15 replies to this topic

[lawrence]

hi there, im curently trying to improve the flow for my hif44 carb to let more air in
ive knife edged part of the throttle spindle but as you can see from the piccture theres a weird spring thing stopping me doing the other side so well,
can this be removed?

[jaydee]

The laptop, yes it could be detrimetral to flow..

You'd better get hold of a plain butterfly for an HIF44, and knife edge it ;)

[lawrence]

haha :) yh i may just leave with what ive done, especially as ive lost the sodding screws now! ffs

[jaydee]

I dont remember what it was supposed to do, but that valve is madness, its like..well..how would you breathe with a tangerine in your mouth?

[bmcecosse]

Simply remove the little valve and solder over the hole. It's there to guarantee a supply of air when the throttle is closed on the over-run, for 'emissions' purposes.

Edited by bmcecosse, 28 December 2011 - 05:45 PM.

[dklawson]

As Roy said, remove the valve and solder the holes closed. The valve is hard to remove though. I seem to remember that part of the valve is threaded to the butterfly then the threads are soldered over to secure the assembly. Therefore, heat and cutters are required.

[lawrence]

well i think a grinder will sucessfully remove it then, when you say solder over the holes what sort should i use? is electrical solder good enough? sounds a bit iffy as i dont want a blob of solder entering my engine a speed! :)

[dklawson]

A grinder will make a bit of a mess of the butterfly disk. Nip the valve off with diagonal cutters. With the valve removed you will see what is left of the valve's threaded stem left behind in the disk. There will be a series of holes or slots around the threaded stem. Use a Dremel or small bit on a die grinder to carefully remove the remaining part of the valve so it is flush with the surface of the butterfly disk. Use fine sandpaper around the series of holes to clean both sides of the disk. Then use rosin flux and a BIG soldering iron to flow solder into the holes. Electrical solder will be fine. However, you need the big soldering iron or small torch to heat the disk so the solder tins the surface. If you leave a blob on the surface you are not soldering. Properly done the solder will tin the surface and fill the holes and there will be no blobs to get sucked into the engine.

[dklawson]

I don't think we are saying anything different.

My point is simply that you have to prepare the surface properly and heat it sufficiently for the solder to wet the surface and flow into the voids. If the solder sits on the surface in blobs it was not done properly.

[icklemini]

just buy a new throttle disc - a plain one... very cheap from Burlen...

removes the danger of the 'valve' disappearing inside the engine due to poor soldering or whatever...

and

will be smoother than that one soldered up and aid your air flow!

(IMHO - on a standard engine a hif 44 isnt going to restricting the flow and these 'mods' aint worth it...)

Edited by icklemini, 29 December 2011 - 11:24 PM.

[jaydee]

just buy a new throttle disc - a plain one... very cheap from Burlen...

removes the danger of the 'valve' disappearing inside the engine due to poor soldering or whatever...

and

will be smoother than that one soldered up and aid your air flow!

(IMHO - on a standard engine a hif 44 isnt going to restricting the flow and these 'mods' aint worth it...)

+1

[dklawson]

Perhaps those disks are relatively inexpensive in the U.K. Over here they are not cheap and it is very common to find the original disks modified and plugged with solder. It really is not difficult and since you are working with the flat surfaces... not easily screwed up during the process.

And... the valve is not going to be on the modified disk so there is no possibility of it getting sucked into the engine. Once soldered shut the disk is sanded flat so solder bumps are not a problem with air flow either. Keep in mind that these mods are typically carried out with narrowing of the butterfly shaft. In the end, removing the valve and narrowing the shaft does result in a much more open flow path that can offer performance improvements.

[lawrence]

Thanks for all your help guys,
Ive managed to fill the hole with solder and profiled it for a better flow, think ive done it quite well :)

Again thanks for the help
Lawrence

[dklawson]

That looks great.

[icklemini]

#Doug, yes I appreciate the theory about why one may want to do this to the carb... I also know it was done "back in the day" as replacement bigger carb was far more expensive and so the desire to squeeze as much as possible out of what was available at the time to suit a modified engine...

Note that the carb modifications will only yield any benefit when the throttle is fully open... which really isnt very often on a road car..
Also that a standard HIF44 on full throttle wont be restricting a standard engine, the valve guide bosses in the inlet ports in the head, for example, are far more restrictive.

My comment on the throttle disc relates to the small risk of the solder or the valve disc coming away from the throttle disk and being ingested into the engine = Not good. Burlen list the throttle disk, with gaskets, for £7.46 so even with worldwide postage its not an expensive item. ( http://www.sucarb.co...earch=&Id=23900 )


Anyway, this of course all IMHO :)

Edited by icklemini, 31 December 2011 - 01:05 AM.