Okay the best description I can give I have a 1973 240z (it had been sitting since 91) with recently added used round top carbs that came with an intake manifold and a cheap new electric fuel pump. I removed all the junk on the balance tube including the line from the exhaust and the coolant lines the coolant line that ran into the manifold was removed but left unplugged when I bought the manifold and I left it that way .I also removed the air pump junk. I have adjusted the float to Haynes specifications. I know that cylinder number two (counting from the front) has no compression.

The symptoms I am experiencing:

when it did move (before major adjustment)it had a major lack in power, it also popped allot and it sounded like back firing which got worse as gears went higher( I didn’t make it past 3rd on my test runs). I was told to readjust the carbs. I bought a uni-syn and adjusted by the Haynes manual's description which was very hard to follow (I can go into detail on its directions if needed). It ran worse after 4 more adjustments each getting more meticulous on little details of how they were balanced and what not. Now it runs like crap! It idles low and seems as if the idle slowly decreases as it sits. When in neutral it revs but a bit slow when put into first as soon as the gear engages it backfires, bucks, and then dies.

The last buck shook the exhaust loose and now it’s as loud as heck:stupid:

From what I have read it sounds like timing or fuel starvation. I think that I read that you have to change the timing after removing emissions stuff??

I figured before making things worse I would ask on here what direction I should go.

Thanks

Corection it bacfires and bucks when starting to move on a hill, on level ground it is hard to move, but bucks moves a few feet very roughly and then dies.:stupid:

what do your spark plugs look like? Are they really black, tan, or white? Have you adjusted the fuel mixture on the underside of the carb?

Sounds more like a vacuum leak to me. Do you have a picture of your setup? Is the vac advance plugged into the front carb? What did you do w/ the rest of the balance tube? If it is running that poorly how did you sync the carbs? Just curious.

Bill

What wfl_colorado said.

When you synched the carbs, did you set the mixture screws? The most common starting point is to set the screws all the way tight, then back them out 2 1/2 turns.

You will want to make sure that all the openings on the balance tube are covered and secured. Also, there may be additional vacuum openings on a 73 that my 71s don't have.

Oh yeah, make sure the openings on top of the float bowls are vented to the atmoshpere. plugging them = not good.

Okay I'll answer in the order that they came.

last I can remember plugs were black, Ill recheck them in daylight

yes I have changed mixture setting (more on that in a bit)

No I have not checked for a vac leak, but I heard if you plug the air inlet on the carbs front and it still runs you have a vac leak

I can take a pic in the daylight

I know of a very thin line near the rear that is hooked up and I belive it goes to the distributor if I remember correctly

What is the vac advance or better what does it run between

The balance tube is all plugged other than the openings to the manifold and the opening that I cant remember what it goes to but it closes itself Ill figure what it goes to in the daylight

float bowls are unplugged

Now the big question of how I synced em

If its awful dont blame me its what Haynes said to do

*loosen balance and fast idle completely

*tighten (actuallly it says "screw up" and in parentheses it says clockwise but tightening would be counter clockwise looking down?!?) mixture nuts all the way then back off 1 turn

*Start engine

*turn throttle speed adj. screws so that engine runs evenly at 600 to 700 rpm

*balance the carbs with flowmeter by adjusting throttle speed adj. screws only

*this step it says to tigthen mixture screws equally 1/8 turn until fastest smoothest idle is achieved, but I substituted this with the disable one carb by lifting each piston one at a time and adjusting mixture so that it runs roughly with one disabled

*unscrew throttle speed screws to reduce idle to 650 rpm

*balance with flowmeter by adjusting throttle speed screws

*turn balance screw so that pistons visually lift simultaneously

*turn fast idle screw so that engine is between 1000 and 1500 rpm

*use flowmeter and balance by adjusting balance screws

*release fast idle to 650rpm and rev engine to allow to return idle

*recheck balance

*book doesnt say to but I recheck mixtutre by using the disable technique

*I dont do this part because I dont really get it but it says" set fast idle so that there is a clearance at its tip between 1-2 mm when balance screw is lightly depressed with the finger"

thats all I can tell you tonight

thanks for the help

You mentioned that cylinder 2 has no compression. Have you determined if it's because of bad rings, bad valves, or a worn camshaft? What were the compression readings for each cylinder?

Have you adjusted the valves? Did you set the ignition timing yet? Have you looked at the distributer cap, rotor, points & wires?

A cylinder with no compression is not a good sign, hopefully the engine isn't about to give up the ghost.

I opened up the valve cover and everything looked good, I just guessed it was rings and I would rebuild when I had a garage money and I knew how the engine went together better

any way to checkwhat is wrong with the cylinder

distributor looked decent last time I checked

what is the diffrent timing with no emissions??

New Plugs, Wires, and timing adjusatment and it runs like a champ

I just had a similar problem with my '73. I have come to believe that the hays and clymer manuals stink. I have each. I spent about $75 on a copy of a shop manual and have found it invaluable.