Mercury Mark 40-H

[Mark75H]

You can PM him or email http://www.boatracingfacts.com/forums/member.php?u=562

Steve77T@aol.com

He is always willing to help. He's probably busy getting ready for the Worlds in Florida ... might want to wait a week for him to get back ... or if you are going you could meet him there and pick up anything you need.

[Aeroliner]

I would love to be down in Florida but I'm working on an engine development program with Rolls-Royce here in Indianapolis. I will try him after the Worlds.

Thanks,
Alan

[Aeroliner]

Well I had a chance to see the prototype Mercury 444 modified engine built by Tim C. God is that engine outstanding. Well there were three sets of casting made so as the story starts. I asked Doug Kay if he wanted to build one. Next thing I know I have a set of castings and if I understand correctly another old racer by the name of John T. has a set and an engine being built. Now understand I have not comfirmed that rummor yet! We will build the engine a bit different than the prototype adding a full Brinkman port job and a beveled crank to go with it. We might try to run a different carb setup that would align them but this is still in the planning stage. Keep tuned and one day I will post some photos as it gets further along.

Alan

[John (Taylor) Gabrowski]

Aeroliner! LOL! old racer????? LOL!!!

I may be in my 50s but that is not old!! LOL!

The crankcase castings are not those of Tim Kurzc's type but are those made by Ray Nydahl for Alky Flathead uses from either the very late 1960s or very early 1970s.

Peter Nydahl told me that the casting was used on a "reversed" block Quincy class C Flathead using 2 large carbs but could have used 4 individual carbs as well but that was not done. On 2 Alky carbs the setup had velocity problems (see pictures of this reversed Quincy Flathead here on BRF, it also sported 4 expansion chamber exhausts).

*See it, the Ray Nydahl reversed Quincy C Flathead in the Quincy section for pictures here on BRF.

From Tim Kurcz's 444 project Merc 44 engine I can not tell from his pictures if it is a New 44 Merc block with offset sparkplugs or the older version? I am going with the old version 44 Merc block with sparkplugs centered in the cylinders as I see no difference in performance between the 2 types. I am also using the newest Merc 44X pistons with the newest type of fractured connecting rods.

I am not sold on beveled crankshafts as that process adds CCs to the crankcase volume slowing down air/fuel transfer velocities and decreases crankcase pressures too. Some of the fastest Merc 44 Mods have standard dimension crankshafts being used on older Merc 44s so that argument will always be a lively one.

The Nydahl casting also requires closing off the reed blocks from any air/fuel transfer making each of the 4 openings into the crankcase very wide and directly into the crankshaft radius area making for tight CCs all the way around. The Merc reed blocks remain only for their labrinth seals separating the sections of crankcase from each other. I am not going to install any bearings systems of any sort in the sealed reed blocks like Mark 20Hs or Mark 25s used but that remains an idea as I have one crankshaft like that ready to go built years ago for Alky racing I would sooner look at then use. You get more bearing support and better crankcase sealing with it maybe, but there is also more rolling friction so would I be better off using it too is highly speculative if there would be anything gained is unsure?

I just want to take the inspiration from Tim Kurcz and his "unlimited" 444 gasser Mod FE and run with it my way from his ideas and now his results too. Keep it up Tim, your an inspiration to the rest of us.

[Aeroliner]

Old Racer!!! Well it's better that me as an antique racer. I plan on using new Tilloitson HR serices carbs without the pumps on them. Looking at the dimensions they will stack nicely and not that costly.

Alan

[John (Taylor) Gabrowski]

LOL! Hey Aeroliner? its old guy!!! lol!

I have some Tillotson HDs that are pumpless but never knew that HRs now come that way? One of the HDs without the fuel pump does have a accellerator pump on it too taking any flatspotting out of sudden wide open accelleration open butterfly conditions but its the only size (HD) that I ever seen that on.

They sure would stack nicely and would feed off a couple of Mikuni or for that matter old remote OMC fuel pumps. Would the carbs require a remote fuel bowl or do they use a return line to fuel tank for overflow or over pressure?

[Aeroliner]

http://www.tillotson-fuelsystems.com/manuals.html

Hi John,
I have the Tillotson carb manual if you want to down load it. I plan on using the regular Merc fuel pumps so it will look more or less stock. Remember the old merc twister had 6 inline carbs. this will be a 2/3 scale engine.

Alan

[Mark75H]

The pump section is basically an accessory. The carbs can be assembled with or without pumps. Just like the alky "conversion" (which you are right about, I think there is a different check valve ball and spring or something if you need higher fuel volume like alky, but it doesn't come close to the "alky conversion" of Carter N's or Tillotson K's)

[John (Taylor) Gabrowski]

After Tim Kurcz gave me some inspiration on his 4 carb now known as the 444 and Pete Nydahl gave me the low down on velocities entering crankcases that his father Ray worked on, really played on theortical thinking when it came to carbs choices for such a project. Tillotson KA series carbs are well suited and proven on normal Merc 40s and 44s for such purposes but would they slow velocities of air/fuel going through them due to their size for a more direct feeding 4 carb 444 project? Using OMC pyramidal reed blocks straight into the crankcase right at the crankshaft was faster, less tortuous air fuel streaming and direct that the conventional Merc crankshaft surround reedblock was not. It would seem to indicate that a cluster of 4 Tillotson AJ47s or AJ51s (Mark 55A - 44 cube engines) would have tremendous velocities but would they choke the wanted effect by being too small and acting like power restrictors too? Enter the thinking on using Tillotson KB series carbs. Again, slightly larger than the largest AJs but here is where the Tillotson KC6s overlapped into the AJ, KB and KAs. Tillotson KC6s seem to embody the best of all the Tillotson carb variants it seemed with its long tapered high velocity tight choked barrel and at the rear it was a full 1/8 th inch larger venturi at the throttle butterfly than the KAs giving the carb large opening access to the pyramidal OMC reed blocks not seen in the AJs, KBs or KAs.

Does this thinking make sense for a carb selection? Good question.

Food for thought when it comes to a Unlimited Merc 44 FE 444 project of your own?

[John (Taylor) Gabrowski]

Aeroliner:

Went right to the site and downloaded the works on the Tillotson carb manuals. Thanks very much.