Hopping up 22 cube Hurricane

[mercguy]

Top speed is ALL I care about in this case, even if I have to sit on the bow, feet dangling in the water, to get the sucker on plane.

I have a race scheduled next Spring, see, and the bragging rights are huge! Unless I can sneak a hot motor inside that Merc 200 cowling (and not get caught) I will have to buy the beer for a month! (Like I said: this is serious stuff!) So,any mods that can pick up a bit of speed--without "obvious" cheating (hee, hee) is what I need. Hell, I don't care if the bloody thing blows the hell up at the end of the run, long as I was out front before it does.

Jeff

Jeff, just swap out your powerhead with a 250 of the same vintage........it already has the bigger KA carb and reed block.

[Fastjeff]

Ah-hah! So, let me see if I got this straight, a Merc 250 (rare as hen's teeth) has a bigger carg and makes more power. Hummm.... I thought a bigger carb woudn't work?

Jeff

[mercguy]

Ah-hah! So, let me see if I got this straight, a Merc 250 (rare as hen's teeth) has a bigger carg and makes more power. Hummm.... I thought a bigger carb woudn't work?

Jeff

it is not just the carb Jeff! Never mind, you obviously no more than the rest of the people.......

[Fastjeff]

If it's "not just the carb", then maybe the ports are a bit, you know.... Oh, I forgot, porting doesn't do a thing on these motors without a header. (And it ain't the reed valve either.) Always wondered how Merc got 25 hp. (if they did) out of a Merc 250. Maybe it was just advertising?

Jeff

[Fastjeff]

Found the "choke point"

Man, I can't understand how air can flow into that motor with a crappy reed valve design like that! How I never really noticed this after messing with Hurricanes for 45 years (hear that, Daren) is a bit embarrassing to say the least.

Here's what I observed: The air slams into the web of the cage, along with the nut and bolt sticking out there, then hits the front 4 (total) reed openings. Not too restrictive a path to these reeds, and on one side (at least) the whizzing crank might even help the air enter. (The whizzing crank opposes air entering on the other side, however.) But the rear 4 reeds are a mess--the air has to jam its way around the center of cage, nuts and bolts, etc. to simply arrive at the rear 4 reeds. Ugly! No wonder Don Muncy and others have suggested opening up the cage and crankcase to get a better shot at the 8 reeds. This I shall do.

Jeff

[sam]

There certainly is a choke point there, but I really don't think there is that much room for improvement beyond what the factory did on the 20H block (the big throat cages as found on 25's & 28's and some grinding work between the KA carb and the cage) without major work. 25's and 28's are by no means "rare" or hard to find as you suggested on BRF. If you look you WILL find them. A 28 would give you 90% of your work, PLUS 10% more displacement.

The back reed pairs are far from the inlet, but they can feed straight back to the underside of the piston (if enough air can get thru them). You are right about the front pair being affected by the crank rotation. I have used reed material that is too thin and all of the facing with rotation reeds survived, all of the reeds opposing rotation fractured or broke. Look at the air stream out of each reed at the front ... it has to bump into the stream from the reed right next to it - a physical restriction without solid material. Around 1970 Merc went away from the 2 pairs of reeds on their blocks and beveled the crank cheeks to make more inlet room for ten reeds that were now anchored at the center.

Lon Stevens side stepped all of this and mounted extra carbs & reeds on the transfer covers (one for each 2 cylinders; Rich Fuschlin's 6 is famous for this set up). Lon said the AJ carbs work well there.

Tim Kurz is working on a 4 carb on front set up for a 44ci Merc with a v reed block behind each carb like the big inline 6 racers of the early 1970's.

If you have enough time this winter you could try something like either of these or combine them and put 3 carbs on a 28.

There is another scheme that has been tried many times but has no proven results and that involves making piston port controlled intake ports. Usually this is fed thru the reed block but not the reeds, but it could be fed by a carb mounted directly over the piston ports. 4 carbs on a 28?

[David_L6]

Lon Stevens side stepped all of this and mounted extra carbs & reeds on the transfer covers (one for each 2 cylinders; Rich Fuschlin's 6 is famous for this set up). Lon said the AJ carbs work well there.

Tim Kurz is working on a 4 carb on front set up for a 44ci Merc with a v reed block behind each carb like the big inline 6 racers of the early 1970's.

If you have enough time this winter you could try something like either of these or combine them and put 3 carbs on a 28.

There is another scheme that has been tried many times but has no proven results and that involves making piston port controlled intake ports. Usually this is fed thru the reed block but not the reeds, but it could be fed by a carb mounted directly over the piston ports. 4 carbs on a 28?

I don't think that all the intake work in the world will make much difference with stock compression, closed exhaust, and fishing motor lower unit.

[Fastjeff]

Thanks, Sam

Very interesting stuff! I've seen the Hubbel version of the 'reeds in the transfer port covers' (with the carb set richer to compensate). Neat. Quincy added an extra pair of reeds to the usual one to make a weird deal that stuck out in front (and probably worked great as most of his stuff did).

I was especially interested in your 'disentigrating reeds' statement--I've long believed that half of the reeds on an 8 reed cage point the wrong way! I'd love to get a reed cage that's rough machined and set the reeds up all going the right way, but...

Tomorrow I'll start some 'laboratory' testing of various intake arrangements, motoring my spare Merc 200 power head with an electric drill and taking crankcase pressure readings. Hopefully, some interesting data will result. If not--what the heck! I'm having a great time.

Jeff

PS: Mark 28s are 22 cubes, like mine--no advatage there. And I have yet to see a Merc 250 either in person or for sale, so I dispute you on that point, Pardner!

[sam]

Oh yeah, you did say 22 Hurricane.

The conflict buzzer goes off, because 22's are SUPER Hurricanes. Does your block say Hurricane or Super Hurricane? Is the carb an AJ or a KA?

[Fastjeff]

Super Hurricane. Couldn't find any numbers on the carb, but it's got a 1 1/8 inch bore.

Jeff