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Hi all, new to the forum and over the past few days been on the site alot seeking answers.  I am very familiar with small block chevy's and everything about them, I recently bought a 1978 Datsun 200 SX dirt track race car.  The engine has issues and I am working through them, but at some point I will more than likely need the expertise I have seen and read on here.


First off, when I went to purchase the car, it sounded sick and I noticed the carb was not flowing properly and it was popping through the carb not to mention the electric fuel pump died while we were running the car, I got the price down so low I couldn't resist taking a chance on the car thinking it was a fuel related issue.....or not.


Last night I changed the carb from a holley 350 to a holley 500 from the shelf and it was off and running, but it would still occasionally popping back through the carb, after rotating the distributor fully clockwise, no more popping, however the car wouldn't get past 3k RPM.


Tonight I popped the valve cover to check the timing chain and tensioner and everything look good, but I noticed a rocker was off the valve, then I noticed a second one off as well.  I put them both back on and adjusted the valve lash to the specs I had seen listed everywhere, put the valve cover back on, fired it up, same issue with the popping back through the carb until I rotated the distributor fully clockwise, then it smoked like there were 20 guys vaping non stop in the engine, after a few minutes all the oil and whatnot burned off and it ran very well, I gave it a few revs and it sounded very good actually, I was about to rev up past 5k, but this engine (assuming was actually built as advertised) is a L20 but it is a 2.4 and I assume (assume being the operative word), that the engine should be capable of more RPM's though I didn't feel comfortable with the timing and what not so I stopped, not to mention the oil leaks I was discovering while doing this. I know nothing about these engines and I am picking it up as fast as I can.


I need to verify TDC is what is marked on the crank pulley, if it is, the distributor is not pointing to #1, it is almost 180 or more actually, some of those details are blurry as I was in a mad rush to fix the obvious.  If any of the info I have posted is incorrect let me know please, lot of work to do!



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350?? 500 CFM???? These are V8 carbs and probably why it won't rev. You really need around 250 to 300 CFM for a 2 liter engine for good overall drive ability. A Weber 32/36 is ideal for this.



The first gen '77-'79 200sx uses a mechanical fuel pump. If someone had to replace it with an electric it would be good if the output pressure is no higher than 3.5



Backfire through the carb can be a bad valve or a super lean mixture. (again carb too large for the engine) Firing order is 1 3 4 2 in a counter clockwise direction. (it's easy to get 2&3 reversed)



The L20B identification is at the top of the block just below the head and behind the dip stick. There is a flat boss with the displacement stamped there.



To be 2.4 liters, an L20B head is put on a Z24 block. If a Z24 block, the ID is on the opposite side and will be hidden behind the two center exhaust pipes from cylinders 2&3. 



The timing scale is near the alternator and the pulley will have a small v notch in it. Turn until the v aligns with the 0 on the scale. There are two TDCs so be sure you are on the compression stroke. You can confirm this by observing the #1 cylinder valves are both closed. If on the exhaust stroke TDC your distributor will appear 180 out.



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