Bowl Blending

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Jp5

Jp5

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Gents,
i'm currently porting, gasket matching, bowl blending my head, and still am not 100% sure how far to go in the bowls. And i cannot tell by any picture i've seen simply because i think it's a difficult thing to photograph. so, is the goal to remove all the casted material within the tube so the valve essentially comes out of the smoothed wall of the port? i've attached a sketch which shows the original vs, what the completely smoothed tube would look like in case that helps clarify the question. any thoughts?

jp
 

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What you are proposing isn't bowl blending, rather a total removal of the
valve guide/boss.It will definitely improve flow if you could do that, but not
a ton w/ stock size valves, however cooling jacket resides in a portion of
your diagram. So, before you ruin the head, determine what you are hoping
to accomplish w/this engine. Is porting necessary to accomplish that, the port
sizes are plenty for the stock valves, are you stepping up?
Just trying to get a feel for where your project is targeted, the head is capable
of decent flow with the right valves and port work, but it's not a guessing game.
They generally can be made to flow enough to support 300HP and a little change.
An 8cyl. would be at 400HP w/ that flow, so they aren't bad for the valve sizes
possible, quite good actually.The port primary section can easily be enlarged
to the same maximum area the "C" brands "double hump" SB heads can be
adjacent to the pushrods, but would be entirely unnecessary in 80% of the
slantys being built.:coffee2:
 
I wouldn't cut down the guide boss that far. If you want to you can cut it down and smooth it but definitely don't eliminate the boss, you will do more harm than good.
 
I just did this. Strictly an amateur mind you, but I streamlined the valve guide area cutting away some of the "shelf" where the valve stem protrudes and blending it down port. The tunnel between the valve guide and the side wall looked very narrow so I widened and smoothed that. I cut away some of the metal just under the valve seats so there wasn't a sharp edge. I did a little on the short turn to get a slightly greater radius. I took a little off the side wall where it narrows. The exhaust ports seemed to be worse than the intakes. I also unshrouded the valves a little on the deck. The easiest and quickest thing was port matching. After scribing it only took a half hour. About half of them had an extra 1/16" on one side that I removed. I think I spent 10-12 hours all together.
I just imagine myself being an air molecule rushing in (or out) and look for areas I would crash into.
I did this on my 318 (only 2-3 hrs using a Dremel) and improved the ET by a half second. I have no comparison for my 225 because I have not driven it yet because it wasn't running when I got it.
 
years ago chrysler had some temptlets you cut out of plastic. and centered on the valve guide hole. of course each head had diff ones.
 
thanks, killer 6. yeah good point about having a target in mind. i'm not going crazy with the motor, just trying to get some gains where i can. not a racer but a weekend cruiser. i have the head off for a valve job and intake/carb swap so i jumped into the porting. at this point i've removed just enough material to smooth all the contours around the valve boss. no hard angles left in there. perhaps i'll leave it at that. next is valve work. i'm not adding a cam so i'm just going to go for same size, new valves and 3 angle grind. would larger valves do me any good without a cam upgrade?
 
64, those are great. exactly what i needed. thanks, man.
jp
 
Tried to send this last nite, but my crappy IP dumped my connection just as i sent it.
In a word yes bigger valves are a good idea.However, done incorrectly it can
result in marginal or no improvement, so find someone performance knowledge-
able to do the work. HOT ROD online has MoparMuscle articles archived, they did
a series of articles on moding BB heads, demonstrating that just cutting an over-
size "3-angle" & done can be disappointing at best.Glad 64 hit you w/ the .org
link,good guidance there for you. Bigger valves done correctly always improves
performance, even on small cams.For reference,the 3.9L mopar V-6(239ci) has
the same chamber & 1.78/1.50 valves as the 318 SB of the era,they run fine &
the 225 is WAY under valved.A compression bump by knocking .050-.060" off
the head will be fine w/pump gas,and improve power & efficiency.Just be sure to
back off the rocker adj. screws to account the increase in pushrod ht. before the
rockershaft assy. goes on. A little more carb.,exhaust, and you'll definitely feel
the diff.! Speaking of diffs.,a little bump in gear ratio........:coffee2:
 
Glad to help jp! (and I'm a jp, too - my uncle used to call me that when I was little)
 
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