chevy43

Can I use the vent to get tank pressure? If so do I have to have a "T" and a restriction on the vent or the tank line? Will I loose lubrication doing this?

Campgems

If you are talking about the vent on the crank case or nose around the cam, the answere is no. That is simply a vent to allow the crankcase to breath. If you hook it up to a fuel tank, it will suck air from the fuel tank on the up stroke and push it back on the down stroke with no net gain in pressure at the tank. In fact it may result in a pressure loss. The exhaust port provides continous puffs into the tank without drawing anything from it giving a net slight increase pressure above atmospheric pressure. Not much, but it doesn't take very much.

Also, a restricted chrankcase vent can, should I say will, effect the performance of the engine. One of our guys ran the vent to a small vial with some cotton in it to catch the drips from the vent. He couldn't get the engine to run right no matter what he did until he went back to just a short line just longenough to clear the cowl. After that, the engine ran right.

Don

chevy43

I have a .30 Magnum I want to install in a HOB Pietenpol and there isn't enought room for the carb assembly behind the engine. I wanted to flip the intake pipe over and have the carb pointing up to get it out of the way and make it easy to choke with my finger. This will put the spray bar much higher than the tank..... I have also been thinking about mounting the car right to the intake port but it will still be higher than the tank.... I could get a perry pump but that adds weight and complexity......

Campgems

You don't need to choke the engine at the carb, just put your finger over the exhaust and crank it over one or two turns then hit the starter. Just keep the glow starer off until you are ready for it to run.

Is choking the engine the only reason to move the carb, or does it jus place the engine to far forward?

If you really think it is a choke issue, you could rig a choke similar to the one that comes standard ont the 70 and 91 Magnums, which I pull before mounting the engine. They are just a flapper that will cover the throat and a long wire that extends out of the cowl. It would be quite easy to come up with a 30 sized one.

If you just can't get the engine back far enough, you could cut a port in the firewall for the carb to go back into. Just make a sloping bottom on it to drain fuel back to the front. Most 4 strokes spit some fuel out of the carb and you wouldn't want it running inside the fuselage if you can help it.

I agree that pumps and regulators is getting complex. One thing that might get you out of the woods a bit is to use a check valve on the exhaust port to gain some additional pressure on the tank. I've not tried this but have heard of using one before. One other option is to use a bladder tank like the quicke 500 class guys use. Even then, I'm not sure rotating the intake 180 is going to work. How to you plan to hold the carb on the intake?? That question just came to mind.

Don



Edit addition. How do you plan on running linkage also?

chevy43

OK - you are right of course about choking not being nessasary. I have been flying too many non mufler pressure engines lately and forgot...

As far as holding the carb on I would just drill a two bolt flange and JB weld the carb to it. After that it just comes on and off with the two allen screws.

As far a linkedge I'd just run the push rod out the top of the fuse at a nice shallow angle kind of like how we do it on the tail.

To mount is as is I will have to junk the mount and cut the fire wall up.... I'm just trying to avoid that....

Campgems

Chevy, my method of solving a problem is to poke holes in every idea that comes up, and the one that ends up with the least holes is probably the best choice. My comments are along that line. When I poke, I'm not always that accurate so keep that in mind also.

If I understand the above quote, it sounds like you are going to rotate the carb so it is a side draft and eliminate the intake manifold. I would think this may cause problems with the short intake path not allowing a good fuel air mix by the time it reached that valves. Just a guess here but one that could stand some investigation. I would also worry about a JBweld holding the carb for long with the heat of the head and the vibration. Just a couple things to consider.

When you decide how to go with this, take some photos and post them. New approaches and their success or failure are always good things to pass on to others.

Don

jaka

Hi!
Why not just modify the firewall so that the engine/carb will fit! This is much easier than making modifications to the engine.