Greetings . . .

Spent some quality time with a triple beam balance and a set connecting rods I purchased off ebay several years ago. They are machined for insert bearings - and were sold as ready to go.

I am weighing them for balance and was surprised by the variability:
Assembly...Rod....Cap...Pin Bolt..Rod Bolts..TOTAL
A..........475.0...202.5...21.9.......88.7......788.1
B..........456.8...172.0...22.5.......88.8......740.1
C..........461.5...221.6...22.0.......88.1......793.2
D..........445.4...198.3...22.5.......87.6......753.8
E..........458.3...186.4...22.0.......89.4......756.1
F..........466.8...185.0...21.9.......88.7......762.4
Average..460.6...194.3...22.1.......88.6......765.6 grams

Max Var....29.6....49.6.....0.6........1.8..... 53.1 grams

Ave Var..6.426%...25.5%...2.711%....2.033%....6.936%

Abs Var..6.646%...28.8%...2.740%....2.055%....7.175%

With so much variability I am wondering if they are worth any more investment in time. Perhaps I should pursue another set?

I guess I will grind the parting lines off the beams and weigh them again. But the one 'runt' cap will cause me to have put the others on a 25% diet . . . seems extreme . . .

Thoughts?

Thanks in advance.
stock49

Do you have more rods to choose from?

All I have is the babbitted set that came out of the car. I had put them aside with the stock crank because the bearing surfaces are still serviceable. The rods were babbitt serviced by Federal Mogul . . .

Might be worth a second look . . .

Do you have any or much varaibilty with pistons? Just thinking light weight pistons/heavy rods might help lessen the difference.Merry Christmas Jay.

Thanks Jay . . .

I am stroking 3/16 with a Hi-Torque crank. The pistons are custom built from Ross. I expect them all to weigh the same . . .

I would weigh them too . . . but I had them drop shipped to the machine shop so the machinist could final hone the bores to Ross' spec and directly measure clearances . . . the shop wouldn't have it any other way.

You'll need to find another set. Removing the parting lines will only take off around 5 grams, so it won't be that much of a reduction. Also, the babbitted rods are real flimsy in the beams and everywhere else so its doubtful you could trim enough off of the ones that are the closest in weight, much less the heavier ones.

Thanks CNC-Dude . . . I figured as much. I am going to spend some time with some mics trying to understand where the additional weight is coming from. There has to be a reason for the variance . . . they all have the same part number.

I am not going to pretend that I know anything about this engine.I think that the pin is too big to use the 261 rod? but what about later model 235 rods? Will they work? There is not much going on right now, give me a number that you are looking for and/or what other engines' rods will work and I will keep my "eyes open" for parts. Jay

Since he is limited to using the babbited rods, that is the only style he can use, as the later insert rod is not compatible with the early crankshafts.
Stock49, the weight variation in the rods, even with the same part number is just the nature of the beast. It is normal to have a 10-15 gram difference in a matched set of rods, except in aftermarket rods where the manufacturing processes are much more precise.

Just did a little work on the parting lines of the heaviest rod. You were spot on about those 5 grams!

My mics have revealed other variations. There are flats ground into the rod side and cap sides - the big end balance pads. There is a lot more meat left on the heavier rods. Also the pin bolt boss' are ground differently. I am going to even these up and see where I get.

I have also found quite a bit of variation in the dimensions of the caps. The shoulders that extend off the caps (that mate with the troughs in the oil pan) are all different. I am going to true those up.

You are right about sticking with Babbitt style rods - they are the only kind that will work with the jet oiling system . . .

Before you get too deep into this, you might want to verify that the housing bore of the rods is correct for the journal size you have ie, standard crank/standard rod housing bore, .010" crank journal/.010" housing bore, etc... An undersize housing bore will have more babbit in it, thus more overall weight, and that could be why there is such a weight difference between some of them also.

Hi CNC-Dude . . .

Just to clarify. These are Babbitt 'style' rods - but they have been machined for insert bearings. A must for any boost in compression ratio. So we are talking the weight of bare rods and caps . . . worth some tinkering no?

As for journal sizes. The crank is an NOS Hi-Torque just magna-fluxed, polished and balanced at the machine shop. So the bearings will be standard not oversize.

The Babbitt angle seems to be confounding the thread. 'tlowe' asked if I had any more rods "to choose from". In fact I have two sets: the machined for inserts set that I am working to 'balance' and a set of babbitt lined rods that came out of the previously running engine. This latter set would require machining for insert bearings to enter the fray . . . $

regards,
stock49

When doing an insert conversion you have to also get pressurized oil to the rod journals, since splash oiling cannot provide adequate oiling for a bearing. How are you going to do that?

Looks like you need to replace rods B&C with rods that weigh closer to the rest. Ideally rods that are babbitt type that have been cut for insert bearings. Is this correct? I don't know of any around here right now but will be on the lookout at swap meets ect. Maybe someone else here or at stovebolt has a set of rods with the same problem, the 2 sets could be combinded to get both parties clooser to equal weight. I would love to see a picture if possible of one of the rods. Wish I could do more to help. Jay

The babbitted rods are going to be a lot heavier than the finished machined insert rod, so its going to be difficult to estimate what rod weight you'll need to start out with to arrive at the inserted rod weight. As keep in mind that 60 years ago when these rods were made, the set you have may have been considered to be a matched set and close enough for GM at that time, since they didn't weigh things in grams back then, only pounds and ounces.

The use of insert bearings with the jet oiled system has been a rebuild option for quite sometime now - for practical reasons. There are very few places that pour babbitt anymore.

When setup correctly the jet oil system is good for around 15 psi at the rods. This limits the RPM and C/R in a jet oiled engine. But the thickness of the babbitt linings is also a factor.

Roger Huntington discussed early mods to babbitt rods in his book. The shops would first pour brass as a 'shim' and then pour a thinner babbit lining. This allowed for higher C/R loadings that would have distorted the normal stock spec babbitt linings.

I am following Huntingtons specifications for jet oiled clearances but with insert bearings.

Grams versus ounces is certainly a factor here . . . but I have since read that GM typically would match rods/pins/pistons in pairs for balanced placement on sister journals (1-6, 2-5, 3-4) . . .

Guess I will have to work in pairs as well . . .

Thanks Jay . . . for now I am going to try to work with this 'set' . . . using the term loosely. I bought them for $100 seven or eight years ago. In hindsight I should have bought two sets - I would have more to choose from!

Chev's of the forties has a pic of a machined rod:

Funny how VW in Germany in the same time period (well from the 50's at least) picked their rods to fit within 8 grams of each other, if one was heavier, it was rejected and put in a pile of "next weight group" with other heavy rods. You saw three different weight group rods produced through the years and it is even noted in most decent manuals.
I match mine to within 1 gram, and caps to each other and big ends to each other. Then wrist pins and pistons, if I have a "heavy" piston, it is sometimes easier to remove metal from inside the wrist pin at the end, than it is to reduce the weight of a piston. You don't need to shave nearly as much steel compared to aluminum.

The end result is not only matched weights, but matched centers of weight (If that is how you call it) on the length of the rod/piston assembly.

Haven't checked my Nova rods, maybe I did when I first had them out and replaced the pistons, pretty sure I did.

That will work for a 4 cylinder that has 2 opposing cylinders to counteract the imbalance, but because of the 120° crank angle of a 6 cylinder crank, it takes 3 cylinders to counteract the imbalance because they never have another cylinder 180° away to oppose the weight difference. So you will need(2)sets of 3 R&P, not(3)sets of 2 R&P to do that.

Just woke up and read that and did not understand a thing I'm sure it makes sense but not to me right now, being sick and barely awake.

In VW land, the different weight group rods go in different engines. Not mixed in the same engine. All 4 are within 8g.
So one engine has rods from the same weight group only.
I have found it fairly easy to go from 8g to 1g accuracy.
I know race engine builders that go to 0.1g accuracy... I think that's overkill but if you have a scale that can do that and time to kill, go for it.
We built 10.000rpm aircooled VW engines that ran just fine with 1g

Thanks Stock 49 for the photo. To me that rod looks thin compaired to todays product,yet millions of Chevies ran with them with no trouble. I also understand that when new these rods came with poured in bearings and just splash oiling. Can you tell me what a jet oiling system is and what is a safe rpm/compression limit for this kind of set up.Just trying to learn more about these engines. Jay

Those millions of chevies also made no power or compression per cylinder to speak of

This is one cheap way to make wrist pin oilers, just notch the rods. I have done this on VW rods with no ill effects, a well known trick and some engines are made this way. Wrist pin lubrication is still only splash oiled, but this adds a more directed, additional splash aimed towards them.
http://www.youtube.com/watch?v=7wuNuuEoN7Y

Edit: looks like the rod in the picture above already has a squirt hole where the neck begins, 12 o'clock.

Here is another way to make a stationary oiler/squirter jet by robbing oil from the main bearings instead: http://hotrodenginetech.com/pin-oiler-prep/

I believe BMW used poppet valves at th eend of each squirter in some of their engines (I watched a VW builder adapt these jets to an aircooled VW case) which helps maintain good oil pressure at idle, when oil pressure drops down, and the poppets would only open when there was more oil pressure available.

Here's another way to do it with add-on pressurized hard lines aimed directly at the writ pins/piston tops:
http://mngforce.typepad.com/nc450vdev/engine-modification-piston-cooling-oil-jet.html

Hi Jay . . . 'splash' oiling is a misnomer. There are in fact hard lines to jets in the pan that supply oil under pressure to the rods. There is an opening in the bottom of the rod cap and dipper to catch the stream of oil.

The 1937 short "Riding the Film" documents fully what was then the cutting edge of GM technology:
1937 Short by Jam Handy

'37 was the first year for the 216. Based on the writings of Roger Huntington the stock oiling system is good to 150hp with a redline in the low 4000s. One needs to convert to full pressure to rev higher or put out more ponies . . .

regards,
stock49

The stock oiling system supported 105hp in the powerglide cars of '50 thru '52. California Bill Fisher's speed manual and dyno testing was all done with the stock oiling system delivering 125 to 150 HP depending on the mods.

The pin oiler hole is part of the stock system. Some shade tree guys would peen the hole over thinking it would raise the oil pressure . . . only to starve the pins . . . :-(

Many did experience problems with these rods, but not because of the babbited end so much as it was the pinch bolt design that resulted in failure on these rods. Thats why the GMC rod conversion was so popular, even for just mildly modified Stovebolts. They swapped right into the babbited engines with no mods required to the rods or crank. For the later full pressure engines there was some minor fitting that had to be done, but you ended up with a bulletproof set of rods by doing it.

Stock 49, that film completely explains the rod oiling system. The only question for me is why anyone would go to the trouble of oil jets and dippers when all you have to do is drill the crank,a very easy job at the factory IMHO compaired to all that plumbing! I am probably missing something but can't a machine shop drill the crank and get full pressure to the rods? Maybe the way the crank is made there is not room inside it for the oiling holes to be drilled without "breaking through". CNC-Dude, am I correct in beliveing that GMC rods are pressed on at the pin instead of bolted with a pinch bolt? If so it's pretty easy to see a big improvement in strength. Thanks everyone for taking the time to help me learn about these engines. Jay

A question that can only be answered by some long since dead engineers from 1930's GM . . . or perhaps the accountants from the same time period.

Transferring oil pressure from the mains to the rods involves so called 'rifle' drilling from the crank journals to the rod bearings . . . this must have been more expensive then the plumbing . . .

For me I am just working with what GM delivered at that time . . .

Great video, I know nothing about the older chevy engines and I didn't realize there is no pressurized oil feed to rod bearings.... amazing... that it works at all

All the GMC rods are full floating with a bushing. They also have full oil pressure to the wrist pins as well. Many top shelf aftermarket rod companies have now begun to incorporate that feature into some of their rods as well.

Just trying to learn something. How hard are GMC rods to get? Are they big $$$ ? IF Stock 49 used them would the engine have to be converted to full pressure oiling? Would the expence be worth it or are you (Stock 49) trying to stay with the original system on purpose, just like some people convert to an open driveline while others want to keep the torque tube. Jay

GMC rods are cheap and plentiful. This swap began long before the insert rods were available for the Stovebolts, so they were used successfully in the pre-full pressure blocks. The GMC rods are also longer than the Stovebolt rods, so there are a few benefits associated with that as well for using them. You also have to remember that the average hotrodder back in the late 40's and early 50's was straight out of WWII and had a craft or trade skill they had acquired on Uncle Sam's nickle, most everyone had welding and machinist type trade skills. So doing something like that was no big task for them to undertake.

The big truck engines that come to our shop all have full floating pins with bushings. The rod is drilled from the big end to the small end so that the pins get get full oil pressure. I have never seen a pin failure or any visable wear. We do not check them because the piston,rings,pin,and liner are all just replaced with new and reconditioned rods are put in. On the newer engines the pistons are 100% steel. How they stay together being that heavy amazes me. Are GMC rods drilled through the center also? Jay

Yes, the GMC rods are drilled through the center.

Thanks CNC-Dude. I think this would be a good upgrade to a jet oiled engine. Having seen pictures of some of Stock 49's engine and parts here (they look like works of art) he could easly do the conversion if that is desired. IMHO no one can see inside the engine and there is no way to tell if this has been done by the sound ect. makes using GMC rods the way I would go for increased durabilty. To each his own. After all a lot of people think I am crazy for running an intergrated cylinder head on purpose. Jay

Over a decade ago I decided that I would not transplant an engine into my '49 fastback. I decided instead to pursue a California Bill spec 216 'hop-up' that preserves the stock chevy oiling system. Nothing has deterred me.

The planning is long since done and the build is now underway. The pistons have been forged. The block, crank and head are back from the machinist . . . and I am ready to start assembly.

The disparity in weights of the connecting rod set (currently in hand) is but a minor setback. I have just purchased 3 NOS rods for 10 bucks a piece. I will send these off to the machinist to have the big ends prepped for insert bearings.

With 9 rods to choose from the bench mark I am targeting for this aspect of the build is:

Rod: ~450 grams
Cap: ~185 grams
Pin bolt: ~22 grams
Rod bolts: ~89 grams
Piston: ~535 grams
Pin: ~94 grams

Total weight: 1375 grams

Stock 49, I know what you mean when you say "Nothing has deterred me". I am the same way when it comes to using a intergrated cylinder head on my 250. IT would have been easy to transplant a 235/261/ or a later six into the 49. Can you please post the the mods done to the engine? Iknow about the stroker & the dual carbs but nothing else. Where can I get a copy of the Speed Manual? Thank you for the good opertunity to learn about these engines. My Aunt had a '50 powerglide 2 door that I remember riding in as a kid. Found out about a year ago that my cousin (who is still alive) got it as a first car! I will have to talk to him to find out more. Jay

This new book should be out at the end of Jan. 2014

Looking forward to the new book Scott.

I like the idea of building a 216. They have been beaten up for years mostly by those who don't understand the oiling system. For longevity and dependability I'd take a 216 over a Ford flathead every time. In fact I did several times.

Thanks Beater. Im starting off the new year with(2) brand new books. I'll have a printed proof for my first book next week, and then the first 200 books will be shipped within 10 days of that. Then the Stovebolt book will follow afterward. I just bought (10) ISBN numbers so they can be distributed through major retailers. I plan to write and publish the remaining (8)books in 2014 as well.

Scott, I too can't wait to read the new book. How will you be distributing it?

Thanks for the encouragement Beater . . .

integrated - the particulars of the build have been discussed on several different posts here over the years. Most of them in Bench Racing . . .

Here's a quick summary:

'49 block bored .030 over with custom pistons/pins by Ross and Hastings cm rings.
NOS Hi-Torque crank from '52 with stock journals recently polished and balanced
NOS war surplus head from '42 mildly ported and polished with particular attention to the exhaust ports.
Obscure Isky DP#2 spec cam reground by Delta Cams 247/264 - 204/232 @.050 (extended duration on exhaust lobe to promote scavenging).
Various valve train tricks from McGurk (inner springs/hold downs etc). I also have a set of Barker high lift rocker arms (not sure that I will use since cam is already lifting .41 and not sure about coil bind not to mention push rod canting/flexing).
Eddie Edmunds water heated two duece intake with twin Carter WCDs
Tube Headers with provisions to heat auto chokes
6 volt electrics with NOS '39 Delco #1110008 dizzy - preferred by Fisher because of advance curve. Modified with Harman Collins dual point conversion plate.

regards,
Keith

Im finalizing things in the last chapter of Book #1 now, but I will be the exclusive publisher and distributor for my books, so they can be purchased directly from me. As the title states, it will be a series of books, so as I acquire more props and parts to do a continuation, I will release them as they come available. But right now, I have enough material to do a Book #2 and #3.

I just bought (10) ISBN numbers so they can be distributed through major retailers.
I will be the exclusive publisher and distributor for my books, so they can be purchased directly from me.

This almost sounds counter-addictive lol

If I can't sit down and get something completed start to finish pretty quickly I lose interest in it quickly. I had been working on the Stovebolt book for almost 3 years, and finally got back on it this summer to try to finish it. Around Thanksgiving, I was waiting on some parts to get shipped for it, and while I was waiting I sat down and wrote another book from idea to final draft, cover design art and all in just 3 weeks. So now that i'm on a roll i'm going to finish up some other book projects. But its fun though.

I want a copy of the pictured Stovebolt book when it comes out. CNC-Dude, can you share what the other books are about? Titles? Thanks Jay

Sure Jay, Book #2 is going to be an assembly guide for engine building with a trip through the machine shop showing all the recommended steps for prepping a shortblock for street and performance. Book #3 will focus on cylinder head porting and modifications to complement Book #2 mods.
By breaking it down into a series of books, I can go into greater detail about each phase of engine preparation and engine building, which is my specialty.

Stock 49, that is going to be one hi-powered 216! If it's OK I'd like to learn a little more. How many cfm does each carb flow at 3.0hg? What is the total CID with the new crank and .030 over? Is the Hi- Torque crank an aftermarket part at the time? Thanks in advance for filling me in. CNC-Dude, this sounds like a great series of books to have and pass down to my Grandson. Am I correct that at least the first series of books are about the "Stovebolt" series of engines 1962 and older? Thats fine with me, I just hope that there will be a follow-on series covering the later engines. Let me know when Book 1 is avalible. Jay

Yes Jay, there will also be a series to cover the later 194-292 engines as well.

Hi Jay . . . the arithmetic on the bore and stroke mods is straight forward - call it a 230 CID (3.53 x 3.9375). I don't think I have ever seen a CFM rating published on a Carter WCD - it can't be more then 130 or 140. But the head is the limiting factor on this build.

Hi-Torque is Chevrolet branding for a bored & stroked stovebolt engine introduced in '41 for trucks (the original 235). The same engine was re-purposed in '50 on the Powerglide cars (because the automatic transmission slipped - wasting horsepower and torque. So they needed to provide more.). The crank I am using is an NOS GM part for a PG car:
Inliners BB post circa '06
regards,
stock49

Show us some pics of your assembly process.

Stock 49,X2 on the pics please! Is the head also for a 235? What I have read the "best" head is one with 848 as the last 3 digits of the casting #. Did you install the larger intake valve in the head that you are using? Has the head been milled down for a compression increase? I have to admire and respect the time and trouble that it took to find all those NOS and period correct aftermarket speed parts. CNC-Dude, glad to hear about a second series of books. Jay

Greetings . . .

I will post build pics . . . after the cold weather breaks of course!

The 3836848 head from the '56 235s is indeed a famous piece. But it is not compatible with the early stovebolts that utilized a tall push rod cover which extends beyond the block on to the head. Not to mention a different head bolt pattern.

Also, I am not milling or filling the head to get CR. Since the stroke/compression height of the build requires custom pistons - added CR is coming from pop-ups included in the piston design.

regards,
stock49

Stock 49, About an hour or so after I posted yesterday I rembered that the number of head bolts was increased sometime in the 1950's. I had forgot about the side cover differences until I read your latest post. If I was going with custom pistons I would only have the head and block checked for straightness,removing nothing from either if I did not have to.If I may ask what is the final compression ratio going to be? What valve sizes? When you do the build please post a picture of the "Jet oiling system". I and probably many others have never seen this type of system.(born too late) Jay

The deck and the head have been milled just enough to prepare the surfaces for gaskets. The valve diameters are all the same from '41 to '52: Exhaust 1.5" Intake 1.64". There are pictures of the head here:
Inliners post circa '06

In '53 the intake valve diameter grew to 1.875" but that is in the newer style (short push rod cover) 235 head.

As for the static CR for this build - I am expecting it to be somewhere north of 8:1.

Aren't NOS castings beautiful? Even 8:1 is a nice increase over stock. Compression is like almost anything else a person gets to a point if diminishing returns. Going from 7.5 to 8.5 will add more power than going from 14 to 15:1. Something that I have always wondered: 1. Why do all older engines have such a low CR ?and 2. All big truck engines also have very low CR's even in the 1960's when good gas was around? Was gas in the 1950's low octane? Look at Chevy specs for "car" 283 and "truck"283 to see what I mean. Also look at 1960's 292 engines. They did not lower compression for unleaded gas no need allready low. I take it then that newer style 235 heads valves won't fit the '41 to '52 head. Thanks Stock49 again for taking the time to teach a newbe Jay

I think that older cars had low CR because the engineers wanted to leave room for abuse in the lower end. Higher CR is harder on the lower end. A driver of a high CR engine needs to be mindful of lugging such an engine. Trouble is the I6 is a torque monster that will tolerate low RPM lugging. The same is true for truck power plants - the engineers are mindful that the operator is likely to encounter circumstances that could cause him to lug it . . . pulling a load on a grade in traffic can easily lead to lugging, even with a mindful operator armed with a tachometer.

There is also a need for higher octane fuel (which an overly cheap operator may not want to provide) . . . leading to pinging with otherwise properly set timing . . . which abuses the top end.

Low CR is a safe design construct for reliability in a world without a tach - let alone mass air flow and oxygen sensors and an engine management computer to dynamically adjust mixture and valve events . . .

What? 1949 Chevys don't have mass air flow sensors? LOL. You have jolted out another childhood memory. This time it's of my parents turning a corner in 2nd gear (3 on the tree) and the engine "groaning" a little bit because the car was just a little too slow for that gear. Going to first was not an option because of a no syncro in first. Now I can understand what would happen if this was tried in a loaded dump truck. Jay 6155

Greetings . . .

The weather has warmed a bit and the shop isn't frosty - so I got back on the die grinder:

Assembly...Rod....Cap...Pin Bolt..Rod Bolts..Dipper...TOTAL
A..........467.4...202.5...21.9.......88.7.....16.0......796.2 (H)
B..........454.8...172.0...22.5.......88.8.....17.0......755.0 (L)
C..........460.4...221.6...22.0.......88.1.....15.5......797.0 (H)
D..........443.1...198.3...22.5.......87.6.....16.5......767.7 (L)
E..........455.9...186.4...22.0.......89.4.....17.0......770.2 (M)
F..........464.1...185.0...21.9.......88.7.....16.5......776.1 (M)
Average..457.6...194.3...22.1.......88.6.....16.4......777.0 grams

Max Var....24.3....49.6.....0.6........1.8.............. 42.0 grams

Ave Var..5.310%...25.5%...2.711%....2.033%.............5.405%

Abs Var..5.484%...28.8%...2.740%....2.055%.............5.563%

The dipper turns out to be another variable . . .

Getting rid of parting lines and polishing things up reduced the variabilty quite a bit. I also focused on the shoulders of the bearing caps.
They vary quite a bit from cap to cap (thickness and in how far they extend down into the oil trough). The heavier caps definitely carry more weight here. So I can take another pass to further reduce variability.

The Scott's point I am working them in pairs 2xH, 2xM and 2xL but I am trying to get two sets of H, M and L assemblies that are about equal in weight:

Cylinder
..1.. H...796.2 |
..2.. M...770.2 |
..3.. L...767.7 -> 2334.1 grams
..4.. L...755.0 -> 2328.1 grams
..5.. M...776.1 |
..6.. H...797.0 |

Matched together into sets of three - reveals only 6 grams difference front to back.

Leading to the question - which holes should the get the heaviest assemblies? The lightest?

regards,
stock49

If it were my engine, I would either put the two heavyest in the 3,4 med in 2,5 and light in1,6. This IMHO would reduce twist on the crankshaft. From a balance standpoint it would give light,med,heavy,light,med,heavy. Another way to consider 1,2 light,3,6 med,4,5 heavy. This would give light,heavy, med,med,light heavy. Probably the second way would be the smoothest. A tough call to make. Jay 6155

Stock49,
Is that the best that can be done to bring the rods into balance?

No. That's just the second pass. I think I can do better.

It's too bad caps can't be magically switched between rods. If that was possible you would be a lot closer. Jay 6155