426 pistons in a .060" over 413 - WTF?!

[62 Dart Convertible]

Dang right Rusty. I will post some happy snaps when I start getting it together!

 

[PolyJon]

426 pistons in a 413

Dang right Rusty. I will post some happy snaps when I start getting it together!

Hi Dart convert.
Yep seen this arise a few times now.
413 bores are 4-3/16 which is 4.1875in.
When you go +60 its not 4.250 as you now know, its 4.2475.

Fitting a 426W standard bore piston is not the same as a +60 413 piston!

If a piston doesn't fall down the bore UN-AIDED, then its too TIGHT!!!
Cast/hypers need at least .002 clearance.
Forged need double that at .004 up to .006 for racing.

Drove a friends 413 +60 Dodge a few years back and it seemed more powerful than my 10 second 452 Dart!!!

PolyJon

 

[Garys1969RR]

So how does your 413 run now? Haven't heard since you started the assembly.

 

[Photon440]

Can it be bored .0625 instead of .060 ?

 

[Garys1969RR]

Can it be bored .0625 instead of .060 ?

I would think you could do that. Thats only two and a half thousandths (.0025) more , right? Thats not much. I have heard of those old 413s being bored to .080 oversize. I believe the early 60s motors had more cast iron around the cyl walls. Has anyone here ever checked that?

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I had an old 413 with 13 to 1 C/R that ran low 12s at 5400 feet in a 65 Belvedere. 915 heads, Racer Brown mushroom lifter cam., TM 6 intake with a 3310 Holley carb. Those old motors can really haul a_ _ when built well.

 

[Glenwood]

I would think you could do that. Thats only two and a half thousandths (.0025) more , right? Thats not much. I have heard of those old 413s being bored to .080 oversize. I believe the early 60s motors had more cast iron around the cyl walls. Has anyone here ever checked that?

I have a 413 in the shop (FHO) at the moment. Tim sonic checked the walls and found them to be quite thick. He thinks it could be bored out .100 but this was a preliminary check. It's out being blasted and we're planning to bore out to 426 spec. to be safe.

 

[Garys1969RR]

Hey Glenwood, what type/brand pistons will you be using? I used an Arias with a dome, but that was 30 +years ago. Just wondering what company is making them these days. Will they be forged or cast? Thanks.

 

[Glenwood]

Hey Gary, I haven't ordered anything yet but I believe Egge makes them. A guy named Dave (69Bee) in AZ offered sell some and ship to me when I'm ready if I'm having trouble getting them directly. I'm waiting to see what the final bore will be before ordering. I'm expecting to use flat top forged depending on what Tim recommends.