Drivetrain 78 Ii 8" 3.80???

I swapped mine with 4.62s for a couple of years running a T5 and 265/50-15s. Since mine is more of a driver, it was revving too high for me under my normal habits. I switched them for 3.55s and love them! Mileage wise, which really isn't a concern but I was curious, I got about 20 MPG on my trip from the Atlanta metro to Myrtle Beach for Mustang Week last year and the RPMs were tolerable at 80 MPH. I realize this isn't an apples to apples comparison, but if you use your car for more race duty, the 3.80s would probably serve you well. For more street duty, I would more than likely be a little more conservative but 3.55s should wake it up a little and probably be a good compromise. Not having an OD transmission will be your limiting factor as far as driveability goes. You could also think about a stall converter if you haven't already. Again, you probably don't want something outrageous, maybe something around 1500-2500 RPMs? That will also help with off-the-line acceleration since it basically raises the RPMs of the engine before engaging the transmission, essentially acting like a manual transmission when you pop the clutch. Just another angle to look at.....

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=78/prd78.htm

78mIIman said:

Hi guys, Have a '78 II, with a 302- mild crane cam, forged rods, hyperuectic pistons, weiand intake, headers, and a holley 600 vac sec carb roughly 210hp to the wheels-with a c4 trans. Currently have an 8" rear end with 3.00:1 gears. Looking to change the gear ratio out to a 3.80 or a 4.11:1 ratio. Leaning towards the 3.80. Has anyone done this with their II?? Pros? Cons? Did it wake it up? Never drive on the highway, will take it to the track occasionally and would like something off the line pretty fast, like to blow the doors off the 4 wheel imports that put down mustang 2's and still have some guts higher end too. Have a 235/60-14 BFG's in the rear...roughly 25" tires, red line probably 5900rpm...Let me know your opinions. Plan on supercharging it next year with Weiand 177 charger.Thanks!

Click to expand...

To give you an idea how close our combos might be here are the specs of my car, which are updated here to my current combo, that I have listed under the first YouTube video I posted about it. Like josefsz mentioned, you didn't list your heads which is a pretty major component as far as making power is concerned, but this might help steer you in the right direction with your build.

68 302 short block with flat tops
Melling cam 290/300 duration (214/224 @.050) .507/.533 lift
Dual feed Holley 650 Double Pump
1.7 roller rockers
Trick Flow Twisted Wedge heads
Metallic ceramic coated headers
2 1/2" H pipe exhaust through Thrush chambered mufflers
High flow fuel pump
High flow aluminum water pump
Ford Motorsports oil cooler
High volume oil pump
Electric puller fan
Full MSD Ignition system
T-5 Swap from a 95 Mustang GT
8" rear with 3.55 gears and Detroit Locker
165/80-15 front 265/50-15 rear
Hood scoop is from an 83 Mustang GT, modified by myself
Gas tank is from an 89 Mustang modified by myself
Desktop Dyno estimated 370 HP @6000 355 ftlb @4500
It has not been actually dynoed to find out.

Since then, I have swapped intake manifolds from a Weiand 360 to a Chinese knock off Edelbrock Performer RPM Air Gap. I'm sure those Desktop Dyno numbers have changed a little, more than likely bringing the torque band down a few RPM.

Also, here is a video of it taking off from a car show a few years ago. This was while it still had the 4.56s and the Weiand.

View: https://youtu.be/oIreFUOfLZw

I had a response the other day for you, but we lost internet and subsequently lost my response. I will try to replicate it for you here.

I think your current heads would be pretty decent for forced induction compression wise, but as I'm sure you know, they don't flow very well at all compared to today's offerings. Personally, I would invest in some heads before the supercharger. There are a plethora of options out there from Edelbrock, Trick Flow, and RHS to name a few for every budget and power objective. It sounds like you have some money tied up in the short block, the heads are going to be a choke point no matter how you approach it without a lot port and valve work.

Here is an article from fordmuscle.com testing a number of SBF heads. They list the specs for them all as well as give flow numbers. While the D8s aren't listed, I'm pretty sure they don't flow quite as well as some of the other stock offerings in this comparison. They also test a set of "home ported" heads. They just won't measure up to a good aftermarket head.

http://www.fordmuscle.com/archives/2000/05/heads/index.php

Also, as I'm sure you know, the engine is basically a pump. The more air you pump in and out, the more power it will make. A supercharger magnifies the effects of everything else about the engine, so if it is built to flow it will make power. As we already determined, the heads you have really aren't good for that at all and you will need to do some work to make them "acceptable." So, if you can swing it financially, a set of heads aren't a bad investment whether you intend to supercharge your engine or not. Then, if they are a choke point, you can always do the work that you inherently need to do already in the form of porting/polishing.

With heads now-a-days claiming 50+ bolt on horsepower (again, not an apple to apple comparison...), imagine your car with instead of 210 to the wheels, it had 260. Then, add the supercharger. Estimates may range from 25-50% increased power output depending on the application. Let's take a conservative number, say 30%, and add it to these numbers. 210 + 63 = 273 hp, or 260 + 78 = 338. That's a 65 hp difference overall just because of a theoretical head choice.

And I know our cars are light, mine weighed in at about 2800 with my fat ass in it on a scale iirc. And we know that power to weight ratio is where it's at. It would be a good time to at least debate buying aluminum heads for the engine. They will both increase power and reduce weight, which in theory, will make the car quicker/faster. Another good point for a better set of heads.

Now I realize I'm here on my soapbox and not in your shoes either financially or where you are in your life. But it would be a good investment all around to look into a set of heads. If money is the problem, Speedway has a set of Flo-Tek heads that aren't too shabby as far as magazine testing goes. They aren't the best, but definitely better than the anchors you have now. And they aren't too expensive, <$800 for the pair. You will more than likely, of course, need to buy different rockers.

https://www.speedwaymotors.com/Flo-Tek-203505-Small-Block-Ford-Aluminum-Cylinder-Head,46332.html

And here is a link to a magazine article from Hot Rod that used them in a comparison with some of the bigger dogs in the "economy" aftermarket world...

http://www.hotrod.com/articles/ccrp-1302-six-budget-ford-heads-that-work/

Now, if you were to add this to a rear gear swap and a possible converter upgrade, you'd have a potent little machine. I'll get off of my soapbox now......

P.S. Speedway is having a promotion starting today, spend $200 and get a $20 gift card. They also give $10 off for signing up for their email list. So if you were to get them this week, they would be closer to $765. Not a bad price at all.....
(I wonder if you bought them on 2 different transactions if you would get 2 gift cards?? )