Weber problem

[darrenhall]

Hello everybody,

I am a new member. I have a problem and I hope someone can help me. I just rebuilt the motor on my 1967 911. and I rebuilt my Weber IDA's . BUILD SPECS: I used 1969 E Heads, S cams, The jugs have been bored from 80 mm to 81 mm for new JE 9.8-1 COMP Pistons.

THE PROBLEM:

The motor runs very well and revs very very quickly. However it only revs quickly at about 1/2 throttle. If you go wide open on the throttle the motor bogs out/down and just flat wont rev.

Any Thought out there? any suggestions on jetting, venturi etc...?

Thank you in advance,

Darren Hall

1967 911
1970 911T Targa
1970 911E Coupe
1963 356B

[Steve@Rennsport]

Hi Darren,

First off, my compliments on a pretty engine; well done!!

Two things:

1) Check fuel pressure and make sure its 3.5-3.8 psi, then make sure your float levels are PERFECT.

2) Jetting will need to be changed to accommodate the engine modifications. What jetting package do you have?

[darrenhall]

Steve,

Thanks for the reply. Fuel pressure was set as 3.5 I bumped it up to 4 yesterday to see if that made any difference. It didnt change anything. The float level is perfect, well lets just say I spent more time adj. the float level then I probably did rebuilding the motor LOL. Idle jets are 50 main jets 130 venturi 30 my elevation is 3000 ft.

I hope this helps , thank you for your help.

Darren Hall

[Steve@Rennsport]

Hi Darren,

Weber float levels are designed for 3.5 psi so thats where it needs to be,...

Emulsion tubes?

Do you have any 135 MJ's on hand?

I would also confirm fuel pump volume to ensure that its able to keep the float chambers full at high demand. You'd never believe what I've found regarding plugged filters, tank screens, failing pumps, etc. You want 1 litre/minute.

[darrenhall]

Steve,

Thanks again, as for fuel volume/flow. I havent measured it . However. I had the fuel tank boiled and sealed. I put a new fuel pick up filter in the tank, all new fuel lines everywhere, brand new hardi OEM fuel pump, new regulator, and of course inline fuel filter. As for the imulsion tubes. I dont know what they are. In fact, this may sound absolutely foolish but I dont even know their purpose. Please educate me. I am still pretty new to the classic 911 world.

Thanks again,

Darren

[Steve@Rennsport]

One bit of wisdom here learned from 38+ years of doing 911's,...

Never, ever assume anything about a brand-new part: Trust, but verify. Check the volume so you KNOW it works correctly. This is true now, more than ever. I could tell you soooooo many stories.

Emulsion tubes regulate fuel delivery from just above idle to 50% throttle. These can be found just under the air correctors and easily fished out using a wooden toothpick. Its likely you have F3's in here, however one shouldn't assume that.

If you don't own one yet, get the Hayne's Weber manual as it has a chapter in there on all the 3bbl Weber carbs and an exploded illustration.

[PFM]

I will add one for not so happy fuel pump. New or otherwise.

Stay tuned,

PFM