IDA3C Weber Troubleshooting Options

[Cfletch]

In General everything about those carbs is not correct spec for a stock 2.0 , venturis ..what is the jetting ?? compare to posted chart..should be like 911L on chart.. unless you have a hopped up up 2.0 ..

what fuel pump? if its the Im thinking , a shop I know of was buying them and they where the wrong pressure,, and needed a propper PN..and then all was right.

As mentioned, this is on a 2.7 from a 1974 CIS engine (stock).

Jetting and all carb related settings were based off recommendation from Paul Abbott and I do not have them in front of me, but know many others used the same with success so I trust those.

The fuel pump was ordered from Pelican- Pierburg pump. Pelicans number is:7-21440-51-0-INT

[930cabman]

In General everything about those carbs is not correct spec for a stock 2.0 , venturis ..what is the jetting ?? compare to posted chart..should be like 911L on chart.. unless you have a hopped up up 2.0 ..

what fuel pump? if its the Im thinking , a shop I know of was buying them and they where the wrong pressure,, and needed a propper PN..and then all was right.

As mentioned, this is on a 2.7 from a 1974 CIS engine (stock).

Jetting and all carb related settings were based off recommendation from Paul Abbott and I do not have them in front of me, but know many others used the same with success so I trust those.

The fuel pump was ordered from Pelican- Pierburg pump. Pelicans number is:7-21440-51-0-INT

Fuel pump may be fine, do you have an inline fuel pressure gauge? I am running the same setup, 2.7 CIS with 40 IDT 3C carbs, 3PSI runs fine. try to post your venturi, jets, ... sizes if you are able

[Cfletch]

In General everything about those carbs is not correct spec for a stock 2.0 , venturis ..what is the jetting ?? compare to posted chart..should be like 911L on chart.. unless you have a hopped up up 2.0 ..

what fuel pump? if its the Im thinking , a shop I know of was buying them and they where the wrong pressure,, and needed a propper PN..and then all was right.

As mentioned, this is on a 2.7 from a 1974 CIS engine (stock).

Jetting and all carb related settings were based off recommendation from Paul Abbott and I do not have them in front of me, but know many others used the same with success so I trust those.

The fuel pump was ordered from Pelican- Pierburg pump. Pelicans number is:7-21440-51-0-INT

Fuel pump may be fine, do you have an inline fuel pressure gauge? I am running the same setup, 2.7 CIS with 40 IDT 3C carbs, 3PSI runs fine. try to post your venturi, jets, ... sizes if you are able

I put a temp inline near the carbs and blocked off the outlet to check max PSI and it read 12PSI, if that is not correct, I assume the more accurate way would be to have the outlet of pressure gauge hook up to the carbs when car is running to see what pressure is at idle?

Mains: 135
Idle:55
Air correction: 180
Emulsion tubes: F26
Venturis: 32

[sixnotfour]

I apoligize wrong Weber carb problem post..

[brant]

Are 135 mains the norm for a 2.7?

I don’t have a 2.7.


I run any where from 180 mains to 210 mains on the track. But race car. 2.0 liters. Depends on the altitude of the race

[Cfletch]

Are 135 mains the norm for a 2.7?

I don’t have a 2.7.


I run any where from 180 mains to 210 mains on the track. But race car. 2.0 liters. Depends on the altitude of the race

Not sure if there is a 'normal' for these engines as I usually see 2.7 being way more built than my stock one if running carbs, but based on what I have seen in general it seems like that is a good starting point at the least and again, Paul Abbott recommended them so I would trust that at least for getting a baseline going

[sixnotfour]

(IMG:style_emoticons/default/beer.gif)

[Cfletch]

(IMG:style_emoticons/default/beer.gif)

Looks like I'm right on the money then!

[porschetub]

In General everything about those carbs is not correct spec for a stock 2.0 , venturis ..what is the jetting ?? compare to posted chart..should be like 911L on chart.. unless you have a hopped up up 2.0 ..

what fuel pump? if its the Im thinking , a shop I know of was buying them and they where the wrong pressure,, and needed a propper PN..and then all was right.

As mentioned, this is on a 2.7 from a 1974 CIS engine (stock).

Jetting and all carb related settings were based off recommendation from Paul Abbott and I do not have them in front of me, but know many others used the same with success so I trust those.

The fuel pump was ordered from Pelican- Pierburg pump. Pelicans number is:7-21440-51-0-INT

Fuel pump may be fine, do you have an inline fuel pressure gauge? I am running the same setup, 2.7 CIS with 40 IDT 3C carbs, 3PSI runs fine. try to post your venturi, jets, ... sizes if you are able

I put a temp inline near the carbs and blocked off the outlet to check max PSI and it read 12PSI, if that is not correct, I assume the more accurate way would be to have the outlet of pressure gauge hook up to the carbs when car is running to see what pressure is at idle?

Mains: 135
Idle:55
Air correction: 180
Emulsion tubes: F26
Venturis: 32

Sorry but not sure why you needed deadend the pump ? ,supplied as making that max pressure ,you still haven't mentioned a regulator or gauge ?....any tests you do need to be done after fitting them if you have them ?.
Paul Abbott knows his stuff so your specs should be fine for your carbs.
Cheers.

[porschetub]

In General everything about those carbs is not correct spec for a stock 2.0 , venturis ..what is the jetting ?? compare to posted chart..should be like 911L on chart.. unless you have a hopped up up 2.0 ..

what fuel pump? if its the Im thinking , a shop I know of was buying them and they where the wrong pressure,, and needed a propper PN..and then all was right.

As mentioned, this is on a 2.7 from a 1974 CIS engine (stock).

Jetting and all carb related settings were based off recommendation from Paul Abbott and I do not have them in front of me, but know many others used the same with success so I trust those.

The fuel pump was ordered from Pelican- Pierburg pump. Pelicans number is:7-21440-51-0-INT

Fuel pump may be fine, do you have an inline fuel pressure gauge? I am running the same setup, 2.7 CIS with 40 IDT 3C carbs, 3PSI runs fine. try to post your venturi, jets, ... sizes if you are able

I put a temp inline near the carbs and blocked off the outlet to check max PSI and it read 12PSI, if that is not correct, I assume the more accurate way would be to have the outlet of pressure gauge hook up to the carbs when car is running to see what pressure is at idle?

Mains: 135
Idle:55
Air correction: 180
Emulsion tubes: F26
Venturis: 32

Sorry but not sure why you needed deadend the pump ? ,supplied as making that max pressure ,you still haven't mentioned a regulator or gauge ?....any tests you do need to be done after fitting them if you have them ?.
Paul Abbott knows his stuff so your specs should be fine for your carbs.
Cheers.

[Graydingo]

He "deadend" it so he could check PSI. I think that was temporary.

OP needs the PMO pressure regulator. Many out there. Can get it with AN or hose barb.

It's really a bypass.

So FP--------> Fuel Filter --------> PMO regulator set to 3.5 PSI ---------> dual outlets to small inline filters ------_> each carb.


PMO regulator ------> return line.

Optional: Carb crossover line to equalize fp. (I don't run one but I've heard it can be helpful for overall performance.

[930cabman]

I am running FP ---- FF ------- PR-------GA ---------T-------Carbs

no return line

works fine at 3psi

[Cfletch]

He "deadend" it so he could check PSI. I think that was temporary.

OP needs the PMO pressure regulator. Many out there. Can get it with AN or hose barb.

It's really a bypass.

So FP--------> Fuel Filter --------> PMO regulator set to 3.5 PSI ---------> dual outlets to small inline filters ------_> each carb.


PMO regulator ------> return line.

Optional: Carb crossover line to equalize fp. (I don't run one but I've heard it can be helpful for overall performance.

Right, did that to check ma PSI if valves were shut, wanted to check and see how strong the pump would be. Anyway, yes today I plan to do: FP---Filter--regulator-- stock 6 hard line--- carbs. Im not doing a return line back to tank, blocked that off at the tank with a hose bolt combo.

I am using the return line as my feed because the return line diameter matches everything else and didn't want to mess around with going up and down sizes. I have a regulator mounted kind of near where the stock 914 4 fuel pump was, and then its going up through the metal to the stock 6 hard line which does the branch to both carbs. Because of that, no PMO regulator.

[Cfletch]

Hey friends, bit of an update for you all:

I've been sick/busy with work so slow progress on the car from the past weeks. I was able to get the regulator plumbed and set it for 3.5PSI to carbs and also mounted the gas tank. I tried to start it the other day and it just refused to start so I broke out the either and it fired off right away then ran and barely held an idle so I was lost as to what had happened. If seemed like the passenger side bank just did not want to run well at all and I babied the throttle to keep it alive. I also noticed the car just refused to go back down to a proper idle even when I was not babying it.

Come back to this weekend, I decided I needed to just pull that carb. Main reason was I wanted to blast some compressed air through everything once again because my idle mixture screw on cylinder 1 didn't seem to impact the engine at all so I figured it must have been clogged. Additionally I noticed that the same carb just had 0 accel pump. Meaning it just wouldn't squirt a single drop out of any of the pumps furthering my idea that I just needed to take off the carb and see what's going on.

I pulled it and blasted everything with air and confirmed airflow through every hole I could easily check. The accel pump was clogged in the center hole of the 3 in a horizontal line on the block that sends air signal to each of the 3 throats. Not sure proper name of that block I am referring to, but if you rebuilt them you'll know what I'm talking about. I used some compressed air in each of the brass little holes at the perimeter of the block and something shot me in the face from the middle hole when blasting which made me certain that was my problem.

I also noticed that one of my new needles was sticking and that was evident because the float was extremely low with fuel. I replaced with an older one that I took off when I rebuilt them and then reassembled that bank with the new carb after doing some baseline settings once again.

Turned on ignition and let the pump fill up the bowls and then gave it a few pumps and watched the pump nozzles to see if they squirted any fuel down (they did) and it started pretty much right away. My idle issue was resolved and it ran infinitely better than the prior attempt from the other week.

With all of that being said, I need to go back and now tune it a little better. My current issues is that 1 bank is running cooler (richer??) than the other because its backfiring out of the exhaust more than it should even when holding a rev at around say 3k. Need to start researching more to see what might be going on there. I have my synrometer and that seems to be reading a lower value than it should at around 2. From my quick searches people are usually up around the 5 mark? I'm not sure how to increase that without changing the idle speed drastically so I need to spend a good portion of my night looking at videos to see what might be going on there.

Tomorrow I have the day off so will go back to it to keep working on everything. One goal is to get my tach to work with a unit I got online that amplifies and changes the signal to work with my MSD box and my 4 cylinder tach. I'd like to get that up so I know where I am at on the gauge.

[Cfletch]

Hey friends, bit of an update for you all:

I've been sick/busy with work so slow progress on the car from the past weeks. I was able to get the regulator plumbed and set it for 3.5PSI to carbs and also mounted the gas tank. I tried to start it the other day and it just refused to start so I broke out the either and it fired off right away then ran and barely held an idle so I was lost as to what had happened. If seemed like the passenger side bank just did not want to run well at all and I babied the throttle to keep it alive. I also noticed the car just refused to go back down to a proper idle even when I was not babying it.

Come back to this weekend, I decided I needed to just pull that carb. Main reason was I wanted to blast some compressed air through everything once again because my idle mixture screw on cylinder 1 didn't seem to impact the engine at all so I figured it must have been clogged. Additionally I noticed that the same carb just had 0 accel pump. Meaning it just wouldn't squirt a single drop out of any of the pumps furthering my idea that I just needed to take off the carb and see what's going on.

I pulled it and blasted everything with air and confirmed airflow through every hole I could easily check. The accel pump was clogged in the center hole of the 3 in a horizontal line on the block that sends air signal to each of the 3 throats. Not sure proper name of that block I am referring to, but if you rebuilt them you'll know what I'm talking about. I used some compressed air in each of the brass little holes at the perimeter of the block and something shot me in the face from the middle hole when blasting which made me certain that was my problem.

I also noticed that one of my new needles was sticking and that was evident because the float was extremely low with fuel. I replaced with an older one that I took off when I rebuilt them and then reassembled that bank with the new carb after doing some baseline settings once again.

Turned on ignition and let the pump fill up the bowls and then gave it a few pumps and watched the pump nozzles to see if they squirted any fuel down (they did) and it started pretty much right away. My idle issue was resolved and it ran infinitely better than the prior attempt from the other week.

With all of that being said, I need to go back and now tune it a little better. My current issues is that 1 bank is running cooler (richer??) than the other because its backfiring out of the exhaust more than it should even when holding a rev at around say 3k. Need to start researching more to see what might be going on there. I have my synrometer and that seems to be reading a lower value than it should at around 2. From my quick searches people are usually up around the 5 mark? I'm not sure how to increase that without changing the idle speed drastically so I need to spend a good portion of my night looking at videos to see what might be going on there.

Tomorrow I have the day off so will go back to it to keep working on everything. One goal is to get my tach to work with a unit I got online that amplifies and changes the signal to work with my MSD box and my 4 cylinder tach. I'd like to get that up so I know where I am at on the gauge.

[930cabman]

sounds like a victory, or getting close to it. These carbs can be fussy, but when dialed in (or close) are fun. The passages in these carbs are tiny and when clogged will wreak havoc

[gereed75]

The airflow at idle is very dependent on idle speed. If yours is a bit low that could account for low flow readings.

One of my cautions on these is to invest in a really good pressure gauge. I never trust the $19.00 cheapo. Not worried so much about accuracy, more concerned with failure and then leaking and then bad stuff happens.

Also highly recommend a wide band O2 sensor. Not saying it is absolutely necessary but sure does simplify/streamlines the process and avoids any uncertainty

[gereed75]

The airflow at idle is very dependent on idle speed. If yours is a bit low that could account for low flow readings.

One of my cautions on these is to invest in a really good pressure gauge. I never trust the $19.00 cheapo. Not worried so much about accuracy, more concerned with failure and then leaking and then bad stuff happens. Alternatively- use the gauge to set up the system, set the regulator, get it all right and then just remove the gauge. Eliminates a potential leak point.

Also highly recommend a wide band O2 sensor. Not saying it is absolutely necessary but sure does simplify/streamlines the process and avoids any uncertainty

[930cabman]

I generally get about 4 - 5 on my snail when adjusting to idle speed, 950 or so rpms

[Cfletch]

My goal today was to do the tach stuff so I could see what my RPMs were at and do some more tuning, but that took a turn and instead I pulled the pedal board for rebuild and attached the new throttle cable. Also picked up my 911 front suspension from storage and will need to look into rebuilding all of that. No movement for engine today.