One more chance for the big block

435 grams total weight . Took the piston off , so 4.46 c-c is darn close.
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Finally pulled the head on the alcohol big block. I was thinking it would be a rod failure. Wrong. The exhaust valve snapped and was in the cylinder. The piston got beat up, cylinder wall has a few scores and the exhaust side push rod is bent.
 
Looks like the valve snapped at the weld. The valve tip was still in the retainer. No evidence of the exhaust valve becoming overheated. Clearance was adequate, it was a conservative build. No valve float, max rpm was 6675. Lash was .002. Most likely the valve simply failed.
 
Yes, valve spring and rockers look all good. I took them out to check for a broken spring coil. Retainers and caps look good too.
 
Hi Tim,
Honda makes a steel rod for the GX390 that's used in the Honda Tractor. I got one for Vmax several years ago for a project he was working on. I don't remember the part number or price, but I will research it for you if interested.
 
For what it is worth... Observations of the ARC billet rod with bearing insert.

Mind you - I am not knocking a product. It just does not serve our particular application.

We could never get the ARC bearing insert rods to last in an Animal in Enduro Road Racing. The World Formula Billet rod was the answer.
The ARC rod cross sectional area is notably less because of the bearing insert. There is a oil groove around the diameter and oil hole at top and bottom. To my mind that subtracts even more material and allows oil in and right back out. An Animals design has limited space for the rod at the journal. Additionally the ARC rod is made from 7075-T6. About the strongest aluminum available without a doubt, but it has a low fatigue life compared to other aluminum alloys..

Fatigue life is the ability of a material to withstand repeated tension to nearly its yield point and return without failing. We are talking millions of cycles.

2024 at about half the ultimate strength of 7075 alloy has about the best fatigue resistance of any aluminum alloy. The forces a connecting rod sees are within the ultimate strength of 2024 and the ability for it to withstand the repeated load cycling make it the better choice. In addition the coefficient of friction of aluminum on polished steel is nearly equal to the 'Babbitt' insert.

Look into top fuel connecting rods, 2024 alloy. Yes they have inserts but the also have pressure lubrication and the room for them. The inserts often are replaced after a run.
 
Thanks B-man. You are taking me to school with your metallurgical knowledge. I'm in agreement with you on the ARC rod in the sense that the extra oil port they drilled for "superior lubrication" may actually compromise the strength of the rod. There is visibly less surface area at the big end as well. It gets confusing at times bc some builders swear by them and others have stopped using them. The variables that place stress on them are many not to mention the precision of the installation. I have a lot of information to work with now regarding which rod to use, compression ratio and rpm. Fortunately I also have plenty of time to figure out good options. Now only if work wasn't so busy.....
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The problem with the ARC animal rods was a lightweight version that they had in early years. I don't know of anyone using that rod anymore. We've all gone to the "beefy" rod that they offer. It is considerably stronger and will work just fine.
On the 390 rod, I've not seen a lot of failures with the ARC rod, BUT, I haven't had many customers running them in endurance races either.
On the Honda steel rod...I remember there being a "marine" application rod available in (forged?) steel. I never had one in my hands, but saw pictures of it and availability was scarce at the time (maybe 10 years ago.) You might look into boat motor applications with Honda and search from there. I would think marine application = endurance. :)
Now, what that does for the balance, will be another issue -- you will undoubtedly need to internally balance your crankshaft for the heavier rod. Then you get into the whole balancing of a single cylinder engine debate. Depending on how heavy that rod is, I would seriously consider adding weight to the crank counterweights.

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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Imma go ahead and answer several posts with one reply.

#1... Compu-kart, I told you in person that you are using the wrong engine for a 30 min endurance racing over a year ago when I drove your kart in Savannah to help you with your carb issue. The big blocks have a large crank pin that is difficult to properly lube no matter whos rod you use, or what material it is made from. The larger crank pin has more area to lube and the oil smear runs out quicker than a smaller journal rod. Let's remember this is a splash lube engine. You can make it out of steel, titanium or Superman's pecker and you will still have the same oiling issue. When this happens the bearing wears at a more rapid pace than in short track racing. This enlarges the oil clearances and hammers the rod until it breaks. These engines work great on average size dirt or asphalt tracks, and should last most of a season even at the higher RPMs we run them at as Open/UAS engines. Which are way more modified that what you are running. However one weekend at a road race is close to half a season on an oval track in total run time. Do the math. This engine will never last at long distance road racing with it's current splash lube set up, again it is great and a lot of fun on short tracks.


#2... B-Man I think of you as a fairly intelligent individual, but your research skills are your weak link. We use 2024 back in the mid 90's and switched to the current 7075 in the late 90's when we began manufacturing more variety's of stroker components. Then we phased in other styles of our rods to the 7075 in the early 2000's. We did the research on materials with top automotive manufactures and concluded that 7075 was a better over all materiel to produce our products with. There is a fine line between strength and fatigue resistance in these particular parts with them being single cylinder and splash lubed. As far as the design of the Animal rod. We've had several different designs of rods for this particular engine, with the current 6249 beefy rod as Brian mentioned above being the latest and greatest when it comes to long distance road racing. The cross section oiling in the rod has little to zero effect on the over all strength of the rod, yet offers the oiling needed for this particular application. Again we've researched that more than I can count. The Animal has the worst rod ratio of any engine used in racing. Long stroke with a tall piston and very short rod creates very violent stops and starts during revolutions. This is havoc on any rod, made of any material, with or without bearings.
 
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Oh yes! I remember you drove it at Savannah. Thank you for you input on that, we got the carb issue taken care of and it ran fine after that. I've had a lot of people comment on the engine and jackshaft set up and I must say it does have it's fair share of supporters and detractors. I'm not necessarily convinced this is the wrong engine, but I'm pretty sure it doesn't have the correct tune on it yet. As a side note: The mechanical failures we have had on the big block are the same exact ones we had while running the small block clones. To date we have broken one rod, snapped one valve and had one carb failure in 3 years of racing them. We also won at Charlotte and Daytona. That's the beauty of racing with the WKA, they allow for mechanical innovation, experimentation and imagination. We have made a few changes in our maintenance schedule that can help us down the road and thank fellow karters for their comments and advice. The bottom line is this is the girl I brought to the dance. She can be a little tempermental, expensive and overweight but she is fast and a lot of fun.
 
"The Animal has the worst rod ratio of any engine used in racing. Long stroke with a tall piston and very short rod creates very violent stops and starts during revolutions. This is havoc on any rod, made of any material, with or without bearings."

Jody, you are absolutely correct and this is exactly why 2024 is the material of choice in the Animal.

And of course splash lubrication is a joke, we all know that.

Allow me to repeat and clarify: Mind you - I am not knocking a product. It just does not serve our particular application.
Animal engine, endurance racing.

Jody your words wound me, my research is limited indeed. Limited to never having five out of seven insert 7075 rod last more than one or two race weekends. The two survived because we removed them before use. On one particular WF rod I have recorded just over 8 hours at between 4,500 to 7,500 rpm. Two times during this endurance test the rod was removed, inspected and carefully measured and dye penetrant checked and new bolts were installed in reassembly. It was replaced only because I was uncomfortable pushing it further. I have no idea how much time is on my current motor, not so much I suspect. We have lost motors to Noil, low oil and crank breakages but no rod main bearing breakage.

Heres a question; What if it were made from Cale Yarboroughs pecker? I bet that would be sumptin!
 
"Heres a question: What if it were made from Cale Yarboroughs pecker? I bet that would be sumptin!"
"very short rod creates very violent stops and starts"

All jokes aside, Jody, B-Man has done his homework to help us all and has no problem sharing his thoughts and finds
Rookie
 
Big block handled the practice well at the Roval. Good power, no breakage. Spinning it at 6600 along and about 6900 on the draft. Taking gear out of it, track keeps getting faster....
 
Mixed reviews at the end of the race weekend. We got t-boned and run over on the right side during lap 2 by another kart. It took both karts out. Thought I had the damage fixed but it stripped the belt during Sunday morning practice and now its leaking oil. We got the back-up kart ready and it started the race strong. It snapped a throttle cable on lap one. Going to tear them both down and prepare for Savannah. Thank you WKA for a well organized weekend and the Team MTS Competition drivers. Big shout out to Nick Tucker from Nitro-Kart for helping us with our CIK/LO206 karts.
 
You and me both my friend. I will have the crf450 kart ready for Savannah. It's been a real journey getting that together. Story to follow...
 
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