I bought my 87 about 2 years ago and the P.O. told me he installed a 'new' engine and the engine had about 15k miles on it.

It appears to be a factory reman L98, although I can't seem to match the numbers to anything. (it does have the aluminum heads)

Since I've owned it, I've put an additional 21k miles on it.. (it's just plain fun to drive)

The concern I have is, when it's cold out (below 45), the engine has a slight 'knock' on start up (sounds like piston slap) until the oil pressure builds up.

Warm weather driving has no knocking during cold start.

I don't plan on driving it in the winter but wonder if this is a long term thing that I should worry about and do a rebuild now or just ignore it?

BTW. The engine seems very 'tight' in warm weather and there is absolutely no 'smoke'. Either on cold start or warm start.

I should also mention that the 'knocking' started around the second year I owned it.

 

LS motors do that even when new. Especially the early ones. It can run a long time like that. I think it would bother me though. I have a spare motor on the stand also. Maybe you could start putting one together, for the future . Just in case it gets worse.

 

What grade oil do you use? put a thicker oil in and that should help it.

Also what is your oil pressure like when idling at 600 rpm hot ?
Some engine builders like to have more clearance and that will show up in oil pressure, you can always fit a high volume oil pump.
That should fix the knocking with more oil volume and pressure at idle.

You can easily drop the sump without removing the engine and fit a high volume oil pump, GM made the cars easy to work on

 

I've been looking at a complete LT1 for $150 near me. I'm thinking I might get it and put it on my stand for the future.



Thanks guys. I appreciate the feed back.

It sounds as though I should be fine.

The oil pressure at idle is around 40, (if I can believe the display) and 60 when driving fully warmed up, with no noises at all.

I do remember last year doing a 'quickie' oil change before going to North Carolina and just put in standard 10-40 oil.

The old oil was pretty black.. Maybe it was synthetic? Don't know.

At least your comments means I can relax.

My old 95 Blazer did the same thing, but It had 165,000 miles on it so I was concerned that a 'low mileage' engine shouldn't be knocking.

 

Sounds like piston slap, don't worry.

 

Yeah. That's what I thought at first, but I just wanted to ask to be sure..

Thanks!

 

[QUOTE=Keystring;1582064720]I've been looking at a complete LT1 for $150 near me. I'm thinking I might get it and put it on my stand for the future.


Thats great ! buy it....and sell it to get something appropiate. You can;t drop an LT in your 87 without a bunch of changes to the harness, ECM, cooling and pretty much everything under the hood. LT is a whole different animal. Your L98 is 1st gen SBC and the LT is the 2nd gen where the biggest changes that were EVER made, took place.
For the price you can certainly flip it and make some money toward something else that does work in your yr model.

If your 'knock' is bearing related, (which its not) it might be piston slap as everyone has indicated. Thats common. If its only during the first couple seconds when it fires during cold starts...thats more likely a lifter. Lifters collapse as the eng cools overnight...then the first crank gets a little rattle as the oil gets pumped back into the tiny hydraulic cylinder (lifter)...or it might be a wrist pin. Not a big deal if it goes away with oil pressure. Just let it warm up
a bit before standing in it...

There are other things that can cause a knocking or bumping like sound...if its an auto trans..the torque converter bolts can do that. At idle it goes away the instant rpm increases and some load is placed on the T/C. This is a lifter if its very brief.

If it were me, I'd run a pt of Marvel Mystery oil in the crankcase with fresh oil and see if that didn't help. The MM seems to have detergents or something that cleans sludge off and helps free sticking parts. I use some in gas every few months to provide upper cyl lube and cleaning of the inj system.

 

[QUOTE=leesvet;1582064902]
The knocking is definitely 'low level' and clears up as the oil pressure builds.


The LT1 'build' would be a direct replacement for the L98 solely because I have no real conflicts since this car was switched to carb and that's what I would stick with.

BUT... and that's a big BUTT ..

If I decide to return to TPI, then selling the LT1 for what I want would be a better Idea.

I'd like to switch back, but there is so much missing, including half of the wiring harness, that I'm not sure it's worth the effort on a car with over 200k miles on it..

Here is what I was confronted with when I first bought the car...



And that's just the drivers side..

There are a lot of cut wires on the passenger side too...

(the gray, white,orange,brown and black wires (lower) are actually for the wipers)

Don't know what the PO was thinking there...

 

a harness complete is only about a hundred for a TPI,
If you can do one of those adapters where there is throttle body bolted to carb manifold, That would be the ticket for you.

You can get back the fuel injection mileage, and get a couple of ponies for the cost of the adapter and harness. the sensors, you would probably have about $1000 total.
If you drove the car as a daily driver, with the cost of gas, you would get back your outlay in 3 years.

 

And I've actually got the throttle body to do that.. Another option.

I've actually got TPI from an IROC Z, with most of the sensors, that I picked up for $50, with the intent of switching back.

My biggest problem is not the parts, but the 'labor'.

I can still do a lot on my own, and I do have the knowledge to do it, but just not now.

I recently (7 weeks ago) had lung surgery and so I'm still in 'recovery' mode.

I have two son's in law, but as with many things, they either aren't available or when they are it's only for a very short time.

I still think I can do it myself, it will just take longer than usual. I just don't want to have the car tied up through the summer.

Working on it in the garage in the winter is not an option right now.

My body doesn't do 'cold' real well....


Thanks on the info about the harness... Most of the ones I've seen have been a couple hundred and more.

Since this will probably be my one and only Vette, I don't want to use it for a DD. I have a little Hyundai for that and the Vette will be my toy until when ever.

Although I did put 21k on it since buying her, I had no choice at the time because I had nothing else to drive.

 

If you used the LT1 what do you plan on doing about ignition?

 

Don't know...

Possibly this.....

 

I mean how are you going to get the Optispark/dizzy to work without a controller. Im pretty sure they offer Lt1 carb intakes that use a traditional Dizzy. That may be your ticket.

 

Yeah.. this one looks pretty cool.....