10 replies to this topic

[Pavel]

I'm going to be rebuilding a 998 hopefully.

It'll be rebuilt to 1030, with a MG head and camshaft if lucky.

I'll have access to a HIF44 carb or my 32/34 dual downdraft weber.

I was told that the HIF44 is far too large for this engine. What is the problem exactly with too much carburation?

[Bluemini]

Over fueling will be the main problem, but if you get it tuned right it should be ok. Its all about air speed thru the carb too, if the carb is too big for the engine, it wont draw the air thru at the right speed , causing mixture problems.

[Pavel]

Hmm interesting thoughts creep into my head...

That dual weber would be well suited though wouldnt it?

It opens the small venturi first and then the second when you REALLY give it some gas.

That would keep airflow pretty fast through the 32mm venturi, and I think that 32mm will prolly be enough by itself... Then opening the larger venturi only a bit will simply give it a bit more air to work with...

On the other hand since its dual 32/34 venturis then shouldnt the speed of airflow be pretty fast through both of them anyway since they are rather small compared to a 38 or 44 HIF carb?

[Bluemini]

The secret to a Weber is gettin the choke size right, yuo want it small enuf to have a good air speed, but not too small that it suffocates it. If its too be your gonna use more fuel tryin to get a good air/fuel mix because of the slower air speed and it will cause it to bog down.

Some of the 998 racers use a '45, but use a manifold so that it only uses one barrel of the carb, this would probly be good on your engine.

[Pavel]

But my weber had a manual choke

[Bluemini]

This is the choke...

Attached Files

•  40_DCNF_04.JPG   0bytes   1 downloads

[Pavel]

1)

Attached Files

•  carbbottom.jpg   0bytes   2 downloads

[Pavel]

2)

Attached Files

•  carbtop.jpg   0bytes   1 downloads

[Bluemini]

Looks like a Ford weber that, they used somat similar on the old 850's if i remember correctly...

[Wil_h]

I think that the HIF44 will work ok but you will loose low down torque due to its size. A 38 is ideal for a 998 I reckon.

If you have the inlet manifold for the webber though I'd give it a try. My mate once put one on his 850, it worked fine but it did nothing for his fuel economy. Either way people will think you've got something special if you put it on.

Wil

[Woody]

I once tried a webber 28/36 downdraft on my mini van , this was a progressive twin choke , small one first to about 3/4 open then the other started to open , the mini was no faster but i think throtle response was improved and acceleration up a little but it was tall so no room for an air filter if i wanted to shut the bonnet !, I took it off as it drank petrol .