squishing block

[Fast Fred]

i spose on a Merc that mite work,cave in the head, ware i'm from if it don't have a head gasket......... well you know

[Ron Hill]

The KG-4 was the Mercury "A" Stock motor. And most blocks measured very close to APBA's specs. The CC's for "A" were 14.2 minmium, I think.

When Mercury built the Mark 30-H, they basically copied the "A" spec sheet as a "C" was two "A's". So, the spec was written 14.2 minimum. My dad was an APBA inspector from about 1949 til his death in 1997. Or almost 50 years. He said he never saw a Mark 30 block get anywhere near 14.2 that he owned and the early BLACK MARK 30-H blocks were around 22 CC's as I recall.

As time pasted and all Merc 30 and Wizard 30 blocks were made legal, CC numbers started to drop. My dad noticed this while inspecting. The "Mexican" Wizards were rumored to be 16 CC. The story, of which I have no proof, was that Mercury made some high compression blocks, but because the Mark 30 was on a Mark 25 gearcase, all the gearcases blew up and a high compression motor would make this problem worse. So Mercury they sold them as Wizards with 4 reed reed blocks.

It doesn't make sense BECAUSE all Wizard blocks had no markings on the intake side with the words Turbo Four. It was blank, so if high compression Mercury blocks would have been on Wizards, they would have said Turbo Four or you could have seen where it wasTurbo Four was milled off. Wizard blocks had a clean die cast face.

About this time blocks started showing signs of being lined bored, but these could be caught when measuring the ports heights.

Mark 30 blocks were four individual cylinders and I believe that with the right heat, and the right press many "FAST" blocks were in fact "SQUISHED" to about 16 CC and called Mexican Wizards.

My dad and I were great ones to look for parts, "Treasure Hunts". My dad came home from Nebraska one time with a pick up load of Merc 30 powerheads, all fresh water, something we never found in California. In that mess of blocks was one Wizard. I got that block bored along with another one we liked, and my dad put the engines together and as I recall this motors had the exact CC's as the Mercury block.

The Wizard was a good motor, but the Nebraska "C" as we called it was better. But my black Mercury block was better.

My dad would have died before he ever "Squished" a head in a block, but we both believed it was possible.

12 years ago, I was talking to J.A. Lon Stevens the greatest "Cross Flow" builder of all times and he told me he used to bore the heads out of Mercury 30's and put in his own castings, weld them in nicely, acid wash them and they were all about 15 CC. Lon told me who he did most of these blocks for and I believed him.

Lon said he could "Squish" blocks, by heating them in his oven, but he preferred to weld in a head that he made, as he could control the shape and CC's. My dad would have turned over in his grave if he knew Lon did this.

I knew Lon welded heads in his "F" motors, and 44's (The 44 river racers in Oregon ruled Lon's heads out. You must run a stock block in Oregon River Racing).

In my opinion, no one ever squished blocks for stock classes but "C", as "C" was the only class where the CC's were way off the spec.

[88workcar]

Thanks Ron

[Seagull 170]

"i was told years back about squishing the block on a motor and just wondering is this a true statement and is there any big gain in this"

This was the question, not how do I beat the inspectors?

There is some confusion whether the questioner was talking about increasing the cylinder compression of the crankcase compression, from some of the answers I get the impression that crankcase stuffing is not an art practiced in many parts of the world amongst the outboard fraternaty.

Just have a look at any of the 50cc twist & go scooter tuning websites, full circle cranks, really tight crankcases, these kids are riding around on two stroke that are better than 6 hp per cubic inch, for several thousand miles.

There is no doubt in my mind that crankcase stuff is as important as increasing the head compression, providing you don't create weird inlet tract resonances in the process.

If there is anyone out there with a tiny tach, a GPS, a Minimax, a 5hp single two stroke fishing motor (piston or read ported), & plenty of time.
Would they increase the cylinder compression to 150 lbs, test, & then increase the crankcase compression to 1.5 or 1.6 to 1, test & not do anything to the port timing, apart from a light cleanup.

The main jet & the prop pitch might have to be increased, then publish the before & after results on a new thread here.

That would answer the gentleman's question, it could be a very interesting read,

[50hptiller]

to me....... crankcase compression increase does help, but there is a point were increase is not helping. it will charge the cylinder better and in doing so it will blow more good mix out of the exhaust port. that is were a custom expansion chamber will really shine. the more you blow out the more the pipe will have to push in. in doing so with a single set of pipes you will probably see a peak hp rpm shift.

[88workcar]

Well it never made a BIG GAIN from what I was told, it was another piece in the pie. I am a firm believer that a bunch of little things will add up to something big. The whole purpose was to gain a little compression, and it only worked on a mercury because the head was part of the block, all in one.

[Bill Van Steenwyk]

Since I have been playing with 2-strokes (50+ years) I have always heard, as some previous posters on this thread have recounted, that an increase in crankcase compression will increase performance. Based on personal experience some 25 years ago, I can tell you that is not always true. Perhaps with an engine designed with plentiful intake tracts, big, non-restrictive reed valves, or rotary valve/piston port induction that has no restrictions in the intake tract, that may very well be the case, but not in every situation.

BUT, take an engine with a restricted carb venturi size to meet class rules, designed with a small, limited number of reed valves that the engine was originally designed with for longevity and dependability purposes, and then try to make that engine rev almost 2/3 more RPM than it would in stock form still keeping the carb venturi size it was manufactured with to meet class rules, and you have the "perfect storm" to have an INCREASE of crankcase volume work for you. This was done by Harry ZAK in the 1980's to try to increase performance on a 322CC Yamato 80 motor, and with this modification in addition to many others done previously, a gain of approximately 2 MPH was realized from this increase in crankcase volume alone. This motor achieved a Kilo speed of almost 91MPH on a Hydro with one carb with a 25MM venturi diameter, in April 1985.

The theory was to have an increase in crankcase volume to act as a "storage" or increased volume to allow as much as possible fuel/air mixture to be available for transfer into the cylinders as the piston came down on its power stroke and refilled the cylinder, as was possible based on the restrictive carb venturi and reed valves the mixture went thru on the way to the crankcase. In other words, maybe you could only get so much in on each intake stoke, but by having a larger crankcase volume to hold what could get in, after a very limited number of strokes you would have more in the crankcase than you might get if you did not have the extra room to start with. Probably sounds far fetched insofar as the "conventional wisdom" is concerned, but the proof was in the results, and in this case it worked.

Harry did try this on regular Alky racing engines such as the reed valve Yamato 350CC 4 cyl engine, by removing the aluminum plugs put in the balancing holes in the crank disks to take away that empty space left when the balancing holes were drilled in the disks. I never really heard what the results were there, but that motor was not restrictive on either intake or carb size, so there might not have been an improvement.

[88workcar]

This motor achieved a Kilo speed of almost 91MPH on a Hydro with one carb with a 25MM venturi diameter, in April 1985.

This is one of the most impressive statements that I have ever seen/heard of. And the best part is that I DO NOT DOUBT IT in the least amount. That was having your stuff right.

[Bill Van Steenwyk]

Charles (Seagull)

Thanks for the phone call this AM. It was a pleasure to talk with you and become more knowledgeable about what others are doing regards two stroke engine tuning/modification.

Best of luck in your future endeavors. It must be difficult testing your work due to the speed limitations on the English waterways. It's hard enough getting more performance without having obstacles put in the way of finding out if you have accomplished anything.

[smittythewelder]

So far as I can see (maybe I overlooked it), nobody here has yet talked about "squish" as the rest of the motorized world knows that technical term.

The easiest place to see it is on an ordinary loop-scavenged 2-stroke, and particularly on one with an absolutely flat-topped piston such as a good ol' Quincy looper. The cylinder head is also flat except for the combustion pocket, shaped like half a golfball, where the end of the sparkplug is seen. The flat area of the combustion chamber around that half-golfball is the squish area or squishband, and the top of the piston is very close to touching it when at TDC. HOW close it comes is the key point in the usual discussions of squish, and it really is important.

The squishband head was invented by the great English engineer, Sir Harry Ricardo, during the First World War, in his efforts to control detonation. Despite the very low compression of the engines of the day (I think Ricardo worked almost entirely with 4-strokes), the octane (a measure of detonation resistance) of available gasoline was low, and during wartime shortages, rather variable. Ricardo found that by designing a squish (the Brits call it "quench") area into a combustion chamber, and having the corresponding area of the piston come right up close to it, detonation was dramatically reduced or eliminated. The entire auto industry quickly adopted variations of the Ricardo head, which they retained until the advent of emissions regulations. These "closed-chamber" heads remain superior, in most cases, to "open-chamber" or "smogger" varieties for performance purposes, even when (get this!) the compression ratio is exactly the same.

The usual explanation of "why it works" is something like this: the close proximity of piston crown to squishband entraps a bit of fuel/air mixture that doesn't burn, therefore cooling the periphery of the combustion chamber. Other explainers also cite the advantage of a last-instant puff of compressed mixture that's squeezed out of the squishband and swirls into the combustion pocket, promoting more complete combustion.

Getting closer to our interests, racers of air-cooled roadracing and off-road motorcycles in the late-'70s, early-'80s were used to seeing their engines gradually lose power through the course of a race with heat build-up, often with an onset of detonation. Some sharp tuners measured the factory squish-height, the clearance between the piston crown and the squish area of the head, and found dims typically in the .055"-.070" range. With lathe or milling machine they got this down to, say, .030"-.040" . . . and noted that their bikes now maintained initial power levels throughout the race and didn't detonate . . . despite the slight increase in compression due to the tighter clearance!

While the advantages of a tight squish dimesion are more obvious in air-cooled racemotors, the detonation resistance is improved in engines like ours. I learned about squish from Jim Hallum and Ron Anderson, who were re-setting the squish-height on their alky motors some years before I first saw it mentioned by a motorcycle racer (Gordon Jennings, in his little red book, the title of which I forget), and twenty years before I started seeing reference to it in Hot Rod and similar car magazines.

The actual squish height you'd want for any particular engine depndes on a lot of variables: rpm (or more accurately, piston accelleration), rod materials, crankshaft support , . . . basically, you want it real tight, but short of the piston smacking the head.

Changing the squish is not a big deal in a moderate-performance water-cooled motor that doesn't detonate in the first place, and probably illegal in any stock class. In an engine that makes lots of power, a tight squish not only quells detonation, but does that so well that you might be able to raise compression even beyond the slight increase that comes with tightening the squish.

For better explanations than this, google speedomotive, dale alexander, macdizzy, or squish/quench.