75 degree plunge-cut in valve seat

[Canadian1968]

Getting ready to do some basic clean up / porting of my 906 heads .  Before I have people telling me it's a waste of time just buy the aluminum heads , blah blah.   I don't have the $$ for them plain and simple and I have already been quoted the price for the work I want done and it is FAR less then the aftermarket .!
Not to mention this is a numbers matching R/T .

That outta the way, I have been reading that a good step in the search for some extra head flow is a 75 degree cut in the valve seat, this apparently removes very similar material that the mopar templates suggest.

I am just curious what is typically the measurements that make up the other two angles of the seat if a 75 is used ??

[fy469rtse]

just like the bare metal talk, then they go and and put filler back in
hardened valve seat inserts , good three angle cut to seats , thermal coating to at least exhaust valves, i think you can now order them this way ?
port the heads or at least a clean up bowls, look at coating to your pistons as well , or we look forward to your thread on detonation issues in the future, 
stay away from mopar performance cams , dual pattern modern grind ,
valve guide stems cut  to except positive seals,
just what i would do now with modern fuels,
Ive opened up a can of worms now

[Challenger340]

When applying a 75* throat cut to simulate many of the porting template benefits, you are still using 3 standard seat angles, you merely apply the 75* higher up in the bowl.

From the Chamber side,..... a 30*.... then your 45* "seat" that the Valve sits on..... and a 60* bottom cut to trim the 45 to desired width.
THEN
you "trim" the 60*.....  to approx .100" wide.... by applying a 75* throat cut UP INTO THE BOWL.

Should be standard practise nowadays on ANY "stock" Head rebuild, it is at our shop.

Here is a Pic of what I am talking about.
(This is a Jeep I6 Stroker Head, but you get the general idea, same for a 906 BB Mopar)

Far easier to see the larger 75* "throat" cut on the exhaust side where we were installing MUCH larger Exhaust Valves, but you can see the 75* on the Intake side as well DOWN into the bowl, below the "3" std seat angles.
The end of the 75* cut then acts the template to be smoothed and radiused into the port wall.... FAR less work than trying to apply the templates from scratch.

Hope this helps your efforts.


On this Pic,
you can see we have "lapped" the 45* Valve Seat contact on the Valve(the grey area at the edge of the Valve), and applied a 30* backcut to the top of the Valve, that extends down to the grey 45* seat.
You do this to your 906's.... and you will see big flow gains !


 

[500Jon]

WoW 340 DuDe!

Thats stunning seatwork there!!!
But, all that casting 'roughness' is making me feel queasy LOL!

Spend a week on each head, after 'PORT-MATCHING' and cc-ing everywhere.

THEN DO THAT STUNNING SEAT CUTTING AND LAPPING!!!

You can run Nines and make 600hp with 906 heads BUT, they are not UNLEADed friendly.
I would find a pair of 452's and port them to the MAX!!!
BEST of both Worlds.
5J

ps, Dick Landy told me via Robert Landy that the intakes port and valve should be left fairly stock.
Then fit BIGASS 1-88 exhaust valves and 'port' the exhaust-port till it squeals!!!

[Canadian1968]

Thanks 340,

That's exactly what I was looking for. I am actually following your " lowly 440 " build , pretty close for this build . You had mentioned you used it with a set of iron heads on a 6 pak motor and dynoed around 450 I believe which is what I am looking for .

[firefighter3931]

For best results the 75* throat cut should be blended into the bowl. With these mods it will flow as well as a set of template ported castings. 

Bob, nice machinework 



Ron

[Canadian1968]

Here is progress shot of my porting so far. 

The carbide burr I have is only 2" long , so I have orderd a porting kit, with longer mandrel to reach further into the ports with some sand paper rolls !

[Scaregrabber]

I did this with my last set of 915's, the blend took like 10 seconds with a die grinder, it's the only way to fly. I'd previously waste days with a die grinder and the results were worse I'm sure.

Sheldon