350 heads on a 305?

[faulkner32]

Anyone know if you can put a set of 041 heads from a 350 on a 1983 305? I got them for free and the research I've done on the heads says they're pretty good. I know that just about all chevy small block stuff is interchangeble, but I was concerned about the coolant holes and the bore to chamber area. Any help is appreciated!

[broughy84]

I'm pretty sure they will fit. I know i have had 305 heads on a 350.

[faulkner32]

Do you have any tips or suggestions that you've done or did you just bolt them on? I was also wondering about a cam and/or carb. I don't know what kind of cam it has in it know, and it has the stock (I think) quadrajet. I have a Holley 750 but I know that's too much right now.

[quaddriver]

in 99% of the cases I would not do it.

First issue: valves. 194/150 valves will fit inside a 305 bore, 202/160 wont.

Second issue: combustion chamber size - the 350 has a larger combustion chamber. the 305 has typically a 58cc chamber. the 83 305 uses a cut piston, therefore with any 350 heads that are under 10:1 (and those that are not have the aforementioned 202 valves) the compression will be lowered and hence power will be lowered.

before you go much farther, rip off a valve cover and tell us what castings you DO have. GM makes some rather decent heads for the 305 that were used on the Z's, montes and in marine usage that have the proper combustion chamber sizes (to get you around 9-9.5:1) and have valves better suited for the 305 (184/150) 83 was a pretty crappy year for the 305 (actually 76 up to 84 were all pretty crappy in the non-performance applications). Id recommend the EFI swirl port casts.

if you really wanna spend money and dont want a 350, world products makes a 305 torquer head that are not too pricey, but gives you the big valves and proper compression

[faulkner32]

Yeah, I was thinking it might not work. I just have these heads sitting here and really wanted to make use of them. I'm sure you're asking, why don't you just do a 350? I can't right now because its my daily driver.
I do have a 454 .060" over short block that I was working on. NOW THAT WILL BE SOME MEAN POWER!!
I acquired a Holley 750 4160 that is for the BBC program, but since I got delayed, I was wondering if it would be fun to put it on the 305 and mess with it. I know, 305's are a waste, but that's all I can mess with right now and I got the bug bad since I got the BBC. Any ideas would be appreciated.

I'll have to look to see what the heads are, but I'm pretty sure the're not anything special.

[Rbraczyk]

YOur gonna have a greater compression ratio if you put those heads on i think...

[faulkner32]

greater compression ratio as in higher and good or higher and bad?

[quaddriver]

Originally Posted by faulkner32

greater compression ratio as in higher and good or higher and bad?

I was a little confused about what he meant also.

a 350 head will have a larger combustion chamber than a 305 head so compression will go down. That is bad if you want to retain hp

illustration:

compression ratio is the volume of the cylinder assembly at bottom dead center (BDC) divided by the volume at top dead center (TDC). If we assume that the piston at tdc occupys all of the space, then the TDC measurement is simply the head volume.

sample calculation: 580cc cylinder volume at bdc / 58cc head volume at TDC = 10:1, if a 350 head has 70cc, then 580cc / 70cc is a little over 8:1.

Its a little more involved than that, but you get the point.