Alfa Romeo Forums banner

1 - 20 of 42 Posts

·
Registered
Joined
·
218 Posts
Discussion Starter #1
I have a pair of 48IDA's I'm trying to sort out....figured there'd be some excellent advice from some Weber gurus here...but before I get too involved here and upset anybody, I thought I'd ask first...

Thanks,

Jim
 

·
Premium Member
Joined
·
2,811 Posts
Remove them from their current mounting and place them on top of the hood of an Alfa.

That'll be close enough. :D
 

·
Registered
Joined
·
9,287 Posts
I have a pair of 48IDA's I'm trying to sort out....figured there'd be some excellent advice from some Weber gurus here...but before I get too involved here and upset anybody, I thought I'd ask first...

Thanks,

Jim
I see no problem -- especially if it's a question we all can learn from.
Give it at try!
 

·
Registered
Joined
·
218 Posts
Discussion Starter #4
Well....alright...here it goes...
The engine they are on is an air cooled VW, albeit highly modified. It's approx 2200cc (94mm bore x 78mm stroke), 9.2:1 compression ratio, heads flow about 185-190 cfm @ 28", cam is 263' @ .050", 1.75" 4-into-1 merge header into 2-1/2" Magnaflow muffler. MSD 6AL ignition, NGK D7EA's gapped @ .036", I drive it semi daily on the street on 91 octane.
The carbs are set up as such:
40mm venturi
170 main
175 air corrector
F2 emuls. tube
65 idle jet in 120 holders (air bleed)
2.00 needle
4.5 aux venturi
floats set as per Weber
3.5psi @ idle fed by Holley red pump, AN6 lines

I'm having a couple of issues. First I am running into hard starting (engine will crank but not fire) after engine has come to temp and then I shut it off, and then try to restart 20 min later. Once it starts, it idles poorly and there is a "hole" in progression...between idle and mains, only after hot start. Anybody know what could cause it?
Second, I'm having what I think are lean issues once into mains and air corrector segment of powerband....3700-4000 and up.....especially steady state on highway. After a few plug checks, it seems plugs aren't getting much color to them....pretty white after hard run and clean cut. Looking thru magnifying glass....I do see some grey specks...peppering....to me meaning lean and molten piston on my plugs. But with a big 170 main?
Some sources say with F2's that air correctors need to be smaller than mains....anybody agree with this?
And has anybody set up a homemade AFR meter using 3 wire Bosch 02 sensor and digital voltmeter? I think I might try this and see what millivolts I come up with on freeway.
Thanks for any comments......sorry it isn't Alfa related.
 

·
Registered
Joined
·
3,807 Posts
Well....alright...here it goes...
The engine they are on is an air cooled VW, albeit highly modified. It's approx 2200cc (94mm bore x 78mm stroke), 9.2:1 compression ratio, heads flow about 185-190 cfm @ 28", cam is 263' @ .050", 1.75" 4-into-1 merge header into 2-1/2" Magnaflow muffler. MSD 6AL ignition, NGK D7EA's gapped @ .036", I drive it semi daily on the street on 91 octane.
The carbs are set up as such:
40mm venturi
170 main
175 air corrector
F2 emuls. tube
65 idle jet in 120 holders (air bleed)
2.00 needle
4.5 aux venturi
floats set as per Weber
3.5psi @ idle fed by Holley red pump, AN6 lines

I'm having a couple of issues. First I am running into hard starting (engine will crank but not fire) after engine has come to temp and then I shut it off, and then try to restart 20 min later. Once it starts, it idles poorly and there is a "hole" in progression...between idle and mains, only after hot start. Anybody know what could cause it?
Second, I'm having what I think are lean issues once into mains and air corrector segment of powerband....3700-4000 and up.....especially steady state on highway. After a few plug checks, it seems plugs aren't getting much color to them....pretty white after hard run and clean cut. Looking thru magnifying glass....I do see some grey specks...peppering....to me meaning lean and molten piston on my plugs. But with a big 170 main?
Some sources say with F2's that air correctors need to be smaller than mains....anybody agree with this?
And has anybody set up a homemade AFR meter using 3 wire Bosch 02 sensor and digital voltmeter? I think I might try this and see what millivolts I come up with on freeway.
Thanks for any comments......sorry it isn't Alfa related.
How hot are your manifolds and carbs after it is warmed up? I had 44 IDFs on my 2084cc Beetle and the manifolds used to get very hot and heat up the carbs, especially after standing or idling and it caused similar symptoms because the fuel in the bowl was almost boiling. I think they need some sort of insulating material between the carbs and the manifold or the manifold and the head. You could also direct air around them somehow. I never got round to solving that one but my brother, who has the car now might one day. That car had an asymetric cam, dry sump, Okrasa crank, big valves etc and easily pulled 8,000 RPM. Sorry but I can't remember the details on the jets etc.
 

·
Registered
Joined
·
9,287 Posts
I think fuel temperature is indeed worth looking at. Fuel injected Triumph TR6s were notorious for not starting when hot because there were gas bubbles in the fuel lines from the fuel pump running hot (cooling fins on the fuel pump solved that problem). Have a close look at anything that can create heat transfer to carbs, fuel lines and fuel pump.

I guess warm or even hot fuel would change the AFR towards lean (fuel would have more volume for same energy). If possible, see if you can temporarily supply fuel from an alternate source (e.g. a canister).

When you put in an AFR meter, I'd suggest to make this a fixed installation with a 5-wire sensor (because the reading is suposedly more accurate than with 3-wire sensors). This comes in handy for proper tuning at all speeds and for all temperatures (and who knows, maybe you go megasquirt some day).
 

·
Registered
Joined
·
296 Posts
Once it starts, it idles poorly and there is a "hole" in progression...between idle and mains, only after hot start. Anybody know what could cause it?
Are we talking about an off-idle stumble between idle and the progression circuit? Or a flat spot between the progression and main circuits?
 

·
Registered
Joined
·
218 Posts
Discussion Starter #8
Are we talking about an off-idle stumble between idle and the progression circuit? Or a flat spot between the progression and main circuits?
It pulls off idle ok, not as crisp as when cold, but if I open throttles (and this is after "hot start") and try to accelerate, it will nose dive around 2700rpm, only if throttles are open at pretty wide angle.
 

·
Registered
Joined
·
9,287 Posts
Maybe a couple of silly question:
Is the car a beetle or another car with a Volkswagen engine or chassis?
If it's a beetle, do you have the engine hood closed (or half open or removed)?
 

·
Registered
Joined
·
1,095 Posts
I had a different but perhaps related issue with my 1600 Duetto. It had a mechanical fuel pump and the carbs were jetted correctly, but I was getting symptoms of lean conditions at certain times because the mech. Fuel pump wasn't keeping the bowls full enough. $30 Electric fuel pump = end of problem. 2.5 - 3 lbs. of fuel pressure. The stumble? Accelerator jets and circuit good and clean? Good luck -Clark
 

·
Registered
Joined
·
416 Posts
Along with Reudi's question, if the engine is in a full-bodied VW, you might consider these ideas if fuel temperature is a problem:

Is all of the engine sheet metal in place?

Do you have an external oil cooler? It has been a while since I was into hot-rod VWs, but it used to be popular to mount an external oil cooler across the air intake on the front of the fan shroud. I always thought that this was a mistake because of the heat that would be added to the intake air and also kept in the engine compartment. I mounted mine on top of the transaxle.

Is the fuel delivery system (lines and pump) picking up heat from the case or elsewhere?
 

·
Registered
Joined
·
218 Posts
Discussion Starter #12
Along with Reudi's question, if the engine is in a full-bodied VW, you might consider these ideas if fuel temperature is a problem:

Is all of the engine sheet metal in place?

Do you have an external oil cooler? It has been a while since I was into hot-rod VWs, but it used to be popular to mount an external oil cooler across the air intake on the front of the fan shroud. I always thought that this was a mistake because of the heat that would be added to the intake air and also kept in the engine compartment. I mounted mine on top of the transaxle.

Is the fuel delivery system (lines and pump) picking up heat from the case or elsewhere?
Yes this engine is in a '67 Beetle. It has all of the factory cooling sheetmetal in place including a stock VW late fan housing, factory cooler, and a dual-fan Setrab cooler mounted next to transaxle. The fan intake is open, as a stock VW is. The bottom of the decklid is propped open about 4" to allow more air.
The fuel line is routed through floorpan tunnel, away from heat. The regulator is mounted in front of fan housing, on firewall. Pump is up under fuel tank, in nose of car (cool).
Did some very rough tests tonight with 3-wire oxy sensor and digital voltmeter....under acceleration, things look lean....idle and part throttle cruise, they look to be about 13-13.5:1
If I really belt it hard and run it up to 6500 or so, it seems it is running out of fuel.....the bowls. What's the trick needle valve these days? Grose ball valves? Stock Weber? The glass ball needle valves?
Thanks again,
 

·
Registered
Joined
·
9,287 Posts
If I really belt it hard and run it up to 6500 or so, it seems it is running out of fuel.....the bowls. What's the trick needle valve these days? Grose ball valves? Stock Weber? The glass ball needle valves?
Thanks again,
What you describe seems to relate to insufficient fuel supply, not a problem with needle valve and or floats or the carb per se. Possible culprits for insufficient fuel supply are (in order of likelyhood): fuel filters, pump capacity, fuel lines too small.

Given what you describe, the first thing I would try is creating and alternate, temporary fuel supply, e.g. a portable 2-5 gallon tank with fuel filters ahead of twinned fuel pumps that feed the carbs (or one pump per carb, if this is easier) and see if the problem changes or disappears.

BTW: Do you have a fuel pressure gauge you can use to see if the fuel pump craps out when it's warm?
 

·
Registered
Joined
·
3,807 Posts
The original fuel tap/outlet on your tank might be on the small side. If I remember correctly we put one from a type 3 on mine because it had a larger diameter outlet pipe. Have you taken the outlet unit off and checked that it is clean and unobstructed? As I said my car ran easily to 8,000 RPM once we fitted dual valve springs. I too had an electric pump up front and the needle and seats etc were stock 44IDF. Before that it was only pulling 6,000 due to valve bounce. The springs that were in it at that time were single, supposedly high performance ones. The dual springs made an incredible difference.
 

·
Registered
Joined
·
9,287 Posts
The original fuel tap/outlet on your tank might be on the small side. If I remember correctly we put one from a type 3 on mine because it had a larger diameter outlet pipe. Have you taken the outlet unit off and checked that it is clean and unobstructed? As I said my car ran easily to 8,000 RPM once we fitted dual valve springs. I too had an electric pump up front and the needle and seats etc were stock 44IDF. Before that it was only pulling 6,000 due to valve bounce. The springs that were in it at that time were single, supposedly high performance ones. The dual springs made an incredible difference.
Did you notice any difference in the performance when the engine was cold vs. hot?
I'm guessing valve spring bounce would be RPM related and not prevent an engine from starting when hot.
 

·
Registered
Joined
·
3,807 Posts
It is 7 or 8 years at least since I drove the car but the rev thing and the heat related issues were two different things. We didn't realize that the fact that it revved very quickly to 6,000 and then choked was due to valve bounce because we thought the springs were fine. We were looking for fuel related causes like pressure and flow etc. From memory the heat in the carbs caused flat spots, trouble idling and difficulty in starting. It was more of a problem in traffic than on the open road or drag racing. The carby heat wasn't due to the engine running hot because according to my cylinder head temperature gauge it was OK and it never felt any hotter than a normal engine. I am sure it was due to heat soak through the short cast alloy manifolds. As I said, I didn't come up with a solution at the time. My youngest brother has the car now and is rebuilding it gradually and will have it going better than ever I should think. It was never really daily driver material but good fun. It is a 1956 Beetle and my mother christened it "Big Bertha".
 

·
Premium Member
Joined
·
291 Posts
It pulls off idle ok, not as crisp as when cold, but if I open throttles (and this is after "hot start") and try to accelerate, it will nose dive around 2700rpm, only if throttles are open at pretty wide angle.
Well, I have the same performance with a '65 Spider Veloce (totally stock setup for Webers, cams and mechanical fuel pump with stock filter/ pressure regulator). The flat spot around 2700 rpm has been there for the 10+ years I've had the car. Carbs / jets have been cleaned at least once, synch is dead on, float levels per std. At times I think there could be an electrical issue (changed the coil lead once which helped a lot, for a while). Cleaning the contacts on the coil and making sure the junction between the leads and connectors to the coil are tight (no frayed wires, etc.) will also help. But I still have the 2700 rpm stumble.:confused:
Jim
 

·
Registered
Joined
·
3,807 Posts
My 1984 GTV 2 litre stumbles at around 2300 RPM and it has Dellortos. I improved it a lot when I disconnected the fuel breather system in the boot and loosened the cap a bit and readjusted the mixtures, but I haven't managed to eliminate it altogether yet. The trouble is that it corresponds to city speeds. I plan to check the ignition leads etc at some stage. I haven't stripped the carbies yet because I am not sure it will help at this stage and the kits are $50 each. Any ideas on this would be helpful for me too.
 

·
Registered
Joined
·
416 Posts
Yes this engine is in a '67 Beetle. It has all of the factory cooling sheetmetal in place including a stock VW late fan housing, factory cooler, and a dual-fan Setrab cooler mounted next to transaxle. The fan intake is open, as a stock VW is. The bottom of the decklid is propped open about 4" to allow more air.
The fuel line is routed through floorpan tunnel, away from heat. The regulator is mounted in front of fan housing, on firewall. Pump is up under fuel tank, in nose of car (cool).
It looks like you have the cool fuel thing handled, Jim. I'm not much of a Weber carburetor tech, so I'll just sit by and watch :D

Good luck!
 

·
Registered
Joined
·
218 Posts
Discussion Starter #20
The original fuel tap/outlet on your tank might be on the small side. If I remember correctly we put one from a type 3 on mine because it had a larger diameter outlet pipe. Have you taken the outlet unit off and checked that it is clean and unobstructed? As I said my car ran easily to 8,000 RPM once we fitted dual valve springs. I too had an electric pump up front and the needle and seats etc were stock 44IDF. Before that it was only pulling 6,000 due to valve bounce. The springs that were in it at that time were single, supposedly high performance ones. The dual springs made an incredible difference.
Back in 1991, when I first went to 48IDAs, I had to upgrade entire fuel system....3/8" outlet on bottom of tank, 3/8" line to Holley pump, AN-8 back to carbs. Earl's AN6 banjos to carbs.
 
1 - 20 of 42 Posts
Top