mudkip777

When I took apart the front carb, I checked every fuel passage from the inlet nipple to the metering rod and found no blockages or debris. The only thing I did notice was the needle and seat seemed a little sticky, which was solved by removing it and reinstalling it. The hose between the bowl and the nozzle doesn't seem very old (its not cracked or very hard). I don't know how old the fuel was because I got the car in December and it already reaked and was very yellow. I drained and refilled the tank in January (refilled it with 5 gallons of premium and a bottle of seafoam to stabilize it). I only got it back running earlier this month. I know the previous owner "rebuilt" the carbs, because he gave me a box full of old and new carb parts and gaskets. Im not sure what all he changed, or adjusted. I'm also not sure how to measure or adjust float level.

I dont think its doing much even under load. Based on the fact that I took a look in the fuel bowl and it was full of old yellow fuel. I've drained my fuel tank and have had new gas in it for a while and have been driving for at least 100 miles since. Plus like I said at the beginning, it struggles to rev past 4k, which leads me to believe the vacuum advance isn't working (it's run off the front carbs vacuum). I don't think the issue lies in only idling.

Not sure if you read all of my previous messages, but the front carb is removed, so the front manifold was completely open during the compression test.

Well I just redid the test with all 6 plugs removed, spinning it until it stopped building compression, and with the rear carb throttle held open for good measure. 1. 120 psi 2. 125 psi 3. 125 psi 4. 120 psi 5. 118 psi 6. 122 psi They went from being within 20 psi to within 7 psi but they are still a little low. I haven't tried adding oil to the cylinders, because I'm not sure how much or what kind. I'll have to see if any of my friends have a compression tester. The one I'm using is a rental from O'Reilly.

I just compression tested all 6 cylinders. I did the test with the engine cold and 1 spark plug removed at a time. I had the front carb removed, not sure if that made a difference or not. I didn't have the throttle open on the rear carb either. If it will make a big difference to have engine warm, I'll have to do some work to get it back to running shape. So I won't be able to get those results very quickly. Cyl 1: 105 psi Cyl 2: 125 psi Cyl 3: 115 psi Cyl 4: 115 psi Cyl 5: 105 psi Cyl 6: 110 psi To me that seems a bit low, but they're consistent at least. Hopefully these might show something to someone else.

These are the 2 flowmeters i have. I tried both on the front (both read nothing) but i only tried the silver one on the rear. Yes i checked and set all 12 valve clearances to the same specs. The throttle adjustment screws were both set to 2.5 turns out from the bottom.

I've pulled the front carb off the manifold and looked inside and can't find anything unusual. I don't have a borescope to look deep enough right now. I also haven't checked compression yet, so not sure if the valves are sealing correctly at the moment. Also the oil in the carbs is SAE 20 not 30.

https://youtu.be/tbbZOlJrnjw Here is a video of it running. I runs decent, but i know not enough air is getting pulled through that carb because it has old fuel in the bowl. Ive been running and driving it plenty enough with all new gas in the tank where there shouldn't be any old gas left in the system. Also it struggles to rev past 4k so I don't think the vacuum advance is working (not enough vacuum). The way I found this issue in the first place was because I tried to adjust the carbs according to the service manual. So I had set the idle nuts to the proper turns according to their chart, the first idle screw wasn't touching the linkage, the balance screw on the rear carb was barely touching the linkage, the idle was set the 650 rpm, and when I went to put an airflow meter to the front to measure it, it didn't read anything. I put the same airflow meter on the rear carb and it killed the engine. I tried it with 2 different flow meters. I have also verified valve clearances between the cam lobe and the top of the rocker. Cold it was set to .20 mm for the intake and .25 mm for the exhaust. I'm not sure if thats the same as the valve lash (if not, I've got no clue how to measure that).

I have a 1972 240z with SU carbs. My front carb has no vacuum being pulled through it. Not sure why. The front 3 cylinders are firing (based on new plugs being carboned about as much as the rear 3) and it runs and drives decent (struggles a little to rev past 4k). I went to try balance the carbs and put an airflow meter on the front and it didn't read crap. I can block the throat of the carb with my hand and idle isn't affected. I also don't feel any vacuum being pulled through the vacuum advance (which is hooked to the front carb). If I block the rear carb it kills the engine. I checked valve clearances and all are good. I'm a bit lost to be honest. The slide on the front carb does go up if I give it throttle. And both front and rear slides go up and down at the same rate. They have sae 30 oil in both carbs. Hopefully someone can help.