KrisR

iTrader: (2)

Having a problem with my 2000 C5 6-speed. It has been doing this since I bought the car last fall. It has a stock 80k-mile shortblock, with a head/cam combo that has been on the car for about 5 years consisting of PRC stage 2.5 5.3s and a 228R cam. I recently installed a FAST 92mm intake.

I have a catch can on the line between the valley tray vacuum connection and the FAST intake vacuum port. The 3 ports on the valvecovers have breathers. I have never seen a hint of steam come out of the breathers and they are not collecting oil. There is a small amount in the catch can but I have never had to empty it. It uses maybe a quart of oil in 1500-2000 miles.

It never smokes on startup, idle, decel, cruising around, etc. It puts a steady stream of dark grayish/bluish smoke out of the exhaust only at high rpm (above 4500 or so) during a WOT pull and a little after the pull is done, then it stops again until I do another WOT high rpm pull.

I read somewhere that some of the ported 5.3 heads had some oil control issues but I tried a search again and didn't find it.

It's not a huge issue but it's a bit embarrassing and I'd like to fix it somehow if I can.

The plugs stay relatively clean but there is some oil that collects on the threads of at least one of them, maybe 2, I would have to re-check. I have not done a compression check or anything. It makes around 425rwhp and 395rwtq which is about right for the combo I guess.

EDIT: Also, when I bought the car it had an LS6 intake; I added the FAST intake. I assume it also has an LS6 valley cover, but I'm not sure if it even matters?

I have had 3 different tunes in the car now from 3 different tuners, each with reasonably good (not too rich) air/fuels at WOT so I'm pretty sure it's not excess fuel smoke.

98cobrakiller

Ls1 pcv issues get a catch can

KrisR

iTrader: (2)

As I said, I have one already, plus breathers on the valvecovers, not sure if that's the best setup or not but I'm open to suggestions.

andrewss

iTrader: (1)

My old cnc 5.3 heads ( not prc) had pipe thread tape on the intake rocker bolts. The intake runner was machined enough to see a small hole thru the port.

KrisR

iTrader: (2)

Good to know, thank you.

98cobrakiller

ls1 are notorious for that mine does it. because off the amount of oil that gets throw the pcv and oil sets on the valves thats why on start up some times you will see a little blue smoke. plus with the mileage on it the piston rings are starting to get alittle warn. mine does it around 5500 to 6200 rpm

HCI2000SS

iTrader: (2)

OP what is your a/f? Does it vary at all?

KrisR

iTrader: (2)

Air fuel at WOT has been anywhere from 13.5 to 11.5 (depending on which tune was in it at the time) with no change in the amount of visible smoke.

Marc 85Z28

iTrader: (8)

There are a few possible sources. It seems you have the PCV covered with the catch can. So you're looking at either poorly sealed rocker bolts, worn valve guides, or a ring/piston problem.

Sealing the rocker bolt threads is fairly simple.

For the guides you can pull the intake manifold and look at the back of the valves for signs of oil getting past the seal. The exhaust side is a bit more difficult. If you have access to a boroscope you could just pull the plugs and insert the scope (focus on the cylinders that have oil on the plug threads). Leaking valve seals will leave telltale carbon deposits on the pistons.

Unfortunately most times it ends up being a ring issue.

supergt99

iTrader: (1)

Mine did that and it turned out to be cracked ringland on #7 piston

mkvamso

iTrader: (2)

Id check valve seals while your at it
I had one bad seal on #8 piston and it would smoke a little at high rpm
Didnt really notice it much but when i swapped the springs i changed all the seals, stopped the smoking and even idled a little smoother

KrisR

iTrader: (2)

Thanks for all the info.

Just as an experiment today after the engine got up to operating temp, I slowly climbed up to around 5500-6000rpm in 2nd gear, coasted there for a little bit, and decelerated in gear, no smoke. Put my foot in it from 4000-6500rpm and there was some smoke. So it seems to ONLY be at WOT / high rpm. If I got WOT through a couple gears and shift at, say, 4000rpm, no smoke.

sreve

iTrader: (3)

If they are the stock bolts they may be long enough to hang down inside a ported head. I use the liquid Teflon pipe dope on mine.

93BlackTa

iTrader: (17)

mine did the same and the result was cracked ringlands and rings on number 7 and 8 cylinders....the car idled perfect, and drove perfect on the street with no smoke...until it was WOT....do a compression and leakdown test on the 2 rear cylinders and compare to the front....i bet you will be suprised.

KrisR

iTrader: (2)

I'm going to do a comp test soon to see if I can learn anything. If we can determine if the issue is in the heads, I might switch to some PRC 225s or something while it's apart.

Can valve seals/guides be done with the heads on the car? Sorry I'm a newb at this.

Latest dyno sheet. I think it seems relatively healthy?

babbage1109

iTrader: (11)

Mine too! High rpm wot start seeing smoke out of the back of the engine. Few months later I got detonation and lost cyl 7

KrisR

iTrader: (2)

I'm hoping its just valve seals. This cam has XE-R lobes which I've heard are pretty violent and has been in the car for 5 years or so. I'm guessing the rockers are stock too. I'm also guessing the heads have not been gone through in 5 years time.

babbage1109

iTrader: (11)

I believe you can change seals with the heads on. Just get one of the spark plug bungs for an air compressor to keep the valves up and change one cyl at a time

Marc 85Z28

iTrader: (8)

The seals can be replaced on car.

If the guides are worn the heads need to be removed and completely redone by a machine shop.

Dmitriy

iTrader: (15)

Hey - my setup behaves the same way. Does it smoke like this at high rpm:
dyno vid of my 5.3/228r setup, made same power too: