C4 LS1

Here is a little background. I have a 93 c4 Vette with an LS1 swap (my username). I did forged internals T9 cam with heads my friend sold me that had the valve springs with rates that match the cam. The problem I am having is that my spark plugs are getting covered in oil. Its to the point where I have to start my car multiple times until it fires long enough for me to give it some gas and burn off the oil on the plugs then it idles decent with an missfire here and there do to the plugs. under hard acceleration the car missfires multiple times and jolts a little. The rings are brand new and gaped to NA specs so I dont see blowby being the issue. Has anyone had this problem? I am leaning toward bad valve seals are allowing lots of oil to leak down onto the valves. I dont know how many miles are on the heads and they sat out in his garage for a few years since the last time they were used. Any help would be great THANKS!!

Old Geezer

iTrader: (3)

PCV hooked up and working?
Leak down and compression tests done?
All 8 plugs wet?

C4 LS1

I have been running with the PCV system both hooked up and then unhooked with a breather with the same results for both. All 8 plugs are covered its not just 1 or 2 of them. I have not done a compression test yet but the rings/pistons are brand new and freshly broken in. I thought once I broke the rings in the oil might stop but I have over 150 miles on them now and its just as bad as the first time I checked it.....

Gunslinger09

You built the motor or bought it second hand? If you built the motor this lessens the chances that the oil is blow by from the rings. Did you have a valve job done on the heads? It not it could very well be bad valve seals causing the problem.

C4 LS1

Yes I built the motor myself from intake to oil pan so I know all the tolerances are spot on with rings pistons etc. However the heads I got from my a buddy of mine and I did not have the machine shop do any work to them for the reason that I know they were a good pair of heads when they came off the car without any problems. Since those heads sat for 2 years I think maybe the seals have dry rotted around the guide and I just did not see it when I put the heads on. I just need to know if that much oil can leak through the valve seals and cause this problem or might it be something else.

MIKELMOTORCYCLE3398

iTrader: (3)

Sounds like valve seals. Do a compression test!!

Gunslinger09

Yes that much oil can leak through the valve guides if the seals are bad. You can pick up new Viton Seals and put them on yourself. I would try that and see if it corrects the problem.

C4 LS1

I think thats what I am going to do. Ill pick some of the seals and a spring compressor and knock it out this weekend. I am still open to ideas as well but I will be doing that job regardless.

onefast84

I would check the guides too. Seems like these ls engines seem to eat valve guides with with aggressive cam in them.

99Bluz28

iTrader: (35)

I'd also put thread sealant on all the rocker bolt threads that have bolt holes that open into the intake runners. Easier yet, just put it on all of rocker bolt threads.

mlmedina26

As long as you know the ring gap is in spec and they are clocked correctly it sounds like valve seals to me.