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Old 01-31-2008, 08:27 PM
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gas mileage V6 vs V8

Hi, I have a 1988 Ford Bronco II with a 2.9 V6. It is fuel injected and gets around 24 mpg during highway driving. The only problem is that it does not have much power. What do you think a motor like the one below would do with respect to gas mileage compared to the current V6?

302
AFR 165cc heads
10:1 compression
~212 @.050 .500 lift hyd roller cam
fuel injection
free flowing exhaust

Has anyone built a relatively mild motor like this and tested the gas mileage?

Thanks
Adam

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Old 01-31-2008, 09:12 PM
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Automatic or 5 speed? Roller or flat tappet cam?

Shane

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Old 02-01-2008, 01:12 AM
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can't be sure without more info like gear ratios, tranny, etc...I don't know much about fords in general but if you took it easy mostly you could probably squeeze mid to high teens out of it...from what I've seen though gas mileage can be quite difficult to predict and won't always turn out the way one would expect...
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Old 02-01-2008, 07:24 AM
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Going from a 2.9 to a 5.0, you wont be able to keep your right foot out of it, and mileage will suffer.
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Old 02-01-2008, 07:26 AM
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It is a 5 speed. I dont know anything about the gears except for that they are stock.

Thanks
Adam
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Old 02-01-2008, 07:34 AM
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2 or 4 wheel drive?.........

Generally, if driven the same a v8 will get just as good as mileage as a 6....it doesn't have to work as hard to pull the same weight. ....But if you are going to drive it the same, whats the point?
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Old 02-01-2008, 08:49 AM
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since you're going with a mild cam gas milage should be relatively the same, it may even improve if you use a good exhaust setup and tune your fuel injection yourself. I would recomend a lower compression ratio though. 10:1 with AFR's can be ran easily in a pinto or a Maverick, but in a Bronco it has a god chance to detonate. Trucks and SUV's can put more load onto an engine and as a result are more detonation prone.
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Old 02-01-2008, 11:05 AM
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Thanks, it is 4 wheel drive. I wondered about the 10:1 with the small cam, I tend to agree that it may be a little high.

Adam
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Old 02-01-2008, 11:29 AM
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Another thing you have to think about is, being a 4x4, is there a bellhousing available to adapt a v8 to your tranny/transfer case......and is there even room for that v8......I know on s10s there are parts available, but for the Fords, I don't know.
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Old 02-01-2008, 11:33 AM
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I had ran 9.5:1 cr with that cam that size in a sbc 350cid with stock iron heads in a 4000 lb truck with a 3.08 gear and auto trans. Took 93 octane.

You should ok with an extra 0.5:1 since the heads are aluminum and are fast burn heads (need less total timing). and you have more gears.

I predict mpg should be the same on the highway, but 2 mpg less around town due to the size of the cam.
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Old 02-01-2008, 11:39 AM
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93 octane.... that is an option if you want to keep 10:1. I build my engines to run 87 octane. I think with AFR's and 9.5:1 you could run 87 octane, get decent milage, and have plenty of power. You could even run 87 octane on a 10:1 engine, but you have to build it just right, tune it to the gnat's ***, and hope the car gods are smiling on you.
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Old 02-01-2008, 11:44 AM
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Quote:
Originally Posted by poncho62
Another thing you have to think about is, being a 4x4, is there a bellhousing available to adapt a v8 to your tranny/transfer case......and is there even room for that v8......I know on s10s there are parts available, but for the Fords, I don't know.
They have ranger/bronco swap kits http://www.jamesduff.com/broncoII/v8conversion.html

http://www.broncoii4x4.com/v8swap/302swap.htm



Shane
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Old 02-01-2008, 04:44 PM
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Thanks for all the replys.

Adam
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