561 casting flow #'s
 

I finally have flow #'s for the 561 casting LT1 head. They are about 10-12 cfm better than the other LT1 heads. The ports are the same size as the other LT1's but the external roof casting is about .100 shorter than the others so if you try and maximize the port you will fall through at the spring seat area on this head before the others. The shortside seems to be a little better shaped than the others and I am guessing this is where the extra CFM comes from. The exhaust ports flow the same as the other LT1's.

Enough talk, here are the #'s

lift---cfm
.050-30.1
.100-59.6
.150-84.1
.200-115.9
.250-144.2
.300-170.8
.350-191.4
.400-213.5
.450-223.4
.500-221.0
.550-218.8
.600-218.5

NightTrain66

What year cars do the #561 come from? I guess thes would not be very good to do a max port on because it has less meat in some areas?

Joe

I've never heard of the #561 castings, are they the iron Impala heads?

Thanks for the info Lloyd ;)

These heads would be good for a mild port job but I wouldnt go with them for an all-out portjob..

Cody

I am not really sure what year these come on.

They are an aluminum head and look just like all other LT1's except the ports look a lil diff. (lower) from the top of head while looking below the rocker arms. The easiest way to spot em if off of the car is by looking on the deck side and where the intake ports branch off from chamber side of the deck. It is hollow like on a LS1 in this spot and also has "561" stamped here and other LT1's are solid all of the way across from the quench pad of the chamber to the intake mounting flange.

Until about 6 months ago I never knew of a diff. LT1 head and then Phil (SkarodoM) asked me about em and I started looking for em. I had seen 2 sets since then but both were ported already and I knew they could not be taken out as far as the other LT1's but Phil mentioned some pretty good flow#'s with minor portwork. Cody brought a set over and we measured the ports and they were about .100 shorter on the outside of the castings but the inside was the same as others. I had finally got my hands on some "un-molested" 561's and thought I would post the #'s since several people have e-mailed me wanting them and I did not have any until now.

NightTrain66

Yeap, I got the first set I'd ever seen a few months back. I went ahead and did a quickie job on those, and it wasn't very difficult to have peak numbers in the mid 260's, so I think there's a fair amount of potential there.

If someone wanted an Econoport, i think they'd be a good choice, since you'd end up getting more for your $ IMO.

If you want a full port, I'd still have to suggest going with a "normal" 93-95 LT1 casting :)

whats the real difference with the 93-95 heads verses the 96-97 heads,

I have 561 casting #'s on my 97 trans am stock heads. As I am building a 383 right now we have come to the part where its time to port the heads. Eddie has a set of LT1 heads from a 95 z28 in his shop on the shelf. And we are going to port to the MAX....which set of heads would flow better ported all the waY??
my 97 trans am 561 castings? or the older style 95 Z28 heads?
:confused:

The roof cam be raised a lil higher and the shortside can be widened and layed back a lil more on toe "other" LT1 heads. By "other", I mean "not 561's".
The 561's that I did came out right where the other LT1's end up at. They were a set with stock valves. If you are installing oversize valves you may have to shape the shortside a lil diff since it is thinner here and maybe can not get the same #'s.

It depends on what ya mean be "fully ported". Some opinion of "fully ported" may be another persons "econo port".

basically, here are my feelings.................
Mild port ------------preferably 561's but any will do.
Full port with stock valves- --------ANY LT1 casting.
Full port with over size valves----------not 561's.

NightTrain66

By porting to the max I mean porting as far as we can go, No econo junk.. We are going to use 2.02 /1.60 valves. Im stil la bit confused on the benefits of using the older style heads vs the 561's.You said that the 561's flow better ported with stock valve size. But to use the non 561's if im going with over sized valves.....

Iguess waht I really need to know is which set of heads would i get the most CFM out of using 2.02/ 1.60 valves? And the porting is going to be as far as he can possibly port. No porting held back here.

Im just not getting enuff evidence to chose going with the older heads over my 561's.
I need more details please:(
I need to make my decision by tomorrow or hes gonna kick my butt and chose for me.

Do you really want 'max porting'? I mean, it's not hard to get the max out of a head... you just hog the thing out. The bigger it is, the more volume it will flow... common sense.
Generally speaking, I think this fascination with peak flow numbers is putting alot of undue stress on the realy experienced head porters. Let's say you've been porting heads for street and competition engines for the past 20 years and a guy brings you a set of heads and just tells you... "I want them to flow the max they can".... nothing about his application, just that he wants the 'max'. I don't know about you but I'd be a little ticked. It's a catch 22 for the head porter..... does he port the head to make best performance in that application or does he do the 'max' port like the customer wants. Everyone's a pro nowadays and if the heads don't flow as good as someone elses hog-job then the guy is going to smear the name of the porter.... regardless of the performance increase. I'm just happy I don't port heads.

One thing I've found is this... find someone who you know really knows their stuff and then trust in them to make the port fit your application. If you need a 300cfm port job, then I'm sure that's what the porter will work for. Otherwise, I'd just say... buy or borrow a sonic checker and port them yourself. Seen alot of 350-383 cid small blocks w/260ish cfm 190ish cc heads go 550 hp with extremely flat torque curves. Makes you wonder.

-Mindgame

Thanks for the help guys, and Mindgame I think you went off on a totally different direction.
I wasnt asking your opinion on Head porting techs LOL....u kinda missed the whole subject of this post. But thanks for your input.

And as for the guy I chose to do my 383 stroker build, He has owned his own business for 11 years and has been building engines for twice as long. He has already built an L98 for my 88 GTA I used to have and he did a wonderful job porting those heads.

But we decided to go with the 561 castings off my car, and to port them to best suite the 383 stroker. Did I mention he is an expert aluminum welder? He can do many " trick" things to aluminum heads. I hope to see over 300 CFM. hes gotta flowbench in his shop. I will be sure to post flow #'s

Before you cut them up, would you be interested in selling your 561 heads and matching intake? I race Stock Eliminator and need untouched castings. I have searched locally without luck.

Daren

Hey gang...

I have a friends pair of non 561 LT1 heads and have been working on porting them. This is my first set of Chevy heads. I've done lots of Ford heads in the past.

Anyway, someone mentioned 300+ cfm on the intake side???? Is this at 28 inH20??? At what lift? I don't really see how that is a possibility, from the pair that I have.

Would the 561's be good with a econo port and 2.02/1.6 valves?

hey turbo, we have been testing both the 561's and the non 561's heads. I dont see getting 300+ CFM....actually you wont, its impossible. We only got a max of 247 on a rough port. we expect to see 260-270 when completely done with more bowl work and different valves. Ahhh the Flow bench is great tool.

so what year can the 561 casting be found in f-bodies, '96-'97?

Yes!

Nightrain I want to compare apples to apples. Have you flowed a set of stock 93-95 and also a set of iron heads on your flow bench?
If I compare numbers to another bench it means nothing....
Mike

Here are #'s..............

lift----561---other
.050---30---30
.100---58---56
.150---84---83
.200--115--106
.250--144--137
.300--170--164
.350--191--185
.400--213--205
.450--223--212
.500--221--210
.550--218--209
.600--218--209

These are "core" or "pull-off" heads that are brought to me and the only thing done before flowing is basic cleaning. Just clean enough to use on the flow bench. They are also flowed with the valvajob that is on the heads when they are brought to me. The shape and condition of the valve job could effect the flow #'s a lil but since these heads are being ported and usually cut for larger valves it makes no sense to do a valve job before this. I had originally thought the exhaust ports were about the same but the last few sets of 561's that I tested flowed about 10-15 cfm higher on the exhaust than usual. Most LT1's flow about 145-155 at .600 (depending on the valvejob and cleanliness) but these 561 flowed 160-165 at .600 lift. There is a bump that is uaually on the shortside/floor of the exhaust that was not there on these heads. I am sure that is what makes the exhaust ports better.

The cast iron heads have a larger chamber and will lower compression as compared to the aluminum. I do not have a flowsheet handy but they flow about 230 (intake) and 150 (exhaust). There is little room for improvement unless ya wanna remove LOTS of material and the average portjob will get #'s around 250-255 (intake) and 175-180 (exhaust) and to get better #'s you have to remove LOTS of material and you are just chasing peak flow#'s and not making the car run better (probably worse since the port is so big).

NightTrain66

One more question for you and I'll leave you alone...
:)
What kind of #'s would you expect out of the 561's with a 2.0 - 1.56 valves using stock seats?

Thx
Mike

Well after testing both the 561's and the 643's castings on the flow bench we are going to continue forward with using the 643's.
there is jsut more meat to port them. the 561's do flow better on the exhaust side and weigh less. However its most likely we will see bigger #'s from teh 643 castings due to more room to port.
Below is a flow bench of the STOCK 561's and the STOCK 643's

This was done a 28" of H20

lift----643's lift 561's
Intake Exhaust Intake Exhaust
.100---67 ---47 --63 --46
.200--121 --90 --120 --93
.300--170 --120 --170 --121
.400--205 --139 --198 --142
.500--206 --147 --201 --150
.600--205 --150 --202 --154

the 561's have a better flow ratio between the intake and exhaust by about 3%

this shows that its nto always how much air you can cram in....but the balance between getting the air out too.
notice hte 561's flow less on intake but more on exhaust yet they make 10 more HP then older LT1 heads.
:eek:

As far as expected flow #'s, we are going with 2.00 and 1.60 valves we are shooting for the 265/220 range. i will post #'s once the work is all done.

The 561 end up flowing 270-275 (intake)and 195 (exhaust). These #s are with a valve job and shortsides that give good flow #'s at low and mid lifts. If you want flow #'s at .600 and that is it you can lay back the shortside a lil more and/or get a valvejob that flows great here but poorly at low and mid lifts.

I am not sure what "recipe" GTP uses on their heads but I have "touched up" some of their heads and they flowed 215-217 at .600 and still had good low and mid #'s. The intake valve job was nothing special but what ever they do to the exhaust valve job made it flow 10-15 cfm better than I usually get. ???????????

As long as you concentrate on the low and mid lift flow #'s with a good flowing valve job and correct shaped shortsides, shape the port correct and make sure that the port doesn't go turbulent at high lift and get at least 265 cfm or better from the intake port you will be happy with the performance. Do not try to get 285 cfm or look at the .600 lift flow # only. When porting the head if you keep looking at the .600 # or trying to get 285 cfm you need to watch what you are doing to the low and mid #'s when the head finally flows 285 cfm at .600. If you have a 270 cfm and pick up 15 cfm at .600 but lose 5 cfm from .500 and below you are hurting yourself. As long as the port is shaped correct, has a good valve job for low and mid lift flow and never goes turbulent than the .600 flow # is nothing.

NightTrain66

Re: 561 casting flow #'s
 

just tracking

Re: 561 casting flow #'s
 

INteresting info...