FAO TurbDave- Fabricated Carb Jet holder
Turbo Mini Forums

Dave,

On your carb mod's article on manchester minis,
you mention replacing the bimetallic jet holder with a fabricated one.

Seeing as I have my carb stripped down,
I thought I'd look into getting one made.

What should I be fabricating it out of?

Presumably I want to have it made of a singe piece?

Cheers

John

Edited by iain on 21st Oct, 2003.

Too many projects!

Easy peasy this John,

All you need to do is take out the whole metalic jet holder assembly, and grind the heads off the rivets holding the bi-met plates to the silver angled bracket. Punch the pins through, and remove the strips. keep the rivets however!



Next, get a piece of steel of the same thickness as the centre (largest) bi-met strip (0.8mm ish???). Using a scriber, mark out the outline and shape that locates around the jet of the central bi-met strip, and using a saw, drill and files, cut out the same shape!

Now get the original central strip, and place on top of the new steel piece you've just made. Carefully lining up the hole for the jet, clamp the two together. Now grab a drill, and using the original as a guide, drill out the rivet holes in your new piece (to the same diameter).
Now, you can position the new 'strip' onto the silver jet holder, using the rivets to line up exactly. Once you are happy, simply tack weld the two together, then remove and discard the rivets. You only need to tack it - don't go mad, as it's best to keep it flat.

Finally, all you then need to do is find one ot two washers that are a simiar internal diameter as the large hole that the screw with the spring goes through. These need to equal the thickness of the two bi-met strips plates that have been removed and discarded.
If you omit to do this, the jet is loose - meaning under vacuum it'll lift up, so you have to 'increase' the mixture to suit (lowering the jet), but under boost, it is then pushed down, making the mixture super rich, and leading to a probable misfire which is nigh on impossible to figure out why!

Don't ask how i know this... But suffice to say Jimsters solid Jet now has a washer on top of it!!!!

Hope this helps - if you have a digital camera, why not take some pics as you're doing it and post them up here for others to see and copy?

Giz a call if you need any more help.
D

Edited by TurboDave16V on 15th Oct, 2003.

Top stuff Dave,

I will indeed take some photos.

What problems does the original strip normally cause?

I've got a load of stainless in the shed, I'll use some if that for the replacement.

Thanks again.
John

(I'll mail you a couple of pics of how my van is coming on.)

Too many projects!

Under general driving, the original is no problem. When you come to a stop with a hot turbo sat less than 1" under the carb, the whole thing gets hot - heat sheild or no heat sheild!!!

When you come to start up, you still have a hot carb, with hot fuel (assuming it hasn't evaporated - LOL!!!) and this throws the mixture out!

It is most apparent on rolling roads - even with the bonnet up. If you shut down after a run to adjust the timing or something, after a few minutes the carb will be too hot to even touch the dashpot - this is the whole carb!!!
Remember, this Bi-metallic feature was designed for the 'then' new HIF carb - in nat asp situations - ie sensitive to changes of air temp between -10 to +30 degrees C at the absolute limit... Cooking the carb with a turbocharger will send the strip to the extremes of its adjustment in one hit!

Back to the rolling road....Suppose you do a power run, then shut down.
If you fire it up and do another power run straight away, the mixture will be wrong - and the power won't be the true figure.
I always insist the engine is fired up, and is 'driven' on the rollers for at least 30 seconds, under light load, to ensure fresh (cold) fuel is in the float chamber, and the carb is at normal operating temperature - then, you can do a power run...
By making the strip solid - you are basically removing something else that can cause head scratching whilst trying to perfectr needles on the rollers, but also prevent hot starting problems at the petrol station, or other occasions when you turn the motor off for a short time!

D

Sounds very worthwhile.

Looks like my saturday morning is now booked up...

cheers again.

John

Too many projects!

Some very worth while info by the sounds of it.

Could this be moved to the How to / FAQ section please Admin.

don't forget the washer(s) I've still got a bald spot on my head from all the head scratching I did.

Team www.sheepspeed.com Racing

After annoying the neighbours for the last couple of hours (dremel, welder, etc) I've finished this.


I've got a few pics but currently have no webspace ( or knowledge on how to).

Who want's to be a great help and host them up?

6 images (only 100K in total)

Cheers.

John

Edited by jpboost on 20th Oct, 2003.

Too many projects!

e-mail them to me at billy@billydude.f2s.com and I'll post them in this thread for everyone to see

Billy, I've mailed the pics.

Cheers.

all,

each of the original bimetallic strips are 0.8mm

I used a bit of a inner sill panel for the main replacement strip.

the washers are stainless M6 washers from screwfix. handily exactly 0.8mm thick (and cheap).



John

p.s. TurboDave, if you see something in the pics I've done is drastically wrong,please let me know as I'm not building up the carb for a few days yet.....

Too many projects!

Picture's
1.bimetallic jet holder as original


2.bimetallic jet holder as original


3.rivets removed and split into it's component parts


4.the replacement strip


5.new assembly ready to tack together (locating rivets in place)


6.finished item, welded up and ready to fit back. (washers to maintain thickness)

Edited by billydude on 21st Oct, 2003.

I think I need to do this myself to cure my flooding on hot start
something I might do later useing one of my spare carb's holder ready for fitting at a later date

where abouts is that located in the carb?

A-series power! 1972|1310|T3 turbo|Omega pistons|Cantre main strap|Orange clutch diaphragm|AP race plate|Comp pressure plate|Lightened steel flywheel|13-row oil cooler|Vernier duplex timing gear|Phase 2 Piper cam|Green air filter|Hi boost carb needle/spring|2"Stainless exhaust|3"Play mini stainless rear box|Jack Knight s/c 4spd gearbox|Jack Knight s/c drop gears|Silicon coolant hoses|Lumenition HT leads|GAZ lowered height shocks all round|Steel flip-front|Rear safety devices cage|Group 5 arches|6x12 deep dish Minilites|Surf blue/Old english white|

also another question, when you throw away the bi met strips, couldnt you just keep the largest piece which is riveted to the angle bracket instead of making up a new plate, or is the idea of the mod to replace the largest strip with a different material!?

cheers

A-series power! 1972|1310|T3 turbo|Omega pistons|Cantre main strap|Orange clutch diaphragm|AP race plate|Comp pressure plate|Lightened steel flywheel|13-row oil cooler|Vernier duplex timing gear|Phase 2 Piper cam|Green air filter|Hi boost carb needle/spring|2"Stainless exhaust|3"Play mini stainless rear box|Jack Knight s/c 4spd gearbox|Jack Knight s/c drop gears|Silicon coolant hoses|Lumenition HT leads|GAZ lowered height shocks all round|Steel flip-front|Rear safety devices cage|Group 5 arches|6x12 deep dish Minilites|Surf blue/Old english white|

It's in the bottom of the carb. It's the bracket that holds the jet in position. It's also the past that moves the jet as you turn the mixture screw.

I think you've answered your own questions about keeping the middle part of the original strip... The whole point is to make the braket fixed. i.e not made of material that deflects with temperature changes.

Too many projects!

i cant seem to view the picscouldyou repst them? :(

'I swear to use the Boost, The whole Boost'
'And nothing but the Boost..... So help me God'

I'll try and find them if I still have the pic's on my hard drive

unless jpboost still has them and can send them to me again

it's my stupid hosts fault for wipeing me out

any luck with the pics??

And on the 7th day........... God created turbochargers!

I've not got them anymore :(

Neither can I, see only red exxes

I've got some pics, I'll sort them out later today

Team www.sheepspeed.com Racing

great lets have them!!

'I swear to use the Boost, The whole Boost'
'And nothing but the Boost..... So help me God'

sorry about the pics, as soon as I get home I'll do them

Team www.sheepspeed.com Racing

Here's a few pics from my attempt at it, following TurboDaves Instructions

Original In bits


Template drilled and marked for cutting out


Original and New One side by Side


An Original complete and My new one


the all important washer of correct thickness
Aparently Jimster knows all about this little bit


Turned out OK. Took a tiny bit too much off on the right on the inside where the jet sits but I'm pretty sure this was good enough. Jet sat in fine and was in no danger of falling out.

wow thanks a lot for those now i can begine mine :)

'I swear to use the Boost, The whole Boost'
'And nothing but the Boost..... So help me God'