1973 390FE Mirror 105 block

[Alex_Curry_116]

I recently picked up a mirror 105 block 390 fe, I bought it for very cheap thinking it needed a rebuild. I took it apart and everything was rebuilt no sludge or anything on the inside of the motor. But back to the point can any of the veteran FE owners shed some light on this block for me? I am trying to get it to a 400hp and 450-475 tq range. I guess this block has the reinforced webbing that is desired for performance use.

[jayb]

You shouldn't need any special prep work to get to that horsepower level with that block.  As long as the bearing clearances and bores look good, you can add the bolt-ons and make your 400 HP power level.  450-475 torque may be a little more challenging, but you should be able to make 440 without too much trouble.  Are you looking for suggestions on what components you need to make that power level?

[Alex_Curry_116]

Yeah I would definitely like to hear some suggestions.

[turbohunter]

Hi Alex
I have a 105 block in my truck.
I stroked mine to 4.125 and a 4.125 bore.
Went with D2 heads, Comp HR270 cam.
Got 400hp and 500ft lbs.
Really great truck motor.
Since your block is apart and you don't know its history I would check the oil gallery from cam to heads for cracks.
The 105 blocks seem to be a bit suspect there.
Here is what the reinforced webbing looks like so you can compare to yours.
I'd be happy to share any details of my build you would like.

[ChiefDanGeorge]

Probably late to the party, but I just got a 390 block bored 0.040 and I am looking to make about the same power.
Did you go with any particular stroker kit?
I'm interested in your parts choices for sure.

This is my first build and it;s for my wagon, so I am looking for just a good cruiser that will get up and pass when I need to.

Hi Alex
I have a 105 block in my truck.
I stroked mine to 4.125 and a 4.125 bore.
Went with D2 heads, Comp HR270 cam.
Got 400hp and 500ft lbs.
Really great truck motor.
Since your block is apart and you don't know its history I would check the oil gallery from cam to heads for cracks.
The 105 blocks seem to be a bit suspect there.
Here is what the reinforced webbing looks like so you can compare to yours.
I'd be happy to share any details of my build you would like.

[turbohunter]

Any of the guys like Barry or Brent can sell you what you need.
As far as my parts go, I bought a Scat crank and rods ( 6.8 ) with Ross pistons.
I have a builder I work with close to me.
If you don't have a relationship like that I would suggest giving the above mentioned guys your consideration. They give out an awful lot of info here online and deserve the thought at least.

[ChiefDanGeorge]

Thanks for the info. I have a buddy that is going to help me with the build.
I've definitely been looking at the Survival Motorsports site.

Any of the guys like Barry or Brent can sell you what you need.
As far as my parts go, I bought a Scat crank and rods ( 6.8 ) with Ross pistons.
I have a builder I work with close to me.
If you don't have a relationship like that I would suggest giving the above mentioned guys your consideration. They give out an awful lot of info here online and deserve the thought at least.

[ChiefDanGeorge]

What stroke did you go with?

Any of the guys like Barry or Brent can sell you what you need.
As far as my parts go, I bought a Scat crank and rods ( 6.8 ) with Ross pistons.
I have a builder I work with close to me.
If you don't have a relationship like that I would suggest giving the above mentioned guys your consideration. They give out an awful lot of info here online and deserve the thought at least.

[turbohunter]

I stroked mine to 4.125 and a 4.125 bore.
Went with D2 heads, Comp HR270 cam.
Got 400hp and 500ft lbs.
Really great truck motor.

 

[ChiefDanGeorge]

Reading, how does it work?!?!?!
Ha, thanks!

I stroked mine to 4.125 and a 4.125 bore.
Went with D2 heads, Comp HR270 cam.
Got 400hp and 500ft lbs.
Really great truck motor.

 

[Lenz]

Hey Chief, I went with Survival, running a .030" over 4.250" stroke "prison break" kit.  Came with Scat crank and rods, Mahle pistons and all the trimmings, great value in my book.  Don't know the power output as it was not on a dyno before install, but I'm certain that it's hitting the numbers you are looking for.

[ChiefDanGeorge]

Is there a reason you didn't go for the 4.250 crankshaft?

I stroked mine to 4.125 and a 4.125 bore.
Went with D2 heads, Comp HR270 cam.
Got 400hp and 500ft lbs.
Really great truck motor.

 

[Joe-JDC]

On any of the FE blocks that started as 4.050" bores, it is always advisable to sonic test the cylinder walls for thickness if you are thinking of boring them over .040 or .050 or more.  At 4.125" bore,  a block is extremely thin in most instances, and to put a longer stroke in that block would put excessive side loading on the cylinders, and promote splitting them.  A 4.250" stroke is the same cost in most examples as the 4.125" stroke, so pick whatever size you want, but remember the cylinder walls will be the weak point in the build.  Joe-JDC

[ChiefDanGeorge]

The block I have is bored 0.040. It's a 390GT block from '68.

On any of the FE blocks that started as 4.050" bores, it is always advisable to sonic test the cylinder walls for thickness if you are thinking of boring them over .040 or .050 or more.  At 4.125" bore,  a block is extremely thin in most instances, and to put a longer stroke in that block would put excessive side loading on the cylinders, and promote splitting them.  A 4.250" stroke is the same cost in most examples as the 4.125" stroke, so pick whatever size you want, but remember the cylinder walls will be the weak point in the build.  Joe-JDC

[Lenz]

Hey Alex, almost looks like we ran away from you, but this stuff fits your quest for info.  Heed Joe's advice, as you travel the forum you'll note his expertise along with others.  I sourced my block through Survival, the longest readily available stroker crank wasn't a concern for me with a well prepped .030" over block.