SPITTING CARB - 914-6 all stock, Need assistance - please see latest post to this thread Options

[ctc911ctc]

1970 - 914-6 All stock

Got the car off the rack after a 1 year clean up documented here:

http://www.914world.com/bbs2/index.php?sho...3371&st=100

- tightened the lugs, check one more time for leaks.......

Car started first try, backed out of the driveway and went around the block

Drive strong.....very strong......

#2 cyl-carb is still 'spitting' definitely not backfiring. Chasing this through my trusty guide:

https://www.performanceoriented.com/special-procedures-1

See "notes" section

Seems that when I performed the Lean Best Idle procedure #2 failed during the procedure......the diagnosis within the document states that either the path in that carb #2 is blocked or the jet is the wrong size - my bet is a clog......though the carbs were very clean when I got the car.

There is a little noise from the right side, that in a 914-2L 4Cyl would be considered quiet, my hope is that it is not valve noise and may be exhaust leaking......did I tighten the heater manifold small nuts????? dry.gif

Carb advice sought from those that have chased a SPITTING Carb

[Ninja]

Just re-read thread. You're stock so the original stuff should work fine.

The issue seems to have changed too. Thread started out with popping through the carbs and most of the replies were spot on for diagnosing that.

Backfire through carbs is caused by fire getting past intake valve and igniting the fuel in the venturi. It is more commonly a valve issue rather than a carb issue. Significant timing screw up might cause it as well, but the puppy would NEVER run properly.

Often, I'll see ITB carb setups with a "dirty" barrel and it's always the engine that did it...

You compression test looks GREAT, very close to each other.

Your leak down test numbers makes no sense to me but it may be my unfamiliarity with your equipment.

The leak down testers I've used have two gauges, the first for inlet and the second for what remains in the cylinder. Most have standard couplers and an air tip (blow gun) can be plugged into it. Blow gun not running should show 100% retention. Blow gun depressed will show a low number 20-30%. It will NEVER show zero so they are not as accurate as the technician would want.

Normal leak downs are shown as a percentage. As every gauge I've ever used had an initial setting of 100psi the numbers made sense.

I'm not sure what your numbers mean but they DO show loss. The Hawk's suggestion about finding out exactly where it's leaking are excellent.

My first 914 (a ratty 70 1.7L) would throw fireballs ten feet above the car on cold start then run like hammered shit for the first 30 seconds. It was set up with the center mounted progressive 2 bbl. (the set up everyone hates). This reduced performance but was very reliable and easy for beginners to understand/work on.

The hard starting/fireball BS was so bad it burned up a couple of air filters before I left the filter and engine cover off.

I set a friend's tree on fire one memorable night... (IMG:style_emoticons/default/ninja.gif)

I was 17 and didn't know then what I do now...

I'm positive I had poorly sealing intake valves that required heat before their sealing properties improved.

I traded that car off for my first 240Z (a straight trade 1983) and have always had a Z car since.

Look closely at the engine before damming the carbs.

Do a leak down on all cylinders the next time you have the carbs off. Spray a little WD/40 in the intake ports before each test. All will leak a little (small bubbles). When the leak down blows the WD out of the port you've found your puppy!