Max RPM of Jeep Engine

[Plechtan]

Well for the oil pump i was looking at the Moroso external pump, you have to scroll down to see it http://www.moroso.com/catalog/categoryd ... code=14444

Ihe EFI I was going to use a Megasquirt http://www.megamanual.com/index.html Or if you want to just use a carb, and looking for a electronic replacment for your distributor, look at this http://www.autosportlabs.net/Main_Page

Mud boggers would love it, they could get rid of their distributor.

Anyway that is how you get rid of the distributor and relocate the oil pump. The timing belt drive? I'm working on it. I will let you know how it is going.

[Plechtan]

I did a little more research, the chevy 6 only uses 4 cam supports, and they can get some crazy HP out of them. 500hp out of a 260cid. That is naturally aspriated. So the cam supports in the jeep block could be weaker than the ones in the chevy block, the cam itself could be weaker then the Chevy. Making a billet cam eeould solve that problem. Another difference i saw was that the distributor drive was between cylinders 1and 2 on the chevy and the distributor drive on the jeep was between cylinders 3 and 4. I wont be using a distributor drive, so the location of the drive will not be a factor. I have never heard of a chevy 6 having a cam harmonic, but i will do some more research.

[TurboTom]

Could someone lead me to the info or posts about this harmonic? Who found it, what happened and so on.
I am building a Turbo 4.0 for my Spirit drag car and would like to do more research on this.
Thanks
Tom

[Plechtan]

Try this:

http://www.jeepstrokers.com/forum/viewt ... t=harmonic

Or the Hesco BBS has a lot of information on the "old posts" section You can also search the work "harmonic" in the box located in the upper right of your screen.

[TurboTom]

So would it help if I made a belt drive for these engines?
I used to have some drawings of an overhead cam conversion for a 258 I was going to do many years ago( Long Gone)...that may be the answer.

[seanyb505]

I think at one point Mopar made a gear drive instead of the chain to combat the harmonics. I wanna say they were aftermarket and have been discontinued.

[Plechtan]

The Gear drives were Made by Hesco for Mopor performance. They have been discontinued

[Plechtan]

So would it help if I made a belt drive for these engines?
I used to have some drawings of an overhead cam conversion for a 258 I was going to do many years ago( Long Gone)...that may be the answer.

To my Knowledge, nobody has ever made a belt drive, it would probably help the problem, but not solve it. From what I see nobody really knows the cause of the vibration. It has been speculated that it is the cam deflecting because it only has 4 bearings, however the Chevy 6 is a similar size and shape engine, the cam is just as long, and it only has 4 support bearings and does not have any problems with a cam harmonic. When they stroke those motors, the rods come so close to the cam, that they actually have to reduce the size of the cam for rod clearance. You would think this would make the cam very weak, but still no harmonic.
So maybe the theory is wrong, maybe there is a vibration someplace else in the block that is causing the cam to vibrate.

[SIXPAK]

A buddy I race with has made a "jesel" belt drive from a BBC unit for his stroker. You have to use an idler with that set up. I will go that route some day but my gear drive is fine for me now. . Rumor is an OLDS 350 Rocket has the same center to center distance, HINT HINT!

[Alex22]

I'm about to type something that some of you may not want to believe. Maybe Lee at Hesco is wrong about the source, cause or even the existence of a harmonic in the camshaft or crankshaft.

Option 1: The harmonic IS in the camshaft
A gear drive will NOT be the answer to that problem. Gear drives have the worst harmonic characteristics of the three types of timing sets. As seen here http://www.compperformancegroupstores.c ... de=G-Drive on COMP's website, the gear drive description says nothing about harmonics, just that it makes the engine sound cool and is a strong item for high power applications. The billet gears will not absorb any of the harmonics, they will reflect the pulse and eventually create a harmonic. If you read the item description for the COMP and Jesel belt drives, they do help to eliminate harmonics in the camshaft.
http://www.jeselonline.com/v2/index.php?categoryid=22
http://www.compperformancegroupstores.c ... ode=HTBelt
Another thing that can cause a nasty harmonic in the camshaft is using the camshaft above the RPM it was designed for. I checked on Comp Camps website and here are the RPM ranges of their Jeep I6 cams.
COMP High Energy: 68-201-4 &68-200-4&68-115-4 1000-4200
COMP XTreme 4x4: 68-239-4 1400-5700rpm 68-231-4 800-5000
Crane grind# H-192/2667-2S-10 part# 750501: 800-4200, valve float at 4800
Crane grind# H-260-2 (REPLACES HMV-260-2) part# 753901 1400-4800, valve float at 5200
Crane grind# H-272-2 (REPLACES HMV-272-2) part# 753941 1800-5400, valve float at 5600
Crane grind# F-228/3334-2-12 part# 751101: 2200-6000, valve float at 6600
Crane grind# F-238/3467-2-12 part# 751111: 3000-6500, valve float at 7000
Hesco doesn't list a rpm range or a valve float number for their camshafts.
All camshafts that are advertised as "high torque" will have a low operating range with a low valve float rpm. On high torque cams that are marketed as "high torque" or as an RV or truck cam will have the most aggressive ramp possible. At high rpms, the cam will open the valve so fast that the lifter will leave the face of the camshaft and will land abruptly on the back side or base circle of the cam. The abrupt impact on the cam will cause a much larger shock wave within the cam than it would when its operating within the specified rpm range. The shock wave will travel down the length of the cam and will be reflected back towards the source by the cam bearings, some will continue to the end of the cam. Now there are multiple harmonic frequencies within the cam and one very large one that some claim will destroy the camshaft. If there is a timing gear set in use it will effect how much the end of the camshaft can flex due to the harmonic but will not actually eliminate it. The timing gear set will also transfer the most harmonics into the crankshaft. A timing belt will absorb the harmonic and allow the engine to run smoother for longer. A timing chain set will dampen some of the harmonics but it will transfer some to the crankshaft and some back into the cam.
It is possible to extend the rpm range of a camshaft by using a stronger valve spring and/or lighter valve train components. Your best bet for an accurate rpm range with different components would be to ask the camshaft manufacturer. At work one of our customers had to run a high torque camshaft in the race division they were in but they needed higher rpms for the straight aways. We went with a stronger valve spring to keep the lifter on the cam profile. The valve springs were worn out by the end of each race and had to be replaced. The following season lighter valve train components were used so the valve spring didn't need as much tension on it and the set of springs lasted much longer.

Option 2: Harmonic is in the crankshaft.
The engine was not correctly and the vibrations are being transferred through the engine block and the timing set to the cam which would happen to be the weak spot in the engine causing a failure. This option is not as likely as the other two.

Option 3: The harmonic does not exist.
The engine builder has selected the proper components for your application and you don't over rev the engine causing damage which could result in paper weights and ash trays. As I stated in a previous post I asked Charles at Camcraft Cams about harmonics in I6 engines, he said that he has a few camshafts for the I6 jeep engine that turn 6000rpm and 6400rpm. His customers never contacted him about any harmonics or broken camshafts. I'm waiting on a response from another cam grinder about harmonics in a jeep engine. I had never heard of harmonics causing problems in camshafts before I started reading stuff on jeep forums. None of the guys I work with had heard about that problem either.

I was looking into making a COMP 350 chevy timing belt work on my stroker. I worked on it until the cost to necessity ratio went too high for me to justify the time and money. A few notes to those working on making a belt drive system work on a Jeep engine. Not all belts can work when exposed to engine oil, the kits that cannot be run in oil come with the proper seals, you will need to find a way to make the seals work in the jeep engine. The belt used by comp in their timing belt that can be run in oil is a Gates Power Grip belt (I have to double check, it might have been the Poly Chain belt) If you download the Gates Design guide it has all the information you will need in order to make your own setup.

~Alex

[Alex22]

A few things I forgot to mention.
One thing that is completely out of your hands is how well the cam core was straightened before it was ground and how much damage was UPS able to do to it while using it as a baseball bat, pry bar or maybe they just felt like throwing something across the warehouse.

~Alex

[Plechtan]

We plan to make a belt drive for the Bonneville car, it will run dry. The first reason for doing it was to reduce the HP required to turn the cam. If it helps the harmonics, thats even better.
on your comment of the lifters losing contact with the cam, has anybody tried installing springs between the lifters and the head? I have seen this on a chevy motor. The springs are designed to keep the lifters in contact with the cam. I understand that the Hesco head has large holes in it for the pushrods. you could probably tap these holes, thread in a piece with a hole in it for the pushrod to retain the spring. This would let you use smaller valve springs and reduce the strain on the valve train.

[John]

I think the large holes in the Hesco head improve lubrication and allow the lifters to be removed without removing the head.
John

[John]

Gear Drive Systems did nothing to reduce the harmonic, but allowed them to survive a fast trip through the rpm zone without breaking a chain.
John

[Plechtan]

I think the large holes in the Hesco head improve lubrication and allow the lifters to be removed without removing the head.
John

Yes i understand why the head has the large holes, my suggestion was to use them for another purpose. the lifter springs i saw on the chevy were between the lifter and the bottom of the head, you had to remove the intake manifold to access them(V8). If you made something similar for the 4.0 you would have to remove the head to change them. by having so screw in retainer the could be serviced without removing the head. the screw in piece could have a hole the same size as stock, and when it was unscrewed you could still get the lifter out.