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Carb needle question - amongst others!


Anglefire
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I've recently fitted a "new" engine to my spitfire - it came with carbs so used them as they look fine and everything moves nice and free (especially the choke, which on my old engine tends to stick - and the throttle which i had to fit extra springs to get it to close the butterfly properly)

But I've noticed some things - like they don't seem to have overflow pipes like my old ones. But I think they are newer - I've not checked the part number yet.

Anyway, apart from that, any ideas what needles and I guess springs, should be fitted?

The cam is just a Newmans road cam, so not wild, but the exhaust is a 421 stainless manifold and has been matched to the head.

 

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Hello Mark.

Although I cannot give a specific answer the following link may help you on your way and a call to Burlen may well secure a finite answer; it's an excellent website with a great deal of support information. It looks as though there is an overlap with the 1977 Spitfire but I am certain all will be obvious to you.

http://sucarb.co.uk/cf/vehicle/list/?manufacturer=Triumph&vehicle=Spitfire

Regards.

Richard.

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Perhaps when you have a the correct needle and spring sorted, a trip to a decent RR will add the finishing touches ??

One tab worth looking at on the Burlen site is their new range of ethanol proof carb floats - speaking of which do you think there might be an issue with the floats not adjusted / gapped identically ??

Regards.

Richard.

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As I am on a roll, Mark, have a look at this link which is excellent at identifying the origin of your carb provided you have an ID Tag. Failing that, this chap (cannot recall his namely, but superb knowledge) can work out your likely carb by needle information - that's knowledge for you !!

http://www.carburettorspecialists.com/CHLAUG2016.htm

Regards.

Richard.

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Thanks Richard, I'll have a look - floats - very good question - I've not touched these carbs apart from balancing them and adjusting the idle.

Rolling road is something I've thought about - just not sure who to go to around here (I'm near Solihull in the West Midlands)

Many years ago I took my Nova 1.3 SR to one in Birmingham - they certainly made it fly (It had a sports exhaust on it!) and developed about 70bhp at the wheels in the end. Drank the fuel though!

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Thanks Clive - I'll have a look and see what's fitted - I was going to look now - but saw the time - and I think something on the Tv (Vera - but recorded so we can skip the ads!) - so I'll have a look in the morning. Won't take long :D 

I don't have K&N's fitted - I don't think the ones on the engine when I had it are very good so I've gone back to standard. 

But I do have a road cam, tuned exhaust and flowed head. So could be either AAT. AAM or AAB. 

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8 minutes ago, Anglefire said:

I don't have K&N's fitted - I don't think the ones on the engine when I had it are very good so I've gone back to standard. 

But I do have a road cam, tuned exhaust and flowed head. So could be either AAT. AAM or AAB. 

Hello Mark.

Your car will be breathing better and getting rid of waste more efficiently, so I would expect there to be a greater requirement for air induction; I'm not sure the standard air filters will cut it for that requirement - perhaps something else to consider ??

Clive, will certainly be able to give a more informed view than I.

Regards.

Richard.

 

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AAR, AAU would be good alternatives. And if you can, get some stub stacks in the filters. And yellow carb springs....

If you are up for it, something like theoriginal airbox, fed by tubes and a K+N type filter picking up cold air would be good. Not sure if you could use a Dolly Sprint modified airbox with a single 3" tube. I started one but never finished it for my Spitfire, but ran out of space for the long trumpets I needed to use.

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1 hour ago, Anglefire said:

Thanks Clive - I'll have a look and see what's fitted - I was going to look now - but saw the time - and I think something on the Tv (Vera - but recorded so we can skip the ads!) - so I'll have a look in the morning. Won't take long :D 

I don't have K&N's fitted - I don't think the ones on the engine when I had it are very good so I've gone back to standard. 

But I do have a road cam, tuned exhaust and flowed head. So could be either AAT. AAM or AAB. 

Hello Mark

                  I have a set of K&N,s ram stacks and various needles you can have for postage and a charitable donation not needed now as on EFI !

pm me with phone number and we can sort  something out? I can not remember what cam you have fitted now?

Roger

ps I am local

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As i also said to Roger, I can't see what spring is fitted - and I also found the 90' connector to the dizzy was not a good seal to the thin plastic vacuum pipe and sucking on it did nothing to the timing - I replaced it with one off the old engine which was fairly new and it now does move the plate in the dizzy. That's not going to help acceleration!

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Hello Mark

                   The filters are on the way 1st class so you should? get them tomorrow?

I have put the 2 stub stacks in and 2 yellow Springs(they did not seem to suit Spitty?) I would try a richer needle first and be very accurate when you fit them to the piston(I always hold them in with a straight edge as I nip the screws up) try it you will see what I mean!

It is important as there is no real change for the first 4 stations on the first 2 needles so if you put them in accurately there is no need to touch the adjusting nut(if your mixture is right at bottom end) then it will richen up as you put your foot down but come back to leaner on light throttle.

There are 3 sets of needles ABG leanest AAU middle AAA richest(probably to rich for your engine as the cam is not wild)

There is a chart in the docs enclosed sticker which shows how they compare.

I cleaned the filters and re oiled them (do not worry about the colour((blue)) its just a different make of filter oil(a lot cheaper than K&N!) my son used to use it on the Moto Cross Bike!

Have fun? A nice bit of straight quiet road is what you need and no PC plod and do some plug chops(rolling road is easier but you should be able to get it reasonable with patience!)

plus put a few miles on before going to a rolling road

Roger

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Thanks Roger and Pete - I'll probably try the middle ones first and see how it goes and then go up or down depending on the feel of everything. I'm sure a bit of playing will be required!

As long as I can get it running nicely, I can finesse the rest once a few miles are on it and get to a rolling road - there was one near where I live a few years ago that seemed to be popular with the clubs - but it is no longer trading as far as I can tell. :(  

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3 hours ago, Pete Lewis said:

ive found cars running hopelessly rich with the fat yellow  bed springs   

idle is adjustable but mid range is neat juice  far to rich , reverting to std  spring and cured all the problems 

must depend on all mods being in harmony .  its  all  a bit trial and error 

Pete

Hello Pete

                   That,s what I found it was not to bad if you accelerated very very slowly but foot down just seemed just dump fuel in!

Roger

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1 hour ago, Anglefire said:

Thanks Roger and Pete - I'll probably try the middle ones first and see how it goes and then go up or down depending on the feel of everything. I'm sure a bit of playing will be required!

As long as I can get it running nicely, I can finesse the rest once a few miles are on it and get to a rolling road - there was one near where I live a few years ago that seemed to be popular with the clubs - but it is no longer trading as far as I can tell. :(  

Hello Mark

                    I would fit the K&N,s and ram stacks then fit the ABG needles and then adjust the lower range as it will be lean now! to slightly rich then take it for a run.

You may not need to to much richening farther up as your cam is quite mild and has the head been ported?

What grade of oil do you put in the dampers?

Roger

 

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28 minutes ago, Anglefire said:

Hi Roger,

Yes I was going to fit all of that first - I meant that before :lol: 

I put SAE 20 oil in the dampers. I know Triumph recommend 20/50 but SU recommend SAE 20 - seems to work ok!

Yes the head has been ported. 

Hello Mark

                   I always used 20/50 if you use 20 sae it could allow the piston to rise quicker so go lean!

Roger

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I don’t  know how hot the carbs get to know if the difference in viscosity is enough to make a measurable difference. They do sit above the exhaust manifold so there is heat - but I like many have a heat shield. Again how much that helps is difficult to determine - though with my job I could strap some temperature loggers to various places around the carbs etc and drive it about a bit. I can’t remember off hand the logging times - but it’s certainly a second and possibly less. 

I’m guessing the only real way to find out the power and pickup etc is to put it on a rolling road so you can actually measure the difference.

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The one that gets my goat is guys who use 3 in 1

 heck knows what cats pee that turns into when it hot

Some use ATF  guess thats more temperature stable but  again not much viscosity to act as a damper

I mean whats wrong with what SU or Triumph specified ,,  Grrr.

Its your accelerator pump to enrich on opening the taps   it has to damp the piston rising or its going to be flat spotted

Pete

 

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