Hey,
I've got a 1975 XB, it's running a rebuilt 250 2V, ACL pistons & rings, 0.30 thou over, a mild cam (nothing huge), extractors, 2.5" exhuast. The inlet manifold has been modified to fit a 4-Barrel carb, which it runs a 450 Holley.
It has been dyno tuned, carb jetted to suit the engine (60 jet size), runs perfectly, however it uses oil. By this stage the engine had done about 8000 kays. Every 500 k's or so it uses about 400 mls of oil, could see it blowing out the back on deceleration. The car had maybe 1000 k's on it before it was tuned properly. I talked to the guys that rebuilt the engine & they suggested the bores were glazed from over fuelling before the carb was sorted out which It hought was fair enough because it was quite bad.

So I have since then re-honed the bores & replaced the rings.
Put some running in oil in there has I was told to by the engine recon people & took it out for strope. Over 500 k's it used 500 mls of oil. People said that it would use oil but maybe not that much.
I've since changed to a 20W-50W Valvoline oil & have had a mechanic do a cylinder leakage test on it(only done about 10k's before test was done). The test's showed cylinder leakage thru the rings, crankcase area. He also noticed oil on top of No: 4,5 & 6 pistons too. He said the carb is too big for the set up, but i'm under the impression that it's not, since it's been tuned to suit.
So I took my falcon back to the guy that orginally did the tune on the car to have it checked & tuned again. It was running a bit on the rich side, it showed on the machine 8% at idle & 6% at 100 k's. He change jet sizes to 59's & adjusted up the idle mixture screws. It then showed on the machine when run up 3.8% at idle & 1.5% at 100 k's. That is quite a difference in readings. Hopefully with it tuned properly now (which I thought it was when it was first paid & done for)that my problems are over. Maybe with it leaned up the rings will have a better chance of bedding in...
So after putting 700 kays on the engine I noticed it was still using oil, on deceleration it will blow smoke out the back. Talked to a few mechanics & they sugeested the valve stem seals, so I replaced them but still it is still blowing smoke out the back on deceleration.I noticed that when i removed the plugs the back three had oil on them. Also noticed that when i had the head off doing the rings the back three ports on the manifold had oil in them. Could it quite possibly be the PCV valve? The PCV valve does sit in the back of the rocker cover...
Anyone out there running a similar set up, anyone expericened this problem before?

There's only one sure thing in life & that's doubt, I think?

No just ACL rings. Pretty sure they're not chrome moly...
Is it possible for the carb to be too big for the set up?


There's only one sure thing in life & that's doubt, I think?

hey horangi250 do you have a bro living here is aus?
i have a mate that uses that name a lot and he has a bro in nz with a xb.

I am mate with craig aye!
Didnt you go and get a eb v5?
juz