its still surprises me how much work i'm doing with OE BB heads.
shortly after the E heads came out, the market for reworked OE heads disappeared.
however, in the last year or so, ive seen a renewed interest in having OE BB heads refurbished, and/or reworked.

my guess is that with the value of BB powered Mopar muscle cars continuing to climb many people feel that the more original the appearance of the car, the better it will retain its value.

personally, i'd rather have something with E heads on it myself.....but if you're planning on using the car in some sanctioned events(like F.A.S.T.) that require the use of OE heads....thats not a viable option.

i don't get this too much anymore, but when OE heads were quite popular, people would send me some heads they had done some home porting on, to have me finish the valve job, or set up for dual springs, flow test, etc.
often times, they were heads that had been bought used, that had been previously ported and were being sent to me for a freshen up.

i have a set of 906's in the shop now that were bought by someone putting together a 440 RR.
i dont recall all the details of the story with these heads, but IIRC the port work was done by the shop that did the valve and guide work.
its obvious that whoever ported them doesnt do a lot of this type of work, but the guide and seat work were fine.

what port work was done did improve the flow somewhat, and they did little enough so as not to ruin the heads for more extensive port work down the road.
i think these heads were bought pretty reasonably, and everything is new, and they had not been run yet.....so they were a good way to get into a set of ported OE heads for reasonable $$$.
new bronze guides, new 2.14/1.81 stainless valves, flat milled, valve job, Comp dual springs with 10deg retainers and locks, new seals, etc.
from a functionality standpoint, these heads were good to go.
the guide fit is decent, and the valve seat work was fine.
they could have been bolted right on, and the motor would have run fine.

well....they did have some exhaust bolt hole issues, but other than that, they were fine.

the buyer brought them to me to have me check them out, flow test them....and give them an overall evaluation/recommendation.

i suggested installing hardened exhaust seats, and touching up the port work to take better advantage of the larger valves.

however, installing hardened seats creates a small problem with heads that are already done.
when you install the exhaust seat, it distorts the intake seat next to it.
so, you end up having to do the valve job over again.

nonetheless, the decision was made to go ahead with that plan.

this presented an opportunity to show the difference in flow that is actually pretty typical when comparing heads done by someone doing them at home, or by a shop that doesnt really specialize in race head prep, and heads done by someone who does this type of work for a living.
esspecially when the heads in question are 915/906 castings, as opposed to the later 346/902/452 style heads.

i figured the best way to show the difference......is to start with a set of ports thats already been done by a DIY type....and then rework that same set of ports.

what you'll see is that there can be a pretty significant difference in flow between what boils down to the same basic job.....which in this case is a set of 906's with your basic street/strip type port job.

attached is a pic of the head as i rec'd them.

this is really pretty typical of what most of the home ported heads i see look like

exhaust bowl

intake bowl

intake opening

exhaust opening

its important to point out that there was no short turn work done on this intake port. it was still as cast.

while its true that the old MP engine manuals warn against reshaping the short turns at all, the fact is....on the 906/915 heads....the intake short turn rules the port.
no short turn work......no big flow.

here is how this set of ports flowed as they are in the above pics:

lift----I/E
.100--73.1/55.9
.200-133.7/112.3
.300-196.4/151.5
.400-237.1/163.5
.450-241.9/167.4
.500-240.3/168.7
.550-243.5/168.7
.600-241.9/167.4
.650-233.9/167.4
.700-230.7/166.1

the first step in the upgrade was to install some hardened exhaust seats

first...you bore a hole for the insert....

...drive in the blank insert...

....then machine the desired angles onto the seat.

nuthin' fancy here.....just the std 30/45/60, with a 75 deg bottom cut.

I'm in no way an exspert, but it seems alot more could have been done to the bowl areas, i spent 25+ hrs. on my 906s, practiced first on a dummy head & got some good pics & info to help, i picked up about .2 & 2-3 mph from what i did, total cost was right around 200.00 including gaskets, i don't think i'll enjoy doing another set but i'll never ever complain on what it cost to have a set done by a pro

It was always nice to lift my hood & show them iron heads & no juice

1.609 60ft.
10.87@ 123.58 in the heat

after the exhaust seats are installed, you can recut/regrind the intake seats.

same angles used for the intakes on these heads.

i'm now ready to tweek the port work, and reblend the bowls into the valve job.

Looks like you got some grinding to do Dwayne.

What flow #'s will you shoot for, and how much time will you put into the heads to achieve the #'s ?

okay....here's an excellent illustration of how important the short turn is on a 906/915 head.

i intentially did not do any short turn work at this stage of the rework, just to prove the point.

the bowl has been reblended into the valve job, and some minor cosmetic guide trimming done as well.
the short turn side of the bowl has been carefully blended into the seat, but none of the hight of the short turn has been removed, and i was careful not to make a "peak" where the blending and casting meet. it is a smooth transition, just as the MP manuals and porting templates would have you do.

i also back cut the intake valve for the follwing tests.

as you can see by the pic.....it has a more professional look to it...and there is a nice little gain in the .200-.300 area......but without fixing the short turn.....no real gains were made in the higher lifts(actually, a slight loss of peak flow).

lift---flow
.100--69.5
.200-145.5
.300-206.1
.400-237.1
.450-241.9
.500-241.9
.550-241.9
.600-240.3
.650-235.5
.700-233.9

if this was as far as the rework went....very little HP gain would have been had.
there would be some power gain because the exhaust port picked up nicely(no real short turn work necessary on those).

So Dwayne, what would the stock head flow before
cutting the tree limbs out of the way(nothing done)
just a average number intake and exhaust?

I did lots more bowl work on my 452s then added the 2.14 1.81 stainless valves cost less then 1/2 of the edelbrocks. I blow 11+ psi though mine though. They make plenty hp for the street.

this is what the finished job looks like.
i didnt do anything to the port openings because at this stage of the game, thats purely eye candy.
well...additional eye candy.
the major lumps in the exhaust ports had already been removed, so i didnt want to spend the customers $$$ on just making them look prettier.
but, had they been left untouched, i would have had to go in and work that part of the port a little bit for this level of flow.
you usually dont get 200cfm from a stock exhaust port with nothing but a bowl job.....some work has to be done to the whole port.

from this angle, the intake port doesnt look any different with the short turn fixed.....but it makes a big difference in the flow numbers.....and power output(if the motor is good enough to be able to use it).

heres another shot of the finished exhaust bowl.

the intake port picks up big time when the short turn is done correctly, and you have the bowls opened up enough to let some air through.

the only added work between the previous test and this one is reshaping the short turn.
this is a fairly aggressive amount of hacking on the intake short turn, but not as much as you'd do for a motor that was going to see a high lift(.600"+) camshaft, and/or a lot of rpm.

this motor will be getting a mid-.500" lift flat tappet cam, so i left the final approach from the short turn into the bowl pretty steep.
this is a trade off....better low/mid-lift flow.....some high lift turbulence remains.

finished results:

lift----I/E
.100--69.5/56.3
.200-145.5/112.3
.300-208.5/158.4
.400-257.9/179.2
.450-270.7/187.1
.500-265.9/189.7
.550-269.1/194.9
.600-270.7/197.5
.650-267.5/201.4
.700-261.1/204.1

That's why you Da Pimp.....Snoop Doggy D.....

one of the inportant things to remember here is....the 346/902/452 heads have a very different shape to the intake port.
one thats MUCH more user friendly for the DIY type head porter.
they have essentially no short turn, and no guide boss.
the two areas that you spend the most amount of time reworking on a 915/906 head if you're trying to get big numbers out of them.

the down side is they generally dont flow as good in the mid-lifts.
however.....i say that as someone with quite a bit of experience and flow bench time fooling with 915/906 heads.

as you can see by the numbers in the first test....the mid-lift numbers on the 906 arent going to be very good either if you dont get the short turn right.
on the 346/902/452 head.....you basically just need to put a radius where the bowl cut meets the floor, and you're done.
the 915/906 head requires careful(and somewhat substantial) reshaping of the short turn before the heads start to give up decent results.

great post Dwayne......very informative...and finished with good numbers too.