Not all rods are created equally

[Mark75H]

Here are pics of 2 completely different Merc 600-4 rods. I've been told that the legendary H beam heavy rods were back door parts supplied to Quincy by Merc, hand delivered by Charlie Strang.

Is there any truth to this story?

[Aeroliner]

Hi Sam,
Years ago I was testing my old Speedliner "B" and dumped it which wan't a pleasent thing. I broke the block, crankcase and tower to the point where it really couldn't be welded. I ordered a replacment set of parts along with new rods for my 20-H and the replacements were heavy rod in a 600-4 box. I didn't think they were right so I put the old rods back in after checking them and put the new rods away. Well I still have the rods in the original box. I will take a photo of them when I get home from a business trip I'm on. I also have two four cylinder Quincy Mercs and I will see what they have in them when I open them up.

Alan

[John (Taylor) Gabrowski]

Aeroliner:

There were Merc 600-4 rods that had 3 machined oiling holes and there were a host of different weights (in grams to them)

Similarly there were later model 600-4 rods with solid bottoms and again a whole host of different weights were as light as 135 grams to others as heavy as 178 grams and everything in between.

The rods that commonly came out of Quincy Flatheads here as well as some Quincy-Merc padded block and 3rd port padded block deflectors were a specially made 600-4 series rod with a special heavy duty cap bolting system designed on the rod, the bolt having a special heavy duty head for such high horsepower and high recing methanol racing duties.

Many engines ripped down to salvage for the local parts bank our old club had showed some Merc 4 cylinder engines with rods that had a more or less matched series of weights say all 140s, 155s, 170s in terms of grams per rod in each set of 4 connecting rods and so one but many had rods all over the place in terms of extremes. Pistons seemed relatively closer though in terms of sets of 4s coming out of engines. This sort of stuff was going on with 30, 40 and 44 cubic inch engines. Some engines were so matched inside for weights across the board you could not find at times 2 to 5 grams between complete cylinder sets though and not necessarily in racing engines either. The assumption must have been for ski/fishing/pleasure engines that they would not be operating past 5,500rpm so things didn't have to be critical but were built strong none the less and would last half a century anyway.

Cool thing is one could match real light per cylinder set of assemblies to so heavy sets you in effect could make a faster spinning up engine to a slower high torque beast at the top end spinning engine just doing internal weight juggling. Its all neat stuff!

[Mark75H]

Well said John

[Aeroliner]

Excellent post John,
I have been playing with rod weight for years now and agree that there are a number of weights that come to the table. I used to use an analytical balance to match my 20-H pistons and rods. Of intrest there were also variations in pistion pin weight. Pistons seem to be closer with the new flat top desig as compaired to the old fire slot one. I assumed the variation in forhing them contributed to the weight varation. This was born out when I CC'ed the combustion volumne and found that the lighter piston usually had higher CC's. All in all the ideal situation was to get all the pistons as close as possible and the rods as close as possible and them matching the heay rod with the light piston. Fine tuning of the set was then done with the pins. This worked great in my "B's". Four cylinder engine were a considerably bigger chore to get things matched up.
The old three hole rods gave me fits when I coverted my 20-H and found the end cap segment flying out odf the case. The solid ends worked fine and I have never had one fail.
When I take the two Quincy cross flows appart I will get the weights of each piston/rod assmbly to see what they are. Most likely there will be quincy pistons so I assume they should be fairly close. I will post photos and weights.

Alan

[John (Taylor) Gabrowski]

Alan:

You had the 3 hole misfortune others had too, totally a disaster. Seen the same thing happen to some 30H and 55Hs but once their bad news got around most looked and switched real fast even though the engine was a KG9, 40H, Mark 15 A type older Merc engines and so on. What is strange is that KG9s and 40Hs had an earlier version rod with the 3 oiling holes on their big end caps too before the 600-4s came out where if there were failures nothing much ever came up in terms of warnings then with those.

The center pivoting points of these rods are also noteworthy in terms of finding neutrality balance differences positionally between the small and big ends of the rods. You would want them all the same too to cut vibrations to the bone along with everything being equalized everwhere else in the rotating mass.

Distances between big and small ends are well noted they happened as well as some piston crowns going up further than others as per wrist pin machining that piston putting the wrist lower in the boss/skirt area.

Wrist pins were just as all over the map too in terms of the open ended thick wall types that in cases were around 30% heavier than the old thin wall one closed end versions you find on the older 15/30 cube engines as well as the the older 20/40 cubers too. Variations in weight on all the one close ended thin wall wrist pins were way less than the later both side open ended pins.

I am hoping some day to try a set of 20/40 one closed ended set of thin wall light weight wrist pins in a 44 Merc using end plugs to take up the slack being the wrist pins are shorter than used on Merc 22/44 cube applications before the wire keepers go on but will that put too much strain on the wrist pin bosses where the pin actually rests has scared me off from doing them as no one so far has identified any experience trying this before or if they did they are not saying, so it stays as a "what if" for now?

Thanks to computers and the easy ability to make parts data bases and merge the data into combinations before you ever get to assembly that would be utterly tiresome before usng paper grid charts of yesteryear.

It was last fall that I completed the lightest possible from parts here internal reciprocating weight per cylinder assemblies for a 40 cube D Merc engine I ever though possible to be done right down to using a machined down flexplate core where the flywheel nut will end up being used (no rope plate) with a remote removeable 12 volt Chrysler automotive geared electric starter to get the engine running. Will it just run away when it starts will be interesting. To tune it wearing your kevlars with every matter of other and extra body, head and hearing protection will be the only way to approach that thing safely. No other way!

[Mike Schmidt]

A long time ago, no a long, long time ago I bought a bunch of looper parts from Dick Fickett. Had a pair of the "I Beam" merc rods that had been milled down to clear the counter weights on a Quincy crank. Mint, like new. I thought they were the greatest thing going. Put together a second A looper with them.

Big bang. Lost the case, block and crank. After some research, I found out the rods you need are the ones that are NOT milled across, but the ones that are spot faces for a roundish rod bolt. A ton stronger.

35 years latter, my gut feeling is they are still what you want.

Michael D-1

[John (Taylor) Gabrowski]

Mike:

From the Flatheads restored here none of them had the I beam milled across versions most where the roundish bolt head your referring to. There was a variation too that was different in that the bolt reminded you of a kind of angular C clamp kind of heavier duty a head that was again different from what the standard 600-4 rod used but here they were fewer than the roundish bolt head version found around here. Some of those angular headed bolts which are definitely stronger they were also silver plated from the big end to half way up the rod too.

Interesting stuff in their variants. Its too bad it cost you some real severe damage in what happened then.

[Tim Weber]

I've never built a looper but I've put together a number of 55h's. Something I've found is there are a whole lot of rods that are not straight. I recently restored my grandfathers 55h and went through it with a fine tooth comb.
I decided to find as balanced of set of rods as I could. After weighing a bunch of rods, I took them to a surface plate and bout 1/3 of them were bent.

My guess, is this must be a big problem with a looper because of the extra horsepower and higher compresion.

Tim

[John (Taylor) Gabrowski]

Tim:

I love the plate glass test as well as a great thing to simply use with some fine sandpaper and oil to resurface a carbs base flanges that can and do warp etc. Very inexpensive.

With that happening to rods I suspect that the big small end wrist pin and its end of needle roller washer spacers would have something to do with it in Merc 40s and 44s even. Sometimes the combos up there are too loose and differences in thicknesses have been noted before. Similarly the big end piston fit to the crankshaft throw could have something to do with same. I went over that with Jim Hallum several times because I saw it on Anzani crank and rod systems as well as Flathead and Mercury Alky Deflector rods by then too. That is what he told me the rods plated on the sides with silver were all about. The layer of pure silver not only makes good bearing material but its plated thickness takes up some of the excess slack keeping the rod centered better containing side to side thrust along with a good fit at the small end contributing to same.

It pays to measure and guage them all. Knowing Merc rods just how could they twist otherwise unless hydraliced with water ingestion, severe over timed ignition, poor manufacturing, something from the heat treating, poor assembly fitting with small end components too loose or crankshaft width grinding to wide?? Or any combination of all of these or some?

Eliminate all these bugs and you should have one nice running engine. :)

[Aeroliner]

Looking through my parts today I found one of the heavy beam rods in its original box. The forging number is 600-4. Had a pair of these but who knows where the others went.

Alan

[smittythewelder]

Did or do any of you guys get your used Merc rods re-sized? The big end gets elongated, isn't round anymore. But any good auto machinist with a rod-honing machine and the dimension you supply can grind both of the mating surfaces of the big end, then re-size the I.D.. Nearly always this will leave a very small area in a corner at the mating line where the hone didn't quite clean it all up, but you can't keep grinding, and I doubt this makes any difference, especially compared to having a round hole. I would speculate that a used Merc rod that has been trued in this manner is likely to have stretched about as much as it's likely to, and should hold its restored shape fairly well.

[R Austin]

When reconditioning these rods, the bearing surface of 60 rockwell C is only about .025 deep. To much removal will lead to unwanted results. Bearing failure.

[smittythewelder]

Right, and even if you don't go clear through the case-hardening, if it gets too thin it might suffer Brinelling and flake off.