Difference between 305 & 350 heads, or is there?

[superiormgmt]

Is there a difference between 305 & 350 heads?

 

[ron7000]

Re: Difference between 305 & 350 heads, or is there?

yes

 

[Silvertip]

Re: Difference between 305 & 350 heads, or is there?

Valve sizes and chamber volume.

 

[paulie0735]

Re: Difference between 305 & 350 heads, or is there?

yep, and there must be at least 50 different head castings for the 350 just in cast iron and just from GM. and there has to be at least that many again in alloy and after market. which engine do you have the 305 or the 350?

 

[superiormgmt]

Re: Difference between 305 & 350 heads, or is there?

I'm building twin engine boat and I purshased 2 350 motors and was donated 2 305 motors. I'm using the 350's but one set of heads are shot. I know most of the componets are compatable but not shure about heads. Someone did tell me that 305 heads on a 350 block can make more power ?? That Didn't sound right to me based on sheer valve size.<br />Thanks for the help

 

[Bondo]

Re: Difference between 305 & 350 heads, or is there?

You'd end up with Big Compression #s,+ Tiny Valves.........<br /><br />I wouldn't do it.......<br /><br />Buy a couple sets of Vortecs........ Then you'll be Pulling Big Torque...........

 

[paulie0735]

Re: Difference between 305 & 350 heads, or is there?

it all gets down to your budget, i would just replace the heads with the originals, converting both to vortec will cost ya a bit! they aren’t a bolt on replacement. <br /><br />go here for some info on fitting the vortecs to a non-vortec 350. <br /><br /> http://www.2quicknovas.com/vortecheads.html <br /><br />good luck.

 

[Buttanic]

Re: Difference between 305 & 350 heads, or is there?

Most of the issues in the link above would not apply to a basicly stock marine engine. Only if you were building a high horsepower performance engine would they be a concern. The only revelant issue and extra expence is you would need a different intake manifold and gasket. If it doesn't break your budget I would go with the vortec heads. They are the best production head Chevy ever built.

 

[Bondo]

Re: Difference between 305 & 350 heads, or is there?

Ayuh,.........<br /><br />That Heavy-Duty Exhaust Valve Seat is sort of a Plus in a boat motor..........<br /><br />I've got 906s........

 

[MrPink]

Re: Difference between 305 & 350 heads, or is there?

where do would you find the best prices and products for Vortec heads. I have a 96 5.7 and would like to upgrade to the vortec heads.

 

[Silvertip]

Re: Difference between 305 & 350 heads, or is there?

GM Performance parts catalog.

 

[Bondo]

Re: Difference between 305 & 350 heads, or is there?

ebay......

 

[lilmandavis]

Re: Difference between 305 & 350 heads, or is there?

if your goin to spend the money, take 305 heads and revalve them. 1.940 valves just fit nicely in them

 

[Buttanic]

Re: Difference between 305 & 350 heads, or is there?

Putting 1.94 valves in 305 heads is a waste of money. The machine work will cost more then a usable set of 350 heads and with the 305's you still have to deal with a small chamber and too high a compression.

 

[I/O WALDO]

Re: Difference between 305 & 350 heads, or is there?

96 engine should already be vortec.I understand the only diff.in stock V.heads is the size of the exhaust stem.(either 5/16 or 3/8)Emma right??

 

[coalbucket]

Re: Difference between 305 & 350 heads, or is there?

Vortec heads have a different combustion chamber design, runner ports are slightly different, require different intake manifold, valve train will be different(comparing a stock vortec engine vs. non-vortec engine.

 

[I/O WALDO]

Re: Difference between 305 & 350 heads, or is there?

Not comparing apples to oranges,stock V.heads,according my machine shop man,only come 2 ways.

 

[Bondo]

Re: Difference between 305 & 350 heads, or is there?

You're Close Waldo,.......<br /><br />There Are in fact 2 Different Casting #s available,....... The 906s,+ I believe a 669 or 6?? something or rather,.....<br /><br />The 1s with the 6??# have Less Intrusive Exhaust Valve Seats.......<br /><br />The 906s are a Larger Exhaust Valve Seat,...... Better for Trucks,+ Boats,......<br />Bad for Hot Rodding,....... The Go Fast Hot Rodders prefer the 600series of castings for the Slightly Better Exhaust Flows........<br /><br />And,..... Even though Chevy introduced the Vortecs in 1996,.......<br />The Boating world is Slightly Behind the Times on these,......<br /><br />The Only Way to Know,.. For Sure,... Is to count the bolts retaining the Intake Manifold,........<br />Pre-Vortecs will have 12 bolts,....... Vortecs are held in place by 8 bolts........<br />The Center 4 were eliminated......

 

[I/O WALDO]

Re: Difference between 305 & 350 heads, or is there?

Thanks 4 the Vortec 101,Bondo!ALWAYX learnin!