350 vs. 305 Cylinder Heads

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85t5mcss

Master Mechanic
Apr 24, 2006
343
2
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Indy, IN
Will there be a noticeable difference or not. Currently have 350 "881" heads with the 1.94 Valves and 76cc Chambers. I still have my 305HO 58cc, 1.84 valve heads. Switching them wouldn't be a problem but I don't want to do it if there is no noticeable gain. Have u done this? If it matters, I'm running a .447 lift Hyd cam, 1.5 roller rockers. Most recent issue of HotRod makes it sound like a good idea. The better flow and compression outweighs the smaller valves. TIA
 

mrapii

Greasemonkey
Jan 5, 2006
198
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0
Waipahu, HI
I doubt that it will make any difference. Those HO heads were still smog heads. If you really want to make a difference bolt on a set of Vortec heads. PACE has a kit with everything you need (heads, new intake, gaskets, rocker arms) for less than $800. Yes, I know that is a lot more than the 305HO heads but at least you will make a noticeable difference after going thru the effort of replacing the heads.
 

SBCregal

Master Mechanic
Jan 22, 2006
261
1
0
I read the same thing in Hot Rod. What I was wondering was are the heads the same for the low output, and the high output 305's. I've heard they were the same heads but I'm not sure, I have a set of 416 casting heads... are they the same ones that would be on my lg4 305 in my 87 buick?
 

85t5mcss

Master Mechanic
Apr 24, 2006
343
2
0
Indy, IN
IIRC they r a smaller chamber than the LG4 heads, runners r probably the same though.
And $800 ain't so bad, since I was originally looking at AFRs. I appreciate that tip, gives me more alternatives.
I could always port, grind for bigger valves and so on and have more $$$ in a set of stock Cast heads. I think I'll start price shopping.
 

mrapii

Greasemonkey
Jan 5, 2006
198
0
0
Waipahu, HI
In the last few years there has been a tremendous amount of technological advances in head design. Even inexpensive aftermarket heads will out perform the most radically modified stock heads of the '70s and '80s.
 

87MonteSS

Master Mechanic
Jan 3, 2006
304
1
0
Winnipeg, Canada
mrapii said:
I doubt that it will make any difference. Those HO heads were still smog heads. If you really want to make a difference bolt on a set of Vortec heads. PACE has a kit with everything you need (heads, new intake, gaskets, rocker arms) for less than $800. Yes, I know that is a lot more than the 305HO heads but at least you will make a noticeable difference after going thru the effort of replacing the heads.

There will be a noticeable difference going to the HO heads as well. 76cc to 58cc chambers is a considerable drop. Plus the HO heads do flow well. The "smog" part that you refer to is all around resticted exhuast and detuned carb.
 

mrapii

Greasemonkey
Jan 5, 2006
198
0
0
Waipahu, HI
Yes picking up points on compression is a plus but he 305 heads have smaller valves and less port area, in my opinion it would be a wash.
 

85t5mcss

Master Mechanic
Apr 24, 2006
343
2
0
Indy, IN
mrapii said:
Yes picking up points on compression is a plus but he 305 heads have smaller valves and less port area, in my opinion it would be a wash.
Now thats what I was kind of thinking. But why would HotRod Mag even put that into print? I would assume for low buck mods, but thats not how it was written up. Thanks and I'll just stick to my original plans of AFRs.
 

mrapii

Greasemonkey
Jan 5, 2006
198
0
0
Waipahu, HI
Well Hot Rod is pretty reputable so maybe they are on to something. However I find it hard to believe that a 20 year old cast iron smog head for a 180hp engine can make for a viable performance head on a modern high performance street engine. I donna know, but I don't believe in the tooth fairy also.
 

85t5mcss

Master Mechanic
Apr 24, 2006
343
2
0
Indy, IN
mrapii said:
However I find it hard to believe that a 20 year old cast iron smog head for a 180hp engine can make for a viable performance head on a modern high performance street engine. I donna know, but I don't believe in the tooth fairy also.

LOL. I'm with u on that, too. And as u mentioned, HotRod is reputable. I'm not gonna bother with the downtime right now. Maybe I'll try it later just to satisfy my curiosity, then I'll go to the AFRs afterwards. I must be a glutton for punishment to do the same job twice.
 
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