Mercury Mark 40-H

[Mark75H]

John, I think all of those carbs are good possibilities and your thoughts on this subject are 100% correct.

[Aeroliner]

In trying to think things out it appears a stock engine carb size running at say 4,500 is choking the engine after that say to 5,500 RPM. Now when we run a MOD engine at close to 9,000 RPM we really need some air. From the Tillotson info I beleive the carb is rated for 150 to 350 CC engines and a 44 Merc has about 180 CC per cylinder. The carb also has a boost venturi so it should work well when you need throttle movement. Also we will use the OMC reeds in it like Tim did.

Alan

[John (Taylor) Gabrowski]

Aeroliner:

Using Tillotson HRs to me is as close in terms of thinking and merit as using a Tillotson KC-6. Years ago I put a couple of HRs on a Merc 44 with finally turning them 90 degrees to have verticle butterflys and they worked
very well but with them not being the service carbs found on the engines as KAs or KCs were, they went back on the shelf. They did look neat though, aluminum velocity stacks and all!

On the other side though I installed an HR Gas version on an Anzani 322cc Alky engine, used racing gas and cut back the timing and got the engine to spin over 9,000 rpm on a test wheel. A little later put an Alky HR on, reset the timing again with using methanol and no nitro got the engine spinning real qick comparing to gasoline into the 9,000 rpm range on a test wheel and this time you could really feel the difference in engine torque too between gas and alky, Methanol under that compression really releases different, faster and more torque in the power output.

Through all this both Gas and Alky Tillotsons did not falter, they self pumped real well and tuned well though the delay between tuning on gasoline and methanol is something to get used to. Gasoline responds faster to rich or leaner adjustments where Alky is way way slower to respond. As a sidelight I put a non pumping fuel pump fed (OMC) Tillotson HD Alky carb on a huge ported west coast 322cc Alky Anzani instead of a Vacturi A0-500 with its huge & long velocity stack to control fuel spitback and it worked good too but any better??? Its debateable as the locals got upset with all the open stack noise and before you knew it bylaw control made a visit after a couple of hours of tunning mayhem so that session ended with that question un-answered.

One way or another I think we are going to see 4 Tillotson KAs, KCs or HRs clustered on these these unlimited 444 type Merc Mod FE 44s making for some kind of competition amongst them not seen before. *There is also a set of KAs that have some of the venturi characteristics of KC6s to look at yet too. Here is to seeing it grow!

[Aeroliner]

I have asked the Tillotson folks for a technical evaluation of what I'm intending to do. I have also worked out the throttle linkage to the point where I need to do the detailed design. Seems like it should work out well. What are the thoughts on ignition. Could go with the Merc KD-4 mag but there are a number of others that might work well. Any ideas on the subject?

Alan

[John (Taylor) Gabrowski]

The Merc 4 cylinder magnetos with the larger points pivot pin are a good product to use (P4Ds). The earlier Merc and FM magnetos with the small points pivot pin are not as good but work just the same. They all have some but not gross magnetic drag that does not seem to be anyones great problem.

To eliminate magnetic drag completely putting a total loss battery system Merc CD system from the larger belt driven Merc 800 - 4 bangers (same system they used on Quincy Flathead 4s) are real good too.

The Merc system that has a lot of gross magnetic drag is the Mercury "Lightning" system that combines the distributor and alternator as a unit being belt spun similar in housing to a magneto but more parts. The drag is at least tripple that of the mechanical magneto and without a spring loaded idler pulley against the cogged belt your going to break drive belts to the extreme. Even with a idler pulley cogged drive belts take a beating. I don't think they are a good idea.

So far I have not ventured into the newer individual coil to sparkplug versions of Merc 4 cylinder ignitions because of lots of magneto and CD system parts.

Then there is the Steve Roskowski version 4 cylinder breakerless CD type ignition seen on the Kurcz 444 that has great reviews from other racers too.

It all comes down to a matter of cost in any case.

[Aeroliner]

I have a Roskowski system that I can use but I think the Merc late model Mag might be my starting point and if that is a problem then I will go to the Roskowski. It is quite simple to install and appears to work well. If the weed wacker parts are available then were good forever.

Alan

[RogerH]

Alan,
Take a good look at the 444 and you will see that the boss where the mag would mount has been machined off. That almost mandates you will have to go with something on top, like Steve's unit. The throttle cables also come out on that side too and would be in the way.
Not sure if you got my eMail, but I should be receiving the 2nd unit from Tim "shortly". I'm still debating about what gearcase/mid to put it on. Thinking Bass right now.
Roger

[Aeroliner]

Hi Roger,
If I line the carbs up it looks like a mag might fit. By usung the Tillotson HR series carb I will have to come up with a new throttile arrangement. Doug and Tim are getting together to make sure its done right.
Alan

[John (Taylor) Gabrowski]

Aeroliner:

On Tim's 444 type project 44 unlimited Merc FE engine type a person can still use a belt drive Merc or FM magneto or CD system somewhere else around the top half of the engine and not necessarily where it was on a stock engine front case.

Notice how they did it on full Quincy cast Flathead front cases with a made up plate adapter. It can be mounted on the fuel pump side or even just around the bend from the exhaust system. With Merc's cogged pulley belt drive pulley system with using top cylinder in TDC and the pointer on the ignition side cog drive pulley it sets up the same no matter where you locate it with the only dictating factor being that the installation gives you a good belt tension (with tension adjustment built in).

When it comes to carb throttle control rod actuation looking at a Quincy Flathead 4 cylinder with Carter Model Ns there is the Bowden wire to carb linkage carriage and bar system that handles the 2 Model Ns with no difficulty. Making up the same system to run 4 carbs is adding a second set of links in fabrication to control 4 carbs staggered one in and one out until all 4 are reached. Tims 444 system using 4 cables opening 4 carbs is just fine too and simpler is always more fail safe and better. The wheels have all been invented, it just visualize and fabricate for this application.

Studying the reed valve systems one could drop in, in variance to just using OMCs allows for so many variations. Search reed valves on Ebay and see the variety many of which are adaptable into the space there is gives one access to power reeds, multi-stage reeds and reeds using carbon fiber, bakelite, teflon, metal ones of various kinds that don't have to be expensive to get everything flowing at maximum.

One thing that I am dead set on doing is having not only the standard and ported 3 intake and 3 exhausts per cylinder but also one that is modified where your down to 2 intake and 2 exhaust ports per cylinder. I have one FE Merc 44 - 2 carb with that configuration now. There can be felt a noticeable improvement on accelleration and power with that configuration. You are removing metal not adding it and there is no critical block strength losses either as a result. Still you have to keep in mind widening the intake or exhaust ports that there still is a 20% of circumference rule to observe so you don't snag rings.

Lots of food for thought and all of it easily doable.

[RogerH]

Having read the various responses, there certainly are plenty of ways to "skin the cat" on this one. It seems to me that Tim has hit upon a great new design that is performing very well on its first outing. Surely doesn't mean it can't be improved upon. Alan, I'm not sure why you want to have the carbs in-line. I've finished my 650X and just hate the thought to touching those Tillotsons largely because they are to tightly mounted. I think it took me an hour to get the carb nuts on!!! LOL I do agree with John's comments about reeds. There are a bunch of pyramid valve configurations (motor cycles etc..) but suspect that Tim used the OMC's because of his experience / knowledge he has with the OMC triple. For what it's worth, I have another complete intake and carbs for a 650. I haven't looked at the 650's bore spacing to see if it matches the 44cu.in. I suspect it doesn't - will be wider. I built a 4 carb-reed cage intake for a Chrysler 150 Stacker using two 3-cyl. intakes. Will the Tillotson carbs you mentioned actually fit the 44 spacing or will you accommodate that with the new intake casting?