my oil is thin and smells like gas...

[sclay115]

the motor is a l28 bottom end with a l24 head with a big cam and some high compression pistons. it has triple 40mm webers, with unkown jetting, i got the car like this, so it's hard for me to try and figure out what is wrong or where i need to go with tuning. but anyways, my oil is visually thinner and smells of gas, so my first reaction is, much too rich, rich enough to soak the cylinders with gas, and to seep past the rings into the pan. second thought is that the rings are flat out bad, haven't compression tested it, just brainstorming. and i'm also burning it a little, no doubt because it's so thin... but my thinking is that with an unknown camshaft with unknown pistons, and jetting that could be way far off, would it be wiser to just ride this motor out as long as i can, and be putting together a very mild rebuilt l28 of my creation to drop in there, one that i know all the specs on, or am i better off figuring out the one i have now? half of me wants to just rebuild my own motor so i can eliminate the guesswork, fuel inject it with megasquirt and TWM throttles, and just call it a day, but there is just a certain attraction to carbs, i'm just not very good at them.

any suggestions/critiques/guidance would be great...thanks

steve

[beandip]

First off drain the oil and change filter. Do you know any one that has a spair set of SUs on a intake that you can use untill you get this sorted out? This way you can still drive the car with out damaging the engine further. Is this a car that is to be driven on the street , or track only ? The trouble with a radical cam is that they make there HP at high Rs and run like $^!# at street speeds. There is a member here that turns in the 12s running SU in his 240 with street tires , and it is his driver . To me that is quick . Tripples do LOOK cool though . I am running a cam that gets into its power band at 2K through 5500 , and I am vary happy with it so far . I am still playing around with the needles and ordered some from Nissan the other day. I have a ZX flat top with a little head work also . Post a thread asking for help with the webbers as the topic . there should be some one here that can help with them , I am sorry I have no experience with them . GARY

[=Enigma=]

Could this be a bad mechanical fuel pump leaking fual into the crankcase? I'm new at this so someone else should chime in if this is worth looking at.

[beandip]

Enigma is right the mechanical pumps can fail and do this vary thing. Good call !

[sclay115]

it actually has an electric fuel pump, so the mechanical one is not at fault..but as far as the SU's, there really isn't that many 'Z' people that i know around me, how much does a set with the manifold run thereabouts? but yah i'm under the impression that the motor has one job, and it's to run at WOT all the time and be happy doing it, the street is not where it's supposed to be, or so it seems, it has improved after i installed a thermostat, of which it didn't have, so now it can warm up at least. so it can definately be a product of running too rich right?

steve

[Fun_in_my_z]

someplace close to 500 bucks. Where are you located?

[jmortensen]

Get an O2 sensor installed in the exhaust system. Just a simple one wire narrow band O2 sensor is what I use. Hook it up to a voltmeter or get an air/fuel gauge to read it. It will tell you where you are lean and where you are rich, which is very useful info.

Then you need to learn some about Webers in order to tune the air/fuel ratio appropriately. They have a lot of different parameters you can mess with, much more than Mikunis (one of the reasons I run Mikunis). Here is a very good thread on Webers: http://forums.hybridz.org/showthread.php?t=93343

The fact that you have that much gas in the oil leads me to believe the rings might be bad. You might want to start with the oil and filter change then check the compression first.

The fact that you have an unknown cam doesn't make the tuning process any harder. You still need to know when it's lean and when its rich and adjust accordingly. I've never heard of anyone who could tell you what jetting to use just by knowing the cam. You still need to adjust for that particular block/head/compression/intake/exhaust/etc combination so I don't think that your mystery cam is a handicap at all.

BTW Norm would be WAY faster with triples.

[Dans240z]

I'm not really sure why the oll would be thinner, but if it kinda smells like gas, I'd just assume that that's what it is. I don't know if this would cause that problem you talk about, but on my car (with a very similar carb/cam setup) the electronic fuel pump, pumped wayy too much fuel into the carbs, resulting is gas in the combustion chambers. Maybe the gas is somehow leaking past the rings into the oil. The best guess I can make, is that it's the carbs or the pump.

Hope this helps

[=Enigma=]

I've seen this issue before with V8s that had leaking main jets. It leaked fuel into the cylinders even while the car was off wich eventually made it's way into the crankcase. Not sure if this is even possible with side draft carbs.....

Sounds like it may just just be worn rings and consistent heavy throttle application. Dunno. Good luck.