Question about aussie heads
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Laughing Gas
Joined: Aug 2007
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From: Spokane, WA
Originally Posted by FordTrucksKickGM
So if you have closed chamber heads you can run a higher CR on the same fuel? When I said burn more efficiently I meant a more complete burn of the fuel which I suppose would translate to more milage plus more power or is the fuel completely burned off either way.
As for the fuel burning completely off, I'd think that'd have more to do with your fuel system, and how well it's matched to the engine (e.g. proper carb tuning). Granted, in an engine prior to EGR, there was no recirculatory system to assist in complete fuel burn, but a properly tuned fuel system should make unburned fuel negligible. Fuel injection simply removed the need for tuning mixture as in the case of a mass air system, the mass air meter, paired with the EGR sensor, and the O2 sensor would inform the computer of what the current burn and mixture is, and it would adjust injector pulse width to compensate. Basically, it's the equivalent of instant carb adjustment.
Anyway, I'm thinking that the CR shouldn't have too much to do with the fuel burning off as it does with the power produced in relation to pressure and atomization of the fuel supplied when ignited. If the fuel supplied is the right quantity for the engine, burnoff should be complete regardless of the ratio (again, based on octane level needed for related CR).
Or am I talkin out the side of my head?
Freshman User
Joined: Oct 2007
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How does the gear vendors OD work with a transfercase? It seems like it would have to fit somewhere between the transmission and transfer case. That would make an extremely long drivetrain. Much langer than most 203/205 doubler set ups.
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Laughing Gas
Joined: Aug 2007
Posts: 1,107
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From: Spokane, WA
The Gear Vendors OD unit bolts directly to the rear output section of the transfer case. Yes, that means the OD is not applied to the front differential, but in reality, how many circumstances can you think of where you'd need an OD while in 4 wheel drive?
Basically, the unit assumes and precludes you from being able to use OD while in 4 wheel drive. It's a 2wd application only, and I'm assuming it has to be shut down before the vehicle can be engaged in 4wd.
Clear as mud? If you google Gear Vendors they have a website that I'm sure might explain it better than I can.
Basically, the unit assumes and precludes you from being able to use OD while in 4 wheel drive. It's a 2wd application only, and I'm assuming it has to be shut down before the vehicle can be engaged in 4wd.
Clear as mud? If you google Gear Vendors they have a website that I'm sure might explain it better than I can.
Posting Guru
Joined: Mar 2005
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From: western montana
shorter burn = more compact and stronger wave- yet leaves a bit more fuel unburned?
The chi heads are closed as well and some have reported that the alloy head will also increase quench by .5 or so. I'm wondering if the savings didn't come more from cc design vs material it's made of and how the chi compares to cast in octane requirement. If $ isn't an issue why would you rather go cast?
and theres no doubt in my mind that you will save signicantly on fuel with overdive...the conversation wasn't going south at all but just getting more detailed which is a benefit to all. You run 35", 45" 500" tires with or without the transfer case...you will benefit from having it enough to pay for it in a relatively short time. It automatically turns off when 4x4 is enganged and will fit most 4x4's.
Your initial ratio should be geared so that regular 1st gear is very efficient in getting the truck off the line and final ratio should be around .7-.9 higher than it would be without od. ie (example) 4:11 for 32" tires and final drive with od is 3.20 something I think...variables and i'm going off memory.
The chi heads are closed as well and some have reported that the alloy head will also increase quench by .5 or so. I'm wondering if the savings didn't come more from cc design vs material it's made of and how the chi compares to cast in octane requirement. If $ isn't an issue why would you rather go cast?
and theres no doubt in my mind that you will save signicantly on fuel with overdive...the conversation wasn't going south at all but just getting more detailed which is a benefit to all. You run 35", 45" 500" tires with or without the transfer case...you will benefit from having it enough to pay for it in a relatively short time. It automatically turns off when 4x4 is enganged and will fit most 4x4's.
Your initial ratio should be geared so that regular 1st gear is very efficient in getting the truck off the line and final ratio should be around .7-.9 higher than it would be without od. ie (example) 4:11 for 32" tires and final drive with od is 3.20 something I think...variables and i'm going off memory.
Posting Guru
Joined: Mar 2005
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From: western montana
Originally Posted by MBDiagMan
The advantage to aluminum heads as opposed to cast iron is that their better heat transfer properties allow for a little more CR with the same octane fuel.
So wondering how much more of a difference the aluminum makes when compared to oz heads....
another would be flattop piston and those kb hypers designed and cut for the closed cc. The best test would be a 400 with tims kb's and oz heads against same heads and flattops in the hole just enough to make the same SCR. AND chi heads with and without kb's pistons/flattop in hole. Same cam and build in all 4 to include checking for all tolerances etc... even do a compression test to check...
I'd predict the oz with kb's would have.2-.3 more compression tolerence than with oz with flattop... Same with Chi.. AND that the Chi with kb's would have an additional .2 tolerance over the oz with kb's.
I need some money or to get a grant to figure this out...would have to build 10 sets of engines of each to overcome confounds but it's doable. Now is this intellectual masturbation or what. But still i bet i'm right.
Last edited by roger dowty; Oct 25, 2007 at 02:04 AM.
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
My 434 is 10.8:1 static CR, and 8.5:1 dynamic. I could probably get away with another 1/2 point static. I have CHI heads and zero deck pistons.
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Posting Guru
Joined: Mar 2005
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From: western montana
so my '72 351cj with flattoprs and 8.6 Cr should take chi heads and handle the increassed compression w/o issue..should be at least a full point increase...if the bottom end stands up to it w/o rebuild...interesting.
More Turbo
Joined: Nov 2004
Posts: 590
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From: in the woods of Maine!
I would run the Auusie heads. First off, if you've got a carb on it, who cares about gas MPG, as long as it's between 8-12 it doesn't matter, it won't compare to a EFI unless you're going more than 10 miles down the highway.
You don't care about emissions so the open chamber heads are out of the question.
And why run aluminum on a motor like this, where it kills your dependability. Aluminum heads don't warp easy, but on a 30 yr. 0ld truck, I'd run cast iron, because you never have to worry about if it's too cold out, or the motor's overheating, it just runs everytime!
the quench chamber will make more power everytime only because of the turbulance it creates and how it does it. you can def. get away w/ more static CR because of this.
you can run damn near 1 whole point more static compression ratio w/ aluminum heads, and that is because aluminum disipates heat. which is good for resisting detonation. It also hurts power a little at the same time, because the more heat stays in the combustion chamber, the power you make (hence seeing pistons w/ that coating on the top, to keep the heat on top of the piston, and not being absorbed into it.)
unless you are building something running 12:1+ static CR, and still making power over 6,500 RPMs aluminum heads aren't REALLY nessessary.
You don't care about emissions so the open chamber heads are out of the question.
And why run aluminum on a motor like this, where it kills your dependability. Aluminum heads don't warp easy, but on a 30 yr. 0ld truck, I'd run cast iron, because you never have to worry about if it's too cold out, or the motor's overheating, it just runs everytime!
the quench chamber will make more power everytime only because of the turbulance it creates and how it does it. you can def. get away w/ more static CR because of this.
you can run damn near 1 whole point more static compression ratio w/ aluminum heads, and that is because aluminum disipates heat. which is good for resisting detonation. It also hurts power a little at the same time, because the more heat stays in the combustion chamber, the power you make (hence seeing pistons w/ that coating on the top, to keep the heat on top of the piston, and not being absorbed into it.)
unless you are building something running 12:1+ static CR, and still making power over 6,500 RPMs aluminum heads aren't REALLY nessessary.
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