6T5RUSH

Scott, apologize for getting off tangent on your thread here but thought I'd confirm what Joe (65tripleblack) said on aftermarket heads,

You are absolutely right Joe about the 50 year old iron heads that GM provided, properly massaged, giving good flow as compared to the aftermarket heads.

I've posted this before. Here's a crude set of notations on flow I jotted for comparison to my breathed on '461 heads. The AFRs, Darts & GM are 180 runners. The Darts have 1.6 rockers. I'm currently running GM stamped steel 1.5 stock rockers (they work!)

@28 here's the cfm flow:

Lift ............................ Intake/Exhaust

............ 461's........GM Bow Tie..... AFR......... Dart

.100 71.3/62.5.................................... .. 68.4/62

.200 142.4/112.8....116/107..... 140/112.....144.5/108.5

.300 187.1/153.9....169/143..... 201/152.... 200.6/158.0

.400 227.7/176.6....212/166..... 244/190.... 237.8/193.1

.450 240.2/182.9

.500 241.0/188.2....239/169.....260/208..... 252.3/200.6

.550 238.5/191.3....225/172.....262/214..... 257.4/201.9

.600..................... 228/174.....263/218..... 260.1/202.8

.650.................................... ..................262.3/203.7

Unless you are at WOT all the time, the real #s to focus on above are below .500 (more likely .300 to .500 range).

The big advantage aluminum heads have is dissipating heat and just dead weight. But for a street application, iron heads compare favorably to the AFRs. You will spend $ making them flow which negate the initial less costly iron heads over aluminum.

My experience.



Jim
In God We Trust!

65tripleblack

Jim,
The biggest advantage with aluminum heads is that almost all of them use the MUCH improved kidney/heart shaped chamber rather than the wedge. This completely unshrouds the valves, especially with smaller bores. Most of the iron heads use the wedge chamber.

Here's a handy chart:

http://users.erols.com/srweiss/tablehdc.htm#Chevy

When I ported my 461's, they flowed almost exactly same as "Chevy 461 Ported Creative Flow Management Iron" listed. As I said, the 327 with those heads made 358 RWHP.

ghostrider20

Hi Scott. Glad your project ended up so well. I remember visiting a few years ago about the LT-1 cam. My numbers were very similar to yours, and I think your top end power benefited from the LT-1 intake vs. the winters L-76.

- Mark

bluester

That is the one area where I think the aftermarket head mfg. co's are missing the boat,make a head that looks completely identical to a 461-462 on the outside, but modern chambers and ports, I think they would sell a bunch of them !