Hey guys, im putting together a 73 429 to drop in a truck and am contemplating doing a light port job on the heads. i noticed that the "humps" in the exhaust ports are huge and they look quite restrictive. if i were to do a "gasket match" port job on the intake and exhast ports, grind down the those exhaust humps, and then just clean and polish up everything else...would i have to worry about running into anything like coolant passageways? also, how much will this actually help? for example...im sure ill gain some horsepower (anyone know how much?) but will i lose torque down low? or efficiency? i plan to drive the truck every day, sometimes off roading/towing, and of course the occasional street race =) by the way, the engine is basically all stock except for a non-retarded timing chain, a 268 hi engergy comp cam (218/218 @.050, .494/.494 in lift, 110 lobe sep.) and 80's electronic ignition. any thoughts?
Porting the EGR bump out of the exhaust port will help both, torque & h.p. The problem with these heads is that if you grind too far into the exhaust ports' roof you could get into the EGR's main air channel. You should be able to grind EGR port at least flush with exhaust port's roof and not have a calamity. Since you will have the valves out of the head to do any port work, (if there is enough room) try using a tap to make threads inside of EGR port that goes into the exhaust port and then use Locktite Sleeve Retainer & thread in an allen headed pipe plug to seal EGR port. Also seal EGR ports on both ends of each head using the same procedure. A 460 likes a dual pattern cam! Go 10-15 degrees more duration @.050" & .020-.025 inches additional lift, both on exhaust side. The biggest downfall of a 460's head design is crappy exhaust ports! Port match both intake & exhaust, don't do anything within the intakes port, it flows plenty "as-is". The roof of the exhaust port to about 3/4" from the bottom of the port is where you will be most effective, especially at the ports' exit. I hope this helps in any way.
hey todd, thanks for the reply, do you have an estimate on what kind of power gains would be expected from grinding the humps and port matching? so torque isnt hurt at all? not even right off the line? also...with that cam and a port job, headers and duals would probably be a good idea right? (oh i already have the cam so its too late to go with a dual pattern)
You can probably expect 15-20 h.p. maybe more & about the same type of gains in torque. The bigger the cam, usually the bigger the gains, to a point. DEFINITELY use headers & dual exhaust, 2 1/2" pipes with good mufflers(you choose). Stay with a dual-plane manifold (Edlebrock Performer or RPM, Weiand Stealth 8012) it will help build low end torque. The stock 460 "boat anchor" manifold is hard to beat for low end torque, but it gives up mid-upper end h.p. & torque. If you are using aftermrket rocker arms you can "cheat" just a little by using a 1.7 ratio on the intake valve and 1.73-1.75 on exhaust valve to gain a little bit more lift & duration without buying a new cam, just a thought. I hope ths helps.
hey guys ive got a couple of unmodified c8ve and dove heads. one pair of d0ves on my .60 over 472 ci,were moded and has 2.25 intakes with a mild port clean up and 1.75 exhaust valves, i did a huge port job on the exhaust side using a mpg heads article from an old super ford issue. it was done w 10 inches of water, the exhaust port opened out to a rectangular shape and required custom flanges, but it looks like they flow 206 at .580. i had the spring bases shaved down to allow .700 lift but i went mild with .236 246 @ .050 edelbrock cam .556/.586 lift double springs 100 seat pressure 300 open hardened push rods and guide plates. performer rpm intake,stock lincoln rods with arp rod bolts sadly, 850 holly with a KnN stub stack all into 2 inch headers and three inch id huge custom made glass pack mufflers. threw in a windage tray too it seems there is tons of places to make and save hp in the 460! i'd love some ideas on my hp and rpms. i've read many quotes of 12 th 15 hp with mild exhast porting and even more with the 1.71 1nd 1.75 valves. what's the conversion from 10 1nches water to 28 inches? any one know? i'm stoked to hear all thoughts thanks all.
do a search for reincarnation automotive. he is the porting expert on the 385 series heads and has step by step porting instructions on his website for a nominal fee.
shows where to port, where not to port and how to shape the ports for maximum flow. remember bigger is not always better when it comes to porting, proper shaping and eleminating restrictions and dead spots in more important.
used his website to port some DOVE heads (haven't installed yet) and they turned out pretty good.