SU HIF6

cobraboy

cobraboy

Well-Known Member
Guys,
I have been struggling with the above carbs, mixture setting is the problem
I am getting a rich situation at idle and above that I cannot cure, I have had parts from Burlen including a full seal set and gaskets for the start device and new float chamber Viton needle valves and seats.
I have the float level set right.
I have the fuel pressure at 3 psi.
Now, the main needle height is an issue that I am at odds with. Burlens site says that the needle holding bush needs to be flush with the bottom of the piston on flat bottom pistons, but with pistons with a recess the bush needs to be higher, flush with the recess.
The tech staff at Burlen say that the bush needs to be flush with the bottom of the piston on BOTH types of piston !!!
I have pistons with a recess and the car runs poorly if I set the needle bush flush with the bottom of the piston, and I cannot adjust it to run well, but cannot lean it out with the bush flush with the recess.

So................. which is it please flush with the recess or with the bottom of the piston ?

Thanks
 
Hi
I have always set bush flush with the recess and all the spare HIFS i have had the bush set the same. When you adjust the main jet you should be able to wind jet so it can be seen sticking up IE fully weak.If you cant adjust jet like this may be a faulty bi metal compensator/incorrect parts.Have had this problem before due to faulty compensator.Once jet can be seen then you wind it down untill it is flush with carb bore,then turn jet down 2/and half turns which is factory pre setting,do it on both carbs.Have found cars runs almost spot on on this setting
Iwould also recheck float level again,i normally do this before fitting jet,with carb upside down bottom of float just touching straight edge.
hope this is some help.
clive.
 
Thanks guys
Ron you say the bush / collar needs to be flush with the bottom of the piston, but your picture shows it flush with the recess.
Clive I have tried setting the jet flush with the bridge and then down @ 3 turns, the car runs well at this, but a colortune shows the left bank on the richer side of ideal and the right bank massively rich even when the revs are increased slowly.
 
Hi
just a thought were the new main jets the same as old? 1 i have seen were shorter in length,poss incorrectly packaged.Also choke control unit has to be fitted correct way in carb,there is a knotch on brass valve which i think has to be facing upwards with new paper gasket fitted.
With new seal fitted on choke valve was it a nice push fit?
Is there any signs of flooding? had a problem of flooding on a mates 2.2 when new vitron tipped needle valves were used,managed to get plain brass ones with no more problems.
clive.
 
Clive
I have not changed the main jets or needles yet, I suppose the jets could be worn oval.
The notch on the starter valve is upright and they were a nice push fit and lubed so they did not snag going in.

Thanks
Mark
 
Hi mark
sorry i thought you did change them.
My nada had a problem of very poor MPG like 10 to the gallon/did not run poorly/carbs correctly set but smelt a bit rich but no smoke from exhaust.
Carbs are only HS6 but use sprung/bias needles and when checked VERY carefully found needles worn on 1 side and jet hole oval. Once replaced car drove the same but double the MPG.
Might be worth rechecking / replacing.
clive.
 
cobraboy said:
Clive I have tried setting the jet flush with the bridge and then down @ 3 turns, the car runs well at this, but a colortune shows the left bank on the richer side of ideal and the right bank massively rich even when the revs are increased slowly.
Click to expand...

It cant be one bank different to the other because the carbs dont feed a bank each. They are split, the LH carb feeds 1467, and the RH carb 2358
 
OK my terminology.
I am using cylinders 5 and 6 for my tuning as they point forwards and I can see into the plug. As you say cylinder 5 is fed by the right hand carb which is giving a reasonable mixture, but cylinder 6 is fed from the left hand carb which is dumping in fuel at a colossal rate.
 
cobraboy said:
Thanks guys
Ron you say the bush / collar needs to be flush with the bottom of the piston, but your picture shows it flush with the recess..
Click to expand...

The bottom is the base, and that is where it is. No one is going to place the collar flush with the top of the recess.....

Ron.
 
Quote ...... No one is going to place the collar flush with the top of the recess.....

Well it is in the picture you posted in your link.

This is Burlen's assembly instructions from their tech section

(g) Ensure that the needle guide fitted gives the needle bias in the required sense (either toward throttle disc or toward air cleaner). Before tightening the retaining screw, check that the needle guide is in its correct position relative to the piston face, either flush with the bottom of the piston on standard pistons or flush with the recess on recessed pistons.

Anyway I have been onto Burlen tech again this afternoon and their techs are coming up with another new instruction on where the needle should be, I am pursuing this line at present ( for anyone still awake )
 
You know, I have come to the same conclusion, I am sorting the wheat from the chaff there, which is why I am asking you all as well for your real world experience.

There is conflicting info on Burlen's website that is at odds with what the techs say, but I have info now from a guy there with 40 years on these carbs and I am now sure I have the needles in the right place.

Unfortunately one of the carbs is still not fuelling correctly, but I think I now know what the problem is.

I will update this when I have put it to bed.
 
Hi Mark,

I'm just about to refit my pair of HIF6s, having found one of them to have been fitted with an overhaul kit and the wrong length main jet. Wrong by 4-5 mm compared to the other one. That carb was running too lean no matter what I did. If the carbs are already on your workbench I'd consider opening the float chambers again and comparing the main jets and making sure the pin on the mixture adjustment screw engage the bimetal thing correctly.

Oh, and 3 turns and not 2.5 turns CCW (as per the WM) would normally make a noticeable difference to your mixture.

Tor
 
Last edited:
cobraboy said:
Quote ...... No one is going to place the collar flush with the top of the recess.....

Well it is in the picture you posted in your link.
Click to expand...

We obviously see things very differently. ;) The collar in the photo is flush with the base of the recess. If you stand in a trench, you stand on the bottom, not on the top!

A piston without a recess, the collar is flush, with a recess also flush, but with the base of the recess.

Ron.
 
Thanks guys.
I am awaiting new jets and needles, I think the problem is due to an incorrect after market jet in one of the carbs.
I will fit and come back with results, and hopefully an answer to needle location that will end all confusion.
Mark
 
Some years ago I could not get my 2200SC to run properly and I mentioned it to an Engineer at SU ( when it still existed at Wood Lane B'ham). He asked how many miles it had done (73k) and advised that I should change the jet as it will have worn on the top edge due to the bias needle rubbing on it . If you set it at the idle level it will run weak at higher revs. He said the needle wore less because it was being rubbed all along its length,. I changed the jet and transformed the running.
 
Thank you for that info.
OK so new needles and jets arrived and I fitted today, I also re set float height to just show daylight between float and straight edge.
Now the latest advice on needle position was to set the shoulder on the needle that is visible sticking through the bush to be level with the base of the piston.
I set jets flush with bridge then 2 1/2 turns down.
The car started right up and one noticeable thing is that the exhaust note has a much deeper purposeful thump to it now instead of the woolly woofle that was before.

The mixtures are still what I would call on the rich side, but each carb responds the same now when leaning 1/2 a turn - ie the engine stumbles, whereas before on the left carb many turns of the screw had little effect.

The car is now MOT ready and I hope to get it tested this week, I still don't have a V5C though.

If anyone would like a parts list to overhaul these carbs ask and I will throw up the part numbers.

Mark
 
I rebuilt my carbs with standard parts then had it rolling road tuned. With standard needles the mixture was very rich. The rolling road guy changed the needles a few times and now its spot on; I know this because after 500 miles the plug colour is now perfect, something I could never achieve before.
 
You must log in or register to reply here.
Back
Top