4.125 or 4.155 bore size for dart build

[Guest]

[TKFD]

Hi guys, just wondering what your thoughts are on going a 4.155 bore size for a 363ci Dart build?

Going with 4.155 will increase cap to 368ci, but things I have thought about is I got to watch comp ratio (using 56cc TFS 190 11R heads), and whether the head chamber bore will be too small?

Thanks for any advice
Cheers

[al2]

Probably a lot more off the shelf Pistons for the 4.125 bore

[knucklefux]

those extra cubes won't really make a huge difference.

what's the max bore on the block?  might be a better idea to go with the 4.125 bore first so there's room for a rebuild...

[347HO]

I like the 4.155" bore at 363ci for no reason other than that it works.

[TKFD]

Thanks guys. Wiseco make OTS 4.155.

Of little knowledge of engine building I have come up with my own pros and cons:

Pros;
Added displacement therefore power/Tq
Prob better cyl vol efficiency (marginal)

Cons;
Increase CR. I have to watch this as using 56cc TFS heads, and using o-line CR calculator came to 11.9
Have to watch head chamber sizing
can 190 11R keep up with even more displacement
heavier pistons (plan to rev to 7000_
less cya wall material
Wait time is more to make them.
I like the idea of knucklefux, didn't consider a rebuild time.

So it seem more cons than pros, but you know all that doesn't matter most times if more power can be made, lol (come on most of us on here agree with me, or been there)


 

[TKFD]

...also Woody is building the motor, and think he's annoyed with me, making changes all the time,   

[TKFD]

sorry have my CR class wrong, should be:

4.125 piston  - 11.24
4.155 piston - 11.39

Thats at 0 deck, which I think Woody does

[347HO]

You have excellent fuel in your area.  That cr plus dynamic cp won't be a factor.

I was once told...."if you need that much clean-up, the block is toast anyhow..."

[TKFD]

Thanks,
Speaking to Jim, he reckons just keep with the 4.125, so going with that.

To me, not a large gain to be had vs heavier piston (I'm all into lightweight stuff atm), cutting in cyl wall more, heads may not be up to task (pushed anyway with a 363ci), and CR creeping up (even though might try and aim for 11.5-11., and pistons take another 3-4 weeks on the build time.

Anyway it was worthy of a discussion