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Old 11-05-2008, 07:08 PM
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300 six

I have a 85 f150 4x4 with a 300 straight six in it i was wondering if anybody could tell me how to get a little more power out of the old girl, right now it has 325000 on it, i am considering hedders, and maybe a 2 barrel or 4 barrel carb for it. any suggestions?

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Old 11-05-2008, 09:11 PM
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I would not do anything with out first overhauling it. Better yet get a used one with low mileage and stick that in. Great motor.
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Old 11-05-2008, 11:44 PM
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me and my dad had the six out to put all new gaskets in (the thing leaked oil like all get out) it the bottom end all looked good, we did some valve work to it and found six burnt valves the the thing ran like a top anyways but we replaced them too and put new lifters in it while we were at it.
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Old 11-06-2008, 07:20 AM
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too many miles to try to hop it up... 325,000 is a lot, but not really for a well taken care of 300 I6.. but at that milage, it's best left alone
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Old 11-06-2008, 08:31 AM
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Even with a new set of gaskets, your bores are probably a bit egg-shaped by now and I'm sure it has some blow-by. It may run forever, but I wouldn't stress the thing out.

Exhaust may get you a little more power, chances are you won't notice it though. Stock exhaust tends to be of higher quality than much of the aftermarket stuff, so you'll probably be taking off a lifetime system to put on one that may last a couple of years.

Just run it, 300's were really never meant to be a performance motor.

K
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Old 11-06-2008, 10:20 AM
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leave the motor alone...
swap to lower gears and/or smaller diameter tires....
your fighting a heavy vehicle weight with a likely tired/worn motor....
the deeper gears multiples the flywheel TQ which means less load on the motor accelerating the truck weight so it will last longer...
300ft/lbs x 2.46 first gear x 3.25 rear gears=2400ft/lbs on the tires...
300 x 2.46 x 4.10 rear gears=3,000ft/lbs on the tires
my $.02
you will spend $2000 on the motor for what a $600 gear change will do because of the weight...
when it's worn to the point that oil consumption is a problem,,,then address modifying or better, changing to a bigger motor,,,there's only so much a 300 cube can do....

strip every last pound off the truck you can...
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Old 11-06-2008, 10:21 AM
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check out this forum: http://fordsix.com/forum/

I also agree it is probably better to leave this engine alone, its an old man now!

You could always find a second engine somewhere and build it up in your garage then pop it in when you're ready.
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Old 11-06-2008, 10:41 AM
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I haven't personally done this so take it for what it's worth:

I've always heard that a 300 responds well to a small (500cfm) Holley vacuum secondary with the split headers and a small RV style cam. More people might make a 4 barrel intake, but Offenhauser was the only one I've personally seen.

I would go with the others though - 325,000 is a lot of mileage on any engine (even the 300) - I wouldn't try to make a lot of horsepower with it and I wouldn't throw more gear at the thing. It seems like those 300's had the same acceleration if you were unloaded or had 2000lbs in the bed, but they just keep chugging along.

Good luck and let us know what you end up deciding to do!
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Old 11-06-2008, 11:46 AM
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ok well point well taken, its got 3.50 gears in it with np435 running 33x12.50 mud terrain tires and a solid axle conversion up front from a 79' bronco, i realize its an tired motor, and by no means want to push alot of power out of it, but in a previous forum i had heard mention of somebody using exhaust manifolds off a fueley six is there anything special about these manifolds?
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Old 11-06-2008, 11:48 AM
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I had a 95 with an efi 300 - it had a tubular style header from the factory (I can't remember if it was a 3/3 split style or a single 6 into 1 style). I would have to believe that would be an upgrade over the old log style if you can pick one up cheap at the junkyard.
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Old 11-06-2008, 11:57 AM
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EFI manifolds are 3/3 split.. and very good flowing
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Old 11-06-2008, 12:02 PM
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ok. i would prolly get them from a bone yard this isnt something i put alot of money into its just a play around truck. i havnt really messed around with the manifolds on sixes but when i go to split the intake and exhaust manifolds will i have any problems? right now its got maniflolds from a non smogger motor on it
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Old 11-07-2008, 08:37 AM
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the much shorter height oem tires (27"?) are a just barely ok acceleration force match to the stock 3.50 gears...
the 33" tall tires reduces that 3.50 ratio torque multiplication factor to something around 3.00 or less...
plus they work as a lot of added rotational resistance against the motor due to they are heavy....

simple first demo for what a rear gear change does:
reverse gear is just a bit lower ratio than first gear...
floor the truck in reverse and see how quick it gets to the 4400rpms HP peak...versus how long in the taller first gear to reach 4400...
simple demo for the tires diameter and weight, borrow some 24" tall 60 series tires/wheels and test drive...

if you want to mess around for not many bucks and do something that does give results that you will likely feel (atleast a little bit):
replace the timing chain (it's shot!) and put a decent quality rebuilt dist in it (it's shot) and play with the timing curve to better match the wrong gears/tires combo....
you can gain (back) 10HP/20TQ+ over the "whole" rpm range because the spark is delivered when it's supposed to be to make max "power" cylinder pressure ATDC ...
you can add another 10HP/20TQ by tweeking the timing based on the "sweet spot" your motor wants to live at....
factory base timing is a compromise setting, so the car can work anywhere in the world (climate/altitude/etc), almost every motor made responds to from 2* up to 4* more base timing to make more Hg sooner......

my honest opinion, just adding headers to your HEAVY truck and BIG tires will make next to no performance change you can actually feel....
check the cam and heads spec's for the specific motor you are taking the headers off first,,,
if it's not a exact match to your cam and heads those tube headers may well cost you more TQ acceleration force than the added HP is worth....
truck motors are a purpose built design to make the max TQ per rpms possible to accelerate a heavy weight.....
by very carefully controlling the air flow velocity for best possible cylinder fill and A/F mix "atomization" quality when the piston speed is too slow, at less than the TQ peak rpms.....
the stock exhaust and cam and heads set up is part of the total flow equation....

footnote:
LOL! I am so so so happy my son is done with 4X4 trucks!!!
here's his last toy....
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Old 11-07-2008, 09:12 AM
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F150's have 235 75 15 and are 29" tall.. a 215 75 15 is 27" tall and stock on older rangers
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Old 11-07-2008, 12:03 PM
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matt,
point was size does make a big difference....

stock 29" tire, 70mph=2800 with 3.50 gears...
33" tire is only 2400rpms=70mph with 3.50
33" with 4.11, 70mph=2800 to get back to "stock" acceleration and have more timing....
33" with 4.56 would be more "pep" and quicker wind up in all gears....

here's a (bunch of) caculator(s) link you can mess with...

http://www.tciauto.com/Products/Tech...culators.asp#8
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