Malice 1

After months of troubleshooting my LT1, it is finally running on all 8 cylinders. I took it for a couple WOT runs, and noticed a couple issues though.

1)It seems a little down on power. I expected more out of a hotcam car. The lack of power might be an illusion though, since I've been driving an LS1 car for the past 6 months.

2)At WOT, the oil dipstick literally spewed oil all over the place. The dipstick dislodged, and shot oil all over the shock tower and header. It made lots of white smoke.

These two discrepancies point directly to bad piston rings, but I just did a compression test recently, and it had 170-175psi in all 8 cylinders. Plus, I just had the heads off recently, and the cylinder walls looked good, with no marring and good cross-hatching in all holes.

The PCV valve is also brand new. Any ideas what the problem could be?

redcamaroz28

You did a compression test, but what about a leakdown test? Only cause of the oil dipstick being blown out is blowby from the rings.

Malice 1

I just did a pretty extensive search through the LT1 tech sections. Excessive blowby seems to be the main culprit of this problem.

However....

My compression is fine. Furthermore, I did not see the telltale puff of blue smoke out of the the oil fill hole, or the puffs of smoke out of the exhaust. I have not done a leakdown test.

I had to get a new PCV valve and rubber hose, and the hose is very stiff and somewhat kinked in it's 180* bend. That might be restricting the PCV flow enough to cause the dipstick issues. I'll investigate more tommorrow.

bw_hunter

Is the breather on the PS valve cover restricted? Something is pressurizing the crankcase and that points to a restricted or blocked breather or PCV.

175 psi compression seems a bit low but not enough to cause a pressurization of he crankcase.

Just for tests, pull the pcv valve out of the manifold and the hose off the manifold barb. cap the barb and got for a WOT run. If the problem is diminished then look to blockage or restriction is the crancase venting system....

96capricemgr

Lowest compression I have ever seen on an LT1 was on my 95 Roady wagon with 175K miles, it cranked maybe as low as 180 on a single cylinder, after an Auto-RX treatment it was up in the 195-200 range. Keep in mind the b-body motor with the big chamber iron heads is 10.0 compression.

I have never done a compression check on a HOT cammed motor but your numbers look low. Have you used the gauge on anything else to have an idea if the gauge has a tendancy to read low??

Malice 1

Werd. I'll try that and tell you how it ends up.

I actually have the same engine that you have. I had an iron headed impala LT1 in the car when I did the test. That is what the car came with when I bought it. I just recently swapped over to aluminum heads. I have not done a compresssion test with aluminum heads. I just got them installed a couple weeks ago, and the car hasn't been driven since then.

When I did the compression test, the engine was cold. It had not run in a month. The cylinder bores were dry, and that might also have affected the results.

Before I started tinkering with the valvetrain last winter, the car ran like a top. It had no excessive blowby, no vomiting dispstick, and no other discrepancies. I've put almost no mileage on it since then, so IMHO the piston rings should not have wheezed out just from sitting in my garage dormant over the last 6 months.

With my luck though, they probably did.

As far as the comp gauge reading low: that is possible. It's old, and it wasn't a good brand name tool to begin with. I had the gauge hand tightened into the spark plug hole. I didn't tighten it in with a wrench. That might lead to my lower #'s as well. I dunno.

Malice 1

Well..... I'm back.

I pulled off the pcv assembly and capped it off. I also stuck a rag in the PCV hole coming from the crankcase. After a couple WOT runs, there was no oil spewage at all, from the dipstick or the PCV hole. The rag in the PCV hole was dry.

Back home at idle, I did find some not-good clues though. I pulled off the oil filler cap, and there were very light, intermittent puffs of white smoke. There were also puffs of white smoke coming from the dipstick hole.

I tried to check the exhaust for smoke, but it's really sunny out, and I can't see any. I'll try again at dusk.

Soo....

With this new evidence, who wants to talk about engine restore chemicals? Are they all snake oil, or are there any that can provide me with a "band-aid" for a little while?

bw_hunter

Since the car sat so long you might have sticky rings or hardened valve seals. I'd probably try some GM top cylinder cleaner or Seafoam into the intake to loosen things up. I pour ir into the vacuum line for the brake booster, slowly until about three quarters of the container is in then quickly dump the rest to stall the engine. If it doesn't stall, just shut it off. Let the car sit at least a half hour the start it up and go for a drive...like you stole it. It'll smoke badly so pick a neighbor hood that jhas someone you don't like...maybe an old girlfriend, LOL. Anyway, if that doesn't help you might have to try a rebuild-in-a-can but I'm guessing that doesn't actually work.

Good luck!

96capricemgr

http://auto-rx.com/
One of the VERY few additives you can buy that is any good.

Malice 1

I know seafoam. It's quite a show! I'm reluctant to try that though. The short block sat for months, but it has freshly machined alum heads with new valves, seals, springs, etc.... There should be no buildup in the top of the motor. THe intake manifold also got cleaned up pretty well with carb cleaner.

I'll go ahead and try that stuff. Hopefully it'll help me out. I'm kinda bummed that I've spent months getting this engine/car back together and ready to race just to find out that the engine is plain-old-tired. Hopefully the rings will seal better with this chemical additive.

One more question though:

I've been using mobil 1 10w-30 since I got the car. For this last oil change, I switched to conventional advance autoparts brand 10w-40, to try and keep the oil pressure a little higher.

Would that change have any effect on the rings and the smoking problem?

bw_hunter

The oil change will have no effect at all....

Malice 1

I didn't think it would.

SS RRR

Could be serious windage. Could be blow-by. If you're down on power then it is most likely blow-by. Do a leakdown.

Malice 1

It's running fine now, except for that one issue. I'm gonna take it to the local 1/8 mile next thursday. If it runs high 9's or worse, I'm gonna do a leakdown and see whats up.

Malice 1

I've got one more oddity that I'm curious about. I have a vacuum gauge in the car, and it's acting differently now.

I briefly drove the car with the hotcam before, and it would idle at 17" vac, cruise at 17" vac, and if I kept the car in gear and lifted off the throttle, the gauge would pull up over 20" vac.

Now, the car idles at 9", cruises at 10" and it won't pull over 11" on a decel. Besides the different vac readings, it behaves pretty much the same.