hey any of you guys that have ported your stock 305 heads i wanna hear how u did it. mine are coming off this winter and i am gonna try porting them myself. what is the scoop, where do i need to work on the most, and how much grinding should i do? thanks for your help

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86 IROC
43,000 miles
305/700R4/3.23 gears
maroon, gold stickers, black interior, T-Tops.

current mods.
shift kit
headers
cat back exhaust

mods planned for this winter
cam
3.73 gears
subframe connecters

 

Go to the Standard Abrasives website and check out their do-it-yourself instruction (a recent post listed the URL). Or, go ahead and get their Deluxe Porting Kit, which has the same instruction in poster form.

There is also a link in the tech articles on this board. Basically the same approach.

You'll want to upgrade to 1.94" intake valves. Get the seats roughed in by a machine shop first so you have an idea where to go from there.

Edit: On this topic, https://www.thirdgen.org/messgboard/...ML/014928.html , Vader says get a carbide spiral burr to enhance the SA porting kit.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ4 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (ported World 305 heads, Crane PowerMax cam, Hooker 2055 headers, 3" Catco cat & 3" catback w/Flowmaster, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

[This message has been edited by five7kid (edited October 29, 2001).]

[This message has been edited by five7kid (edited October 29, 2001).]

 

I ported the hell out of a pair of 305
"416" castings. I installed 1.94 and 1.60"
valves and got them flow tested.
The intakes came up to 225cfm@.450" (185 cfm stock). The exhausts came up to 140cfm@.500"
(110to 120cfm stock). I took out about 10cc's of metal out of each port. I unshrouded the combustion chamber for the new valves too. After having the heads planned, combustion chambers were 60cc's.
On the intake port, enlarge the bowl under the valve. Shorten, thin and streamline the
valve guide boss. The long side port wall(common wall) needs to be straightened as much as you dare. Especial right near the guide. Raise the port roof a good 1/8"+ from
intake flange to the bowl. The short side in the bowl needs to be radiused and blended into the floor. Widen the floor there and blend into the walls. Don't lower the floor, just clean it up. Gasket match the intake flange to what ever gasket your using.
the port wall at the push rod can be enlarged. Don't highly polish the intake port
Just blend your stone and cutter work with 40 and 60 grit rolls. the exhaust bowl can be enlarged and blended into the runner. Blend radius the short side under the valve
Shorten, trim and streamline the guideboss.
Clean up and enlarge the rest of the port, consentrate on the roof and walls. Do not enlarge it bigger than your header gasket.
Polish the exhaust port and combustion chamber. If you spray water with the garden hose in the port you can see where the airflow is concentrated. Those are the areas
to work. These heads would rival a set of unworked vortec heads. WD-40 really helps
keep the dust down while grinding.
http://photos.yahoo.com/russ_q

 

http://www.sa-motorsports.com/diyguide.shtm

 

Were the 416's 58cc stock or did you know?
Thanks!
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91 RS 5.0 TBI....LT4 cam....Edelbrock headers....3"Dynomax exhaust....5spd.... 3.08.....Ultimate tbi....afpr...ZR 255-50's...Koni's

[This message has been edited by DM91RS (edited October 30, 2001).]

 

Yes the stock combustion chamber was 58cc's
before I started porting. They were 60cc's
when I finished. The increase was caused by unshrouding the bigger valves to increase flow at low lift. I was going to use the on
a 350 so that was ok. you could plane them further to get them back to 58cc's for a 305.