Originally Posted by F-BIRD'88
Everything you posted about porting the 305 heads (and other stock SBC heads in general) is incorrect.
Do not deshoud out to the cylinder wall. The air does not flow in that direction.
It flows toward the spark plug. Flow a garden hose thru the intake port and watch the water flow pattern thru the port into the chamber.
If you only "pocket port" these heads you will get minimum results.
The meat and potatoes (air flow gain) is deep in the port. The whole port.
On a 305 cid motor you can keep the stock 1.84x 1.50 valves or cut down some old usable/regrindable 1.94 x 1.60 valves to a 1.90" x 1.55" custom valve size on a lathe and regrind the valve seat. Or use a 1.94x 1.50 valve pair. Irreduardless only minumum deshrouding is nessessary. The area between the valve edge and cylinder wall zone is not a critical area.
If the new larger valve is .050" bigger radius you only need to clearance deshoud by .050" (or less) around the valve.
You need high speed carbide porting cutting burrs, 1 with a 6" shaft to get deep in the intake port around the guide boss. The sanding rolls are for finishing. (mostly eye wash)
Do the whole port including the valves guide boss area.
Use a felpro 1205 gasket as a guide. Raise the port roof don't lower the floor but recontour the short side radius.
The 110LSA xe cams are not compatable with the stock TPI computer.
Buy a EFI computer friendly XE cam on 113 or 114LSA.
raise the cr 10:1 if you want a larger than stock cam. (shave the heads, thin head gasket)
You will need high 4.10 rear gears and a high stall 3000-3500-4000 converter to get a 305 going. (especially with a big cam.)
Use long tune headers, 2.5" Y 'ed into 1 big 3" exhaust. Use two small case 2.5" cats.
Search my old posts for pics of the desired finished 305 head port and bowl contour. Pocket porting is not going to cut it.
The porting articles cam from reliable sources and its not intended to be a "max effort" port job. Just a simple clean up to make it flow better for a mild cam. Did you ever flow test those cylinder heads in your old posts? I would be interested in how it worked out. The cam that I listed is on a 112LSA. Not a 110. More than a few people from thirdgen.org recommended it because they said it worked great for them. It really doesnt matter either way as I am going to an XE as said in my earlier post, which should be a better cam. I would love to use long tubes! The problem is no one makes long tube header Y pipes and I would not be willing to let a muffler shop press bend some kinked y-pipe. The SLP's are a 1 3/4" header in to a 2 1/2" Y pipe to a 3" collector. This should support a 305 with 300hp just fine.... If the LSX cars can make it work out with more bore size and flow...
Old bogie -
If I could find a 350 vortec for about the same price as this is going to cost me I would. I also do not support ditching the 700R4. I have owned 5 liter mustangs with T5's and both an lt1/lsx car with T56 and being auto has grown on me the past 2 years. I almost want to ask if you have ever had a fast automatic? (Respectfully)......I like not having to shift constantly and having a free hand. Also TPI likes lower RPMs so having an auto actually works out. The shift points can be easily changed via governor. Give it a trans cooler, a shift kit from TransGo and a decent converter with lock-up and its actually a blast to drive. A lot of what your saying about porting goes with my original post and what i've read. I DO have access to a flow bench, FWIW. Everyone keeps saying the 305 will fall short of my expectations, well my expectations are really low. This ISNT supposed to be a 500HP monster. Just a nice driver with a little more power, and what's wrong with using a 305 for that? You can trust me when I say I have had fast cars, and it seems drivability always suffers. The BEST fast and drive able car I had was a 1985 Mustang GT with worked gt40's and a 670 Holley S/A with a weiand stealth intake and a lunati 112 224 .510 cam. It ran mid-high 12's on drag radials and didnt overheat while in traffic with the A/C on. This is pretty similar in what I am expecting ultimately... just a little slower at mid 13's.
wow, this is getting really long...
So my porting answer is answered and contradicted... I guess I will have to make my own decision. I really dont want to do a motor swap... the 305 can accomplish the task.. I want this car to remain mostly numbers matching as it is an all stock, all original 105,000 mile car that has been taken care of REALLY well! I dont want to tear it up, it just needs a little help to be more fun to drive. Understand that I sold a fast car to get something I can cruise/show and hit the track every once in a while that drives really good, has A/C etc.... Thanks guys! I appreciate the feedback!! Keep it coming!