i am a first time engine builder and have a question regarding a set of heads. i have a chevy 350 4 bolt main, powermax 272 cam and the heads i have are 305 #416 56 cc, with 185/150 valves what will happen if i use these. thanks
YA , i gotta side with Henry.To alot of people ,the 305 heads seem too good to be true. But they are a lighter casting and easier cracked and with their smaller combustion chambers, they SOMETIMES, raise the compression ratio through the roof. Unless you have carefull engineered, or biult this motor to compensate for this , you will probably have more headaches than it's worth.
Just my opinion!
P.S. sorry to take the wind out of your sails ,but if you want a good reliable motor, sometimes its worth spending the extra $ .
What the guys said is true. They are usually very thin castings which doesn't mix with high perf.
Also, the chambers don't match the bore size for the 350 and the valves are only 1.85"
Try to locate a set of 64cc 350 heads.
If you have to go with 76cc jobs, have them decked and make sure you are running a thin head gasket with a small bore. Lots of folks forget that the head gasket bore size has an effect on compression too.
Fel Pro 1094 is .015" and has a bore of 4.100" as opposed to .040-.060" and 4.16" and up for other type gaskets.
Cast Iron Vortec Cylinder Head Assembly
This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. The intake and exhaust port are very similar to the Corvette 350 LT1 heads. This head includes 1.94" intake valves and 1.50" exhaust valves, with pressed-in 3/8" studs. This head with compatible valves flows more air than bow tie head P/N 10134392, but the casting may not be as durable. The water passages are the same as the original 1955 small block design. The eight-bolt intake bolt pattern is totally different than the early model V8 12-bolt design. Use new manifold P/N 12366573, 12496820, 12496822.
Technical Notes: The valves seats in these heads can be machined to 2.02" intake and 1.60" exhaust. The rocker arm studs can be pinned or drilled and tapped 3/8". (Casting P/N 10239906 or 12558062.)
Just to give you an idea what new ones cost. At the bottom of the site page is a head chart with part #s and a info list of heads.
I have to kind of disagree with the other guys.
The 305 heads are good for racing on a 350 ci
as long as you don't have any cooling problems.
Get a 3 angle valve job with a slight(maybe none)
porting/polish job.I ran these in a 76 GMC 1500
pickup on a 350.We had top speed of 120 mph(easily)and ran mid to low 13's on the 1/4 mile.
But as a caution we did this running about 12:1
compression and had to change over our hei to a
If you have stock pistons and want to save a buck.
The 305 heads will raise your compression and porting them will help them flow better. Although porting them is tedious and time consuming it is worth while and and like the last guy said, Racers use them all the time. Some stock car guys use them and their constantly in the high RPM's. Also you can have the heads cut for bigger valves. This is expensive but at the same time you can have screw in studs and good valve guides installed and have a top notch set of heads. The only reason I didnt do this was Money constraints. It is quite expensive. Just something to ponder.
I, personally agree with the first guys and suggest you go with a different head set up. We were fooling around in the yard one time and tried this combination with an old pick-up truck just for fun and although everything hooked up well and everything was running well from the two motors before, as soon as we started it up it was hand grenade city.Could have been our mistake but I don't think so by the way the pistons were blown through the oil pan. Is it worth it? I'd say the worked on 350 heads are the way to go. Good luck.
Honestly the discussion of weather the 305 heads can be made to perform or not is not realy intersting in my wiew. with the money you'll have in them between the stainless valves, springs, retainers and keepers, not to mention the porting. you will be much better off with just buying a set of World Castings: Motown 220's with everything installed and a horse power potential way way above the vortechs. and a price arround the same. plus your intake and valve covers will fit.
I'm gonna whup on you the best kept secret in good GM heads. AeroHead Racing heads: $400/pair. Specs: 64CC chambers/3 angle valve job/2.02-1.60 valves/.560 lift capacity/screw-in studs. And, you don't have to have a special manifold as you do with Vortech heads. They are true bolt-on. I'm running a stock short-block 350 with these heads, a Herbert Performance .280-.290 solid lift cam, Holley Street Dominator manifold, and topped off with a Holley 700cfm double-pumper. The car is a very strong street machine/8.3's in the eigth mile. Hope this helps.