Oil consumption problems on my stock 87 305tbi-350 carb

[2square]

I recently rebuild a 350. Bored .30 over new rings pistons,rings, rods, cam, lifters everything is new. The reputed engine builder did the bottom end and heads, I did cam(comp 12-238-2) lifters. ( comp 813-16).I followed the comp cam instructions and broke it in as instructed. ( including the recommended break in oil) Also it's a frame off, so the only factory part of this truck original wrangler is the body. This is where Things get interesting. As of now I have about 50 miles on the new build. I've already put two litres of oil. I've done a leak test..all green. Every spark plug is black with oil dripping off the treads. The pvc/ vacuum hoses are wet with oil? The valve covers have baffles. Not one leak. It does show blue smoke on start up( valve guides) but im talking a cloud smoke after 2 mins. I Never see blue smoke after a good drive( untill I shut it off for a couple mins. And never while driving. But yet the oil is disappearing. By disappearing I mean 20 miles I lose an entire litre. This seems impossible to me to lose a litre of oil after 25 miles with no leaks, runs great, anyone got a idea?

 

[Customblue]

My best guess would be valve seals.

 

[Jerry phillion]

Years ago I had 77 Chevy van. Had about same problem. Tried
About everything, still used a ton of oil . Finally took valve cover
off. Found the oil return hole at back of head was partially
plugged from head gasket. Ran a drill down there and unplugged
hole. Only did one side as I couldn't get to other. It cut oil
Consumption in half. It was partially plugging the return oil and
Flooding the top of the head, causing oil to leak down valve
seals . Custom blue was right on .

 

[2square]

Just in case anyone cares I found the issue. It was the Intake... I had done what I seen online and reamed out the holes on a older model SBC intake and used thick gaskets on my vortec heads. But it did not seal to the ports properly and was sucking oil through the exuast port.. the proper vortec intake solved the problem.

 

[Rusty Nail]

Oh you didnt say vortex heads....thatd always the problem.

It will also be the reason when you go looking for missing coolant.

Vortex heads.

There, i said it for you. I want my view back.

 

[jjester6000]

My '88 chevy with 237k on it seems to lose a quart every 20-30 miles or so. I didn't think it was that worn out when I bought it, but it is. I am seriously going through like a quart a day just driving it daily. It doesn't smoke very much though, only when starting cold. It also keeps foweling plugs like no tomorrow, I have to pull and clean them every week.

I think the majority of the problem is the valve seals though, since its got decent compression.

 

[AuroraGirl]

Thats... a LOT of oil, dude.... like a lot. If you got compression and doing a leak-down test doesnt change your numbers a lot, its SUCKING it in somewhere. But you could have some insane, and I mean insane, blowby. Is your pcv valve stuck open? Sucking oil straight in the carburetor base? Stuck closed, causing increased pressure? Take off a valve cover, check what the 1st responder here said, maybe? That seems like you got engine damage if you got that much oil consumption, and you would probably see a lot of blue smoke in the tail pipe. Maybe a plugged up catalytic converter causing way too much pressure? Valve seals acting one way, let oil in, not let it out? Somethings not right

 

[2square]

My '88 chevy with 237k on it seems to lose a quart every 20-30 miles or so. I didn't think it was that worn out when I bought it, but it is. I am seriously going through like a quart a day just driving it daily. It doesn't smoke very much though, only when starting cold. It also keeps foweling plugs like no tomorrow, I have to pull and clean them every week.

I think the majority of the problem is the valve seals though, since its got decent compression.

Get a leak down tester. You put air into your cylinder while it's at TDC and let you know if it's leaking out. If it's leaking out it will also give you a good indication of where and why it's burning oil

 

[2square]

Thats... a LOT of oil, dude.... like a lot. If you got compression and doing a leak-down test doesnt change your numbers a lot, its SUCKING it in somewhere. But you could have some insane, and I mean insane, blowby. Is your pcv valve stuck open? Sucking oil straight in the carburetor base? Stuck closed, causing increased pressure? Take off a valve cover, check what the 1st responder here said, maybe? That seems like you got engine damage if you got that much oil consumption, and you would probably see a lot of blue smoke in the tail pipe. Maybe a plugged up catalytic converter causing way too much pressure? Valve seals acting one way, let oil in, not let it out? Somethings not right

. Thanks aurora girl but I solved the problem see my post I had bought a used SBC that I rebuilt it came with a older style intake that did not fit the vortec heads. Google will say these intakes will fit and they do. But you need to ream the bolt holes. Also you may get lucky I did not. The proper way to fit these is to weld a bead and have it re surfaced I found mine did not seal and I was getting exuast fumes/ combustion under my intake. And sucking oil through exuast ports.... Just my analysis but I purchased the proper intake for the vortec heads and it did solve my problem instantly... From 1 litre of oil every 25 miles to burning 0 oil in the first 100 miles. Sounds unbelievable but it's what happened in my case. I re did the leak down test 3 times all cylinders came back with just under 20% leakages

 

[AuroraGirl]

. Thanks aurora girl but I solved the problem see my post I had bought a used SBC that I rebuilt it came with a older style intake that did not fit the vortec heads. Google will say these intakes will fit and they do. But you need to ream the bolt holes. Also you may get lucky I did not. The proper way to fit these is to weld a bead and have it re surfaced I found mine did not seal and I was getting exuast fumes/ combustion under my intake. And sucking oil through exuast ports.... Just my analysis but I purchased the proper intake for the vortec heads and it did solve my problem instantly... From 1 litre of oil every 25 miles to burning 0 oil in the first 100 miles. Sounds unbelievable but it's what happened in my case. I re did the leak down test 3 times all cylinders came back with just under 20% leakages

Im actually talkign to jester, I should have quoted him. He kinda latched onto your thread. 20 miles he loses a quart of oil. Thats INSANE.

 

[jjester6000]

Thats... a LOT of oil, dude.... like a lot. If you got compression and doing a leak-down test doesnt change your numbers a lot, its SUCKING it in somewhere. But you could have some insane, and I mean insane, blowby. Is your pcv valve stuck open? Sucking oil straight in the carburetor base? Stuck closed, causing increased pressure? Take off a valve cover, check what the 1st responder here said, maybe? That seems like you got engine damage if you got that much oil consumption, and you would probably see a lot of blue smoke in the tail pipe. Maybe a plugged up catalytic converter causing way too much pressure? Valve seals acting one way, let oil in, not let it out? Somethings not right

I bypassed the PCV valve and installed a breather, so its not that, it also doesn't have a catalytic converter, I am about 90% sure that the valve seals are abolsolutely shot. I'm also running 20w50 oil in the sucker.

Have an of you had good luck with additives such as rislone at fixing the valve seals?

I think I'll try it before doing the seals.

 

[jjester6000]

My '95 suburban had used to smoke due to a bad PCV valve, but now it runs absolutely mint, so that was my first idea.

Also my '74 GMC used to burn a quart every 60-80 miles, and it always fowelled plugs in a similar fashion to the '88, but I just finally fixed it recently after swapping out the cylinder head.

Now I've gone 300 miles without buring a drop.

 

[Havasublue]

Are the piston ring gaps too big...?
All lined up in a straight line.
Would explain a lot

 

[AuroraGirl]

I bypassed the PCV valve and installed a breather, so its not that, it also doesn't have a catalytic converter, I am about 90% sure that the valve seals are abolsolutely shot. I'm also running 20w50 oil in the sucker.

Have an of you had good luck with additives such as rislone at fixing the valve seals?

I think I'll try it before doing the seals.

What do you mean bypass pcv with a breather? Do you mean a Pre-PCV intake with a vent tube? If you mean a breather on both valve covers thats not how that works..

Breahter lets the engine suck air in, but the crankcase has pressure and vapors it needs to get rid of. Another breahter is just gonna bottle those up and its gonna push out where it can. Grommets, valve cover seals, piston rings, probably valve seals, especially intake valves. other oil orifices. thats called positive pressure in the crankcase. they sell a valve for it

now if you mean a pre PCV dick looking oil crankcase vent, then I gotcha. my vote would be valve seals. my 2001 aurora im sure had valve seals as an option because it sure didnt act like it had them.