Description of the car from eBay 

So the block was done by spirit and the head from z car performance and all installed by Eiji

Trust but verify.  Eiji could tell you something, I'd guess.  Chrome rings can take a while to seat.

As Mark M. suggested, a cylinder pressure measurement might be telling also .  Leaky compression rings should show there.  Bad valve seals and guides can allow blowby on the exhaust side.  The head was done by Z Car Performance.  Not sure who that is.

You're still in that short-term vs. long-term dilemma.  Vent the fumes and drive short-term, fix the issue long-term.  Interesting problem.

19 hours ago, Mark Maras said:

 Don't assume the compression is fine just because it runs solid. There's reason for that much blow-by in the crankcase. I'd want to find out why, before I dumped it all back into the intake and then fret about, is there anything wrong, how long will it last. A compression test is cheap and easy.

DING DING DING DING DING DING!!!!!

winner winner chicken dinner

compression test this morning

cyl 1-160 2-165 3-160 4-165 5-160 6-90

 

 OK,  Check the valve lash clearance on #6. If the lash is tight, adjust and check the compression on #6 again.

  Squirt some oil into all of the cyls. and check it again. Compression in #1 - #5 will probably raise a little. #6 will probably raise a lot. This would indicate a problem with the piston rings sealing properly.  If #6 raises about the same as the others, the top side is the problem. A bore scope in #6 might tell you more.

 My gut feeling is the same as grannyknot's. For some reason the rings on #6 haven't seated. You might want to find out what kind of rings were used on the build. I don't have much knowledge about rings but IMO moly rings are the most forgiving during break in. Chrome rings are considered a step up from moly but they have had problems seating and sealing. I've always used moly rings for the street. Another plus with moly is they will reseat, even on on old engine that has been sitting for a long time. "Surely" there are members that can add their knowledge about rings. I think the discussion is about to arise.

 

Do what Mark suggests he is on the right track ^^^^^

Well I'm no mechanic that's for sure. I can do the basics but when it comes to inside an engine....not so much. But I'm down to learn. and thankfully my best friend is the shop foreman at the local Nissan dealership and is a very skilled mechanic. I will say that when I got to the 6th cylinder it seemed to not crank as hard maybe because the battery was getting low. So I put back all of the plugs and wires started her and let her idle for a good 10 minutes and redid the process just checking the 6th cylinder. It cranked fine after the 10 minute idle and I got 90. I'm going to check again and squirt some oil in there for a wet test. I just don't have the mechanical knowledge to adjust valves at this time.  

Take the cover off and have a look easy to check not hard to adjust. https://www.google.com/search?q=1969+road+race+of+champions&biw=1366&bih=673&tbm=vid&source=lnms&sa=X&ved=0ahUKEwjv_uvXk4LMAhXDxIMKHVJyAmAQ_AUIBygB&dpr=1#tbm=vid&q=l28+valve+adjustment

Thanks I will check it out. I just did a "wet check" on cylinder 6 and it went from the 90 to 140

Wouldn't be surprised if Datsun Spirit would fix it for you.  Only 5,000 miles, kind of looks like a broken ring.  Put all of your paper work in order, it probably shows due diligence during break-in and maintenance.  Not a huge job, he could probably do it in-car if he wanted to, although, based on reputation, he might want to give it a good look-over out of the car.

Forgot that you're on the opposite coast.  Still, he might assist financially, at least with parts, if you can find the right shop to work on it.

Edited April 9, 20168 yr by Zed Head

I just texted the previous owner for more info and he gave me Mr. Hosomi's cell number. I called him and left a message. I started taking everything off and was about to remove the valve cover and thought twice about it. I'll have to put a new gasket on if I take it off right? I would rather have my friend take a look at it first and wait to hear back from the builder before I open it up and start doing anything.

 Agree with Zed Head. Poor ring seating doesn't cause that much compression loss. It's looking like a broken ring. You'll want to take a good look at the bore in #6. A broken ring can leave vertical scratches in the bore.

 Give the valve cover a try. Unbolt it and give it a good bump with your palm. Unless someone glued it on both sides, it should come loose easily. As you lift it, be sure the entire gasket either stays on the head or on the valve cover.