318 head flow

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Scary! I like it, though! I have been part of a few things were I thought I was going to have draw a pentagram on the garage floor to reassemble something inside of it in hopes of keeping it together with “dark magic”.
 
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Pic of ex seat.

0203191645a.jpg


0203191645c.jpg
 
I'm doing my 1st set of xheads, so following/learning.
What carbides/tools are you using? Some decent sized chips in the exhaust bowl!
Thanks
 
I'm doing a set of stock x heads. Theoretically the same ideas and technique apply to xheads as well?
 
Depends on the amount of time, money, and abilities. My go to method for any Mopar iron head goes as this.

Core drilling the heads for .5" bronze guides.
Grinding the lead in of the intake guide completely out, like it was never there.
Gasket match intake ports to 340/360 size. Eliminate valve cover bolt bumps. They will break through, don't worry about it, use thread sealant on studs to seal.
Create a trailing vein with the back of the guide boss so that the air doesn't eddy around the back side of the guide.
Profile the bowl and roof of the exhaust port.
Press in new guides and hone to size. .0016 on the intake .0018 on the exhaust.
Cut new intake and exhaust seats, open bowls with 75° cutter, and deshroud cut chamber.
Blend bowl and profile short side.
Blend chamber deshrouding cut using sacrificial valves to protect seats.
Resurface to target CC volume. 6 thou per 1CC

This process is involved and costly to say the least but yields great results if you're targeting max effort gains.
 
I wouldn’t have thought starting with 318 heads was targeting max effort gains ;)
 
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At this point in time, I am surprised no one has started building a 273 stroker into a 318 with a 3.79 inch crank, just to see if it can be done.
 
Thanks for the in depth reply. Not looking for max gains at this point. Just trying to make improvements within my skill level. While learning at same.time. First time was a set of 273 heads. This is my 2nd set of heads. Going on a .030" over 70 340. Daily driver in summer.
Thanks!
 
Good aftermarket stainless nail head valves with a 30° back cut and proper 3 angle valve job will do more for you than porting.
 
nm9stheham said:
Why stop at 3.79"? I am putting together a 4" stroked 273 right now....335 ci.
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My mind wouldn’t let me go that far into the land of undersquare, lolol! Too far past the point of diminishing returns with the valve size limitations of a 3 5/8 bore. Maybe if you had a set of hemi sohc overhead cam heads from the eastern island land that could bolt onto it, I could see it as feasible.
 
Garrett Ellison said:
My mind wouldn’t let me go that far into the land of undersquare, lolol! Too far past the point of diminishing returns with the valve size limitations of a 3 5/8 bore. Maybe if you had a set of hemi sohc overhead cam heads from the eastern island land that could bolt onto it, I could see it as feasible.
Click to expand...
LOL, yes it is; just think of a large /6. One goal is to use off-the-shelf parts with minimal re-work so I am working with what I can find stock. As for the valves, the bore can be notched some to get in some bigger valves.... it'll be shrouded on the cylinder wall side of the valve but still will get more open area for breathing. I'm really leaning towards some Edelbrocks at this point but this article has been of interest for that part of the problem.
 
I would use Magnum heads, edelbrock version if your dropping the large dimes on aluminum. What kind of pistons are you using?
 
Small bores are more detonation resistant, if you put aluminum heads on, I suspect it would be capable of being an 11 to 1 pump gas engine.
 
Didn't mean to threadjack. This ought to be a separate thread, but I've been holding off 'til I get the piston pins fitted and can show the bottom end with good progress. Lemme put this up later as it's own thread.
 
318 heads opened up to 340/360 ports...lots of grinding...sounds like what Steve Dulcich did on their junkyard jewel 370hp 318...
 
Flow numbers are in. Tested on Super Flo 1020 bench @ 28". 1.94 int valve / 1.6 exh. No pipe on exh.
.......int.....exh
.100 63.....45
.150 109...74
.200 142...97
.250 163...120
.300 191...136
.350 202...146
.400 205...154
.450 192...158
.500 192...160

Fell a tad shy of my 210 peak number goal, but close enough. The strong low/mid lift numbers will more than make up for that. These things stall at a lower lift than I hoped for. I was hoping they would flow to .450 hover to .500 then fall on their ***, but these things just don't have the cross section to hang on. The valve and seat profile I used also contributes to the early stalling, but adds to the low/mid lift numbers.

Won't win any bench racer dick swinging contests with these lol
 
This isn’t a slam..... and you’re using a different bench...... but I think I could get to 210 with a 1.88 valve 360 head with about a 5-8 minute bowl job/pinch tweak.
I’m “sure” I could with a 1.94 valve in it.

I refer to what you’re doing as a “science experiment”...... and I’ve done several of those myself through the years.

One other thing.....
This could just be the camera used, because I know it does the same thing on pics I take....... what I assume is the “finished” intake bowl “looks” too small for the valve.

Any measurements?
 
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