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Cammed 4.0?

Yes that should work but might not be want you want if alls your doing is cam.

Any cam for a amc straight six will work there are several manufactures comp, crane, mopar etc.

This sounds like a newbie question. You have over 1200 posts and have never read anything about a cam in a renix?
 
blue95xj said:
Yes that should work but might not be want you want if alls your doing is cam.

Any cam for a amc straight six will work there are several manufactures comp, crane, mopar etc.

This sounds like a newbie question. You have over 1200 posts and have never read anything about a cam in a renix?
Click to expand...

Erm, I think he's Canadish. "Up here, eh?":gag: :cheers:

J/K - nothin' but love for ya!

There are a number of cams available for the AMC six - I managed to dig up specs for some sixty-odd that were in current production in 2005 when I was writing the basic draft of the Power Manual. Not all of them are for "computer-controlled vehicles" or "for use in emissions-controlled equipment," and no-one has told me just why (probably some certification rot. Strokers pass smog all the time...) but there are plenty of them out there.

What, specifically, are you trying to accomplish? Do you want top-end power? Low-end grunt? When there are more than three bumpsticks to choose from, it becomes that much more necessary to know what you're trying to do, so you can choose wisely. The best place to start building performance is on a sheet of paper - saves loads of money!
 
blue95xj said:
Yes that should work but might not be want you want if alls your doing is cam.

Any cam for a amc straight six will work there are several manufactures comp, crane, mopar etc.

This sounds like a newbie question. You have over 1200 posts and have never read anything about a cam in a renix?
Click to expand...

:D Honestly, no. I've never read much into the performance aspect about the Renix.. I've rebuilt mine, but never looked into anything performance wise.

5-90 said:
Erm, I think he's Canadish. "Up here, eh?":gag: :cheers:

J/K - nothin' but love for ya!

There are a number of cams available for the AMC six - I managed to dig up specs for some sixty-odd that were in current production in 2005 when I was writing the basic draft of the Power Manual. Not all of them are for "computer-controlled vehicles" or "for use in emissions-controlled equipment," and no-one has told me just why (probably some certification rot. Strokers pass smog all the time...) but there are plenty of them out there.

What, specifically, are you trying to accomplish? Do you want top-end power? Low-end grunt? When there are more than three bumpsticks to choose from, it becomes that much more necessary to know what you're trying to do, so you can choose wisely. The best place to start building performance is on a sheet of paper - saves loads of money!
Click to expand...

:laugh: Somehow, I knew that was coming.

I'm really looking for low-end torque. Right now, all it has is a home-made CAI and at the beginning of next month it'll be straight-piped with 2.5" behind the rear wheel.

A cam and header combo should help with that, right?
Probably end up going with the Pacesetter http://cgi.ebay.com/ebaymotors/Pace...010QQitemZ200232649315QQrdZ1QQsspagenameZWDVW

Also, I've noticed a lot of these cams are "Smooth idle"... I don't want that. :D I wan't a nice rumble, does anyone still make a cam that still does that?
 
In general most cams that give you a rumble at idle woun't have asmuch low end grunt and they are not all that great with computers. Years ago I used a cliford cam in a renix I had and it was the star o the show. The whole power band was killer to the point that alot of people thought I had swapped a v8 in it. so there are cams out there
 
I too have heard good things about the clifford cam. I've heard it lopes like hell too :firedevil

And it's one of the cheaper cam kits out there to boot :)
 
Bryson said:
Awsome spread Dyno!

Now all we need is a somewhat comprehensive dyno comparison list. It'd be nice to see how the lift and duration specs compare in a dynamic scenario.
Click to expand...

It's on my list... A series of Dyno sims with the only variable being changed being camshaft data.

Just haven't gotten around to it as of yet...
 
5-90 said:
It's on my list... A series of Dyno sims with the only variable being changed being camshaft data.

Just haven't gotten around to it as of yet...
Click to expand...

Do you mean dyno simulation, or an actual dyno?

Dyno simulations are great and all, but it's kinda hard for them to include all the variables (lobe profile/ramp rates for example).
 
Bryson said:
Do you mean dyno simulation, or an actual dyno?

Dyno simulations are great and all, but it's kinda hard for them to include all the variables (lobe profile/ramp rates for example).
Click to expand...

Dyno sims. I have neither the facilities nor the cash to run actual dyno profiles.

Since most performance cam grinders run ramps just as sharp as they can with flat tappets, that's not that great a variable. The "open dwell" is also a miniml variable - controlled by the duration and maximum ramp.

You can run a more aggressive ramp with a roller cam (faster rise/fall, and flatter peak as a result,) but the variables come out much the same.

I find that dyno sims are a bit, er, "optomistic," but running the sim using the same data (save the cam change) should still give relative results that are elsewise valid. They may not give with "actual output" figures (I've noted that most low-buck sims don't account for parasitic drag and only partially for pumping losses,) but it's still a useful baseline for comparison.
 
Bryson said:
Good points indeed! :)
Click to expand...

Yah. I've probably forgotten more than a few, but the idea is still the same.

The tricky thing about modelling pumping losses and parasitic drag is simple - it varies from engine to engine, and that's the big stumbling block.

They also don't usually give you options for modelling, say, a rough-cast head against a CNC-ported head, or allow for inconsistencies in combustion chamber castings (they're pretty good - usually 4-5% or less, but it's still a variance...) so that's why low-buck sims tend to be optomistic in their predictions. I'm sure the higher-dollar ones (I can think of a package offhand that runs five hundred bones or so!) do a better job - making them a bit less optomistic - but a computer model rarely achieves real-world results. Stress engineering is the same way - FEM (Finite Element Modelling) can approach real-world results, and more points mean that it gets closer, but you can't make it "IEM" (Infinite Element Modelling), which is what you have in the real world. That's why engineers always use a "safety margin" (how much margin depends on how critical, intended application, desired durability/reliability, ...) when they finalise a design.

However, a sim can still save you money - either in iterative testing (you have an idea what's going to happen before you start making chips,) in comparison testing (I'd like to run several different cams in an engine on a dyno - but I've got data for sixty-odd cams, so that's sixty-odd cam/lifter kits, plus a few hours each to change them, and dyno cell time!) or just figuring out what's going to happen with part X vice part Y. As long as you know that some 10% or so of your results are going to be stripped right off the top (parasitic drag, pumping losses, and suchlike,) you're good.

That's why simming with all the cams for which I have data is on my To Do list - I can run all of the sims (I've got the datafiles already made!) in less than the time I can run the first dyno tests, not even counting swap time for different bumpsticks. Since the cam would be the only variable that would change, you now know how cam X would perform vice cam Y, in a relative sense.

There are some things that really can't be modelled, as well. Have you ever used Rhoads lifters? They make them for the AMC six - and if they're anything like their SBC/BBC/SBM units, they're damned good. But, you can't really model their behaviour without rewriting the sim package.

A simple polishing of the ports can improve airflow (just smoothing out the surface - not even changing things around!) and you can usually account for that by changing the airflow numbers for the cylinder head - most sims let you do that. But, it still doesn't account for "tumble" or "swirl" in the airstream - both of which are important effects (smoothing out a sand-cast surface will reduce both tumble and swirl, but the airflow numbers won't show that. Reducing tumble and swirl has a greater effect on carburetted or TBI engines than PFI, too! You actually want some tumble in the airstream for carb/TBI engines to keep the fuel atomised...)

Can you tell I've been reading up a lot on the subject of IC engine theory? I've got no-where near all of the books I want, but I'm getting there... I've been swinging wrenches for the best part of thirty years (got an early start!) so I've got the real-world behaviour mostly sorted - but the theory behind it is what I've become interested in. I know how it works, now I want to know why it works...
 
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