourself. If you don't you will be paying a small fortune in labor for a job like this, even just having someone replace the engine. Get a haynes manual and take your time and go to it. If you can turn a wrench and read you can do it! These trucks are very simple to work on.

 

[thejdman04]

Id run it if it is reliable. I dont know how rough it is running, if not terrible and is dependable run it. A quart of oil a week is what 2 bucks a week if you put the cheap stuff in it. If i were gonna put a new motor in it, Id get a long block, used maybe other peoples problems. Remember if the motor has that many miles so does the transmission, etc etc. Dont let a truck nickle and dime you to deathe

 

[J.W Younger]

I welcome the advice from those with automotive knowledge. I am the original owner of a 1994 Chevy Z-71 4x4 with over 350,000 miles. I take good care of the truck and want to keep it for sentimental reasons. The gas mileage is horrible now, like 10mpg and the engine idles and runs a little rough. The engine goes through about a quart of oil a week, yet it does not smoke.
The rest of the truck is in good shape and is great for hauling firewood in a trailer.

Should I get a decent used 5.7L engine or have something done to the original engine? I'm looking for "the best bang for the buck". I hoping for the truck to last another 3-4 years or so. Thanks for any help or advice out there.

if this is not your daily driver chances are the fuel may be old. if this is not the case ignore this. put some fresh fuel in it give it good drive if it still runs rough or misses put plugs in it. no you can't sue me if i'm wrong