Why do the truck gods mock me so? I've got a 93 chevy 1500 350 5.7 tbi.
I got a used engine, not rebuilt but used. This is the third engine
the truck has had. Wife has a lead foot, but more on that later.
Started the engine, sounded strong, oil pressure jumped up to 30 psi as
soon as it started.
Check engine light came on. Then popping through throttle body. Read
alot about timing. Adjusting the timing to TDC as specified in the
Chilton's manual. Popping still heard in the throttle. New plugs, new
wires. With the engine running, I removed then replaced the wires from
the distributor. When I got to number five and removed the number five
wire from the dizzy, the throttle backfire stopped completely. I have
little to no power when I try to drive the truck and my oil pressure
dropped back down to danger zone after I let it idle for about 10
minutes. Should I whip out my compression gauge or should I whip out my
baseball bat and try to get the money back from the guy that sold me
the crap engine?
Any advice would be great.
1993 Chevy 1500
"My Daddy gave me that there truck"
How long have you had that engine?? Has that engine always maintained
30psi of oil pressure or have you even had it long enough to know?
I would look at the compression all the cylinders. Take note of each
and compare #5 to the rest. The fact that the backfiring stopped when
you disconnected the spark plug wire leads me to believe the valve is
burned. If so you could be igniting a mixture that's pushing its way
back up into the manifold (not good) and hence it stops when you
disconnect the plug wire.
For some reason I'd think the oil pressure isn't related. On my old
Dodge Van, the oil pressure would drop significantly while idling after
warmup. It'd be ok when driving. But that sounds like an oil pump
that's worn with age.
Not sure what, if any recourse you'll have against the guy that sold
you the engine. If it's old with a lot of miles on it, there's
probably not a lot you can do. It comes with the territory when buying
I agree with this. Also I have seen a worn exhaust cam lobe cause the
same problem because it was not letting hot gas get out quick enough
and causing it to pop through intake. Either way it does not sound
good and a compression check is a good starting point.
I've had the engine for about two weeks. Put it in last weekend, been
working on it every since.
And just when I was starting to make lemonade, my damn lemons have
spoiled on me.
Well, I took the valve covers off. Checked out the rocker for the
cylinder number 7 exhaust valve. Low and behold the rocker was
completly loose. I thought I'd adjusted them all properly. So I tried
to do it again and no matter how tight I got the nut, the rocker never
even touch the push rod. I even bottomed out the nut and the push rod
still didn't touch the rocker.
Dead lifter, bad cam lobe, burned valve all of the above? What do you
Best scaneario I pull the intake manifold, replace the lifters and
camshaft. Hell, if I do that, might as well pull the heads and replace
the vavles right?
Sounds like I'm gonna be putting engine number three in the truck
right? Is it pathetic that I have three chevy 350 engines at my house
and none of them are worth a crap?
I plan to do a compression test today, but I think it's a moot point
now. I think I get to finally rebuild an engine. Dammit!
93 chevy 350
"Boy, what chu done to my truck?"
Well, if the seller made any guarantees, I'd hit him up first...
Aside from that, yep...looks like you're going to be tearing that one
down. Check the cam and lifters. Based on what you're saying now, I'd
lean toward Snoman's advice that it could just be the cam, and not
necessarily a burned valve.
Are either of the other two cams good? I'd install new lifters and
make sure they're broken in with whichever cam you install. But a new
cam and lifter set will run you under $150. Besides, you can take the
opportunity to install a good "truck" cam that'll give you better gas
mileage and more low-end torque.
I'd pull the heads just to inspect everything. If the valves are ok,
then I wouldn't screw with them.
Did you ever check compression on the other cylinders? I'd compare
them against some known numbers. That'll give you a good idea as to
the condition of the rings. If the bottom end is ok, I'd invest in the
new cam, slap it together, and run it till it dies.
Also... Use the fact that you have 2 extra engine at your house to
your advantage. Inspect both and choose the better of the two blocks.
Strip that one down, and have the block hot-tanked and inspected by a
competent shop. Shouldn't cost all that much. Get a good rebuild kit
and start putting it together. Do this for the heads as well...clean
them up, install new valves, springs, or rockers as needed.
Sell the other engine in pieces (block, crank, heads...) to help offset
the cost of this. The good thing is, this could be a good project that
you can put money and time into when you have it. When the 3rd engine
dies, you'll have a freshly rebuilt engine ready to go. Or, pull the
3rd engine, sell it too, using that money to further offset the cost of
rebuilding one of the others.
You know this kinda sounds like the lifter is completely missing from
bore. Even if lobe was worn he should have still been able to contact
push rod. He might pull another rod and check the length of it and
confirm that valve is not stuck open too. I would like to here what he
finds on this one because it would take some very serious cam and
lifter wear to do this otherwise.
I had the same thought after posting. My thought was that the pushrod
was the wrong length, although I can't imagine how it would've gotten
Also, I think it's unlikely that one lobe would've worn down for just
one cylinder. If it didn't happen evenly across all lobes, it would
lead one to think that something catastrophic had happened and the
lobe, or some other piece of the engine was sheared off. If that
happened, lifter adjustment should be the least of his worries.
I have seen it happen where just one lobe was wiped clean off more
than once and I had it happen to me with a old Slant Six many many
years ago. It was a exhaust lobe too and all the others were fine. It
happened during a 200 mile trip.
All very good thoughts. I compared the pushrod with another and they
are the same length. Dammit. I did, as best I could, inspect the lifter
with a flashlight through the headers. It looked very suspicious. Not
at all like the other lifters. If fact...gulp...it like it was either
stuck or (insert catastrophic music here) missing.
After working on this for two weeks straight, I've decided to walk away
from it for a few days. Perhaps this weekend, I'll try pulling the
heads, and swapping out the lifters and camshaft with one of my other
I'll admit, I am a bit excited about the chance to rebuild an engine.
Although it means a lot to me to get my daddy's truck up and running.
You guys have been great. I'll keep you posted. Did I mention I'm a
writer and really have no expertise practical mechanics at all? Thanks
'93 Chevy 1500
I would pull the intake and see what you find and then go from there.
It is not a lost effort because it will make engine a bit lighter to
pull and give you several options on which bolt hole to hook a chain
to, to balance it on hoist
I posted this yesterday, but it didn't take. Google has been upgrading
Anyway... I visited your website, and saw that you're in Stone
Mountain. I'm about 5 miles away in Grayson/Snellville. If you'd
like, I'm willing to trade services for services. I'm no pro mechanic,
but I'm real interested in rebuilding an engine. I also will need to
chance my cam soon, as it's totally wrong for my truck, and therefore
I'd like to run through the process, or at least be there when it's
done, before I tackle my own.
If you're willing to help me swap axles in my truck sometime in the
next month, I'd make myself available to help in any way I can. I'd
just like the experience.
Let me know what you think.
In 86, I had a buddy with an 81? (the last of the 71?-81?) z28 with a 350.
It had a very light, steady miss at idle. ALWAYS.
But under load, it ran smooth and still had a lot of power.
A good parts guy (our boss) suggested an intake cam lobe was gone. Sure
enough, one intake lobe was as smooth as a bearing journal. There was a
hunnerd dollar bet on it too.... but the boss didn't make him pay. I would
have never believed it if I hadn't seen it with my own eyes.
I've adjusted the timing several times and after each adjustment, the
next time I start it, it jumps time. Is the ECM gone? Or perhaps a bad
ignition moudule? I haven't torn it apart yet, hoping there's
something small that I'm missing and it's gonna work itself out...I
Did a compression test and everything checked out fine.
If it is jumping time there is something loose somewhere because the
ECM does not do much with base timing (you are disconnecting the
electronic advance at jumper on firewall when you time it right?). YOu
might check to see if timing chains is worn out. This is easy to check
by laying on ground under a warm engine and grabing dampner with hand
and seeing how far it will turn before you take up slack in chain.
(turn it back and forth for total range of sloop and you will feel
when you "pick up the cam") It should be 5 degrees or less if it is
still fairly snug and if it is about 10 degrees or more you need to
replace timing chain.
Hmmm. Turning the damper by hand. I would think it wouldn't turn at
all. But hell, I'll try anthing at this point.
Engine number two(that's in the shed)...I began taking it apart. I
replaced that engine because it seized up. Many suspected that during
the year's time it lay dormant in the garage, something fell into the
lifter valley or dizzy hole and jammed it up. Well I loosened the
rocker arms, first on the right side...still seized up. Then I took
the rocker arms off the left side. Suddenly the engine was fine. I put
a socket wrench on the crankshaft and it turned over just fine. Any
Could the lodged item have fallen loose? If so what are the chances
it's down near the pistons rods?
On another note, what's your preference when pulling an engine. Up and
out through the hood with the tranny atached , or do you prefer
removing the front end and simply sliding it out.
Sounds like my recently acquired engine is junk. Because from what I'm
hearing, I've gotta pull the intake manifold, remove the lifters, pull
and inspect the camshaft(probably replace). Nail down my timing
problem and them possibly replace the oil pump.
On another note: Jeez I've got mechanical porblems. Any advice on
crankshaft removal. On the original engine(that's also in the shed) I
started tearing it down and got as far as the crankshaft. Was I
supposed to turn the engine to TDC before tearing it down? Because the
current crankshaft posistion is such that some of the nuts at the
bottom of the pistion rods(not sure what these are called) are not
accesible. And of course the crankshaft on this orginal motor won't
rotate becuase two of the pistions are rusted to the cylinder walls.
Did I mention that I can't pull the lifters out of the orginal motor
either. I think I'm gonna take up bicyle repair as a hobby.
Thanks for any help.
YOu should be able to do it to the point you pick up cam because it
should turn easy in cam chain slack.
Maybe it hydro locked or sieve for lack of oil on piston and no it is
free for moment (not the first time that has happened)
I would pull pan to figure out why it locked up and check bearings for
I take them up and out and usually leave tranny behind in truck. It is
not just the size, it is the extra weight and CG shift to deal with
Before you pull engine again, remove intake and get a better grip on
things. I have had cams go bad and replaced them and rack up a lot of
Rotate block on stand so one set of cylinders is straght up and fill
them with diet pepsi (yes the pop) It has phosphuric acid which will
eat rust and the diet will not add any sugar goo to it. Let it set for
a day or two and repeat for other side. That should free up pistons
though you might stil have to still shck a few with a dead blow
When that happens it is because they are either varnished/gummed up
badly or mushroomed from wear. Invert motor (vallve galley aimed down
and fuel pump removed if it was a carbed motor) and with timing chain
removed spin cam a few times and then remove cam, reinvert bolt right
side up and tap lifters out through bottom.
You know, there's nothing like solving a good mystery and learning a
great lesson from it. As you may recall, I had backfire or popping
through the throttle. Adjusted the timing, still had the problem.
Removed the plug wires to the dizzy one by one and narrowed it down to
cylinder 7. We all sort of agreed that the exhaust valve was not
opening and perhaps there was a flat cam lobe.
Well, for practice, I removed the camshaft from one of my old engines
in the shed. That's a lot of freakin' work! At that moment, I hoped I
would NOT have to do that repair to the engine currently in the truck.
I removed the valve covers and saw that the pushrod for exhaust valve
7, was completely lose and no amount of tightening would take out the
lash. With a flashlight I could see(without removing the intake
manifold that the push rod was sitting rather funny in the lifter.
Back to the old engine in the shed, I started tearing it down, just to
get away from the truck. I removed some of the lifters and when a few
of them came out, the three-sided retaining clip popped out and so did
the small bowl-like object in the top of the lifter. Hmmm. I wonder...
Sure enough, back to the truck I went, removed the intake manifold and
sitting in the lifter valley was the bowl-shaped object from the top
of the lifter for exhaust valve 7. The depth of the bowl was just
enough that the pushrod would sit in the lifter, but now allow the cam
movement to have any affect on rod and open the exhaust valve. I put
another lifter in the older lifter's place, hand cranked the engine
and sure enough the lifter goes up and down as does the pushrod and
rocker arm. I guess I'm pretty lucky seeing how the object did fall
down into the crankshaft.
Anyway, it's time for reassembly and repairing the fuel lines and
throttle body(I cross threaded the inlets on the back of the throttle
body and now it leaks fuel)
Thanks for everyone's help and perhaps this will help someone else in
93' Chevy 1500
"The truck's almost ready, Daddy!"
Good to know Brian. Sounds like you're on the road to recovery.
Hopefully it'll work out well for you and you'll end up with some more
time on that engine. In the meantime, I'd suggest that you do go
ahead and rebuild one of the other engines. It'll be extra
experience, and you'll have another engine ready to go when the time
Again, if you need help, you've got my email address...I'd be glad to
get in on that, as it'd be good experience for me as well.
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