2" SU help with spare parts!

toopy

toopy

Club Member
Hi Folks

So ive got a pair of 2" SU's on a 2.8 standard engine running K+N
pancake type air filters and an unknown stainless performance exhaust.
I should mention the car has not been used for nigh on 3 years due to financial restraints
but im keen to get the ole girl ready for next year :)

I have a Burlen SU reference catalogue but HS8 carbs r only listed under Jaguar and Rover
so my best guess would b the spec for a
2.8 litre XJ6 6cyl 1971-72 which appears to be in the right ball park.
The current jets appear to match what is listed for this engine but the needles r unknown.
I believe u can get reprofiled needles from the states specifically for use in HS8s
on the L series engine but can't remember exactly when or where i heard this!

Any help much appreciated

Thanks, Anthony
 
The carbs should have a little id tag screwed to the float bowl lid.
That should tell you what they are from.
Are the needles not marked?

btw, if it ran fine before leave it be. Just clean them out :thumbs:
 
Thanks for quick reply :)

Carbs have no identifying tags but they do look very similar if not the same
to the pics in your other post.

The engine ran ok but it was lumpy and hesitant, previous to this i had
the 240z carbs and it was much better then. Having no previous history
on the 2" carbs i thought it was prudent to atleast replace the jets and needles,
i have yet to remove the needles so dont know if they r marked or not but
was hoping someone would know the correct needles to use anyways,
i dont want to replace like for like if there not right to start.

I shall read through your other post again, 'slowly' and glean what i can

Cheers :thumbs:
 
Just another thought, as and when i bolt the carbs upto the manifold
with the insulator/spacer's should i be using jointing compound of some description
as they came off so easy it would appear none was used previously!!!!
 
best way to get the carbs right is to get the car onto a rolling road. If you have someone that knows what they are doing with SU carbs and older cars then they will reprofile the needles for you and then continue tuning to optimum performance.
Buying reprofiled needles is false economy as they still will not be exactly right for your engine/cam/carb combination.
 
Toopy,
You mention that you have "pancake" filters on your carbs. If you the type of air filter I am thinking of, there won't be any air trumpet on these carbs..correct? From my understanding, all carbs work much better with some form of air horn/trumpet.... even the OEM 240z/260z had them built into the air box. If they are not fitted, I would fit some, and some different air filters to aid the breathing into your carb.

If your car ran well with the needles in there and you just want some replacement (yes?) I would send them the needles and let the measure and match them with something they have. E.g. I had some 260z flat top carb needles matched by Burlen with something off the shelf...

Just my opinion...

Good luck
Ian
 
Am I right in saying that the P6 carbs are the Rover 2000TC carbs? They're listed as being HD8's and from what I've gleaned, are bolt on replacements for the Hitachi's(?).

As I'm also looking into breathing, after relieving the manifold, is it really as simple as bolting the 2" SU's on and then selecting the correct needle for the rolling road?

Your valued opinion on this one would be great - 2" SU's or the 240z 1.75" Hitachi's? As a combination of power, ease of use, setting up, maintenance, etc, what would you guys go for if starting from scratch???????????????????????????????????????
 
toopy said:
Having no previous history
on the 2" carbs i thought it was prudent to atleast replace the jets and needles,
i have yet to remove the needles so dont know if they r marked or not but
was hoping someone would know the correct needles to use anyways,
i dont want to replace like for like if there not right to start.


Cheers :thumbs:
Click to expand...
Try lowering the needles or highering them a touch to see if it runs any better.
 
My experiences will be useful here.

I have HD8 carbs (Rover TC) on my modified (210 bhp) 2.8 L6.

When I rebuilt the engine I consulted Kevin Irons (of Samuri Conversions). He noticed that although I had 2" carbs my inlet manifold had not been opened out to match the bore of the carbs, so this was done. He also suggested I had the carbs rebuilt and then set-up on a rolling road by an SU expert. Kevin also advised I fit 'trumpets' and then 'socks' to keep dirt/grit out of the engine.

On the rolling road my expert (sadly he has died since) worked on my needles with emery paper to produce the correct profile and also 'stretched' the piston springs to give equal and correct resistance. I was with him and he really got a lot of satisfaction from getting the most bhp for me.

I have NEVER had to touch my carbs in 7 years and it runs really well. So for me SUs have been a good experience.

Ben is absolutely correct, don't guess about needles because you will never get it right for YOUR engine, get the car set up on a rolling road by someone who understands SUs.

As I said my carbs are HD so not the same as yours.

2" or 1.75" ?, well tbh unless the engine is producing a lot of power and you are using max revs (7k) for a long time I don't think you will notice any difference. The HSCC race cars were made to return from 2" to 1.75" and didn't notice a major power drop! It's all about air speed through the carbs and correct mixture.

So hopefully I have confirmed what the previous posts are suggesting:thumbs:
 
Last edited by a moderator:
Rob

Thanks very much for the reply! 210bhp? Bit of a beast...how did you achieve that apart from the 2" SU's?

If the power difference between the 2" and 1.75" is not that great, I'll probably stick to a decent set of 240z Hitachi's to maintain the Datsun look on my 260z project car.

Cheers!!!
 
Mr Ex said:
Try lowering the needles or highering them a touch to see if it runs any better.
Click to expand...

Do u mean the Jet?

I tried to but realised after some fumbling about (the carbs were on the car at the time) that
they dont have a nut to adjust the height of the jet! looking at the pics in the link posted by 900ss
that would appear to be the case aswell.
All the info i have on SU tuning mentions an adjuster nut, have i missed something?
 
toopy said:
Do u mean the Jet?

I tried to but realised after some fumbling about (the carbs were on the car at the time) that
they dont have a nut to adjust the height of the jet! looking at the pics in the link posted by 900ss
that would appear to be the case aswell.
All the info i have on SU tuning mentions an adjuster nut, have i missed something?
Click to expand...
I asumed the SU's were like the 240 carbs where you undo a grub screw & the needle is then loose to move up or down or even take out.
 
toopy said:
Do u mean the Jet?

they dont have a nut to adjust the height of the jet! that would appear to be the case aswell.
Click to expand...

If they are like mine the jet is adjusted by the lock nut and screw from the top
(As you look down on them)
Can be seen here, top left adj screw with spring attached.

Dep on needle type fitted (and carb) they can be adjusted aswell
You can move the needle up and down if the top hat is removed as shown in that thread.


 
900ss said:
If they are like mine the jet is adjusted by the lock nut and screw from the top
(As you look down on them)
Can be seen here, top left adj screw with spring attached
Click to expand...

Just had a look at mine and they appear to be almost identical to yours,
so now the adjustment side of things is clear i can get on and fiddle away.
I think i will renew the jets and needle valves for now, stick with the existing metering needles and see how i get on.

Cheers :cheers:

Anthony
 
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