Where's the hesitation from?

I'll second that opinion.Ask Rocky how well that works.Rite Rok?LOL.Steve

Is it really a vacuum problem of velocity problem? Not picking nits, but just asking. I know its sort of the same thing practically speaking.

Chris

There's plenty of vacuum, really. Is the gas falling out of suspension and wetting the manifold at that flow rate cause the travel is so far and the temp too low? The guys at the buggy hut are shocked I want to go to a .090 primary idle jet. Something must be wrong... very wrong...

I spoke to the muffler guy who put my O2 bung in yesterday. He says, I think accurately, that because of the free-flo exhaust there's no back pressure anymore so gases aren't forced up the pre-heat tubes as it was before. A couple other people I spoke with today say veedubs are very sensitive to manifold temperature (in the stock config).

The muffler guy, very knowledgable, says if he blocks off one and routes it like stock so there's a flow direction happening, there still isn't any back pressure, so it won't help. Hmmm...

So the idea hit me on the way home. How about taking a round piece of steel like the punch-out coins from an electrical box, cut it in half and weld one inside #2's exhaust outlet so flow is forced up the pre-heat, and on #4 turn it around so flow is pulled down. The idea seems right. If the flow is too much, it can file it down. Might melt the piss out of it..

Will try it, and it's cheap, too :) Will post my results in a couple days.

We (I) need some more expert opinions. I know a number of haul-butt, all-out Baja people use a big single carb on a big manifold (perhaps because it's easier to filter?), but they run at high RPM. I don't know any street drivers that use the same but.... dunno. I had no luck, but I'm an idiot.

^ -- not

Grammar error. Don't put yourself down..

When one changes the design aspects of an engine in search of more power/torque/etc.. the balance of how the physics of the parts interact will change. More free-flow exhaust == less back pressure for the pre-heat. Do I know for sure this is causing my idle jet issue? No, but I'm willing to experiment to see. There's fun for me in this frustration somewhere..

scientific method: hypothesize, prove, conclude, repeat.

In article , David Gravereaux wrote: get you more vaccum at low RPMs where your hesitation is.

Instead of talking about vacuum, let's talk about air/gas velocity. There can't be enough to have an efficient charge. If you look at some of the other similar big-carb with big manifold brainstorms that have been put out there off and on for the past forty years you can find some that get all of 9 MPG. And that's not a typo.

Sure. So you are trying to create a very hot spot to cook the gas that's precipitating on the manifold walls. Sounds like too much trouble. You may as well go with duals and be done with it.

As compared to the stock muffler, things are cooler and it didn't have a hesitation problem then. Go your route, I'll go mine.

An electrical box for the coin is what? about $1.50 or search a construction site for free.. How much for the dual carb setup? DIY is good, really. If the manifold needs to be hot, so be it..

I'm all for experimentation. Who knows; perhaps you will be able to do something nobody else has for the last forty years.

My nickle is on the assertion that you can't get it hot enough to make a difference. It will be hot, then cold, cool, hot ... all over the place. Then it will all choke up with soot and crap and it's time to remove and clean out. Sheesh. You may as well be stoking a coal-burner. But, like I said, maybe you will make it work or settle in for 12mpg and be happy.

I've been know to do that ;)

Say, what were you using for exhaust with the single 44 IDF? Some free-flow headers? What temp was your carb base after some highway cruising?

Are you running a 4-1 header? The thing is to create enough vacuum on the low pressure side of the prehat pipe, plumb it straight into the merger point(collector) from behind. This will more or less duplicate the stock setup, which picks up the hot exhaust just outside cylinder #2 and dumps it close to the exit of one of the peashooter flanges.

J.

Yup.

For simplicity, I decided to use some steel flaps (half a coin from an electrical box) I'll weld just inside #2 and #4. #4 will push and #2 will pull.

I thought about plumbing a stock like tube from #2 down straight to the collector, but I don't know just how much flow that would create and whether it would be enough.

Hi.Can you put a baffle up the pipe easily?It might create enough back pressure to create the conditions you seek.Once I was amazed that a motor ran so much better with a more restrictive new muffler than it did with the nasty old wornout glasspak.It was explained to me that this had to do with slowing the power pulses enough to let the cam work.Whatever,it ran better.Steve

As soon as my friend who's got all the metal fab stuff is free, I'll run over to his shop and put it together:

pre-heat output on #4 [---------------] | | | | | | | | | | | | | --------------------------- / /