305 head porting

[rfoll]

Thanks, I think you covered most of my concerns. Do you know of anyone that has cut the ramp out? The port is quite tall, and it would have a lot of volume. Just wondering.

[Carnut1]

Do not cut the ramp out. Take some out of the short side. Open the whole bowl a bit. Deshroud the chamber to the gasket line. Good guides and a 3 angle valve job. They will run with the right cam/ engine combo.

[rfoll]

I had no plans to take the ramp out, but just thinking, the port roof configuration is much taller. Chamber, throat, thinning the guides, and short side is all I will do, likely all that is necessary.

[Carnut1]

Take some pictures during the porting. Let us know about the combo and how it performs. Thanks, Charlie

[pdq67]

Might want to go over to NastyZ28 and read a long time in the top sticky in the Engine Section entitled, "Vortec Cylinder Heads: The Definitive Guide".

Dirt Reynolds started it a long time ago.

And please consider using 305HO, -601 heads..

They are a double quench design like the old -461, "fuelie" head of old, have 160 cc intake ports and 1.84"/1.50" valves along with hardened seats.

Chambers can cc from 52 up to like 58 cc's so MEASURE THEM!!

I measured my pair of -601's and got 53 and 55 cc chambers...

pdq67

[rfoll]

What I have is a set of 187 heads that are like new. These are the heads we are going to use. I can think of many heads that would be better, but we are going to use these. I never install heads without at least a pocket cleanup and a little massage in the chamber. My question is about what to do or not do in the bowl of these unique intake ports. It's just a cheap hot rod, a really ugly but sound 240 Z.

The heads are 54 cc.

[wyrmrider]

That was essentially my position when I built the 305 for my brother's 86 pickup
just a complete rebuild KB pistons, pocket port as described above, ram's horns for exhaust
86 burned to the ground so motor got moved to dad's one owner 69 4 speed and the 6 retired,
Tall tires and 4 speed compensate for low 6 cyl/ 3 speed on the column original gearing
still runs great after lots of hard miles

[wyrmrider]

thanks for the heads up pdq
turns out I built my brothers 305 just before the vortecs came out

from that thread
http://www.nastyz28.com/forum/showthread.php?t=56505
by Dirt Reynolds
The #906 casting head was available in two versions. One has an Inconel exhaust seat with a single angle grind, ...
I used to use the inconel/ stellite seats but find the HD sintered ones better for most applications
there is a reason chevy used them for HD

from an earlier post in this thread


" It's a great opportunity to cut 30* seats if that what you want to do, due to the larger diameter valves."
I'm not the only one?

another quote from Dirt Reynolds page one of the nastyz26 thread

Generally speaking, Vortec's stall at between .500 and .550 valve lift.
This is where flow actually begins to decrease.
But their true strength is low lift flow which gives more area under the total flow curve.
And if you think about it how long are your valves at peak lift?
They spend much more time at .400 and below,
where the Vortecs outperform most other heads.
This combined with high velocity, lack of turbulence and superior combustion chamber design are where the Vortecs stand out.

Unported, with all the other tricks in place,
the Vortecs will flow about 235-240 CFM at .500 I and 165-170 cfm at .500 E, on a 4" bore at 28" H2O, with clay radiused port opening.
With some careful porting there is another 5-10 CFM or so to be had.

But again the low lift numbers are unsurpassed at .100, .200, .300, etc. lift.
For example the Vortecs flow as much air at .400 as .500
and no 23 degree head that I'm aware of can match them at .200-.300 lift for the combination of flow and swirl.
Even the Fast Burn head can't touch them at low lift, it's ports are too big (flow is similar, swirl is less),
it does of course out perform them at lift over .500.

I think flow coming off the seat is important as is flow at .050, .200, .300
I can run shorter seat timing if the head flow gets with the program promptly

[randy331]

" It's a great opportunity to cut 30* seats if that what you want to do, due to the larger diameter valves."
I'm not the only one?

I've had the opportunity to do lots of things I knew not to do.

And if you think about it how long are your valves at peak lift?
They spend much more time at .400 and below,

Actually, a whole lot more time than you'd think unless you've actually measured it.

On one I recently measured at the valve with a peak lift of .710", it spent over half the total duration above .400" lift. Of a total of 293* of duration measured at .006" valve lift, it spent %55 of those deg above .400" lift,.... %44 above .500" lift,...%32 above .600" lift,...and It spent %11 of the time above .700" lift with a peak lift of just .710". AND,.. the piston is going the right way for cylinder filling at these lifts.

The most important part of the flow curve,...is during the lifts the engine has from peak piston speed, till BDC.

Randy

[wyrmrider]

all true randy but here were working on a "small bore short stroke" application with maybe 450-500 lift

[rfoll]

The cam is an XE 268H. Other than a pocket port and some chamber work, these heads could really use a good professional seat grind, but it is not in the budget. This motor will likely come in at around $500 with a fresh bore and the fresh heads.

[rfoll]

Bowl porting pictures. They really don't show very well how much metal was removed. The area next to the intake guide up to the roof is nearly 1/4" wider. I tries to basically enhance what the engineer designed into the port. I ran water through side by side stock and reworked, and I was astounded at how much smoother it became. It also appeared to send flow into the center of the chamber and cylinder area.

PICT0017.JPG

[rfoll]

I didn't flirt with the scribed line much because it was drawn on a 4" bore, not the 283 bore. The block was unavailable. If the chamber work looks a little sloppy, that's because it is. After grinding for 4 hours, my hands were getting jittery and tired. I may go back with a cartridge roll. I should have done the chambers first. There is a limit on how much work I will do to a friends heads for free.