[GeoffSprintGT]

Hey guys, found a nifty part which sounds like it would be much better than the rubber equivalant that currently rests inbetween my dellortos and the engine.
Aluminum Inlet Manifold extender link

Are there any con's to switching to a solid aluminum inlet manifold extender as opposed to having the rubber carb mountings? Wouldn't the rubber carb mountings have more flex in them, and is that flex needed?

 

[Seinista]

in a well running engine no problem!
I have them too.
In a rough running engine you might possibly have float bowl problems, ie frothing gasoline, giving an incorrect float bowl level, but haven't heard of that yet.
No more problems with rubbers ever!

 

[papajam]

The rubber carb mounts serve two purposes; to isolate the carbs from engine heat and engine vibration. With the proper carb support pieces installed (airbox or plate and a support rod), there is very little flex.

 

[Alleggerita]

Extending the intact tract may increase both torque and horsepower - the aluminum inlet pieces are available in standard and extended length. However, lenghtening the intake tract may also cause problems fitting your airbox, fitting air horns and usually requires adaptations to the throttle linkage. Autodelta did the lenghtening bit on the Alfetta GTV Rally (4 cylinder w/ wide angle head).

 

[robtechno]

I use them on my Alfetta 2.1 engine. There is no need if your engine is not tuned. For a tuned engine it's better to have the Aluminum ones as you have no wear on the rubbers. You don't need the support for the carbs from the engine mount up. And you can use rampipes without an support plate. It all saves weight and they are built for race engines. It would be bad to lose a race because of a rubberinlet manifold. You have to check the rubbers after every trackday and when do you have to replace them. So to solve this problem, just buy them

 

[Clayton105]

The rubber mounts are good for at least ten years in normal use. In my experience, I would hardly call them "troublesome". I have worked on Alfas on and off for around 20 years and never seen a failure of an engine directly attributed to the rubber mounts. For that matter, I have rarely seen in-service leakage. Usually they are replaced for asthetics when they are old and cracked during a rebuild.

The race car that I am most recently involved in runs the rubbers and 50 mm extensions. To me, this is the best combination. As I have said many times before: Mr Alfa usually had a reason for doing things, and unless I have a very good reason to depart from a fundimental design philosophy, I tend to not make these changes.

I would agree with papajam on this one.

Robtechno: How is the 2.1 capacity achieved in your Alfetta. Years ago, I heard that Autodelta used to supply a 2.1 crank (and a certain well known Australian racing car driver won his class at Bathhurst with one of these in his car). I know that the late 155 TS cranks are 90 mm stroke, but even this when combined with an 85 mm bore only results in a ~ 2050 CC engine. But then I suppose you can offset grind etc....

Now if I really wanted to build a cheater engine for my mate!

 

[Seinista]

2.1 standard crank, bored out liners and Cosworth pistons. Used to be done a lot here.
not anymore due to excess price of pistons.

 

[Alleggerita]

The race car that I am most recently involved in runs the rubbers and 50 mm extensions. To me, this is the best combination.

105 or 116 chassis. What filter/trumpets do you use w/ that set up? And if 105, how do you deal w/ limited clearance on the inner fender?

 

[harryf]

When I fitted ally inlets for carb mounts I was cautioned not to overtighten and to tighten them to a specific torque setting as the O rings were oversized, thus the O rings provided the antivibration protection.

Seemed to work okay on the spider for years.

 

[Clayton105]

Sorry, I know this is off topic, but I am fascinated! As far as I am aware, the largest stroke crank ever in a Nord derivative was the 90 mm one in the 155/164 TS.

So: I'm still confused: Is this "2.1" crank an Alfa item that I have never heard of, or an special Autodelta item?

84 x 95 = 2106
85 x 93 = 2111
86 x 90 = 2091
87 x 88.5 = 2104

See where I am going? As far as I know, boring standard liners above about 85 mm is not recommended, and you need a monosleeve to go big enough to achieve around 2.1 on a 88.5 mm crank!

 

[Clayton105]

105 or 116 chassis. What filter/trumpets do you use w/ that set up? And if 105, how do you deal w/ limited clearance on the inner fender?

Its a 1972 105 2 litre. The trumpets are very short (about 20 mm) and it is a very tight fit getting the filter (usual type generic filter for DCOEs) on. You have to flex the carbs up on their mounts (and I dont think we run the brace). Could not be done without the flexible mounts. The car runs in Australia group NC (historic touring cars).

 

[mad11]

Inlet extenders are also available in this version. different length 20-45mm and diameters 40/45mm. increase torque and power

tuningparts

before
1600 std 89.000 km
8.8:1 comp. ratio
cams: std.

after:
1600 std 89.100 km
10,4:1 comp. ratio
cams: inlet 284° outlet std

Extenders 25 mm

greez mad11

 

[Clayton105]

Nice graphs, but if you want to prove anything show us an identical engines with and without extenders. Or even better, with different length extenders. May be, that with a full race engine, they do nothing....

I am not doubting that they work, just saying the above is quite meaningless unless the testing is done scientifically.

Someone out there: Am I going to get an answer on these mysterious 2.1 cranks/engines?

 

[robtechno]

I have to quote Seinesta from a link above.
"2.1 standard crank, bored out liners and Cosworth pistons. Used to be done a lot here. not anymore due to excess price of pistons."

I will ask the guy who sold the engine to me maybe he knows.

All the best
Rob

Nice graphs, but if you want to prove anything show us an identical engines with and without extenders. Or even better, with different length extenders. May be, that with a full race engine, they do nothing....

I am not doubting that they work, just saying the above is quite meaningless unless the testing is done scientifically.

Someone out there: Am I going to get an answer on these mysterious 2.1 cranks/engines?

 

[robtechno]

A fixed extension will do not much for your engine unless it's variable like the older Formula One engines from some years ago. A longer intake for more Torque and a Shorter for more topspeed. I am not shure if it's this way or the otherway around but that's the only solution that works. by the way it's banned in F1 as are many high tech solutions.

Nice graphs, but if you want to prove anything show us an identical engines with and without extenders. Or even better, with different length extenders. May be, that with a full race engine, they do nothing....

I am not doubting that they work, just saying the above is quite meaningless unless the testing is done scientifically.

Someone out there: Am I going to get an answer on these mysterious 2.1 cranks/engines?

 

[Clayton105]

I suppose what I was saying is that I would love to see a comparison of the effect of varying the length of the intake on engines in different states of tune.

The effect you describe above is well recognised, and the contra rotating barrels in the variable intake system on BMW V8 engines being probably the most elegant I have seen.

Whether a longer extension makes a difference on a full race engine where the torque is very high in the rev range is the question or is this mod going to be far more of benefit an rally type engine.

I suppose for a given capacity, RPM, cam timing and inlet tract diameter, there will be only one perfect length of inlet tract. One can't have it all, unless you have the above.

However, what I would l love to see is say: 3 Alfa engines (standard, rally and full race) dynoed several different lengths of inlet tract: a large matrix of combinations and results to compare and guide the selection of inlet tract length for you particular application. That is what I mean by science.

Having said that, I have never had the time and money to do this. I just build engines and recommend changes using common sense and the best of my understanding.

 

[o. nart]

please here the same config.
with (black) and without (red) extension.

 

[GeoffSprintGT]

That new graph does seem more convincing for the aluminum extenders. Do they need to be run with trumpets in order to achive those kinds of results?

 

[GeoffSprintGT]

So are these results with trumpets? My fear with running trumpets on my car is that all kinds of dust and crap are going to get into the engine that way, its very windy here in Cape Town. :/

 

[genericwood]

Geoff, to answer your original question. On anything other than a dedicated race car, the aluminum extenders are of very limited value. And even on the race car, you would really have to do a lot of testing to determine what the right length is for a particular set up. The graphs shown in this thread are not showing performance gains simply from putting on the extensions. They WILL NOT increase max torque by 30% as the graphs would suggest! I'm not one of those "the factory knows best" guys. But I am very confident the factory would have lengthened the intake tract if there were obvious performance gains. Many of us have 200hp 2L race engines running with the stock type rubber mounts!

As far as trumpets go, they can be of value. However, I would not run a street car without a filter. You will be grinding the valves way too frequently. Running trumpets with "filter sock" will usually hurt power more than help it. If you want to run trumpets, you need to find a cold air box that will bring in the relatively cool air from in front of the radiator, not the hot air in the engine compartment. A compact air box plumbed to a free flowing cone filter in front of the radiator is a good approach. But remember, the factory airboxes are pretty good!

Erik