amazon twin down pipe conversion. Do it

[wassinkh]

This might not be interresting to most people who run their cars on petrol, although???
My car runs on Liquid gas (LPG), with twin carbs.
Two weeks ago, when doing some maintenance on the 133GT, I accidentally blocked the hose from the air intake just a bit, which caused my car to stall.
Then I pulled the tapered air intake hose from the airfilter housing box (I have the same box as used on the 140 series.)
Suddenly the idle speed changed to 1500 rpm. So I thought that the mixture might have been too rich, read: 'the air supply too low', which expained the high fuel consumption, compared to my 122S.
So I adjusted the idle speed and mixture and started driving without the hose.
My fuel consumption dropped with 25% and performance went up by 10%.
Today I fitted a straight hose, which ends at the hole in the front, next to the radiator, because I want the carbs to get cool air, instead of hot air from the motor compartiment.
It's all so logical, but I stubled on it by coincidence.
To test it, I tried it with another Amazon(121), by blocking the hose a bit, but what made my car stall, made no difference with that one.
Also logical, because it has only 1 carb, so it needs less air.

[classicswede]

The reason the engine stalled is over rich fuel mixture.

What I would imagine is happening you the venturies used in your lpg mixers are two small and removing the air restiction of the pipe has feed up the airflow that they are blocking. I always prefer to run with performance type filters.

[parkesie]

Originally Posted by classicswede

I have found the 4 branch manifold improves both low and high rpm running on the amazon. It also reduces the popping on lift off.

Who manufactures / sells twin and 4 pipe sports manifolds?
I am finding them difficult to locate.
parkesie

[classicswede]

Any preferance to mild or stainless?

[dride24]

I read this thread re: twin pipe conversion and wondered how it might be relevant to my own situation. I have a '66 Amazon estate with B18 w/stock single pipe manifold. The exhaust manifold has deteriorated to the point where it no longer clamps properly to the block and leaks slightly despite new gasket and rigged clamping mechanism. I have been having trouble finding an exhaust manifold used in good shape or new. Are new replacements available? Are there new twin pipe manifolds available? What else is required? Different first exhaust section? I recently replaced the whole exhaust system with a stock type system. Not sure that I want to replace it all again.
Thanks for any info.

[Clan]

cant you use a 140 B20 manifold and twin downpipe ? It may need altering a little ..

[amazondean]

Are you on single or twin carbs. If you are on a single carb I think i may have a manifold i could sell you. I do have a twin downpipe front exhaust as well i believe.

That is all you need for the conversion

[dride24]

Dual carbs. Seperate intake and exhaust manifolds.

[Derek UK]

The best combination is the earlier aluminium twin intake with a later twin down pipe exhaust. The fitting at the head is the same for B18 and B20 but later manifolds are combined in one cast iron casting. They all interchange but the one with the butterflies in is best avoided. However, it only takes a few passes with a grinder/sawzall/hacksaw to cut out the inlet section, leaving you with an exhaust that you can use with the ali inlet. You will likely have to make up some stepped washers to go on the studs so that you get even pressure on the two parts. Nuts should NOT be ultra tight as the manifolds need to be able to move just a fraction as everything heats up. After you've cut the inlet out it's a good idea to have a machine shop face off the gasket to head mating surface to get rid of any bowing or distortion. You might want to check the one you have now for this problem. You'll only need to change the front pipe if you have a standard system but changing it all over to a Jetex/Simons system would give you a noticeable increase in power especially when you are making the jump to the twin outlet exhaust which adds 3-4bhp anyway. Replace the manifold studs before fitting. A support stay between one of the bellhousing bolts and the front exhaust is useful if not already fitted as it takes some of the strain off the mainifold. The F.I. exhaust manifolds can also be used if you can find one.

[Birnie F]

Try www.IPDUSA.com
There you will find 4-2-1 exhaust manifold and complete exhaust systems.