What has to be done to the exhaust port on this head to make it flow? The numbers I'm seeing on these heads are around 210 cfm intake and 110 cfm exhaust at .500 lift. This was a stock head. Does that sound about right?

 

The intake flow (210 cfm) seems high for stock smog-era 305 heads. ME Leigh got 195 cfm peak intake and 110 cfm peak exhuast on stock 081 heads.

On ported heads, also from TGO people:

305 heads
416 iron head: 220 intake; 161 exh (Kitch, 14014416)
081 iron LG4 head: 221 intake; ??? exh (ME Leigh, stock 1.84" diam int valve)
081 iron LG4 head: 230 intake; ??? exh (ME Leigh, 1.90" diam int valve)
601 iron heads: 224 intake; 157 exh (Fast305, 1.84/1.50, 14022601, medium duty truck heads)

You can go to their posts directly by using my post to click from.

Kitch and Fast305 both got in the 160 cfm range and neither said anything special about what they did on the exhaust side. Buy Vizard's Chevy cylinder head porting book, and/or read the porting the 305 heads series on the TGO Tech Articles page.

 

So what makes the exhaust port so bad on the 416's and 081's?

 

I thought the 081's were the Lb9 heads and the LG4's got a different head altogether .

Anyone ?

 

As far as I know the 081's are the same as 416's they (081) just have the center bolt vavle covers. And yea 081's are LB9 heads

 

I suspect that doing a gasket match on the exhaust ports along with a gasket match on the exhaust manfolds (or install some headers) would help a lot. The port openings on those heads look pretty constricted when compared to the size of the gasket openings.

 

They are both factory cast heads used on ordinary passenger cars --- so there was very little attempt (back in the early 80s) to make them flow well either on the intake or exh side. The L98 aluminum heads probably got more attention (during the smog era when they were designed) than any other factory casting and even then it was only because they were Vette heads and specially cast in aluminum. It was probably cheaper for GM to use a hotter cam to get more power from the engine, rather than in development of the heads.

There are other earlier GM heads that flowed better but big flow numbers (via large runners, large valves, or both) and big open combustion chambers don't necessarily result in good power output. The LT1 head development was probably the first major decent GM v8 head developed for passenger car use, and even then it was an outgrowth of lessons learned on the racing Phase 6 Bowtie heads and the phases that preceded it. Other GM heads, non v8, were actually ahead (ahem) in terms of development (flow, quench, plug placement, swirl, tumble), so the v8s didn't really shine until the LT1 head, then followed by the L31 head and LS1 heads.

 

Thats why I was wondering why they were called LG4 heads above by kdrolt ..... when they werent LG4 heads . ( 081.461)

081 was Lb9 , and 461 was the 305 Hi-po ( 190 hp )

LG4 had the swirl port garbage heads ( not 461, or 081) so what are the above numbers for ...the swirlport garbage heads or the 081/461 heads .....seeing how they were improporly lumped together ( and ya I suck at spelling )

 

ME Leigh had them (at one time) on his LG4 --- but as you said they weren't originally on the LG4 so my bad for improperly attributing them.

I've posted the flow #s before on either the swirl port heads (305 LO3, 187 casting) or the 081/416 (also 305 heads). The swirl port heads are not good on the intake side but they are also much better than the 081/416 on the exhaust. 110 cfm on the exhaust side also qualifies for garbage status.