219 replies to this topic

[LC-GTR-1969]

Hi 

The springs should be all the same colour.

you can try lifting or lowing the needles to make richer or leaner .

if its hard to started when cold ,try this give the carbys a squirt with fuel to see what happens .

I have a street car with su,s which was a pitch to start when cold ,was all in the chokes ,now easy .

Cheers Bob 

 

Thanks Bob...

 

It seems ok to start cold as long as its not very early morning or sub 10 degrees. At say 15 degrees it starts easily no choke. 

 

I twigged onto lowering the needles, which helped the idle but I still have it just slightly leaner than I like at high rpm on WOT. If I get the upper rpm where I want it, its just a touch too rich at idle and starts fuel loading a little. Very close though. I just bought some UX needles and will try these today. They are a touch leaner in the center but richer at the bottom of the needle. My gut feel is that I will only get it where i want it by a slight polish of the UP needles on a bench drill though (mainly as its very close, just not quite where I need it). I am fussy with carbueretion.

[LC-GTR-1969]

Ok, so I have installed the UX needles, and the car is now very close to dialled in. 

 

Idle is very clean, around 13.8:1 - 14.5:1. A slight hint of cackle on decel but nothing too bad. The webers cackled more on decel.

 

WOT fluctuates from 12.5-13.1:1 up to 7000rpm.

 

However, the 'pump shot' is still rich on quick snap of throttle. Running SU damper oil, if you mash the pedal at say 2500 she will drop to 10.8:1 for a second which creates a lag- not a miss, just a fat response. If I mash the throttle above 3000rpm you do not experience this rich condition and the car revs very cleanly right through to 7000rpm.

 

I took out the damper oil and re tested, and basically very similar- even with no damper oil still spikes to 10.8:1 or more upon quick snap of throttle at low RPM. not a great deal of difference in driving feel to when I ran the SU oil.

 

I can only imagine that the springs have to great initial tension? Or could it possibly be reversion? 

 

Mind you, the car is driving great, and the rich spike is very liveable- most would not bother to tune it out but I would like to. 

 

I am going to leave the car for a few weeks now as I think I have well and truly pissed off my neighbours with all the noise and so forth. 

 

Thanks again to all who have helped with providing advice. 

Edited by LC-GTR-1969, 22 April 2017 - 12:44 PM.

[warrenm]

My selection of petrol needles UP,UX,UU,UM which are all very close in there profiles, but may help you with a shortlist to compare. WinSU is a program that can be used as well as Mintylamb as Bob as already mentioned.

Your WOT seems to be on the money.

[SA EH]

On a side note Warren, what did you use as a basis for meth? Obviously something much bloody smaller I'd guess.

[warrenm]

UVL needles which are very rich at idle but fine in the mid range & wot, so I added some metal then turned them done to the appropriate size.

[LC-GTR-1969]

Great info...

What mods did you need to do to your fuel system to cope with Meth?

[warrenm]

The biggest change was to use HD8's instead of HS8's, the HD8 has a better float system & can handle a greater flow through the inlet valve. 1/2" fuel line & a Methanol capable pump plus I use a small fuel tank, I didn't want alky in the main tank. The HS8 can be used with alky, but you need to use something like a Holley fuel bowl, if you look at a few front engine dragsters you'll see what I mean.

[LC-GTR-1969]

Cool... I figured a small separate fuel tank would be the go... 

 

I don't plan on running Meth but was interested to know nonetheless... 

[LC-GTR-1969]

Gday everyone... I have a quick couple of questions to the more experienced (than I) SU blokes...

 

So everythings been running pretty well with the HS8s. Tune is good etc,..

 

But Ive noticed the carb vents are overflowing when the car starts - most often happens when cold and the engine is shaking a bit... by overflowing i mean pissing out...

 

I run an electric pump (holley blue) and the needle seems to seat fine when the car is not running, but with the pump on... as soon as I start her up, she pisses out. 

 

The carbs are fresh rebuilt with new seats... Midel sold me some brand new brass jobby high flow ball bearing type seats- but im wondering whether these are rattling and allowing fuel to flow when engine  vibrates when cold... 

 

Fuel pressure about 2.5psi, give or take..

 

Im going to run a few more tests but thought I would see what the thoughts around here are... anyone run these special high flow ball bearing type seats?

[SA EH]

I thought pissing out the vents meant your float levels were too high? I had one of my carbs doing that (because I wanted to get as much fuel in the bowl as possible) so just gave the lever arm a tweak & all was good. I've only just recently changed to the grose type needle & seat but never had any probs with the old type, even at 4psi.

[LC-GTR-1969]

I thought pissing out the vents meant your float levels were too high? I had one of my carbs doing that (because I wanted to get as much fuel in the bowl as possible) so just gave the lever arm a tweak & all was good. I've only just recently changed to the grose type needle & seat but never had any probs with the old type, even at 4psi.

 

Cheers Jonesy...

 

I thought that at first, but I have my fuel pump on an individual circuit.. so I tested by switching on pump without the engine running and no leaks at all- nothing out overfolow... as soon as I start the car though, the vents piss fuel out when it shakes when cold... this settles once engine up to temp and the engine isnt shaking so much. 

 

When your floats were too high was it overflowing without engine actually running, but system pressurised?

Edited by LC-GTR-1969, 04 September 2017 - 05:57 AM.

[warrenm]

When I was running HS8's, I had a similar issue, but with only one carb, I played with the float level until it stopped. That's an advantage with the HD8 carb, it has a better float setup & can handle a higher pressure, mine are set at 5psi with no leaks.

[SA EH]

When your floats were too high was it overflowing without engine actually running, but system pressurised?

I still run a mechanical pump for now, but if I had it running with the fuel pissing out then switched it off, yes the fuel would continue to pour out until the pressure dropped away.

[S pack]

Cheers Jonesy...

 

I thought that at first, but I have my fuel pump on an individual circuit.. so I tested by switching on pump without the engine running and no leaks at all- nothing out overfolow... as soon as I start the car though, the vents piss fuel out when it shakes when cold... this settles once engine up to temp and the engine isnt shaking so much. 

 

When your floats were too high was it overflowing without engine actually running, but system pressurised?

I agree with SA EH, fuel levels set too high.

 

The fuel level in your bowls must be so close to overflowing with the pump on and the engine off that it only requires some engine shake to get it pissing out the overflow holes.

Edited by S pack, 04 September 2017 - 07:44 AM.

[warrenm]

If you can't adjust the float arms fit another washer under the fuel inlet valve to lower the fuel level. I also run the Ball type inlet valve. Sometimes you have to ignore measurements & adjust so it doesn't come out the overflow.

[LC-GTR-1969]

Cheers everyone... I have some shims/ washers that I got in the kits from Midels so I will drop the height of the float and see if that helps... 

 

Thanks again.

[LC-GTR-1969]

Cheers everyone... I have some shims/ washers that I got in the kits from Midels so I will drop the height of the float and see if that helps... 

 

Thanks again.

 

Ok, so I have shimmed the grose jet with the biggest washer I had for them (its about a bees dick less than 1mm) and the back carb is still pumping out the overflow when the engine is running. The front two carbs are ok. 

 

This is the only way I can see how I can adjust the float level- but it doesn't have seemed to have helped with this back carb...

 

I might swap the grose jet from that carb to the front carb and see if the problem follows the jet. I wonder whether the clearance within the grose jet is a bit farked on that carb???

 

Fun and games hahahaha... at least SUs are a piece of piss to work on...

[LC-GTR-1969]

Well I cracked the shytes and took out the grose jet and threw in a Viton tipped needle I had lying round and the issue seems to be resolved...

 

Before I did it I checked the float height with the grose and its the same with the viton tipped needle. I basically just swapped out the grose needle and seat with a Viton tipped needle and seat and she is all good now. 

 

I will speak to Midel and explain that I think this particular grose jet seems faarked (from new). Not their fault at all, but I figure they shoudl know just in case the issue pops up often- they may need to talk to the manufacturers about the jet tube clearances to the ball if this issue has happened a few times before....

 

Ill probably just buy a new grose and re-check.