Knock Knock...

geekinavette · 10-05-02, 12:05 PM

No, not another "knock knock" joke...sorry

Actually, I have a slight knock in the bottom end (actually it sounds more like a "tap", a lot like a lifter). I'm pretty sure it's in the bottom end from doing the "screwdriver to the ear" test. The top end is nice and quiet, but when I put one end of a long metal rod right on the side of the block and the other end to my ear, I can hear a definate "tapping" sound.

The oil pressure also isn't what it should be from what I've seen. I get about 40psi at highway speeds and anywhere from 10 to 20 at idle.

Does this sound like a bad rod bearing? Supposedly the engine was "rebuilt" not long before I bought it. I can say that when I had the intake off it was VERY clean inside...definately not an engine with 150K miles on it.

What I'm hoping to do is drop the pan and check the rod bearings (at the very least). What's the best way to do this, plasti-gage?

Thanks in advance for any and all suggestions.

Bill

vigman · 10-06-02, 12:04 PM

I'm not sure I would do it that way.

Could be ALOT of things.. does it get WORSE with time or temp?

Put a magnetic drain plug in there and see what you catch...

Your oil pressure sounds ok to me. What kinda oil do you run?

I would first take the oil filter apart and see what you can see by ( using a BIG tubing cutter or poke a hole and tin snip it open) and look at the pleats in the filter.

Bronze.... BAD... bearing material.

Lots of metal... BAD... somebodys hitting something.

But if you only hear it with the screwdriver... I would leave it alone for a while and buy another engine... build it and wait for the other to DIE!

I got faked out on my 88 with a pre cat sheild ( which you don't have ).. had me going for DAYS!

Vig!

geekinavette · 10-06-02, 01:51 PM

Vig, thanks for the reply.

Quote:

does it get WORSE with time or temp?

In a word...NOPE! Doesn't get worse, doesn't get better (that I can tell).

Quote:

Your oil pressure sounds ok to me. What kinda oil do you run?

EVERY other '84 owner I've talked to runs around 40-60 psi, depending on temp and engine speed. Mobil 40 weight.

Quote:

I would first take the oil filter apart and see what you can see by ( using a BIG tubing cutter or poke a hole and tin snip it open) and look at the pleats in the filter.

Good idea...will do that.

Quote:

But if you only hear it with the screwdriver... I would leave it alone for a while and buy another engine... build it and wait for the other to DIE!

It can be distinctly heard without the "screwdriver test". I just used that method to attempt to pinpoint the source, wich is without a doubt bottom end. Of course it's not as noticeable since I removed the mufflers, heheh.

I considered just leaving it and having a new engine ready to go in when it does go, but I like to use the Vette for my frequent trips to Denver, about a 2 hour trip. Also, the thing just runs well, good compression...etc. I can't see spending the extra money on another motor when this could be fixed.

I also want to drop the pan to repair the rear main, it leaks something fierce.

Bill

vigman · 10-06-02, 02:03 PM

You will have to ( at least ) seperate the tranny from the engine the rear main in a 1 piece unit! ( stick or auto?)

If I remember correctly you can drop the pan without removing or lifting the engine but it is a pain... with an interesting geometery experiment to do the final removal.

If you do the mains.... might as well do the rod bearings.... but if your gonna go that far... might as well pull the engine and
"GO ALL THE WAY"

Yeah your block & heads and all are probably fine ( after machine shop )... but you in essence will be doing the job 1 & 1/2 times.

A long block for an 84 is CHEEP! and you can take your time rebuilding it... and not making snap decisions because you need the car back online....

If your doing the job yourself ( plucking the engine ... putting a new one in) figgure a long weekend ( if it's your first time )

If you pluck the engine... and send it out.... 2 weeks of down time ( and that's being optimistic ).

So that's my .02 cents

Vig!

geekinavette · 10-06-02, 02:27 PM

'84 uses a one piece rear main? I thought that wasn't until '86 or so? Hmmm

The car is an Auto.

It's not so much that I HAVE to have the car running...it's just that when I do use it, it' usually for a somewhat long trip (if 2 hours is a long trip). I have two other vehicles to fall back on (not like I will drive it much during the winter here anyway).

I hear ya about the price of a builder, and I will most likely do that sooner or later. I just have it in my mind that I'm not pulling this thing out unless I have one on the stand ready to go in

which is not something I can have ready by the end of winter (cuz I can gurantee that it AIN'T gonna be stock!).

This will not be my first engine swap, not by a long shot. Been there done that!

The only thing I would send anything out for is machining/balancing.

And ACTUALLY...I do have to replace the heads, I'm 99% sure one of 'em is cracked. I have a set of stock ones sittin on the bench waitin to go on.

You make some good points...got me thinking for sure. (damn you!) heheh...j/k of course.

Bill

geekinavette · 10-06-02, 02:33 PM

Just looked in the GM shop manual, according to it '84 uses a two-peice rear main seal.

Bill

vigman · 10-06-02, 03:45 PM

WRONG YEAR...duh

Sorry... not that doing a 2 piece is a piece of cake with the crank still in!

Vig!

geekinavette · 10-06-02, 04:55 PM

Yeah, I was thinking about that. The manual describes how to do it with the crank installed. One of the guys on the CFI Vault forum has done it successfully, said it was pretty easy.

We'll see how it goes.

I'll keep you posted, thanks for the suggestions.

Bill

maxrevs85 · 10-06-02, 05:33 PM

IMO ,10 to 20 psi is kinda low. I wouild venture to say that the mains are getting worn. That will show up as low oil pressure. The rod knock can be more evidence of worn bearings too. Excessive clearance. Get the new one ready. Actually you might be surprized how long you can go. Dont hot rod it and dont let it get worse. It aint pretty when they let go.....

vigman · 10-06-02, 06:39 PM

1st thing Castrol 20-50

600 rpm idle 25-30 psi cold ( Lo )
15-18 psi Hot 210 oil temp

2k rpm 45-50psi Cold ( Lo )
39-48 psi Hot ( 210 )

No knocks...... light pinging...132K and it has the oil cooler setup.

Vig!

maxrevs85 · 10-08-02, 09:00 PM

Whoops ,sorry . I was going by the pressure with a high volume pump . I do remember my oil pressure being 15 to 20psi with the stock pump, hot.

c4ever · 10-09-02, 08:33 AM

Hmmmm! I find these pressure readings interesting. My 85 with an ambient of 80 deg;

Cruisin 85mph (2.1Krpm)
Oil pressure:57-60 Steady
Oil Temp: 207
Oil pressure at idle 38-42 steady(520rpm)

Ambient of 90deg.+
Cruisin 85mph with A/C on;

Oil pressure: 57-60 steady
Oil temp: 227
Oil pressue at idle: 28-32 steady
I just took a three hour trip and purposely monitored these readings last week. These readings held firm the entire trip.

Engine is stock with minor mods(K&N,mat re-lo,exhaust,stageII chip)
Seems my readings are quite higher in overall PSI
Oil;Mobil1 20-50(switched over to this weight when I moved to FL)

Carlo

vette-dude · 10-09-02, 02:25 PM

Is this vette and automatic? If so check and see if the bolts have come loose on the convertor. It will give you the sound you are describing and with the oil pressure being what it is it might just be the torgue convertor bolts came loose. ( You had mentioned the engine might have been OH before therefore it has been out of car and re-installed.) Just a shot in the dark!!!

geekinavette · 10-09-02, 03:06 PM

vette-dude,

yes it is an automatic. Actually you're right, it sounds EXACTLY like loose TC-to-flexplate bolts, but I've already checked those, they were nice and tight. Yes the engine was rebuilt...but I just think whoever did it didn't do a very good job of it.

Thanks for tryin' dude!

As for the oil pressure, the only reason I think it's too low is from all the other '84 owners (from the CFI Vault forum), seems to me that most everyone else is running closer to what Carlo is running with his '85. 10psi at idle is not uncommon for mine on a hot day...that's just too low for me.

Is there something different about the earlier years that make them run a little higher oil pressure? Hmmmmm...

Thanks for all the insight guys!

Bill

c4ever · 10-09-02, 03:30 PM

Just to add something. The 82 I have (CFI) does run different pressures.

Since I only have an analog guage to go by it isn't exact but she runs at a steady 45psi cruising and around 30-35 at idle. This is fully warmed up at our normal 90+ degree weather.

Same oil as above.
Carlo