reeds and blocks

[Fast Fred]

been thinkin about sharin the things i've done, seen, have had happen over the years with reeds and blocks, what Works, whats crap, ain't guna do jack but get last place........
gots to run for now, gets my picture show go on it too........:eek::cool::eek:

[chris3298]

Thanks I'd like the hear about this, I just picked up that Evinrude 75 short shaft so looking to learn all I can

[Fast Fred]

ok then, blocks, i know of two styles, plain, wich would be just alu' . the other would be coated or vulkinised with ruber compound, the coated ones seem to offer a better seal.
the block it's self IS a limiting factor, wich is to say once you've maxed out the air and fuel that can pass through the block, you will not make any more power. :cool:

[Powerabout]

Any way to rubber coat aluminium reed blocks?
Can you mill a reed block from rubber/plastic?

[Boatnut]

so i have a spare block to play with, and i have been scratchin my head about the vulcanized rubber bit. seem to me that opening up the block a bit would have to be doable but fer me the dilemma has been replacing the rubber. can i clean the rubber off the block, open it up a bit and mount the fibre reeds onto the bare face? or will the pistons be feasting on shattered fiberglass?? OH gunna be watchin this thread, great topic!

[byrdsperformance@tds.net]

The non rubberized cage's have allway's been used with good result's.
After a period of time the rubber coating on yamaha's will crack anyway.

[Fast Fred]

a set of OMC 3 cyl carb modas, with two stage fiber reeds, the blocks are stock.:cool:

[Fast Fred]

gots a shot of some coated OMC blocks,:cool:

[Fast Fred]

see what else eyes can find for blocks............:eek::cool:

[zul8tr]

What's all that dirt :eek:on the reeds and the stops about?

[Fast Fred]

um, it's about used parts in the used parts pile, with dirt on them, just shots of the styles mention above.........:cool:

[Fast Fred]

so i'll relight this off...

[Powerabout]

great stuff
have you got your CFD package running?

[Fast Fred]

no, no CFD, just old school, what worked, what didn't :cool:, i'm movein right now, so may be slow gettin this up, but it brakes it up for me:cool:

[Fast Fred]

so, the coated block seal up nicer, but ether works. the block, the max amount of air and fuel is determined by the size of the blocks windows. the biger they are the more air fuel gets by.:cool:

[pdt]

would it also help with top end if the reed housings were highly polished to aid the flow of air ?
and also chamfering the edges to get that little bit extra from them again top end.

looking at the 2 stage reeds, are these infact single reeds with the tops thinner ? or two separate leafs ?

[Fast Fred]

linein up the blocks on the intake with a fresh gasket is time well spent, as well for the carbs to the intake with a fresh set of gaskets.
you can remove the ribs of the block, use a full peddle reed on the second stage, this increases the volume, have had problems with cold sneeze, to get around the cold sneeze used a squeez bottle to choke her as she comes up to temp. omc squirt gun style choke or sled hand pump choke works.

[Mark75H]

would it also help with top end if the reed housings were highly polished to aid the flow of air ?
and also chamfering the edges to get that little bit extra from them again top end.

Only if the reeds & cages were the limiting factor to begin with. If something else, like porting or carb is the real limit, all the polishing in the world won't make a bit of difference

[Fast Fred]

polishing it's self, i've found that it's more about makin it flow smooth as in gasket matching, a seamless match of the cases, high spots, alinement corrections, ect..., a buff shine looks nice............ but smooth works about the same, less work.:cool:

[pdt]

that makes good sense, and less work sounds real good.
i have a spare reed housing and looking at it, its realy not that pretty at all.
I shall just smooth it now, instead of polishing to a lustre ha ha

thanks on the tip.
.

[zul8tr]

Fast Fred is right, just remove the humps, good alignment, etc. The slight roughness on the surface helps keep the fuel/oil layer from building and causing some flow restriction. The slight rough surface promotes the fuel/oil layer to break up. Take a piece of wet type 220 sandpaper and place some fuel/oil mix on the paper and blow parallel to the surface, then do the same with a piece of glass, you judge what happens. Ever notice the inside of auto performance intake manifolds, rough cast, we would just do port to port matching and gasket alignment,and trim, remove sharp corners when we were into 1/4 mile drag racing and oval track racing.

On my 25ss engine with the aluminum reed cage with 8 holes of 5/8" x 1-5/16", KC16A carb, long stops and reeds set at 3/16" open the least flow area is the carb venturi. If the 3 -5/8" diameter intake ports are considered they are the smallest flow area. But when considering the twist and turns of the flow from carb, through the inside of the reed cage, then the sharp turn from inside the reed cage through the cage openings, past the reeds, flung around with the rotating crank, then into the intake ports to the cylindere you have some very convoluted flow dynamics the least of which are polished surfaces. Need a flow bench to really find the major areas to improve then test and find something different, Ha!.

Long time ago (in a galaxy far far away) I took a 22 ci block to a milling machine and streamlined the intake ports like the ramp design to input bullets on the old side loading Winchester rifle, rounded corners on the ports. Didn't help a bit. Exhaust porting was the deciding factor there.