Newbie Question 2: Weber Carburetors Options

[amfab]

I just bought a 74 2.0. Previous owner says previous owner rebuilt it out to 2.1 a few years ago but there is no documentation. Regardless, it IS a GA with 3 bolt intakes so I will assume at least 42mm intake valves.

It came with dual Weber 36idfs with 32 venturis.

The motor seems a bit anemic at the higher RPM. To me—quite an amateur at this kind of stuff—it kind of makes sense because the throttle bodies seem a bit small for the motor (it seems that a lot of the type 1 guys use 36idfs on sub-2 litre motors).
I just had the car tuned up and it runs very nicely, but not a lot of power and it flattens out fast above 4kRPM

I considered megasquirt, but because I have linkage and manifolds I was thinking going the easier and cheaper route of 40 or 44 idfs.

After doing a bit of research, my thoughts are either 40idfs with 34 venturis or 44idfs with 36 venturis. Just a little more oomph will be able to carry me until I eventually do a six conversion in a couple years. Are 44idfs too much carb for the 2.0 (or possible 2.1)?

Unfortunately, there is no documentation on the cam either. I (and my mechanic) are thinking its stock or close to it.

Any advice would be greatly appreciated.

Thank you

-Andrew

[colingreene]

sounds like the cam is more your problem than anything else.

[porschetub]

sounds like the cam is more your problem than anything else.

36 IDFs should be ok ,you could be suffering a lean condition @ high rpm,take it for a good hard run and check your plug colour,it should be a rich brown .
Remember that it isn't the throat size of the carbs it is the venturi size that dictates the power,you could go to say 34 vents and end up with better performance over the power range than say 40 or 44's can provide as you will lose some of the lower end power that you drive in most of the time.
Is your ignition really and truly up to the mark ,for instance is the distributor advancing totally at higher rpm,all these factors come in to play,tell us more and that will really help cause you should still be making power @ higher rpm regardless of the cam .
Many members can help you on here,cheers

EDIT....don't wait too long for six conversion otherwise you will be struggling to find a motor for a decent price.

[amfab]

...you could go to say 34 vents and end up with better performance over the power range than say 40 or 44's can provide as you will lose some of the lower end power that you drive in most of the time...

I considered the 34 vents as an option. You are saying that too much throttle body could hurt low end?
I mean if I go to 34s iwith 36dfs I could have more low end than 40idfs with 34 venturies?

Im thinking about getting a weber bookl to learn more about all of this. Thank you for the help.

Also, yes, I am fully aware of how fast everything air cooled seems to be rising dramatically in price.
The reason I jumped into the 914 now is because I had been talking about getting a 914 for years and when I saw how the 911s have gone up in the last 10, I thought I should get in to the 914 pretty quick

Also, I agree Collin, ultimately if it is a stock cam, changing that would give me the most oomph, Its just that right now it runs nicely, doesn't leak, and I don't wanna tear it down right now (I just dropped a bunch on rebuilding my 993). Im just trying to squeeze a few more HP oouta what I have now.

[rhodyguy]

What is the actual rpm where it stops running out of steam? If your car runs cleanly from a stop with no snapping, popping, stutter during transition, backfiring on decel you're doing well. Do you drive around at 5k? In all likelyhood, sizing up the venturis might bring a set of new issues.

[amfab]

Just tuned up, car runs nicely, A little stumble now and then when taking off, and when cruising it can feel kinda hesitant at times.

Pops on decel when not fully warmed up. Pops quite a bit going downhill, Torque kinda fades away around 4200-4500 Im almost never over 5K cuz it feels useless.

This may just be what these motors feel like. I haven't driven another 914 since My 73 I had 30 years ago.

[r_towle]

Try getting larger venturis for the carbs you have now.
None of these motors starve out at 4K rpms....using any fuel system.

So, something is wrong with the tuning.

[Elliot Cannon]

Just tuned up, car runs nicely, A little stumble now and then when taking off, and when cruising it can feel kinda hesitant at times.

Pops on decel when not fully warmed up. Pops quite a bit going downhill, Torque kinda fades away around 4200-4500 Im almost never over 5K cuz it feels useless.

This may just be what these motors feel like. I haven't driven another 914 since My 73 I had 30 years ago.

If it stumbles coming off idle it could be wrong size idle jets. Which ones do you need? Idle jets are relatively cheap. Buy about 4 different sizes and give them a try. You will get real good at changing them out. (IMG:style_emoticons/default/biggrin.gif)

[injunmort]

i am guessing cam as well, if it is stock. i am running 36 webers as well, it is tuned about as good as it can get. fades real fast after 5000 rpm. lots of noise and inlet woosh but no real power. stock fi cam. i was told that this is the way they run with stock cam and carbs. prior engine had a cam in it with these carbs and it had a lot more power.

[amfab]

i am guessing cam as well, if it is stock. i am running 36 webers as well, it is tuned about as good as it can get. fades real fast after 5000 rpm. lots of noise and inlet woosh but no real power. stock fi cam. i was told that this is the way they run with stock cam and carbs. prior engine had a cam in it with these carbs and it had a lot more power.

Interesting. Can you let me know what Venturis and Jets you are running?

[injunmort]

i will

[r_towle]

5k is normal for a stock motor, stock camshaft.
Look at all the dyno charts, it's roughly 5200 rpms the torque starts going down...

But 4K is a tuning issue.

[rhodyguy]

Have you checked to see if the throttle plates are opening fully when the peddle is on the stop?

[injunmort]

not to hijack, but it definitely feels like not enough lift or duration for the carbs. could adjust for a range but at the expense of smooth transitions elsewhere. the stock cam is not suitable for carbs because of the profile. imho. the components should be compatible. stock cam is not for carbs. as i was warned by many. sorting a djet system now as that is the easiest remedy.