Engine builders opinion requested.

I just had my 383 rebuilt and now I'm burning oil. Here is some background.

Before the car even started I did a compression test and I tested about four cylinders. They were all 110 compression.

When the car did start, I had the number 1 and 8 injectors cylinder not firing. Not recognising the issue, the car ran on 6 cylinders and at times I had the car running very rich trying to get the WB sensor to work before eventually finding the problem. It perhaps idled for about 15 mins with this rich condition.

The fans were not working and the car overheated about 3 - 4 times before finding the problem. The first 2 times were whilst ideling on jackstands.

The car has also, for short periods of time, run a little on the lean side but not for long and not under any kind of stress.

It seemed to be blowing blue from the very beginning, although it was also running rich at the start.

I have pulled the plugs and all 8 are oily. They are Plama Moly rings. I also had some AFR heads ported by him and installed.

After 3000 kms the car is burning oil badly, and it seems to me it is actually getting worse. I would estimate a litre every 500 kms. The engine builder does not have much to say except keep driving it and hopefully the rings will seat. I'm not optomistic. The engine builder has however built many motors in his day and though not an LT1 expert, he has done a few and MANY SB chevy and drag race motors. He's not a rookie.

So the first question is, is all hope lost at this time? Is there any chance things will get better.

Next, any speculation on what caused it? The low compression suggests something was wrong from the start. When I asked the builder about the compression he said not to worry until the rings seated. (which of course it appears they did not). But what could be done wrong that would have caused the compression problem. This was the second time this motor was rebuilt. It did not burn oil the first time. I had it rebuilt due to some concern about detonation I had experienced as well as a rear main seal oil leak.

This took me forever to do as I did the re&re myself with MANY problems getting things started again. feeling very despondent espcially since I seem to have the FAST dialed in quite well right now.

Cranking compression of 110 is way low, no matter how big a cam is in it. Something was wrong from the beginning. Unlike my patients, engines don't heal. It needs to come out. Sorry about this, and not to rub anyting in. But did you do a compression test before installing it? That's the best time.

Rich Krause

Sorry Shaun, but what Rich said. I just got finished replacing a piston and it was still 160 with 2" of ring-land missing. If my memory serves me correctly my compression was ~165 when it was rebuilt 4 years ago. 110 sounds awfully low, even for an older engine that has a few hard miles.

Are you sure your rockers are adjusted correctly? Maybe they don't close all the way?

Originally posted by rskrause
Cranking compression of 110 is way low, no matter how big a cam is in it. Something was wrong from the beginning. Unlike my patients, engines don't heal. It needs to come out. Sorry about this, and not to rub anyting in. But did you do a compression test before installing it? That's the best time.

Rich Krause

I agree, it needs more surgery.

If the cylinder bore finish was honed correctly, the rings should have seated very early after the rebuild. With as much oil fouling as you described, bore finish or improper ring installation looks like a possible culprit.

Possibilities:

Is there too much ring-to-groove clearance? Are the rings the correct width for the pistons? It would be possible, but highly unlikely, that 1/16 (.063) rings were installed in 5/64 (.078) grooves.

Could second ring have been installed upside down?

I know you said your builder wasn't a rookie, but maybe an intern (or resident) did your rebuild and made an error and it wasn't checked by the head "MFWIC" (*).

FWIW, here's a quote from Speed-Pro about their file-fit Plasma-Moly rings:


"Rings designed for the rigors of racing. Speed Pro plasma-moly piston rings are designed to stand up to the rigors of racing and high performance street use while providing a long service life. Speed Pro File Fit Plasma Moly Rings include these features: Plasma-moly coated, barrel-shaped, ductile iron top rings that seal against blow-by when the piston rocks in its bore; tapered secondary rings that seal against the oil control ring's upper surface for excellent oil control; and three-piece oil rings with stainless steel expanders that provide proper tension without robbing horsepower."





(*) Old military acronym: "Mother #@*%*# What's In Charge" pronounced "miff-wick"

rich, looks like the ace is giving you vocab lessons now :o

btw- i almost lost some of my Sobe Liz Blizz out my nose because of that one:(

What about the issue of running rich / lean. I guess I need to try and find out what caused the ring problem. Was it the build or a starting tune problem.

Also, is it acceptable for the compression to be 110 before the motor has even started?

No, even a brand new motor shouldn't let that much escape, its probably your rocker adjustments, then maybe not.

Ps.. build or starting tune? most likely build problem if your cylinder pressure was only 110psi.

Dont forget guys. If he did his initial compression test before the rings were seated, and the resault is gonna be lower. Did you do a CLT?

Not sure what a CLT is?

You are right though. Does the compression get better after the initial build? i guess I should do a compression test now and see the results.

even if rings are upside down n god knows what, 110 sounds really damn low for cranking pressure - are they hydraulic lifters? What tends to happen is that people set the valve lash with the motor never run, n the plunger in the lifters goes down too far, then when the lifterrs pump up with oil, it keeps valves hanging open - so even if you are "100% sure" that your rockers are not the problem - redo valve lash anyway!

As for oil - it could also be an intake gasket leak, or head gasket leak - like someone said, incorrect piston ring sizing will also do it, I've had 2 cases where a machine shop firstly gave me big block piston rings instead of small block rings - OK thats frikkin obvious when it doesnt fit - but another case was where I ordered pistons with a weird ring size combination where the top rings were fine but the oil rings were too thick - so I had to get a set of seperate oil rings - perhaps your problem was the other way round and he didn't notice the oil scrapers were too loose.

Sorry to hear about your issues Shaun.

how old are the heads?if it smokes more when you first fire it up then your valva stem seals/guides are to blame.i would sugest doing another compression check.first establish a base line by simply following the standard procedures for a compression check.to see if your rings are allowing an unacceptable amount of ''blow by'' just pour 2-3 table spoons of moter oil down the plug hole.if you jump up more than 30 ,you need new rings and the motor must come out.if it doesnt jump up that much,your valve stem seals or valve guides are bad.

happy wrenching
Dan
p.s. did you remove ALL of the spark plugs when doing your compression test?

if the copression test was done correctly,it sound like excess piston to wall clearance,possably with a ring issue as well.

While writing my last post I was sittin here thinkin "hmmm im sure I missed SOMETHING but what??" - duh yeah valve stem seals! thanks 11secgen, I was losing sleep over it ;)

how old are the heads?if it smokes more when you first fire it up then your valva stem seals/guides are to blame.i would sugest doing another compression check.first establish a base line by simply following the standard procedures for a compression check.to see if your rings are allowing an unacceptable amount of ''blow by'' just pour 2-3 table spoons of moter oil down the plug hole.if you jump up more than 30 ,you need new rings and the motor must come out.if it doesnt jump up that much,your valve stem seals or valve guides are bad.

happy wrenching
Dan