High rpm harmonics and oil issues

[Texas250]

so to start off I know this has been talked about at length with lots of good information. I will provide a few links to what I have been reading and observing.
viewtopic.php?t=391&sid=b365ac9297f359a ... &start=165
This thread talks about cam or crank harmonics at length and was last visited in 2009 I believe and is a great discussion from some popular members here.

https://www.angelfire.com/my/fan/HVOP.html
This goes over some oiling improvements. I believe cheromaniac put this together.

And finally

https://www.thedrive.com/news/36982/tun ... -to-861-hp

Engine builder Keith newcomer gets 861 horsepower from a stroker.


With newer technology out and advances in the automotive industry I think we can incorporate more into these old AMC/ Jeep inline 6’s.
I’m South America a version of a Plymouth/ chrysler? Cherokee is used for racing where an inline 6 is the main power plant which turns close to or above 8000 rpm’s and is pretty fast.

Throughout my searching I have found a few solutions to oiling issues and engine harmonics that have been used and I would like to implement them on a 4.2 mini stroker in the next year. My local machinist has quite a few cranks that he will sell me for $100 each a 258 8 and 4Cw a 232 and a 199 crank. I was going to buy 4 just for future builds or projects.

Some of the solutions I have found is
the ATI harmonic balancers which Keith newcomer uses on his builds. Allegedly it helps with harmonics in the higher rpm’s where I would be concerned.

Keith also moved the crank trigger to the balancer instead of the flywheel,( why I am not sure) but he says it allows him to use the Holley dominator system so that could not help harmonics at all.

The inline 6s now have available windage trays and crank scrapers which could help from frothing the oil at higher rpm’s.

Roller camshaft bearings are now available which can free up as much as 10% friction in our engines also freeing up horsepower throughout and available torque that is no longer being used to rotate the engine.

Ultra thin piston rings are now used to reduce friction and improve sealing since less tension is used over a smaller surface area. (Ring spacers are also available to retrofit pistons such as the 2229s with a thinner ring pack).

HP tuners now gives us the ability to scale injectors, map sensors, raise rpm thresholds, adjust fueling and spark which I have already played with a good bit to tune my Jeep for the mods in my sig with great success.

We have also learned that Navarro has used a 199 CI engine for racing with great success and there is a link somewhere I can’t find at the moment that even breaks down one of the engines that he used with pictures.

Also Gary Hill used an AMC engine for drag racing which turned close to 8000 rpms.

So now my thoughts on all of this. If I could build a standard DR Dino 4.2 mini stroker but incorporated some of these things like a windage tray or crank scraper, an ati balancer; fully balancing a rotating/ reciprocating assembly. A good breathing cylinder head. And good tuning and of course lots of data logging.

What other potential issues have we found with spinning an engine up to that rpm just in the bottom end of the block.

From some math if we could make the 306 lb/ft at 3900 and 260 hp at 5000? Then even if we lost our torque down to 250 lb/ft at 7000 rpm’s that would still increase our horsepower to 333.

I would love to hear some feedback from anyone that has done some in depth reading or direct experience or even those people out there that have a calculator for a brain on the shortcomings of something like this.

[Texas250]

Also here is the high rpm cherokees in South America to get your blood pumping.

https://www.thechicagogarage.com/thread ... pm.158085/

[Cheromaniac]

The technology to build a high rpm AMC inline six is definitely out there, and the requirements include:

1. A balanced and blueprinted bottom end.
2. Strong and lightweight reciprocating and valvetrain components, including forged rods/pistons and ARP rod/main bolts.
3. Preferably a shorter stroke for an oversquare engine design.
4. An oiling system that provides adequate lubrication and cooling at higher rpm. A higher capacity oil pan with kick-out, trap doors, and baffles to prevent oil starvation, a HV oil pump, windage tray, crank scraper, and oil cooler.
5. Ported big valve head, solid lifter cam, and a custom intake manifold to ensure good high rpm breathing.
6. Fuel and ignition systems that can provide adequate fuel and a stable spark at higher rpm.
7. A thick aluminum radiator to provide sufficient cooling.

[Texas250]

Thanks for the reply cheromaniac. I noticed you said blue printed and balanced lower end. Does that definitely solve the harmonics issue?

Another question for you is the thought of the callies take off nascar connecting rods being used in a piston guided rod application for our engine. With a 6.2” length enough space to bush the wrist pin, and a big end measuring 1.850 for a turned down crank through. This would give us a lighter, longer, and stronger rod since a lot of our pistons will be custom made anyways. The only issue I have found is the connecting rod side clearance but with the right piston guided rod assembly isn’t that avoided anyways?

[Cheromaniac]

Thanks for the reply cheromaniac. I noticed you said blue printed and balanced lower end. Does that definitely solve the harmonics issue?

It'll certainly reduce any crankshaft harmonics for a smoother running engine, and it'll prolong engine life.
The camshaft harmonic at ~5600rpm is unavoidable as it's only supported by four bearings, but you can get around that by accelerating through it. Just don't hold the engine near that rpm and risk breaking the timing chain or throwing the distributor out of the block.

Another question for you is the thought of the callies take off nascar connecting rods being used in a piston guided rod application for our engine. With a 6.2” length enough space to bush the wrist pin, and a big end measuring 1.850 for a turned down crank through. This would give us a lighter, longer, and stronger rod since a lot of our pistons will be custom made anyways. The only issue I have found is the connecting rod side clearance but with the right piston guided rod assembly isn’t that avoided anyways?

As long as the rod side clearance is within factory tolerances, there should be no problem.

[Texas250]

As long as the rod side clearance is within factory tolerances, there should be no problem

Would piston guided rods not solve the issue since the rods are thinner.

If the rod journal was turned down to 1.850 diameter I could possibly keep the factory clearance but that would only give .159” to maintain the rod and bearing in the proper channel

[Cheromaniac]

Would piston guided rods not solve the issue since the rods are thinner?

I'm not sure but I reckon Russ would be able to give you a better answer.

[I6FAN]

Thanks for the reply cheromaniac. I noticed you said blueprinted and balanced lower end. Does that definitely solve the harmonics issue?

Another question for you is the thought of the callies take-off NASCAR connecting rods being used in a piston-guided rod application for our engine. With a 6.2” length enough space to bush the wrist pin, and a big end measuring 1.850 for a turned-down crank through. This would give us a lighter, longer, and stronger rod since a lot of our pistons will be custom-made anyways. The only issue I have found is the connecting rod side clearance but with the right piston guided rod assembly isn’t that avoided anyways?

I wouldn't turn down the rod journals to gain rod length. The reason being, you lose the overlap of the main journal's diameter and rod journal's diameter (when viewed from the axis of the crankshaft). The less overlap the less rigid the crankshaft becomes. Flat plane v8 engines usually have short crank throws for this reason and typically have less cu in2 as a result. Most 4 cyl are less than 2.5l for this same reason. I would increase rod length with less piston compression height, but that will have its limits.

There are lightweight rods and pistons available for v8 engines, but they would be custom items for the Jeep I6. The rods would be about 150 grams lighter than a stock 4.0 rod, and the pistons would be about 60 grams lighter than stock 4.0. Stock weights for rods and pistons are ~660 grams and ~510 grams respectively (lighter ring pack helps also). That would be an 18% weight reduction in rotating and reciprocating weight. That would be a good thing for crank harmonics and a less than desirable crank stiffness. Of course, all of this is only relevant for all-out high rpm engines.

[Texas250]

Most of the 4 cylinder engines are under 2.5 liter displacement because of 1st and 2nd order harmonics. There is a new 4 cylinder engine out that is being tested but soon to make it to production for outboard engines on boats. It is 650 cubic inches and can reach 7000 rpms.
https://m.youtube.com/watch?v=8alrpieveDg

I will have to look into how far offset grinding would put the crank throws off of the centerline.
Many engines now a days are moving to a piston guided rod setup where the piston is locating the rod on the crank through instead of rod side clearance. It removes friction of the engine and by taking the throws down in diameter you are also reducing bearing speed.

I’m still digging into the actc race cars from Argentina which are based off of the amc 230 tornado engine that was placed in the Torino Cherokee cars.

Does anyone have any links to the 230 tornado engine, mainly cranks dimensions and as to whether it would fit in a 4.0 block.
That would be the ideal crankshaft for a high reving stock displacement ish 4.0