lq4240sx

Hey guys I've got a iron block 408 that I'm running AFR 230 large bore heads on. Since the bore of the block is 4.03 I figured running a ls9 gasket (4.100) was ok. The car ran great for 2 months and then developed an oil consumption issue. When I run a compression test its even across all 8. I'm also not noticing any oil in the coolant or any overheating. In fact it runs like a champ just smokes on desel and at idle.
I've unhooked the pcv system and just put breathers on the valve covers and it hasnt changed anything. All I can think is that the oil is getting pulled in because the head is not sealing around the gasket.

redtan

iTrader: (5)

Well it must be going somewhere, it's either leaking or being burned off. Since you say it's not in the coolant, then it's leaking externally or burning. Have you checked around the engine bay/ground for oil or can you see it in the exhaust?

People run that sort of stuff (big bore headgaskets on small bore blocks) all the time and don't have this issue. And it's big disparities like LS9 gaskets on 3.78 bores.

lq4240sx

I know for a fact its coming out the exhaust and being burned off. I can run through as much as a half quart in a 5-6 hour time span. When I shut the car down and pull the intake off I see oil on top of the intake valves. With the pcv no being hooked up and new heads I can only think rings or that head gasket not sealing. I've ruled out valve stems and guides because I've replaced them and nothing changed.

redtan

iTrader: (5)

Try a leakdown test on the cylinders.

lq4240sx

I'm gonna do a leakdown as soon as I get back home. The compression came up good but that doesnt tell me a whole lot. It being all 8 makes me think its the head gaskets but I could have 8 bad oil rings I guess

LLLosingit

iTrader: (4)

I'm not sure how you think oil is going to end up on top of the valves if it's a ring or head gasket issue? The only way for oil to get there that I can think of is Valve seals/guides or PVC and you say it's not hooked up so that leaves Guides/seals. Oil does not leak past rings into the combustion chamber then up into the intake tract that would be a major feat considering air/fuel is being pumped in the opposite direction.
So you replaced both the seals and guides?

LLLosingit

iTrader: (4)

This also makes me think it's seals/guides. During deceleration the area from beneath the throttle plate to the intake valves/pistons is under it's highest vacuum. I suspect oil is being pulled past the seals/guides at this point.

ckpitt55

iTrader: (4)

What rocker arms are you running on these heads?

Unless you're running roller rockers or had PM guides installed, you're side loading the bronze guides which wears them out extremely quickly.

Your head gasket seems to be unrelated to your oil problem, but I'd at least double check to make sure you're clearing the combustion chamber. I'm running 4.140" gaskets on my 347 with AFR 215s to clear the combustion chambers.

lq4240sx

I'm running the stock rockers with the trunion upgrade. If the guides did wear out would they leak even through new seals?
The gasket issue is just something I'll address after I pull the heads as I dont think thats the problem. I'm clearing the cylinder bore but not the chamber on the heads

So I'm thinkin now its either guides or the intake rocker bolt protruding through into to runner.

lq4240sx

Here's what it looks like when I pull the intake. In about 4-5 hours of driving it can lose about 1/2 a quart.

s57_s2k

What oil are you using ?

ckpitt55

iTrader: (4)

I'd say it's possible. The seals are a lot more compliant than the guides are, so if the guides are worn then the valve is moving around a lot more than it should be. Hard to say what amount of movement the seals are able to tolerate while maintaining a good seal, but over time the excess movement could lead to fatigue / cracking / torn seals. How many miles are on the heads?

Mounting bolts for the intake rocker arm require thread sealer. Arp ptfe thread sealer is nice to use for stuff like this.

lq4240sx

these heads probably have 2000 miles on them maybe not even that. I didnt put anything on the intake rocker bolts at all.

I'm using valvoline 10w-30. I'm just not sure how much oil could be pulled down the rocker bolt to make this kind of loss.

I think I'm gonna pull the heads anyway and just have then tested to see if thats where they are leaking from and also I can change to the proper head gaskets at the same time.

S10xGN

iTrader: (11)

I'd dope the bolts and see where it gets you first. You'll see up to 25" vacuum on decel and half that (depending on cam) all the time...

Jontall

It looks like the valve seals are unseated. I'd pull the valve covers and start checking.

ckpitt55

iTrader: (4)

^^ both good ideas to start with

At some point, you're going to need to address the rockers or guides - running stock rockers on bronze guides is known to wear the guides out in as little as 10k miles. not sure how many miles a year you put on this car but something to be aware of. either change out for roller rockers or have PM guides installed in the heads