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Author Topic:   What advantages to 305 heads on a 350 block?
rogracer2
Dirt Maniac

Total posts: 119
posted December 05, 2004 07:28 PM  
What are the pros and cons of putting 305 heads on a 350 block? I've heard things about HP and torque - mainly only help in the 3500 rpm or less range?

Any help is appreciated!

mudd on the tires
Dirt Full Roller

Total posts: 42
posted December 05, 2004 09:32 PM  
i run 305 heads on my 350, b/c i got a good deal on them and was told they increase your compression b/c of the small chambers. but i would like to here other opinions and thoughts.

19J
Dirt Freak

Total posts: 370
posted December 05, 2004 09:34 PM  
Depends. Some "305" heads are 76cc so they do no more good than a 350 head would. A "true" 305 head like 58 cc would give you more compression. Unless there is a big secret i dont know about most people use it to get the compression up with a flat top piston.

shifter
Dirt Roller

Total posts: 16
posted December 06, 2004 02:08 AM  
I know alot of drag racers used the 305 head off of a 305 truck motor b/c those are the ones w/ 58cc chamber and 1.94 int. & 1.5 ex valves. We have used them on stock 350's and have seen a 1/2 second shaved off our 1/4 mile times.

MetricMonte
Dirt Maniac

Total posts: 111
posted December 06, 2004 09:28 AM  
I'll add to this...Whats the difference from a 305 High Output head and a regular 305 head, are the High Outputs the 58cc head and the non High Outputs a larger chamber or what?

Raz_900
Dirt Forum Champ
Total posts: 635
posted December 08, 2004 06:29 PM  
quote:
Originally posted by MetricMonte:
I'll add to this...Whats the difference from a 305 High Output head and a regular 305 head, are the High Outputs the 58cc head and the non High Outputs a larger chamber or what?

Correct.

The HO casting numbers are 601 and I think 416? Not sure. The 601 came on early 80s HO Camaro and Firebirds. I've heard the other head was on 4bbl trucks. Basically, if it's a 305 with a 4bbl carb, it's worth a look.

Oh.. and the valves are 1.84" 1.5" from the factory. 1.94" 1.6" pieces fit in without much problem. A little clearancing of the chamber will unshround them for better flow.

latemodel142001
Dirt Roller

Total posts: 5
posted December 08, 2004 08:33 PM  
305 heads do boost compression but ypu also have to remember that they also have smaller intake runners also. So they end up flowing less.

nailngoracing
Dirt Maniac

Total posts: 170
posted December 19, 2004 11:11 AM  
do what your engine builder specifies...
the 305 heads are gonna shroud really bad and cause engine to run severly hot on the red and yellow...even around town in drive thru's and red lights...
to make them work right you will spend as much money with a head shop as if you were to purchase a good set of heads...

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