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Sevensecondsuv 06-30-2008 12:11 PM

300 straight six - do they make stroker cranks?
So I've been planning my next build. It's going to be a 80-86 F-350 4x4. This will be my "truck" for the next several years. It won't be driven daily, just used to haul things.

Anyways, I'm trying to decide on an engine. I don't like convention, therefore a 351, 351 stroker, diesel, and other popular options are out. I like the stroked 460's, but my friend has one in an 87 F-350 so I'd like to do something different. Not to mention that thing is THIRSTY!

So this had led me to the 300. I've always liked the 300 for it's impressive durability and low-end torque to pull anything you can hitch up to it (just maybe not very fast). But a stock 300 just aint gonna be enough for the truck I'm planning.

I've done some research and found that 10:1 compression, port and polish, mild cam, full intake and exhaust mods, larger valves, 600 cfm carb, etc will yield 300 HP at about 4500 and 400 TQ at 3200 (as proven on a dyno). That's enough, but I'd like some more torque. That's where the idea of stroker hit me. That engine at 360 cubes would be a torque monster and would be what I want.

So, does anyone know if they make stroker cranks for the 300 and where can I find them?

Captain Ledd 06-30-2008 12:32 PM

the 300 already has a stroke of 3.98". If you manage to find the forged steel crank (good luck) you can have it welded and ground back out to I think 4.375, which is something like 338ish cubes IIRC. Some company used to make them years back but has since stopped. I've heard the bearings went out much much faster.

The better option is probably a turbo. Turbo's are nice because they only make extra power (i.e. boost) when you're on the throttle, so otherwise they run and use as much fuel (for the most part) as the standard engine. A modern turbo that is correctly sized has darn near instant spool time and lag is almost a non-issue (there's other things that can influence it though).

Also another thing, try here:

TONS of info on the 300 sixes specifically, and the guy running the site is developing an aluminum cylinder head for the 300 six. He's already got one out for the 170/200/250 inline sixes Ford had in the early Mustangs and Mavericks, etc. and it turned out amazing.

AllanD 06-30-2008 06:07 PM

Yeah, a turbocharged 300 six would be "neat"

Though it may seem "odd" I'd actually recommend using TWO turbochargers
One off each batch of three cylinders.

The reason for this is that most common turbochargers are designed for engines approximatly half as big

I'd limit boost to 5-6lbs unless you manage to find forged pistons for the engine.

6lbs of boost into a 4.9 and you'd better have the big ZF trans behind it, because
on the boost it's going to make the transmission think there's a 460 V8 up front.


Sevensecondsuv 06-30-2008 10:08 PM

ZF-5 is what I was planning. I own (and built) a turbocharged Ranger. It's a lot of fun and very fast, but I wouldn't want it in a big truck, that's why I was wanting to stay naturally aspirated.

I'm not afraid of machining a stock crank, putting larger bore sleeves in, using rods and pistons from whatever (even chebby, gasp!) etc. Keep the ideas coming!

Captain Ledd 07-01-2008 02:23 PM

Not to tell you how to build your project, but as a NA engine, the 300 six.. well.. it don't make alot of power, just low end torque.

The stock cylinder head needs a LOAD of work and machining to just make it adequate for the 300 cubes that it is, let alone larger still.

But otherwise to throw some things your way about the 300:

LOTS of porting
bigger valves, but not tooo big
make sure they're unshrowded ^
a really good camshaft, 260-270 durationish which should keep the RPM's low enough for streetability. (were still talking never more than 5000 rpm's here)
Bigger injectors and throttle body (or carb)
cast iron cranks really don't care to be welded on unless by a super qualified professional.
DUI ignition or some other kind of super high energy system
I'd keep the CR down to 9.5 or so.
I don't know if the block can take a much larger piston to make it worth it, even if sleeved.

Until the Classic inlines aluminum head is released, I really feel that's about what you're gonna find in terms of power additions. Except for spray or forced induction.

Now, I have heard that 351C heads can be cut apart and furnace brazed back together and stuck on a 300 block, some drag racing Maverick had those on it. And supposedly GM LS1 and LS7 heads have the same bolt pattern as the 300 six (completely unverified) and can also be cut up and furnace brazed back together. But your left with custom intake and exhaust. Food for thought.

Pretty much no one except for Clifford Performance and Classic Inlines makes anything for the 300 six. Other than that your on your own in the quest for more power.

Sevensecondsuv 07-01-2008 04:36 PM

I might be open to doing 13:1 compression with ethanol and water injection. I'm just trying to stay non-turbo and six cylinders.

I don't really care about HP so long as it's enough to keep up with traffic. I want a torque peak of 500 ft-lbs at or below 3000 RPM though.

I did some research and found a company that will make a custom crankshaft with a 4.75" stroke for any application it will fit in.

I figured if I had the custom 4.75" stroke crank made along with a 0.100" overbore (sleeves?) and 1" deck spacer (to keep the stroke/rod ratio high enough) it would net me 376 cubes, which I think would do it with high enough compression, and right carb and cam.

As for the head, I'm no stranger to porting. I opened up the exhaust ports in my 2.3 from 1.25" diameter to 1.75" diameter. I had it bench flowed and it did 65% over stock on both intake and exhaust. I'd be willing to do this to a 300 head. The other thing is that this project is still a few years off so maybe the classic inline's head will be out by then. I'd want to know it will make good low end torque before I went that route.

AllanD 07-06-2008 01:54 PM


From a 4.9?

Not gonna happen without forced induction.


Will 07-06-2008 02:33 PM

Stroke means nothing when you are talking torque. I know lots of people think it does. The only important thing is how much fuel you can burn in a single combustion. Stroke doesn't help that, only displacement and airflow efficiency matters on a naturally aspirated gas motor.

What stroke does do is increase the airspeed at lower rpms, which helps fill the cylinder more quickly at low engine speeds. That's great for a truck motor like a 300-6, or a 5.4 or a 6.8. Stroke is not about leverage, it's about controlling piston speed. Most of the push of the piston is done near the top of the combustion chamber. A short stroke with a long rod would be the best at getting good leverage on the crank.

A stroker kit is good for adding displacement when you are out of room to overbore.

The 4.6 in the 2009 Mustang makes 1.14 ft# per cubic inch--as installed in the car. If you are going to take a 40 year-old technology and think you can come close to that, you are greatly mistaken. And that would only be 340ft#. The best the fuel injected 300 did was .88ft# per inch as installed, and the carbed ones were around .75 per inch.

Captain Ledd 07-06-2008 08:13 PM


Originally Posted by AllanD (Post 168814)

From a 4.9?

Not gonna happen without forced induction.


Thats about what I was thinking. He was pretty set on getting creative with N/A, and I figured "who knows" (I've messed around with alot, but I don't know everything.). I was kind of curious to see what he came up with.

AllanD 07-06-2008 11:14 PM

Frankly 500ft/lb is above what a 7.5EFI can do without modifying it from stock.

On the other hand if he decided to go turbocharged I doubt he'd need
more than 7 or 8psi of manifold pressure.

Not only that but if he did something completely silly, like drive to Denver
or Cheyenne, he'd experience NO loss of performance with his increase
in altitude, because a pair of T-03's would EASILY be able to maintain 8psi even
going over Loveland pass (~12,000ft)

His "modified" engine? He's going to take a relatively efficient engine
and essentially ruin it for fuel economy by making it a stroke monster.

while turbocharged it would still get the same economy in "cruise"
and an inline engine is EASY to turbocharge....


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