The explorer shows an unequal length for the axles. Doesn't this create an angle from the tailshaft of the trans to the pumpkin? In our application are there any issues with that geometry?

It's only offset a little and no it won't matter. If you look under Phil's FJ40 both the front and rear axles are offset to different sides.

As long as the opposing U-joint angles are equal, opposing, and 3* or less, to provide proper phase cancellation. It could be a problem with a short D/S.
Is the other carrier "centered?"

I'm not sure this is the question you asked, but, the trans will be "very" center and the DS would be quite short as I imagine it. So the U joint angles would not be opposing and the DS would be greater than 3* as I imagine it. :huh: The explorer has the advantage of 31 spline axles and already being a 5 lug. However, I don't think at our power levels 28 spline is such a problem (our trans output is 28 spline), and converting the hubs to 5 lug ain't such a big deal. Please to advise. Maybe the Stang is a better starting point, though we'd have to regear. . .

If the Stag pinion yoke is centered between the wheels, then yes, it would be better. (Short answer):thumbs_up:

So obviously the Exploder is offset for a transfer case, so the Mustang looks like a good fit. If that means gear change, rather than trying to find a LSD, we can get a spool for $90, a gear set for $150., and set it up killer. Maybe I should take Ben down to Unitrax, and see what they might have laying around. Time to start whooing some venders. They might also provide some good advice/guidence concerning this adventure.
As for brakes, as long as the car stops by the last turn off, they are fine.:sm_laughing:

I have a set of 3.55 gears for an 8.8 that only have 7000 miles on them. Switched them for 4.10s. That may work better for that 4 speed anyway with a 25" - 26" tire.

The Explorer center section looks centered. I'll measure mine today and tell you for certain. Also, most Explorers came with 3.73 gears which will be a good gear for the RX-Snake.

Assuming 26.1 tires (275/50x15) our transmission and a 6,000rpm shift point/red line, I think we' could take advantage of the taller 3.55 gears.

3.55 = 127mph
3.73 = 121mph

I think we'll have the power to weight to ring out the taller gear and have a faster trap/et.

Ok, with my 3:55s I hit 119 in third gear. That's with a 27.9 (P275 15 60) inch on the 3,000 pound vette. So.......................I don't see how your math is right. Math and the real world don't always jive. Just not sure about it is all. :drink:

Can you run a 28 inch tire with 3.73 gears and tell me what mph you show for 6000rpm?

Also know that a Slick will grow as you go sown the track. So if we use a 26 inch slick it will act like a taller tire further down.

Glenn, what do think about raising the duration/retarding the cam, installing really stiff springs, and raising the redline? (Think Beehives)

The weight is irrelevant, what was your rpm at 119rpm? Your math might be fine. Mine rocks. :penguin:

Here's a nice accurate graph of a wide ratio top loader, 3.55 gears and 275/50x15 tires. The engine turns the trans turns the axle (not a lop of slop there) turns the tires. Pressure and rotational inertia can have some effect on "real" diameter and effect total final "gearing", but the margin of error would be a couple mph at most I would think.

Ok, when I had my 289 Hipo it would run to 7000+ rpms with the solid lifter factory cam and stock valve springs. The problem we have here is the unknown cam. I think a switch to a known cam with soild lifter/roller will allow the 302 to rev more freely. Beehives are a thought, but cost factor will be an issue.:drink:

If weight is irrelevent, let's make the RX 20,000lbs. Should be good for traction.:smack:

That MUST change . The cam is EVERYTHING.

What about blower effeciency? I was under the impression these smaller roots blowers will start to fall on their face from 5,500 - 6,000 rpm. :huh:

Weight is always a factor:laugh::laugh::laugh:

If I remember correctly it was around 6200 to 6500 rpm. I'm just saying a 3.55 gear MIGHT be too tall in the real world. I remember when I was running the 1/4 I was just shifting into forth just before I hit the light with the 3.55s.


Not saying you are wrong , just stating a little real world testing would help here.:drink:

Weight is irrelevant for calculating gearing and "potential" speed you silly goose.

I have to go for a few hours, I'll run this later. But yes, the tire changes in diameter is where the real world differences in speed as a function of gearing changes.

Without allowing for any growth and/or variances in the tire, a 28" tire with 3.73 gears will be running ~134 MPH @ 6000 RPM in fourth gear.

Just for shits.:D WEIGHT can limit the rpms the engine is able to turn.:p


What ever could be MORE important than Motorgen??????????:rant:




Hey, I just noticed I have OVER 1000 posts on this site. Damn, what the hell would I have to say that takes that many posts???????:huh::o:suicide:

Absolutely.

My implicit assumption was that given our power to weight ratio, the engine would have sufficient power to rapidly reach redline given either a 3.55 or 3.73 axle. I was isolating a single variable in the system. There is basically no cost difference with either axle, but there plausibly could be a few mph and/or couple tenths penalty one way or the other. My hypothesis would be that with the power to weight we're likely to have, the "slightly" taller rear axle, would result in faster ET and Trap in the 1/4. However, it is possible that while the top potential speed is lower with the shorter gear, it may reach that top speed faster enough to result in a faster ET. :huh: To model this properly we'd be changing from simple arithmetic to real math. I'm looking for accumulated experience.

Anyway, this is getting to the kinda splitting hair territory, but I enjoy that, so you have to endure it. :pot_stir: :smack:

Making the scratch that allows me to underwrite this project is pretty important. :bigthumbsup:

A tiny bit slower, but close enough. :bigthumbsup:

6,000rpm (shift/redline)
Wide Ratio Top Loader
3.73 Axle
275/60x15 Tire

If we have enough power to turn this gearing (my guess is around 500 BHP with this much weight, very rough) and make it stick for a wicked 60', and click off clean shifts, this would be a consistent low mid 10 second pass.

You mean endure it....:rolling::rolling::rolling::rolling:like a tooth ache????

Since we're being nitpicky, your math is a little off. Here's how I calculated it.

MPH= ((RPM/(rear gear ratio*trans gear ratio))*60)/tire revs per mile

RPM = 6000
Rear Gear = 3.73
Trans gear ratio = 1
Tire revs per mile = 720.49
MPH = 133.95708

Thus my earlier posting that it would be ~134 MPH.

My sheet does three things a little differently. It calculates circumference exactly on input tire size. A 275/60x15 is slightly less than 28 inches. Additionally for reasons I can't remember and forgot were in there it has built in corrections altering the revs per mile and revs through the transmission. Hence the reduction from your completely accurate pure calculation. I can alter my sheet to remove these built-in corrections and we'll come out to the same numbers exactly. But this would be a totally idealized, perfect circumference, no slop kinda situation. I suspect my sheet may model reality a little more closely, but I certainly can't give you the logical proof for the constants that are used. There, aren't you glad you asked?

"If" I wanted to donate a buck or two how would SOMEONE do this???:leaving:

So how many tire revs per mile does your sheet calculate? Because I calculated the revs per mile using the exact circumference of what a 275-60-15 tire should be. I don't allow for any variances and frankly I don't know how your spreadsheet could do that accurately, considering different variances between tire, tranny, and rear-end manufacturers.

Here is my calculation.

(((275/25.4)*.6)*2)+15 = 27.992125 (Tire diameter)

27.992125 * 3.1416 = 87.940059 (Tire circumference in inches)

87.940059/12 = 7.3283382 (Tire circumference in feet)

5280/7.3283382 = 720.49076 (tire revolutions per mile)

BTW. I'll be going to Pomona. Anything you want me to be on the lookout for?

Don't knwo what all they have there, since I've never been, but:

- Repair Parts for the 174
- Holley 750 CFM Carb with four corner idle set (if on the pretty cheap side relative to new, might give that a whirl first)
- Radiator for an 2nd Gen RX-7, we don't have one
- Alternator w/Bracket
- Starter

These I can get new from Summit, but if you see them cheap:
- Scatter Shield for Top Loader
- Long Tube Swap Headers for SBF

I trust your judgement, send me the bill. :sm_up_there:

Here's the Excel Fomula for Revs Per Mile I'm using:
=(63360/(((B9/25.4*(D9/100)*2)+F9)*3.141597)) *0.99

B9 = Section Width
D9 = Aspect Ratio
F9 = Rim Diamter

It's basically the same as yours, EXCEPT for the last multiplication. This actually reduces the number of revs per mile and therefore increase the speed for a given RPM. I believe it was the original desginers intention to account for growth in the tire as a function of heat/pressure and rotational inertia.:huh:

However, my sheet also inlucdes a big reduction when calculating the speed for a given tire/axle/gear @ RPM x.

=((D18/(B21*B28*H9))*60)*0.97

D18= RPM (shift or redline, or whatever you want to put in, I'm assuming 6k)
B21=Gear ratio
B28=Axle ratio
H9=tire revs per mile

The final multiplication is an additional reduction I forgot about. If I had to guess it's for nonlockup auto trans, but that's just a guess. Thanks for the catch. :thumbs_up:

I'll take out these constants for future calculations so we're comparing apples to apples.

Alt and starter you can get cheap from the zone rebuilt, and forfeit the $10 core charge.
Radiator, I would hold off on. I may get that REAL cheap from a friend. (He owns Anaheim Radiator). He can probably make us one custom.

Quit bench racing. So your off 1mph or so. The traps will tell the truith.:D

I'll call you if I stumble upon a good deal. Is someone maufacturing headers for this swap?

We don't have a car to race for real yet. :smack: And this is (theoretically) for choosing the best possible total combo in the first place.

These appear to be the best candidates for our swap.

Roger. I've been using Duralast alts and starters on other vehicles for a while, and they seem pretty well made and reasonably priced. BTW, what years was this motor in production, or what car can I use as the reference when buying parts?

I have been meaning to ask. What is the latest NHRA on sound? Are open headers still okay? (Dating myself)