391 swap into foxbody

Stangfox

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Jul 16, 2020
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Hello im new to this forum and I was wondering if anyone has swapped a 391ft engine into a foxbody? I recently got ahold of a 391ft or 105 mirror engine and I've read good things about the block. I know people will say I should of just stuck with the 5.0 or a 351w but I'm trying to do something different. Just wanna know if it's worth it to build or of i should just sell it and get another engine
 
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JD08

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I'm not fond of changing my passenger side spark plugs on a 302. I can't imagine how that would be on a big block.
 
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KRUISR

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I recently got ahold of a 391ft or 105 mirror engine
Do you mean a 390 FE series engine? Also, what is a 105 mirror engine?

In either case, unless you are building something for nostalgia drag racing or something, a big block like that will likely handle horribly. Far better to spend money on 302 or 351W based power plant (depending on your goals for the car).

As far as big block in a fox, there was a kit (header, oil pan, motor mounts, etc) for a 460 back in the day. Don't see many of those cars around anymore. I remember a feature article in one of the magazines of one, an '81 with the 2-tone paint and 14" wheels with the factory turbine hub caps. The only thing not stock 4-cylinder looking on outside was a hood scoop to allow clearance for the carb.
 

CarMichael Angelo

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A 390 FE engine isn’t worth the hassle to move it, much less actually install it. The bellhousing pattern forces a C6, and is really rare, the heads SUCK for flow, with an exhaust port that is full of weird bumps and obstacles. The cast iron intake ( which is so wide, it actually extends to under the valve covers) weighs so much you can forget about lifting it over the fenders to install it. It’ll have a front sump pan with no alternative aftermarket option, and Zero headers that’ll fit.

And after all of that...it’s still a giant pain in the ass to change the plugs on.

are those enough reasons to move on?
 

General karthief

wonder how much it would cost to ship you a pair
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Boat anchor.
 

rbohm

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And the 391 is from the ft family for the bigger heavy duty truck engines like the ones from uhaul
yep basically a heavy duty version of the 390FE engine. the biggest thing is the crank in the FT engines are forged where as in the FE engines tehy are cast. you will have to do a bit of machining to the crank snout if you want to use the passenger car balancer.

OP my advice would be to keep the 391, and build it for a truck that would do some heavy towing for you, find a 351w and stroke it out to 393 or 408, or do like i want, and swap in a 460.
 

Steel1

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In the early 70s my mom had an old Mercury 4 door (can't remember model) with a 390 .
I remember thinking it was cool to tell my friends it had a 390 v8...lol what did I know.
My sister's boyfriend at the time ,who was pretty knowledgeable about cars , said to me "that things a boat anchor" .
So my quest to learn something about cars began.lol
 

rbohm

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in stock form the 390 is a decent enough motor, and it is capable of so much more. i like the FEs, though i prefer the 385 series big blocks more.
 

JD08

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It goes to show how things have changed. In 1969, Ford had a 427, a 428, and a 429 and all were different block designs.
 

CarMichael Angelo

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Eventually Ford punched the 390 out to 406 in '62, then to 427 in '63/'64. They were not overly successful against the Chevys of the day...
I believe that to be an inaccurate statement.
Chevy didnt even try to run in Lemans..Ford not only did that, but won that race with a 427 for 5 years straight from 64-69.
TASCA ford kicked ass in the early 60's in Afx with a 427 As did others like Don Nicholson, Gas Rhonda, and the Holman Moody team driving T bolts powered by 427 SOHC ( cammers).
THAT engine was such a heathen, the weenie Bow tie teams in NASCAR bitched so loudly they got that engine banned, which forced it into usage in NHRA.
Follow that up with the factory domination when the 428cj showed up in 1968 as a CobraJet, and SSA, and SS got put on notice that Ford wasnt dicking around. Through the late 60's, the 428cj held C/stock auto in a Mustang.
 
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rdharper02

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Someone said 390? Not my favorite, but a heck of an improvement over the 360 FEs
 
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