"This a pretty amazing thread, On most 11 page threads we would be disscussing the advantages of larger rear speakers by now"
Or what color should it be painted.
Tom is there sufficient material to machine the pulley into the damper, or will a sleeve be required" It looks like there is reasonable wall thickness to work with on the outer ring? And yes I think it is a sympathetic vib. generated by the crankshaft. A couple of us have discussed this off the board and feel this is where we need to dampen.
John
There are many aluminium pulleys out there. I may start with one of those. Serpintine belts are on everything. I may need to machine a new hub.
I will know more after the PRI show as I did not get any drawings from fluidamper. i will be talkin to them next week.
SixPak modified his stock hub for a Fluidamper, but I don't believe he runs any thing off the crank.
By the way, here is how one can reroute the belt on a 2000 4.0 for drag and offroad use with an electric fan
Remember, Sometimes I post after drinking!
1979 AMC Spirit
Building a Turbo 2.5
I am not very smart!
TurboTom wrote:There are many aluminium pulleys out there. I may start with one of those. Serpintine belts are on everything. I may need to machine a new hub.
I will know more after the PRI show as I did not get any drawings from fluidamper. i will be talkin to them next week.
SixPak modified his stock hub for a Fluidamper, but I don't believe he runs any thing off the crank.
By the way, here is how one can reroute the belt on a 2000 4.0 for drag and offroad use with an electric fan
1bolt wrote:You don't want or need PS for a drag car, you don't want any accessory that pulls HP to run that isn't strictly required for safety or practicality.
Well, for off-road use (as he mentions) I would hate to not have PS. And to really simplify the routing, why not delete those idler pulleys and let the alternator be the tightening device?
I see what you mean but Tom is building a 2wd AMC drag car so I'm sure he's not designing a minimalist accessory drive setup with Crawlers and 40" tires in mind.
If you want a picture of what you're asking about find any XJ without AC. Just unbolt the clutch fan and you've got an Alt/PS/WP only setup without mechanical fan drag (not that it would be worth deleting the mechanical fan for a crawler anyway).
An idler is taking up slack in a nice controlled manner that completely eliminates the belt tension guess work and takes next to no HP to turn. It's more of a "why would you want to delete it" than a "why would you add it" kinda thing .
1bolt wrote:Now wasn't somebody talking about a "rev kit" made for Jeep I6's? I may need one for my 8000 RPM street/strip Comanche well... some day...
Ok I read the first 3 or four pages and then the last 3 or 4....1st let me say that rev kits have been tried and tested on various forms of engines and have all but lost any credibility of being useful in most forms of motorsports. Perhaps the only useful application is a hydraulic lifter application in which your spring pressures are such that you are near collapsing the lifter and cannot add anymore spring pressure to the valve spring to keep the lifter on the cam. If that's the case (usually in the 6ooo-6500 RPM range it is time to go to a solid lifter or roller lifter application anyway. Or you could buy a Rev kit and maybe get some success under the right conditions but you have just added approximatly 24+ parts to your engine that can fail and you may be on the ragged edge anyway and basically putting a bandaid on the problem.
As far as the harmonics discussion goes...without reading up on harmonics it is my recollection that the torsional twist between the two ends of the crank when firing results in crankshaft harmonics that will occur at three primary frequencies between 0 and 10k RPM's in V8's. It is also my understanding that L6's in general are susceptible to a bad harmonic in the 5K RPM range due to the lenth of their crankshafts. Upon inspection of the crankshaft i picked up today I noticed it was a cast crank rather than forged, whether it is nodular iron or not I don't know but being as it is cast rather than forged as some of the old GM straight 6's were it is likely that some additional deflection is resulting in a nasty harmonic incident, although there are those that say cast cranks absorb more I think that given the length the deflection is outpacing the absorbtion and honestly I'm not looking to spin the piss out of a straight 6 with a cast crank cause only have one pair of legs
Harrmonic frequencies can have devastating affect when a particular RPM level that coincides with the harmonic incident is maintained for any amount of time rather than allowing the engine to rev passed it thereby minimizing it's duration. If you were to take one of the engines up near 10K RPM you would find an equally nasty harmonic at that level. As others have noted the camshafts are very long to be supported by 4 cam journals and are surely realizing torsionally induced harmonics at some level due to that fact, but it is likely the crankshaft harmonic that is most destructive.
Factory rubber dampners are designed to cancel the harmonics that occur in the designed operating range. The other rubber dampners are able to be tuned to provide protection in a specific RPM band and Fluiddampners are able to cover a very wide range. My only concern with a large Fluiddampner is they are very heavy and the snout on these crankshafts is pretty small to hang a BBC Fluidampner off of...let us know how that works out for you
Interesting additions. I've read some diverse opinions on rev kits, including some professional race engine builders that disagree about their worth... I'm not sure how cut and dried their value is in modern terms, because I think a lot of the problems that Rev kits are supposed to fix can also be addressed more simply by lightening the valve train and perfectly balancing the spring pressures with the components and cam. But then I've also heard of some early hot rodding legends like Tommy Ivo getting Buick Nailheads to rev to 10,000 RPM's with Isky racing Rev kits. Anecdotal, but confirmed by multiple sources and the records he was breaking.
Not scientific I'll be the first to admit, but I'd still be hard pressed to explain how they got anywhere near that with those old Nailheads. Without the kit doing something to curb float. They didn't exactly have Titanium valves back then.
1bolt wrote:Now wasn't somebody talking about a "rev kit" made for Jeep I6's? I may need one for my 8000 RPM street/strip Comanche well... some day...
Ok I read the first 3 or four pages and then the last 3 or 4....1st let me say that rev kits have been tried and tested on various forms of engines and have all but lost any credibility of being useful in most forms of motorsports. Perhaps the only useful application is a hydraulic lifter application in which your spring pressures are such that you are near collapsing the lifter and cannot add anymore spring pressure to the valve spring to keep the lifter on the cam. If that's the case (usually in the 6ooo-6500 RPM range it is time to go to a solid lifter or roller lifter application anyway. Or you could buy a Rev kit and maybe get some success under the right conditions but you have just added approximatly 24+ parts to your engine that can fail and you may be on the ragged edge anyway and basically putting a bandaid on the problem.
The primary function of a rev kit is to keep the lifter in the hole in the event of a pushrod or rocker arm failure. If the lifter comes out it disrupts the oiling system to the rest of the lifters and depending on the engine design it could effect the cam bearings or the rods and mains as well; which would lead to a blown up engine.
The lifter kit does not add much spring pressure to the overall pressure on the lobe. I don't know the spring pressures offhand but I do know they can be installed without a spring compressor. Also, the traditional style of rev kit will not work on a flat tappet cam.
The enemy of good thing is wanting something better.
I didn't read the whole post and it might have been covered but I didn't see it when I did a quick scan.
I've been running my strokers at 5600-5800 for years with no problem I do the pin trick on the cam but what I think is part of the harmonics is our crank shafts are never degreed perfect. When I have a crank ground I make sure they correct the degree of rotation allot of the cranks I've had done are always over 1 degree off some as much as 3 from front to back. If you don't check for it you'll never know because it will still balance. On the new 306.5" stroker I even went as far as to balance the cam and gear. Also I built a tool to check dizzy harmonic basically I hooked it up to a 3000rpm electric motor on a rheostat with a rubber coupler to the pump drive and set a dial indicator up on the body. There is a little harmonic there (not much) and it is easily correctable. I used a timing light hooked to a engine like you would do normally (one that you can disconnect the advance) put a mark on the dizzy put the motor and engine at the same rpm, find the heavy spot and balance it. crude I know but it works
I don't think so, I think there's enough evidence at this point to say that the infamous "harmonic" is mostly a bunch of FUD (fear uncertainty and doubt) unintentionally fostered by Lee Hurley's tendency to not elaborate or qualify his statements about the harmonic mostly being about steady RPM's and road racing with the 8 counter weight 4.0 crank.
We have some oiling issues with the crank that make sense (although I'm not sure they extend to the 258 cranks), and some broken distributors that are probably mainly the OEM dizzy not being designed for high performance.
How's that for coming around full circle on something, at one point I was conviced that it existed, and now I think it's just been blown out of proportion and is not that big a deal if you balance everything rev through it.
I for one have been trying to keep an open mind about this, but now I've made up my mind, until Tom produces a youtube vid of a 4.0 Dizzy popping out and breaking timing chains, I'm in the "its not all its been cracked up to be" camp.
Sometimes I believe you look for ways for your project to fail.
Build your engine as you see fit and stick it on a dyno...find out what breaks, and then fix it.
That is how this works.
Am I like one of a very small number of people that have made over 394HP with this engine????????
Man ... I must be a GOD .. or an Idiot who wastes his time with this old junk design.
Stay tuned 1Bolt...I am sure I'll break more stuff in my new quest for 500HP
Remember, Sometimes I post after drinking!
1979 AMC Spirit
Building a Turbo 2.5
I am not very smart!
Don't get too full of yourself. The hp number you got to was a measure of breaking force not performance
(this post should not be taken at all seriously... The combination of joking along with someone and being a mod is a pain in the ass) Maybe I'll make this my sig...
.
well... some day...
