Topic: opposed twin flow numbers

[fordman21]

I just got the opposed twin on the flow bench because I'm going to be doing a lot of work on the flat heads in the very near future. They aren't fantastic, but better then I thought. The test engine I have on the bench now was ported by the owner so it isn't exactly bone stock. I won't get into detail but the end result was 68cfm and it fell on its face around .400" lift.  I have some bone stock engines coming so I'll test one of those, it should be considerably less than this engine.
Now I have to get to work to make this engine breath, I can't post those end results, those are for the owner only.

[westcoast racer]

What is the CI of the engine?  Are the valves stock?

[fordman21]

42ci, valves are stock but slightly modified by the customer. The block is relieved as well.
I'll do a stock block so you guys can get a good idea of what you are up against. Right now one cylinder flows about as much as an out of the box stock 16hp vanguard head.  I'm sure we can change all of that.

[fordman21]

Here's a pic of the adapter I made up. It works awesome and will sit on the flow bench by itself, all I have to do is operate the intake valve for testing. Its spun around backwards so you can see the adapter, while testing it will be turned 180 degrees.

[leadslead]

interesting  looks like fun

[fordman21]

I was pretty impressed with the +12cfm on the oppy without touching the port or valve seat yet. That is reshaping the already swirl polished valve, more work relieving the deck, and work done to the head itself. I'm going to fill in the head in areas that will not comprimise the flow to raise the compression up as high as possible with temporary puddy, then weld the chambers up. This cfm is now at .500" lift @28"wc.

[fordman21]

For all the guys that are putting big valves in your oppys, you might want to hold off on that. I look at the size of the valve and I know that I can get up to 130cfm out of a valve that size on other engines, the problem (other then being a flat head design) is everything else. I just got another 5.8cfm out of this thing without touching it with a porting tool yet. I basically just closed the port in half with puddy, I can't get into too much detail. The velocity went up very high, to the point that I half to use ear plugs to continue.
The best part is, I haven't even got serious with this thing yet.

[leadslead]

nice wisle while u work

[fordman21]

basically I'm trying to design the port to use the other half of the valve.

[leadslead]

yea that thing drill sargents use makes  noise

[FlatheadPuller]

Ryan what do ou think its capable of after the port work. Will it be able to make some high rpm hp or still be a torque engine. Is there a class the oppy will compete in with a good dual carb setup that is legal in mower racing.

[fordman21]

I'm not sure it will ever be a high rpm hp engine but given the ci, it should make some decent torque. A dual carb set up would make a huge difference in them because you could change the entry angle. You could run something like that in supermod/outlaw, but most would run a v-twin at that level I would think.

Pretty interesting, working on the head is as critical as the port itself, and milling the heads on these engines actually changes the shape of the chambers for the worse as far as cfm is concerned.

[cycloneracer]

Ryan,
I know you can get the ports to flow, but can you make the intake and carb keep up?

I think the carb is the biggest problem with the opposed.

All the breakage issues can be fixed, but there isn't much to work there with the carb.

Paul

[Rooster]

The intakes leave much to be desired. Even if you get "the big one" they take alot of work!

Once you get used to the carbs, they aren't that bad, I have more problems getting too much instead of not enough out of them!

[fordman21]

I never got the carb or intake, my job is to get some flow in and out of the block
Seriously, if you seen how small these intake ports are Paul you would fall off your chair, they probably make that carb look a little bigger, but I am a little concerned about the shape of the intake though. Is there better intakes through out the years?