Starts but runs horribly bad

[Wade]

Let me give you a run down first, 1971 that I put in a L28 about 5 years ago all new plugs/wires/cap/rotor/ect and it ran fine, but the car has never been driven since, just been garaged awaiting bodywork that never seemed to happen. I would start it every month or so and just let it idle and a few times I drained the gas and put a few gallons of fresh in. Progressively over the years it was running worse and worse each time, bad gas or whatever maybe floats stuck.

So here I am now, ready to get it back running and its stumping me what else I can try. I took the carbs apart and cleaned them out and did rebuild kits on them. Drained gas and changed filters (did not look bad to me surprisingly, I had the tank cleaned before the car just sat). I double checked timing and it looks fine. I got spark at all plugs. Changed plugs. Plugs are getting wet tho. I can get it to start but it is shaking and stumbling bad, pulling each plug wire off individually I really do not get much of a difference. Carbs are pulling good suction, no other vacuum leaks. Basically everything seems to be fine but its not, and I am stumped on where to look now. Something with spark/ignition not burning the gas or too much fuel flooding out the plugs.

This is a L28 with SUs, pertronix, electric pump. I am open to any ideas and will test whatever you feel I should, thanks.

I go from one side to the other, nice motor and crap bodywork/paint for 5 years. Now I may have nice bodywork/paint and a crap motor for 5 years

Edited December 17, 2011 by Wade

[5thhorsemann]

Post a pic of the intake and carbs showing the manifolds and hose plumbing.

[Wade]

Here is the manifold, http://www.classiczcars.com/forums/album.php?albumid=471&attachmentid=49934, just have the pcv hose to block, the brake booster hose, and the vacuum advance hose to front carb.

I may have set the needle too deep on the carb piston, http://www.classiczcars.com/forums/album.php?albumid=471&attachmentid=49933. I was unsure of what is considered the "collar" because this piston has a groove down the center. Should the needle collar be matched up with the lower collar of the piston or should it be matched up with the higher collar. Basically I am thinking the needle should be up a few millimeters unless how it is now where the needle collar is flush with the lower collar is correct. Hope that makes sense.

I need to figure out how you guys do the simple links also, always liked that about this forum.

Edited December 17, 2011 by Wade

[5thhorsemann]

Pull the hoses off of the overflow nipples on the bowls and start the car to see if your floats are sealing properly. Gas will run over the top of the overflow if they aren't. And don't use the choke.

Edited December 17, 2011 by 5thhorsemann

[Wade]

Float bowls seem to be set now, not getting overflow, I did readjust the level due to I forgot that these carbs were from a72 and I guess the 72s used a 19mm clearance and not the 14mm clearance that the earlier SUs used. I set it using a 1/2 drill bit between float cover and float and it looks to be all good at 19mm now. Also, like I was curious about on the needles, I pulled them out a bit so the collar matched up with the outer base of the piston and not the actual locking base. Put clean plugs in and it started up and is running much smoother except I am now getting an absolute ton of white smoke out the back. Car sat so long I am getting worried about a rotted head gasket or maybe even the block cracked, I am in Colorado and it has sat thru a few winters. Ill keep looking into that.

[5thhorsemann]

I would look at the carb insulator blocks and gaskets first, you draw antifreeze down the throat of the car if one of those 6 parts is bad. Head gaskets don't rot, so forget about that. And I doubt that the block or the head cracked.

[kenz240z]

Is it white, billowy smoke with a sweetish smell? If so, there is coolant getting into a cylinder (or more than one...). My guess is a head gasket issue or pitting on the head. Had this on my Z a few years ago.

As 5thhorseman suggests, it could be a cracked insulator between the carbie and intake. Check the insulators for any signs of a coolant leak. I have had one crack. Fortunately, the coolant wasn't being sucked into the carbie, but it did cause a small puddle of coolant on the garage floor.

[Wade]

Floats are not set correctly or I have float valve issues, front carb is just dumping gas. Its off and on, sometimes it does it sometimes it does not, but atm I can turn on the fuel pump and watch it jump dump. I drained the oil and had like 7 quarts in it and it was diluted down with gas. Once I drained that and filled back up with oil and new filter I no longer have the smoking issue, hopefully no harm done. I need to take the bowls back off and look around. I will drain and refill oil here again shortly to make sure its cleaned out.

[Wade]

Ok I think I am making progress. Floats are just a hassle, fsm is saying 14-15 mm gap and the rebuild kit as well as other info I have found is saying 19mm. These 72's I guess are supposed to have a longer float valve in the front and a shorter in the back. Front carb is the one by radiator correct? I make sure, because apparently this set of SUs has the shorter valve in front, and the longer one in back, not sure whats up with that. Its hard to get it set accurately by measuring anyhow so I am resorting to using the clear tubing method and making a 23mm mark from the top of float bowl and doing a trial and error routine, I am currently on my 10th or so time of removing the front float cover and getting close!

[Wade]

These SUs are a real learning experience thats for sure, went back at em again today using the information the user Blue has up on here (that step by step article is awesome), and it started to make a little more sense to me. The front float just kept throwing me for a loop because in order to get 23mm level from the top of the housing the float is not level at all in the bowl and fairly tilted upwards. The lever attachment to the float is slightly loose so I chalk it up to that. I need to fully adjust everything correctly still, I tried for a bit using the book and it feels like I am not getting much air flow and when I do get the air flow up my rpms are high. I have a leak somewhere I need to figure out, I am getting a real high pitched whistle from somewhere but have not been able to find it yet.

[EScanlon]

As a note from memory, and I'm not the mechanic these other guys are, I recall a discussion some time back regarding there being a FRONT SU Carb and a REAR SU Carb.

With your mentioning that your carbs were set up with the wrong float distance actually being inverted, my thoughts run to this possibility FIRST before you modify the carbs as they are in place now. It might be easier to swap the carbs and not modify them.

FWIW

E

[Bruce Palmer]

I think those two diifferent float level settings come into play if you have the two different length needles and seats to go with the two different length standoffs. If you have both the same length (needles and seats) then use the .55" on both. I hear that there may be some kits still out there that have both length needles and seats.