Okay just wondering, what can i do with 305 heads, and how much better will they be? Besides porting them, can you go with bigger valves? Just wondering, i had a set of them on my 350 with dish pistons, i figured the car would run faster with the 350 heads so i bought a set which were GTA heads 64cc. Took 20 thousands off so my compression wouldnt be soo low. There is really no difference between the 2 except for bigger valves on either the exhaust of intake side. The car does not feel as strong due to the lower compression. So what can i do with the 305 heads to breath and perform better Thanks

Buy some aftermarket ones


Realistically, Not much performance to be found in the 416's If your serious about it.

A Good port and polish will open them up considerably, But not enough to feed a healthy 350.

You would be much better working with the L98 heads you have, If the aftermarket is Not a financial Option.

Well ultimately i'd rather not dish out the money for aftermarket heads, because i'm lookin into getting a supercharger, and i know it would run better with aftermarkets but i'm planning to expand in the next few years. Basically i'm wondering, can i get the 305 heads to work better than the 350 heads i have now. If i can by porting the snot out of them then fine. My plans are doing a cam and rockers, while i'm doin that, maybe swapping heads, then save up for the supercharger. Main question can the 305 heads work better than the 350 heads if ported.

Those heads are like 58CC chambers. I did the math one day, and figured I'd be at like 12 or 13 to 1 with them on a motor we were toying with..

I'm still running them on my Z28, but I just have the correct block under them - a 305, and its still like 10:1.

-- Joe

You can get some ok power out of these heads, if they're really the HO castings if they're not junk em, but only if your building on the pretty mild side. Check with the guys on the Montecarlo SS board, lotsa those came with the 305 HO and those guys are pretty good at boostin the power level's. There are lots better stock castings out there though.

The L69 and LG4 heads are exactly the same, dude...

There is no way In hell I would try to build power out of a 350 w/ those heads.

The L98 heads will Blow them away.

I guess I just need to be more blunt...

305 Heads on 350 + Supercharger = dead motor ?????

well lets see, with about 70 pounds of iron we could make a really big doorstop, a couple hundred bullets, or even a small fireproof safe.... hope this helps

Yeah you guys are right, they will be junked, or maybe i can find somebody who needs a set, they were rebuilt no more than like a year and a half ago. So if anyone needs a set of 305 heads for there 305 motor, hey they know who to contact. Final decision, is to do a cam that will match a supercharger instead, but Thank You for your advice.

There is a difference in 305 heads 416's are junk 601's(Monte SS heads) are much better. They do have smaller intake valves but big enough ports to open them up..... Have a set a stock valved ones just mildly opened on a 350 with a mild cam in a 2nd gen Firebird. Just ran 13.2 yesterday at 105MPH with a stock converter. These heads pulled hard to 5600 or so. Considering a TPI(stock intake) usually doesnt pull even to that very well they seem like the ticket? Besdies bolted onto a stock flat top block they are 10.7 to one! JMHO