Z Therapy Carbs

AliK

Vehicle Dating Officer
Staff member
Club Member
Z friends!

I've never fitted carbs before, so any advice on what I should do or do differently would be greatly welcomed.

Having received the carbs on Thursday and not able to put them on the car yet, I couldn't help myself, especially as it's gonna tip it down tomorrow!! So I got started with a flood light as soon as my toddler went to sleep at 20:00.

What you get in the package is in the photo below + an interesting three hour video on everything carbs for the Z and I mean EVERYTHING!!

4e7atuqe.jpg


I particularly like the engraving on the butterflies!

a5uveqev.jpg


The finish is not quite the mirror polish I was anticipating, it's kind of a dull shiny greyish colour, but I don't think it is paint.

They have a very cool mechanism for adjusting the mixture with definite steps that you can feel when bolted on the car.

aqy3ytym.jpg



patagypy.jpg



Before pulling the carbs off I thought I'd show you what my wobbly float chamber looked like - I bet it was responsible for a number of air leak sins but I'd be guided by the more experienced in the club as to what the effect of such a defect would/should be.

https://www.youtube.com/watch?v=44u3HHFXex8&feature=youtube_gdata

Interestingly I seem to have a strange white milky discolouration on the heat shield, not sure if that is the effect of a fuel leak from the carb? Anyone else had this?


u7yje9aj.jpg


On the linkage between the carbs, the z therapy linkage has an extra bit (bottom one in pic) where my white gloved finger is pointing. It rotates freely of the rest of the shaft and I have nothing to connect it to. Anyone know what it's for? I can only assume it's for some US specific application?

erydyme9.jpg


Finally got it all bolted on (pretty easy but faffed much cleaning things) and cranked the engine at an unneighbourly 22:05. Once the carbs filled up, the engine fired but when I pulled the choke lever it coughed and died, followed by a mist of fuel vapour steaming off the warming manifold!! Gulp!!!

The fuel was dripping out of the air intake part of the carbs just below the piston, I definitely need to learn more about adjusting the choke.

The car is idling pretty rough, but I imagine I would need to balance or look at the mixture. I thought ZT do that already on the bench but I ran out of time to investigate and didn't want to also run out of neighbourly goodwill (some curtains were twitching) so I'll get the air flow meter out tomorrow and investigate.

On the upside though, they make a very satisfying hiss which sounds much louder and far more even than my original carbs. Placebo effect? Don't know, but makes me happy! ;)






Ali K
 
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They're a nice looking colour, if they were polished you'd only have to waste your life keeping them like that.

You're right about the rain today! Good luck with getting them on and all sorted.
 

MikeB

Well-Known Forum User
You'll definitely have to balance them, as every time you take carbs off and remount them you need to check the balance, as you may have tightened the mounting bolts unevenly.

It might be worthwhile taking the lids off the float chambers to check that the floats haven't dropped during the shipping from the US.

I would hope that once you do that, they carbs wouldn't be too far out, but then I, like you, am assuming that ZT prep'd them to the standard default setting before shipping.

Good luck
 

AliK

Vehicle Dating Officer
Staff member
Club Member
Thanks fellas all good advice.

The colour is quite good but looking at the photos I was just thinking it would be shaving shiny ;)

I didn't get to play today as an ocean fell out of the sky here, ALL day!! But will update as soon as I make progress. If not tomorrow then it may have to wait two weeks :( I envy you chaps who are able to dedicate entire weekends to this stuff - I only get the odd two hour slots.



Ali K
 

toopy

Club Member
On my 2" SU's there is a similar thing, it is to fit a return spring for the throttle and the other end of the spring should fit on to the heat shield, not sure if the original carbs, flat tops, or 240z carbs which i had before the SU's had a similar system or not.
In fact i have 2 return springs, one on the other carb, but 1 on the left carb is more than enough and i have removed the 2nd.
Ive no idea what year/type of heat shield i have either, but it has hole's specifically to attach the spring's :unsure:

Z friends!


On the linkage between the carbs, the z therapy linkage has an extra bit (bottom one in pic) where my white gloved finger is pointing. It rotates freely of the rest of the shaft and I have nothing to connect it to. Anyone know what it's for? I can only assume it's for some US specific application?

erydyme9.jpg



Ali K
 

toopy

Club Member
The fact the car started on the first asking, would imply ZT have set some sort of baseline adjustment.
However, running rough and dribbling fuel could mean one/both are running very rich and/or a choke issue.
Starting with no choke and then dying when you do pull the chokes would defo imply running to rich ;)
 

AliK

Vehicle Dating Officer
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So, as the wise Homer Simpson once said - Doh!!!

Soon after my last post I realised the perils of doing things in a hurry by flood light - I had forgotten to put in the dash pot oil which once filled, the car fired up and idled beautifully!!!

Idle and 2k rpm airflow is identical now using one of these bad boys ....

u5ebu2um.jpg


Now the question bit - OK, this has probably been done to death ...

Is SAE 30 oil same as say 5w30!?

I've read SAE 30 or 3-in-1 oil is the right thing to put in but even with a first class honours degree in Electronic Engineering, I is too thick to decipher this init!

Also my neighbour who used to run a rally race team told me a while back that he just used to put redex in his SU dash pots !! Anyone tried this?



Ali K
 
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toopy

Club Member
Now the question bit - OK, this has probably been done to death ...

Is SAE 30 oil same as say 5w30!?

I've read SAE 30 or 3-in-1 oil is the right thing to put in but even with a first class honours degree in Electronic Engineering, I is too thick to decipher this init!

Also my neighbour who used to run a rally race team told me a while back that he just used to put redex in his SU dash pots !! Anyone tried this?



Ali K

I have some of the proper SU dashpot oil and some 3 in 1 in the garage

rubbing both between fingers to compare, the SU oil does feel ever so slightly thicker,
tho still not as viscous as say 10/40 engine oil :unsure:

Ive used engine oil in mine in the past and it seemed to run well enough, yet to run her
with the new needles and jets i put in a few weeks back along with the proper SU oil!
 

AliK

Vehicle Dating Officer
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Club Member
Thank you! I have no idea why I didn't think about searching for proper dashpot oil!! :thumbs:



Ali K
 

Rob Gaskin

Treasurer
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Site Administrator
When I had my track car on a dyno the guy told me to experiment with differing viscocities.
 

Rob Gaskin

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And did you Rob? What was the outcome?

Ali K

No I didn't but the theory is that it will alter the speed of the piston lift. So if it's sluggish go 'thinner' and vice-versa.

It seemed unnecessary when tbh the car drove well.
 

AliK

Vehicle Dating Officer
Staff member
Club Member
Fair point Rob!! I'm going to do a highly unscientific back to back test with the 5w30 I put in, the official oil and slick 50 and will post up the difference.



Ali K
 

datty240Z

Well-Known Forum User
I think it may be the opposite. If the car is sluggish at low rpm its cos the oil is too thin causing the piston to lift too quickly drawing in too much air and the mixture to go lean. A thicker oil will cause the piston to lift slower drawing in less air and a richer mixture sort of like a power valve.

IMHO
 

Rob Gaskin

Treasurer
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No I didn't but the theory is that it will alter the speed of the piston lift. So if it's sluggish go 'thinner' and vice-versa.

It seemed unnecessary when tbh the car drove well.

Datty, sluggish was referring to the speed of the piston lift.
 

datty240Z

Well-Known Forum User
Ah good my bad! I'm using 3 in 1 at the minute but my car is spluttering a bit at low rpm under acceleration. I've ordered proper SU damper oil to see if it makes a difference.
 

Rob Gaskin

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Staff member
Site Administrator
Ah good my bad! I'm using 3 in 1 at the minute but my car is spluttering a bit at low rpm under acceleration. I've ordered proper SU damper oil to see if it makes a difference.

If that doesn't work it might just be a weak mixture? Screw down the main jet half a turn and see what happens.
 
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