SU Carb piston lifter

[The Neck]

Hey,

I came across a weird inconsistency while "rebuilding" my SU carbs today. I noticed on the rear carb I have the piston lifter present. On the front carb, I do not have this part.

I'm assuming, based on the Car Parts Manual site that I should in fact have this on both? Or is this specific to the rear due to the vacuum line or something else?

Thanks,

Mike

[Nissanman]

The parts list specifies TWO of P/N 30, so I guess you are one too few






30 LIFTER-PISTON
16324-10400 1.6L 2

[The Neck]

Yeeaaahhhhh That's what I was thinking too. I guess I was sort hoping there would be some off chance the front didn't have one.

Now to attempt to find one of these!


EDIT: After a bit more indepth search on the internets, it seems as if that hole can just be plugged. Can anyone confirm this?

[autoairman]

Dont know about plugging the hole,but Rallye shows a listing for piston lift pin assembly.

[The Neck]

Awesome! $11 bucks with an unfortunate $40 minimum.

With looking at the other carb I don't actually see what this does, aside from create a hole. The pin doesn't function in any capacity that I can find.

[jhayden]

Pushing up on the pin simply allows you to lift the piston to check for a nice "thunk" when you release it. You can accomplish the same if you remove the air filter and lift the piston with a finger.

(As Nissanman's exploded diagram shows, the pin is installed from below with the bottom e-clip in place.)

I will be happy to GIVE you the assembly (pin + spring + two itty bitty e-clips) if you will PM me your mailing address.

Welcome to the forum.

Jon Hayden

[jrusso07]

Lifter is also used when tuning carb mixture. If mixture is correct, lifting the pin on one carb should disable (fuel starve) that carb and engine should idle on the remaining carb. You need to check each carb and adjust mixture on each until you get that result

I might have some used U20 carb throttle bodies with pins. PM me if interested and I will have a look

[The Neck]

This is all some really helpful info! I'll send a pm out shortly and see if I can get these guys back to spec soon.

On a side or possibly related note, I got the car running "fairly well" today. I seem to be running on cylinders 3/4 only. I'm getting spark to all 4 cylinders after pulling the wires, the first one I was a little close and got bit.

I realized after reviewing the firing order and order of the wires from the distributer, the PO had 1 and 2 mixed up. Could that be the cause for the cylinders not firing, or am I going to need to dig deeper? They were getting spark, fuel (cause the garage wreaked of fuel), I guess that is my most educated guess at this point?

[Nissanman]

They will still fire but not on the compression stroke therefore the fuel will not be ignited.
I don't know what it is about Nissans/Datsuns but firing order and distributor sequencing seem to be the source of a lot of woes [lack of knowledge?].
Firing order is 1, 3, 4, 2.

64 1500.jpg

There is a distinct possibility that the distributor is 180deg off but apart from the distributor cap and HT wires looking odd it will still function OK.

[jhayden]

I'll send a pm out shortly and see if I can get these guys back to spec soon.

Mike,
Got your pin assembly ready to mail to you, but your surname didn't come through on your PM to me, and I couldn't locate it in the 311s registry. PM me again with that info, and it will go out in tomorrow's mail.
Thanks.
Jon

[The Neck]

The lever should be here in a few days thanks to a fantastic forum member.

As far as the starting, I reworked the wires for the plugs and they are all in order now. I was able to start it, which seemed like it was running better than yesterday with the questionable timing. Once I receive that lever I'll add the oil to the carbs, which I'm guessing is attributing to some of the acceleration issues. Here's a link to videos of it running, first one is the initial start, and the second is after it idled for a few minutes.

https://imgur.com/gallery/LXHecYt

[The Neck]

UPDATE:

I received the lifter in the mail a few days ago and went to town this weekend on the carbs. I had them both off, completely broken down, and soaking in pine-sol for about 24 hours. Rinsed them and dried very well, then put them back together.

The car fired up right off the bat and ran very smooth right off the bat compared to before.

Turns out that lifter piece was pretty dang important, and while I "could have" gone without it, having it made tuning much easier. I followed the carb tuning procedures on here, and supplemented with the one in the car maintenance manual. At first I was having problems with the front carb piston not sliding up and down freely when pressing the lifter, so I took the carb out, and reassembled from the bottom up. That made it possible for the piston to slide freely.

I fired it up, and started with the air flow, then worked on the air fuel mix. All in all it took about 4-5 hours for me to rinse and clean everything, assemble, install, reassemble the front, and get everything tuned up.

It's idling pretty smooth right around 1k RPM, which I think is still too high. Both the air balance, and the air/fuel are dialed in, which I can say confidently.

EDIT: Here's a link to the videos of it running. The misfire is gone from what I can tell, and it's running fairly smooth, yet is missing a crispness to the throttle response.

https://imgur.com/C27aStA

https://imgur.com/VktiHg2

[Linda]

Try to get some overflow hose or tubes on the carbs that reach all the way down past the exhaust.
All you need is one sticking fuel needle from the corn gas we have, or a sinking float, to overflow the fuel bowls and start a fire. Minus the fire,that happened to me.
Linda

[spl310]

That idle is way too high

[Mackn367]

It seems to have quite a delay on the rpms decreasing after quick acceleration. I'm def no expert but I believe that could be related to the amount of oil used in the dashpot or maybe something is sticking? But again I'm also still learning. Not sure if you have the full books but they definite help with projects like this (I recommend Vol 2).