Do 3rd port Deflector engine ports work?

[John (Taylor) Gabrowski]

Seems like this topic is all over the map on some websites new and old and still the argument carries on. So far there are some pretty close answers linked to previous studies on 2 stroke tunning. Jennings studied loop engines and came up with some plausible positions on so many things the guy is remarkable in his time.

On the Deflector side of tunning the leaders were very much Quincy Welding in terms of getting Mercs to breathe and exhaust. No other firm did so much with the limitations imposed by Deflector technology as they did. They also realized the shortcomings of Merc's crankcases and did some profound work as in stuffing 30Hs crankcase tunnels. With 55Hs and 44s they added 3rd ports that at higher rpms created ram that worked but they never went into carb development with a real tunned velocity stack to ram the 3rd port for the duration it was available.

Quincy also realized that the higher rpms you pushed a deflector the more heat soaked the pistons got plus the efficiency drops off real fast as the technology reached its outer limits of its effective rpm as a pumping chamber or in other words the higher the rpm the more inefficient the engine became plus the heat soak that made them melt down crowns so fequently. Deflectors by their nature are more effective than a looper but you have to keep the revs down to develop best horsepower and torque.

Quincy saw real fast with the Anzanis roaring out there that a loop engine kept getting more efficient and powerful as the revs go up. British Anzanis are 3rd port and beyond loop type engines. With seeing the light that mean't you either changed your racing technology or died and Quincy dumped the Deflector Merc so fast some engines that came into the shop never left but a Flathead replacement was on its way to sit on that tower housing or a complete motor by all accounts when the transition happened. These days you see little loopers pulling 20,000rpm pulling power to displacement no deflector can even come close to. A lot of that is the engine but another big factor is the expansion chambered exhausts deflector engines are problematic to engineer for.

Still there is some room for the 3rd port deflector in Merc 44 FE gassers but like all changes its a little bit at a time and still there is the pesky port and that velocity stack to perfect that will vary with each different deflector engine configured until that ultimate power is attained. Easy said but a lot of work to it that would need to be done. Quincy Welding had it right but what do you do when small loop engines come on the scene to twist everyones necks?

[Seagull 170]

John did you ever look at the Gordon Blair's Queens University Belfast deflector piston design?
Such a simple answer to many of the deflector piston problems, it makes you wonder why it never appeared 30 years earlier.

[Mark75H]

Bell's book on 2 stroke engineering talks about the motorcycle companies experimenting with the combined reed/3rd porting on their loop charged motors. They tried it and gave up.

Combining piston porting with reed intake porting will probably only ever work on motors that are designed with it in mind from their concept stages on such as the Quincy Looper.

Others have said that they "thought" there was some power increase in the high rpm range when piston port intakes were added to deflector Mercs ... my source is O.F. Christner and his dyno, and he told me different.

Just like the theory that stuffing the crankcase as tight as possible will give a big power increase ... the 3rd porting idea seems to stop at the theory stage, too.

No one has ever found a velocity stack shape or size that helped a deflector Merc either. Some of the fastest running Mercs use a truncated Tillotson. This would suggest that more is less and less is more.

[John (Taylor) Gabrowski]

I have never seen or heard about that report. Is there a website to go and have a look at it?

Sam, you reflect some thoughts at the time as well as expressions of Quincy's dyno testing. Thing is when Quincy dropped all Deflector development with a thud and went Flathead Loop all the development just didn't stop with some individual builders who still clung on to some things.

Quincy was so relied upon and especially so with the Flatheads coming on so strong with great results engines were both coming in there and leaving just as fast prepared with the latest updates for the next races. Where a lot of us did our own work when you went to a race the majority had their work done exclusively by Quincy so they was truly busy and money talked too.

Some racers that kept toying found that the Quincy installed third port was found to be so angular that the air/fuel was slamming into 90 degree turns and then hitting a flat surface at the port before dumping it all into the crankcase. That made for some saying that the port only worked at really high rpm but barely so because of that twist, turn and splat effect. Some worked to make the flow more angular and gradual to the 3rd port opening and then chisel faced the port opening to divide the flow better than having it hit a flatspot splattering the flow that were there originally from machining the port in. I have one of those 44 Deflector Fs and it was used far beyond when they should have stopped, it was exceptional.

Some racers looked at the idea of feeding the 3rd ports by installing carbs on the fuel pump side some with a small reed box and some without. Evidently that didn't work either because the air fuel inertia through the reed block of air/fuel to the reed valves was not there to provide that column of moving vapor to stuff/pressurize the 3rd port.

What no one seemed to do was experiment with different carb barrel types combined with velocity stacks to optimize that column of pressurizing air fuel vapour zooming into the reed block at high velocity that would still pressurize the 3rd port and crankcase when the reed valves spring pressure was already closed down. No one went too far out of using Alky Carter Model Ns or Tillotsons converted to ALky. The idea behind the 3rd port was not only that of adding extra pressurized air/fuel to the crankcase but was also to provide that air/fuel cooling to the crankcase to get more in by cooling the under piston crown area that shed heat of combustion to the crankcase during operation. That seems to have worked some as piston crown meltdowns and scoring did decline with that extra cooling in the 3rd port engines you did not find with Merc padded block Deflector Alkys without the 3rd port.

One Fort Dodge racer who had several 3rd port Merc Alkys also reported that at the highest rpm his D Alky would run wide open, when he cut the throttle there was a short delay of rpms staying put present before the rpms dropped off that was not there on the padded block 55H D. The 55H burned pistons frequently where the 3rd port padded block rarely did and if so it was generally only 1 and usually scoring from sticking. He too never strayed from Carter Model N Alky carbs either.

There seems to be some room to make some improvements and some did keeping some deflectors in the game long past when they sould have stopped. That was high compression Alkys where most are talking gasser Merc 44 Formula E motors which are cats and dynamics of a slightly different color still. I give those trying the benefit of the doubt and with the engines so cheap now in recycling trial and error are not that costly anymore either.

[Mark75H]

The idea behind the 3rd port was not only that of adding extra pressurized air/fuel to the crankcase but was also to provide that air/fuel cooling to the crankcase to get more in by cooling the under piston crown areaNever heard of that idea anywhere

[daveswaves]

http://www.wikipatents.com/4622929.html
Here you go John.

[John (Taylor) Gabrowski]

To the old guys the extra cooling aspect of the third port was a given. No one ever disagreed on that merit, there were less piston heat damage ocurring with those 3rd ports I have been told and that was even posted on some old bygone boards. Some argued that the oil from the air/fuel at the piston port found its way onto the piston skirts too helping lubrication. Can't argue with that either.

When I was at Fort Dodge I went through boxes of destroyed Turner pistons, some real crown burners at that and a few skirt scorings with ring jambs, it was if collecting them was the thing. I didn't check any against any of the four Alky blocks but it sure identified that Deflector Alkys sure had overheating problems a plenty. Of the 4 blocks 2 were 3rd ports that were still together, one was okay but even the other had one scored skirt with jambed rings. It was no. 2 piston and the only one out of four.

[Mark75H]

Dave, that is the essence of the "padded" combustion chamber used by Merc racers from the mid 1950's on. I am surprised that it has not been challenged and disallowed. The main difference is the pure rectangle squish area vs the basic "take what you got" bent parallelogram squish area of a padded Merc.

It should work and solve most of the problems involved with getting higher output out of a deflector style motor. I wonder why he stopped at using the pocket next to the intake and didn't put an insert poking down into the deflector notch and stick a hemi or semi hemi combustion chamber squarely over the middle of the piston? I would think that would decrease the possibility of erosion and a hot spot on the deflector lip of the piston.

[John (Taylor) Gabrowski]

Was this not what Lon Stevens was into when he cut the tops off Merc deflector cylinders to make shaped heads for his versions of comparable sized Mercury racing engines to the various loop engines too?

With his using Turner pistons he did some neat re-shaping that rendered those deflector engines he did comparable to loop engines in performance.

Seems that Quincy too thought some more head shaping would help so where it started with compression pads only it evolved into overall head reshaping still using Turner pistons in the process.

Lastly when the Merc 44s went to offset sparkplugs that too was dealing with squish and turbulence of air/fuel charge. When they refined it some more then they called it the powerdome to emphasize that it was an improvement over previous shapes technologies. The remarkable thing is that the older Merc 44s with center of cylinder located sparkplugs, slight factory head padding do a remarkable job of competig with that newer Merc powerdome technology on later model 44s.

Still it all points out that the whole deal with a deflector engine is to produce the best power at the lowest rpm to keep its efficiency up and peaked. Those early padded blocked deflectors were really pushing that engineering envelope and burned up frequently as a result of trying to get the highest rpm possible from the deflector design that just doesn't go there easily.

Even with the re-engineering patent, can you see any company going back so many years to toy with deflectors again and after loop engines with their exhausts have proven themselves so well? I can't.