Mercury Mark 40-H

[Mark75H]

It means 3rd porting is allowed on 44's and 60's.

Page 44 under Mercury 6 cylinder 60 ci, #1 still applies:

"Fueling may only be accomplished through and via a maximum of 3 conventionally mounted, single barrel carburetors of any make or size."

The chart on page 46 also shows a maximum of 3 carbs for the 60 ci motor. Note that the number of carbs block under the 44ci motor is blank. 4 are allowed on the 44, so are 8, 12 or 16 carbs.

The text is the same as it has been for the past 3 years when 3rd porting was specifically allowed. The only change this year was to permit any OMC triple carb to be used on the triple. It is marked in bold text.

[Mark75H]

If you race the 444 motor in 850 you will be eligible to suggest the change to the 60 ci motor restrictions. I will support such a suggestion, as I would also support increasing the permitted size to 66ci.

The increase to 66 is actually moot, because the increased piston weight offsets the increased displacement. Some west coast racers were knocking around the increase to 66 a couple years ago and I was against it. After recalling a conversation with Rich Fuschlin and rethinking some of Harry Brinkman's results, I have reconsidered. Like the 60 & 62 ci 4's the 66 will be at a disadvantage.

[BRIAN HENDRICK]

[QUOTE=Mark75H;67836]...as I would also support increasing the permitted size to 66ci.

We have disussed this often, and I am glad to se your change of heart. [maybe something to do with aging] I may still build a 66" FE,
if the rules were to allow it. However my reasoning differs from yours.
Generally, a 66" is to a 60" six , what a 44" is to the 40" four. What we are seeing in D Classic [ie M58H] is that the 40" M55H block,
even with its porting, and years of intense race tuning, is no match for the bigger and newer block.
I have no particular experience, but I am told that in AOF, and in NBRA, where they permit the 40" in Dmod, but class the 44" as an 'E',
that the difference is significant. I would think that a 66" block built to 44" mod specs, would be superior to the 60", especially in acceleration.
44/66 parts are also more common than the 20/40 " ones are.
But, there may be a problem in getting around the APBA rule about no new mod motors with open pipes.

[Aeroliner]

Hi Sam,
Current plan is to run the 444DK on a New Ropp hydro that Harry had and never used. After testing with Tim and his 444 we will run it on the new boat. Hope out of the box we see about the same performance as Tim is getting. I have a 3 carb six I can use first but that will need a complete block mod to Harrys specifications. That is a ways off in the planning cycle.

Alan

[Mark75H]

The top OMC 850's are running 95 to 99.99 mph in competition set up for good acceleration

Take your GPS with you

[David_L6]

I don't understand why a 66" 6 cylinder would be at a disadvantage to a 60" 6 cylinder? The best 40" D mods can get pretty close to my 44" E mod but they can't beat me.

[Mark75H]

Harry could get a good 30 to spin well over 9,000. 4's seem to hit a brick wall at 8,400 and the 6's hit it sooner.

It will be interesting to see if the 4 carb fronts can make good power above 8,400 or if the wall is still there.

Years ago I noticed Rich Fuschlin (and later Paul) continued to run a 60 in 1100 R when a 66 was legal. I asked him why and he said he had not been able to make a 66 run faster than the 60. I also have not come across a 66ci Lon Stevens motor.

If Rich was not able to make a 66 (even with extra carbs) faster than a 60, I'm thinking there is a physical reason other than intake restriction.

My guess is this: with the longer crank with more throws it is harder to find a crank that is straight, true and balanced well and this makes the added piston weight more critical than it is with the 4's. It may just be the extra weight of the pistons causing internal drag - you have 1/3 more of them in a 6.

[Aeroliner]

I have a 40 and 44 Quincy set of engines. There setup for fuel now but I might run them on gas with KA2A carbs. Mabe even fixed jets to see what the hydro will do with each engine. Have a good selection of props and will have a tack in the boat to check the RPM of each. Could use the same prop on each at first as a baseline and then prop each to get the best performance. What would be a good prop to start with. Have a number of two, three and four bladed wheels.

Alan

[David_L6]

Something close to 6 3/4" to 7" diameter X 12 1/4" to 13" pitch three blade should have you in the ball park. Lean towards the smaller end of the size range for the 40", larger for the 44".

[John (Taylor) Gabrowski]

Alan:

Many of us here have been there and done that, running Flatheads on methanol, methanol and gas and on high octane gas. Some with some success and some more than others but with reduced power outputs.

Your going to have to examine your cooling water oulets for sizes as methanol greatly cools where gasoline warms so steam or rally hot water coming out means too hot and too small are the discharge passages.

Your timing because of your high compression is going to have to be cut way back as a start point. I still used 12 to 1 gas to lube mix.

To me fixed carb jets have always been non-starters though used successfuly by others in Modifieds. Your best is to change the carbs by drilling out and tapering fixed jet inserts and install with packing glands low taper slow opening and closing high speed needles like 20H and or 55H Merc to get the best tune at a given outdoor temperature.

Flatheads react way faster in changes to tunning on gasoline that on methanol mixes. Once you tune one on the carb side with a real conservative BTDC timing, the coldest sparkplugs possible to where they are going to almost constantly fowl and go one heat range up then with instruments tweek the timing as it is sensitive more so with that compression ratio than other racing 40 or 44 Deflectors your used to.

Using a Merc 55H testwheel tunning dynamics on the trailer in water or suitable test tank for greater environment control can pass but using a flat disk high friction Anderson and Hallum type test wheel holds down revs better for tunning.

When tunning use eye protection, head protection, ear protection inside and out and body protection always as Flatheads are not Mods or Stock racers so are inherently more dangerous to explosions than most. This is way more controlled and easy with less risk than fixed jets and bolting on a prop. That comes after tied down testing. Good Luck, Enjoy and Have Fun!

PS: Put some distance between you and your neighbors, authorities and cops too as there are many out there that necessarily like the noise of a giant mosquito trying hard not to explode! LOL!