Installing preheater tubes on HPMX manifold

[islandtime]

I have a 40 HPMX that runs fine other the the icing due to the preheater tubes not being installed. What is the best way to install these? I assume this is best done with the manifold already installed.

1. The tubes seem to be larger than the holes in the manifold - Will I need to ream or drill this out a bit?

2. I assume the tubes just tap in but the way they curve there isn't a good place to hit to tap them in. How should this be done?

3. The two sides do not connect. Should the area between the 2 be drilled out so that they can connect?

[Juanito84]

Is this what you are talking about?

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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[islandtime]

Yes, that is exactly what I have.

[busdaddy]

I encountered one of those cheapo EMPI manifolds a couple years ago that wasn't drilled through as well (this was on a running car), you'll have to finish the job yourself. As for the tube fit how about if you heat the aluminum section first?

Regardless once the heater tubes were finally in and the halfassed job Sum ting wong mfg. ltd. started was finished up it still didn't get very warm, idled like ass as well.
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[bugguy1967]

If they don't fit as is, I'd ream them to the same size as the O.D. Of the tube, then heat the manifold and slip them in. I wasn't aware that the tubes needed to connect to each other. What's the reason?

[busdaddy]

[mikedjames]

This looks like a solution inheriting all the problems of the progressive but doing it with a bigger carb, and an even shorter section of heat riser from the exhaust actually in contact with and heating the manifold as the gas flows between No2 and No4 exhausts or one exhaust and downstream in the header if it is done properly.

If you look at the pictures of the Beetle set up to go to the South Pole, they actually wrapped the horizontal section of the heat risers and the bottom of the inlet manifold together with something that looks like asbestos.
These days fibre glass exhaust wrap may be a healthier approach.

And there may need to be holes drilled in the exhaust header below the heat riser flanges on top of the header.
Certainly my stainless header had flanges but no holes for the exhaust gas to enter the riser tubes. An afternoon with a Dremel tool cured this.

You may also need an air cleaner setup with a hot air takeoff from the cylinder head to keep the top of the manifold warm by feeding it hot air when needed.

Or do all your driving in the hot sunny desert ..

[Juanito84]

1. The tubes must be connected for exhaust flow.
2. Aftermarket mufflers/headers don't provide a high-low pressure heat riser ports without modification. So you need to modify the muffler/header to get exhaust flow.
3. Better contact would be better. Can you cast aluminum onto it? Or maybe wrap the thing in copper wire, then an insulator?
_________________
If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[islandtime]

So far, the carb has been easy to tune. I did have to play with the jets but that is expected even with the original Webers. It idles fine once warmed up and stays that way until I go to test drive it and really get on it, that is when the icing starts. As long as I am staying in the throttle it runs fine. When I slow down for a turn or to make a complete stop is when it stalls. I can easily restart the car and it runs as long as I keep it revved up but will not idle on its own.

The manifold just below the carb will get ice cold and condensate. It'been upper 90"s here with high humidity. I attribute the stalling to carb icing since it will idle fine once warmed up but not after really getting on it.

I hate to have to take everything back apart buy that seems the only way to really get the risers installed. I have read other post that make it sound like riser holes on the CB Performance manifolds are a bit loose and they recommend using green locktite to fill the void and seal them. This sounds like it would make getting the manifold and risers properly aligned while installing alot easier.

[busdaddy]

On the one I was dealing with I had to plug the hole between the intake runners down in the bottom of the cast part to improve the idle (still wasn't great but all 4 fired most of the time) and bolt a thick aluminum plate to the back side sealed with red silicone and divert (drill) the exhaust up through the cavity created between the plate and the V between the runners (regretted drilling out the middle when I had to replug it for that endeavour). It helped alot, I never got to finish dialing it in jet wise as the customer threw in the towel and had me install a 34 PICT3 with bigger jets, solved all the issues and went like stink on an 1835. The aircleaner heat would have helped alot but this was in a bus and I barely had room for short velocity stacks and an aircleaner.
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[islandtime]

The intake runners in this manifold are isolated so no worries there. The car came with an old manifold (bugpack??) that had the passage between the intakes. It also had no heat risers and was taller. The shorter, isolated EMPI manifold actually made thins better.

I'll get the risers installed and let you all know what the verdict is.