One problem still exists that is annoying, my wife is too kind to complain but every now and then an unwelcome odor enters the car. I have tuned in and eliminated most all of the things I’ve wanted to get the most enjoyment from my 2.0L conversion.
I’ve got the carburetor sufficiently cooled to keep the gas from boiling (I’ll be posting more on that on a separate thread). I’ve eliminated the stumble off idle.
I’ve been able to find a little better performance and a little better gas mileage by running just under 36į on my total ignition advancement with no signs of pinging, the AFR is where it should be.
The engine has no measurable oil loss between oil changes (every 3,000 miles).
The last thing on my checklist and seems to be difficult is to eliminate the offensive odor I have that emanates from the crankcase and or valve cover. It seems to be a gaseous odor only present under higher RPM deceleration going down steep enough grades with the throttle plates closed or not during but shortly after I goose it up to 6,500 RPMS, 10 seconds or so afterwards. I also do have “the windy hole” when I remove the oil cap at idle it seems to pulsate in both directions but knocks a piece of paper around pretty good if I hold it above the oil fill hole. Mixed reviews on that, some say that means nothing. Here’s a good post on the subject https://www.opelgt.com/forums/6a-eng...fill-hole.html
Everything I read is pointing to it being blow by pointing to the rings not seated correctly. I’ve got almost 20,000 miles on the engine since the rebuild so it is just about 2/3 fully broken in. The good news is that there’s ways around it. Rolling up the windows is the best LOL. Other ways would be to alter my driving habits. I certainly don’t want to tear down the engine again, if it’s the rings, if it was going through any oil I would, but it doesn’t. My valve seals/guides look a little bit shaky but nothing horrible just residual oil on the spark plug threads and the intake valves had a wet black coating on the back of the valves (see pic) I realize that the valves stems are supposed to receive oil but maybe not that much. I purchased new valve guides from OGTS, They were installed as far as I know. No smoke out the exhaust on fire up or at all while driving. I wasn’t really happy with the cylinder head work as a whole even though he did a few extras like installing the threaded plugs for the oil galleys. All in all it was just okay I suppose. Once I decide the best way to rebuild my 71’ head that I have sitting on the shelf I’m going to swap it out eventually. I’m confident that will change things up considerably in the performance department. My hope is that all of my woes here are related to the valves seals or guides not sealing properly or so I’ve read it’s a possibility? The valves all seat fine as my CC is 150-160 across #4 being the highest. Any signs of oil control issues (must be minimal) seem to be coming from the top.
I’m getting my oil tested for gasoline content along with other things by a well known company called Blackstone Labs they’ll send you the test containers for free and you pay $28 upon the analysis. If I do have anything going on there I’ll know to change the oil more frequently.
All of the internet articles I see relevant to blow by include oil loss. It’s hard to imagine that the engine does an even exchange gas for oil because it’s always spot on when the level is checked. But stranger things have happened. Better to be safe in the oil lubricating department.
This is a difficult subject to research on the internet because I never see many details including the following. If the rings didn’t seat right #1 Wouldn’t I be using oil? #2) No specifics on this wouldn’t this odor be most present during hard acceleration with faulty piston rings? Not 10 seconds after. I’m hoping that someone can advise after looking at the specifics let me know if you have any further questions. My strongest hunch has been to put my finger on the piston ring thing but there’s a lot of good mechanics on our site so I wanted to post this up. Any advice on how to capture and divert this odor would be welcome as well since it seems like I’m stuck with it for a while.
My solutions to eliminate this odor so far:
1)I purchased and installed an oil catch can to be checked at oil change intervals.
2) My theory on deceleration was the throttle plates being closed were not allowing the gas odor into the intake so I ran the outlet hose from the catch can back to the rear of the car. It seemed to have made it better for a while. Not realizing when I was playing around with the timing advancement I was running extremely rich (in spirts I saw it on the AFR gauge) causing worse odors so I ripped it out.
I’m thinking about re installing the hose again now that I have it tuned properly. The hoses are as follows now, small hose to small 1.5mm orfice on intake, the other connected back up to the Weber box filter.
3) I haven’t yet, but my oil dipstick tube has always been loose it doesn’t have any oil leaking there so I’ve always just left it. I’m thinking of sealing it up I’m a little Leary about leaving the dipstick in after doing that I’ve heard from others that they can blow out, so I might cap it off somehow and keep the dipstick in the car until if and when I’m confident enough to put it back in.
4) I’ve regasketed the oil fill cap using cork rubber gasket material but it still leaks a little. I’m now buying the right gasket from OGTS.
Thanks again in advance,