MK3 Spitfire 1300 + SU HS2. What needles?

[Ecozile]

Took Spitfire for a tune up and $400 after car still run bad. No power what so ever..

Tuner said it is not having enough fuel throughout the rev range apart from idle.

Here is the current setup.
Stock motor, cams and head.
Rebuilt SU HS2 with BO needles.
Electric fuel pump.
MK 3 air filter box.
Have checked timing, valve clearance.
Relatively new plugs,condenser,dist cap, contact points and coil.

If run really rich at idle then car is drivable. Setting correct fuel mixture at idle make car undrivable. Correct fuel mixture was determined by reading exhaust gas with the help of Bosch ETT  8.55.

My understanding was that BO needles are correct for this application. Of course that has proven to be wrong on dyno tune.

What needles do you recommend or what do you have in yours?

[BigT-DK]

My spitmkIII (standard worn oil pissing engine, but with K&Ns and extractor manifold) runs on AAQ needles... ran on BO needles before but seems to go better on the AAQ (I still think it can be improved though) I think thee AAQs are "richer" needle than the BO ?
If you like to tinker - I can recommend this book
http://www.amazon.com/The-Carburettor-High-Performance-Manual-Speedpro/dp/1845840739/ref=pd_sim_sbs_b_1/191-1053021-0163512

comes with a needle selection chart and also shows you how to modify your existing needles.

I am sure someone on here has a few suggestions to needle choice to get you started.

[Velocita Rosso]

http://www.mintylamb.co.uk/suneedle/

Have a play around

[Sheepy]

When you say dyno tune, do you mean a guy with a diagnostic computer, or a rolling road?

You can't beat tuning on a rolling road, and a good mechanic who knows his things, (usually the older chaps who used to work with the older cars/carbs)

Just doing a static tune, while car sat there is not enough.

I can tune carbs by ear, but even then there is still room for improvement, Wear in parts etc, i set up my friends car a good few years back now after a rebuild, he said it went well when he drove it, but I told him to take it to a rolling road!
Bottom end was near enough perfect, but under load (heavy acceleration) near the top of the rev range it was going weak, the chap fiddled for a while, and if I remember correct changed the needles.

It then ran like a completely different car, more power and better fuel consumption.

Rolling road tune is the best way to go.

[gfiandy]

Hi, I suffered a similar problem with my car. Unless it was set very rich at idle it would run very lean on the road and especially when the fuel was low.

I spent ages trying to track it down in the end it was poor float chamber needles that would let the float chamber over fill at idle then empty out at higher revs, they looked perfect when inspected but obviously weren't. You might have the same problem, a new set of seats and viton needles for the float chamber from Burlin Fuel systems fixed it (I also changed to the unsinkable floats but I don't think this had anything to do with it).

As you have an electronic fuel pump you could also have an over pressure problem, if the pump is too strong for the float valve you will get the same problem the float chamber will over fill at idle. I think the correct pressure for SU systems is about 3 PSI (I am sure someone will correct me if I am wrong).

I am guessing you have checked this as well but if your carbs were recently rebuilt it would also be worth checking the needles a re centred correctly. The method is in the Haynes but briefly with the air-box off and the damper out lift the cylinder and let it go. It should come down with a metallic clunk on the bridge. If it doesn't your needle is not central against the jet. This means the cylinder will sit a bit high at idle which could be letting a bit to much air in. I had this problem with my carbs after I changed the needles, I am running a BO needle on a standard MK3 engine and as far as I can tell it seems to be fine.

Regards,
Andrew

[Ecozile]

BigT_DK wrote:

My spitmkIII (standard worn oil pissing engine, but with K&Ns and extractor manifold) runs on AAQ needles...

Thanks, it appears from all online reading, AAQ seems to be the needle I should get

michael_charlton wrote:

http://www.mintylamb.co.uk/suneedle/

Have a play around

Thank you, I have found that site and the other link where it lets you enter values for a given needle sector, then bring up all matching needle. But my problem is that I don’t know how to put that cart in to real life as I have had no experience in swapping needles.

4058 wrote:

When you say dyno tune, do you mean a guy with a diagnostic computer, or a rolling road?

It was a roller dyno. I agree, no tuning is real tuning unless it is road tuned or dyno tuned.

He also had Bosch ETT connected. Maybe it is the good mechanic part that is missing here. I may have to take it somewhere else to get a second opinion.

2674 wrote:

I spent ages trying to track it down in the end it was poor float chamber needles that would let the float chamber over fill at idle then empty out at higher revs, they looked perfect when inspected but obviously weren't.

These carbs were rebuilt beginning of the year, they ran somewhat okay. Used to miss on high rpm, eg. above 3.5k or so. But that something worth checking again.

2674 wrote:

As you have an electronic fuel pump you could also have an over pressure problem, if the pump is too strong for the float valve you will get the same problem the float chamber will over fill at idle. I think the correct pressure for SU systems is about 3 PSI (I am sure someone will correct me if I am wrong).

This very well can be the issue here. I have found that pump runs between 3-4 psi. yes, you are correct, pressure for my car, I believe is 2.5 to 3psi.

2674 wrote:

I am guessing you have checked this as well but if your carbs were recently rebuilt it would also be worth checking the needles a re centred correctly.

Thanks, I have done that. I have also done usual troubleshooting on manual, like timing and valve clearance etc.

Since posting here, I have found that BO needles are infact correct needles for Mk 3 1300.
Float chamber tags have AUD257 - can someone with a  MK 3 Spitfire confirm that for me?

Many thanks in advance to all of you.

[Ecozile]

I have just been told AAQ is incorrect as they are spring loaded needles rather than fixed.

[nang]

I've got AAD's on my Mk4 Spit with K&N'S. See good to me although no access to a rolling road here.

Have a look at mintylambs graphs.
Tony

[Ecozile]

Thanks Tony, I need fix needles, so I have picked following using mintylamb graphs.

AN are = AAD
DL DZ or GR seems to be the best matched fixed needle for AAQ.

Anyone using any of those?

Any other recommendations?

[gfiandy]

Hi,

I have a MK3 1970 and it has an AUD257. It is also one of two carbs specified for 1967 1970 on the SU Carb site the other being a AUD275 (1967-1968).

http://www.sucarb.co.uk/VehicleList.aspx?carManID=58&carModel=Spitfire%20Mk3&carYear=

Just to confirm I have AUD257 carbs with BO needles, I tuned the car statically with a colour tune and the piston lifter and dynamically by plug colour. It has a standard cast iron manifold, a standard (but stainless) pipe and the original air box with paper filters.

The car revs well once warm right up to the red-line it gets quite noisy so I don't tend to use above 5K normally, it will idle smoothly and the plugs do not go black if the car is left at idle before pulling them. It has electronic points fitted, this smoothed out the idle.

So unless you have changed the cars breathing i.e. KN filters, tubular exhaust manifold, bigger pipe, I think you have the right needles. If you have changed any of these then you probably do need richer needles.

Best of luck.

[BigT-DK]

4272 wrote:

I have just been told AAQ is incorrect as they are spring loaded needles rather than fixed.

yes, but you can remove the "top hat " and the needle base is identical to the fixed type :P the AAQ are also longer - than the BOs but they work just fine in my HS2s (AUD 257 I think)...

I can take some pictures if you like

[Ecozile]

Thanks Andrew for confirming tag number. You are spot on, everything bar fuel pump in this car is stock as far as I know. So I am still struggling to understand why car is not drivable with BO s in them.  

Thanks for confirmation on those AAQ, wasn't sure if length of needle was an issue. So that clears that  :)

I have decided to ditch the tuner and get the car running on my own. So far have borrowed a gunson colour tune, timing light and a carb balancer. I will start from scratch.

[gfiandy]

Hi,

A tip I found on on a tuning blog some where, sorry cant remember where, for using the colour tune is. When setting the running at idle make sure you rev the car for a few seconds first to get the petrol level in the float chamber at the running level. Then set the colour to the deep blue.

If the colour slowly turns yellow afterwards you know you have a problem with the petrol level or pressure.

I spent some time just going through the possible colours by running the car slowly leaner, this way I got used to what constituted dark blue and light blue as well as where it was changing to yellow.

Best of luck, all I can say in support is it is very satisfying once you finally get it working right.

Andrew

[Ecozile]

So I spent some time adjusting carbs with Gunson colour tune. I adjusted jets from what was a very lean fuel mixture to correct blue as per manual that came with Gunson.

Car can actually pull it’s weight now. Car revs freely up to about 3k and then hesitate and back fires.

Hesitation seems to happen regardless if it is under load or not.
While driving, when it is hesitating, I have pulled choke out, then it seems to get slightly better but still back fires.

I have ordered a pair of AAQ.

I have been asked to check if vacuum advance is working or not. Person who asked me to check that seems to think it is more of a miss fire\timing issue. Any pointers there?

[Dannyb]

It's easy checking the mixture at idle with a colour tune or using the lifting pins. But at high revs under load without a rolling road it harder. The best way I have found is to get the car up to speed on a clear road and then turn off  the engine and depress the clutch at the same time. Pull over and take out the plugs and see what colour they are. Be careful if you have a steering lock not to operate that.

[sparky_spit]

Also, from what you said right at the top of this thread, did you set the static ignition timing to the book figure or to the best amount of advance you can without pinking?  This may not be your problem but nowadays, with variable modern fuel octane ratings, Ethanol content, etc, the book figures of 40 years ago are more or less worthless. Your lack of oomph could easily be not enough ignition advance. The only way to get a correct static ignition advance figure these days is to drive it on the road armed with a 5/16" AF spanner and keep advancing the distributor (turn clockwise) until it pinks under load going uphill in 4th at about 30mph. Then back off a bit until it doesn't pink anymore.

You need to get to this point before doing any mixture adjustments.  You'll also find that subsequently changing the mixture will alter the timing figure required, which then alters the mixture required, and so on. Eventually you get to an equilibrium where the mixture and timing advance are matched.

[trubac]

Hello just copying a post I made in the 1300 thread , maybe a Spitty 1300 with BO needle can help !

The other thing is that I can't get a good carb setting : when pushing the pin under the HS2s the car stall so must be too rich BUT the Colortune color is light blue so too weak ...  
And when I weaken the mixture the idle goes down immediatly.
Must be an air leak somewhere no ? what are the culprits ? Servo works very fine ... dizzy vacum can't affect both carbs (1300 TC) ... breather thing maybe ?

The sparks are fine color, little on the chocolate side.

I wouldn't mine really of all this, but I feel the car is not at full potential : I'm not getting a good bite at starting.
Also when starting from cold with the choke, the car almost stall everytime it gets on charge ... not at all like this with my Herald 1200 (Solex carb) ...
Not used to the HS2 behaviour thou.

[gfiandy]

Hi,

I have ordered AAQ needles for my MK3, these have the top hat on but I need to use the fixed mounting.

Does anyone know how to get the top hat off?

Regards,
Andy

[gfiandy]

Since no one knew the answer to this I went ahead and had a go. I used a dremel disc holder as a punch, it was the right diameter and looked strong enough. I place the part in my Workmate with the top hat holding it in place the needle went through a small notch that is in it.

With a small hammer I knocked it out onto a cloth that I put on the floor. Before I could use it I had to smooth the end out as the top hat was held on by some knurling.

I then fitted them. The car is transformed, it wasn't bad before but now it pulls really well through the gears and the problem I had which was, it a bit soft at high reves, has gone. It pulls in both top and overdrive really well, I stoppd at 85 mph as the front end was gettig abit light and its very windy today.

I don't understand why this made such a differnce as my car is as far as I know standard, it still has the old airtbox and a standard exhaust (although it is SS from Rimmers). If it is now a bit rich I will change to K&N rather than go back. I need to take it for some runs and check the plugs to see how the mix is now.

Andy