DIY Naturally Aspirated 6.2L Build

[Jakenbake]

... back order, back order, back order...

Makes it rough to tinker and work on things. For instance I would like a secondary bypass up front for this summer, so I should have ordered it a couple months ago, lol.

I’m impatient and feel your frustration

 

[bubblehead93]

My thinking right now is a keyed, pressed on sleeve (perhaps with a little crank machining) that would "convert" the 7.3 crank snout to mimic a 6.2 crank snout... one project at a time... I would have less time to think about future projects if all my current projects were not stalled... motor for the Raptor, nitrous and a J2 Fabrication A2W setup for my Cobra... back order, back order, back order...

so with all my free time did some theoretical tinkering on utilizing a 7.3L gas crank in a 6.2L motor ASSUMING the front snout differences can be overcome.

Some basic 6.2L dimensions

Bore: 4.0157" (102 mm)
Stroke: 3.74" (95 mm)
Deck Height: 9.408"
Compression Height: 1.325"
Piston-to-Deck Height: 0.013"
Rod Length: 6.200" (Manley 6.2 rod has different wrist pins than stock rod, 2.239" big end bore (0.978" width) and 0.9281" pin bore (0.978" width) weighing 640 grams)

All good for 378.9 CUI's...

Ford 7.3L crank has a 3.976" stroke with "coyote" size rod journals (2.086" diameter), forged steel, 8 bolt modular pattern

A "coyote" rod is 5.933" long with a 2.239 big end bore (0.940" width) and 0.8671" pin bore (0.940" width)

So a theoretical stroker build could be done as follows...

Bore: 4.080" (go big or stay home)
Stroke: 3.976"
Deck Height: 9.408"
Compression Height: 1.307" (pretty close to stock 1.325" so no issues with pin location relative to ring glands)
Piston-to-Deck Height: 0.013"
Rod Length: 6.100" (Manley SBC rod with 2.225" big end bore (0.940" width) and 0.9281" (0.980" width), resize big end to 2.239" and use "coyote" rod bearings, 575 gram rod)

With a 0 cc dish/dome volume you get 415.9 CUI motor w/11.07:1 static CR

With a stock bore diameter this is a 403 CUI motor... and pretty close to square...

Many unknowns, not all inclusive list, will bottom of cylinder bores need notching to clear crank/rods? Can the snout difference problem be solved? Any hidden issues, crank trigger ring comes to mind?

No parts with dreams of stroked Boss 6.2L's afloat in my head...

Happy Holidays to all...

 

[Pawl8901]

NICE, AHH YEAH! Thank you for all that information. This looks promising, I'm attempting to find those links and video for you as well. Hopefully can find some info for you that is useful in addition to the last post.

Happy holidays as well to everyone!

 

[Canuck714]

I looked into it, also spoke with darton and a couple of their tier one shops about feasibility of a darton MID type sleeve in a 6.2 block (this would be magic when you look at the bore spacing on the 6.2, the damn water jacket around each cylinder ruins it). When you look at the livernois kit, they went through a lot of work to gain 8 cui's (after overboring to a 4.080" bore they work the crank for a 3.82" stroke versus the stock 3.74", all to chase the magic 400 cui number). The 6.2 rods are very wide at the big end, 0.978". A big block chevy rod is wide enough (0.990" so you could narrow the rods) but the big end diameter is quite a bit bigger than the ford 6.2 (2.325" versus 2.239"). Also the only big block chevy rod you could use that is shorter than the ford 6.2 rod is the stock length rod at 6.135". So the whole thing is problematic... I don't think anyone is using a chevy rod to stroke a ford 6.2... again my experience is mostly with SBF and FE motors, so there may be cool techniques out there that I'm not familiar with.... I suspect livernois does a weld and ever so slightly offset grind job on the stock 6.2 crank to gain 0.04" of stroke and retains the stock 6.2 rod with custom pistons that change the pin height by the same amount to keep the deck height (and therefore piston-to-valve clearances) about the same...

sorry long post, when playing with these motors you are on a bit of a windy corner since not many others are doing anything with them and some of the folks that are messing with them are secretive about their product...

If I was going to spend big money I would fully explore the darton MID sleeve path... oh wait, I am spending big money, even bigger money with no guarantee it would work... lol

So it took a minute to find, but I remembered someone building the 6.2 and using GM parts. Found the link...

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BTW.. No idea how this turned out, just wanted to share.

 

[bubblehead93]

I came across that same facebook post when researching stroker alternatives... definitely a route to take... a maybe one I still take... but some challenges exist...

Lets say you offset grind the 6.2 crank for a chevy long rod (6.125" I assume, small rod journal)... this would allow to offset grind the 6.2 crank down from the stock 2.076" rod journal to a 2.000" chevy small rod journal and perhaps also narrow it up a bit (bigger chamfer radius perhaps) since the chevy rods are only 0.940" wide at the big end versus the Ford at 0.978"... this yields 0.076" more stroke... which for a stock bore 6.2 block yields a displacement of 386.5 CUI. If you took the bore out to 4.080" like my current build, you end up at 399.1 CUI.

I just ordered a pair of rod bearings, one Ford 6.2 and the other for a SBC small rod journal... time to compare and contrast.

 

[Canuck714]

Houston's House of Horsepower just successfully dropped a 7.3 Godzilla into a 2018 F150 with everything electrically functioning... so I am really hoping someone figures out how to make this a drop in replacement for the 6.2!!!

BTW they stuck a pro-charger on it at 10lbs and on 93 octane made 727 hp at 5800!!!

 

[akley88]

Houston's House of Horsepower just successfully dropped a 7.3 Godzilla into a 2018 F150 with everything electrically functioning... so I am really hoping someone figures out how to make this a drop in replacement for the 6.2!!!

BTW they stuck a pro-charger on it at 10lbs and on 93 octane made 727 hp at 5800!!!

not to hijack the thread but i thought of doing this for my 16 250 vs building a 6.2 to handle boost.

 

[Canuck714]

@bubblehead93 cant remember if it was this thread or another where someone was comparing cylinder heads (Raptor/SuperDuty) and only difference was part number... Was that you?

 

[bubblehead93]

no, but the only difference is the cams... since the heads come loaded with the cams they have different part numbers, but the physical head is no different...

 

[Canuck714]

@bubblehead93 Thank you sir... Thats what I wanted to hear.