litch2004

iTrader: (1)

Someone told me that my heads in particular are one of the best heads for porting (according to the casting number #10128374)???

Is this true? If so what is better about them?

GIZMO

iTrader: (8)

Larger ports than the later heads and more material to work with.

litch2004

iTrader: (1)

o ok. I was wondering. So mine flow a little bit better than the later model ones from the factory?

GIZMO

iTrader: (8)

About 10 CFM over 561's.

litch2004

iTrader: (1)

thanks for the info

67goatman455

iTrader: (14)

so what would be the years that the better flowing heads are equipped on?

litch2004

iTrader: (1)

mine are on a 93. I actually saw a set of these heads on ebay with the same casting number.

1eyedmaro

iTrader: (11)

374's and 643's are the better heads for porting because they have more meat on them to take off. They dont flow as well as the later heads or the 561's in stock form but flow more in ported form.

litch2004

iTrader: (1)

so mine actually flow less than the later model heads? Where is there more metal to remove at? actually inside the ports?

1eyedmaro

iTrader: (11)

just the thickness of the port walls. more material is there so more material can be taken out.

litch2004

iTrader: (1)

so my ports are actually smaller then the 561's? Which means mine dont flow as well as the 561's. They just give the porter more to work with to make them flow better?

1eyedmaro

iTrader: (11)

exactly

Dragframe

iTrader: (14)

dont make much sence to say they can be ported "more"

if the coolant passages are in the same area along with the rest of the head desgin similar.... then all it is just more material to be taken off that was already removed on the later heads. The limits would be just the same and couldn't be taken "FURTHER" than the next head could...


To me just sounds like there is more material to remove to get the same flow...

1eyedmaro

iTrader: (11)

its not all about coolant passages. I believe they have less pushrod clearance therefor can be opened up more in the intake runner. There is no doubt that they are better for porting. Lloyd elliot recommends these heads when he ports them for his LE packages. A couple years back he was buying them all up.

GIZMO

iTrader: (8)

That is an internet myth. Every set of 561 heads that I have flowed was down when compared to 374/643 heads. the 561's were also cast with less aluminum in them as a cost cutting measure by GM. If you have actually seen a set of 561's that flowed well please post up what you have seen.

litch2004

iTrader: (1)

?????

96capricemgr

iTrader: (1)

Your assumption is that a bigger hole is better. Lots of heads have been ported with that mentality. Doesn't make it right.

True experts manipulate airflow to make it move smoothy rather than just making the hole larger.

I know of one case where a shop removes just 7cc from an intake runner and somehow it out performs ALL the competition in catagories from drivability to max and average power despite the competition removing more material. It is about how the air moves, NOT how big a hole you give it.

SS RRR

iTrader: (2)

Precisely. Many believe the size of the port is where airflow takes place when in all actuality it is quality of bowl work that makes a cylinder head flow well.

za355tx

iTrader: (108)

Size is EVERYTHING No I'm just kidding. Power from head flow is all about air velocity. That's why some head porters out there are making tons of power with a not so large intake runner size. Like Dwayne said just because you see a bigger port doesn't mean it's going to make more power than a smaller port done right.

creepingdeath94

iTrader: (1)

This is where Lloyd comes in though...he obviously like the older head for porting for some reason. And he knows what he is doing and in terms of what makes power based on the results posted by numerous customers of his. I think bigger isn't better for the sake of being bigger, but in each particular style of head/case having bigger ports may make the difference for the air flow where as others don't need bigger so much as a tuned flow to make more power. I would imagine that the bigger ports when utilized properly make more power...probably why Lloyd wants them over the others. Not that more than enough power for most people's application cannot be achieved using the "561" heads. Just for max gains, he wants the other ones.