I just got this information for Keith Craft stage II heads. Numbers will vary from machine to machine on any given day. .650 lift is what we will be using on our build.


Stage II Edelbrock RPM heads, 2.19 intake and 1.75 exhaust valves:

Intake @ .650 lift is 330cfm
Exhaust 247cfm

Stock Edelbrock RPM heads:
Intake @ .650 lift is 252 cfm
Exhaust 205 cfm

Stock 428cj/scj heads:
Intake @ .650 lift is 242 cfm
Exhaust 181 cfm

 

Wish I could afford to bench mine just for ****s and giggles.

 

Our local shop will flow test one intake and one exhaust port for $150.

 

Changed your title to better reflect the subject matter

Thanks maxtor!

 

Lloyd are you sure those #s arent KC Stage III numbers @ .700" to .800" lift?? because Brian has KC's CNCed Max effort Edelbrock 427 heads and there 370cfm on the intake at .800" lift if I'am not mistaken...

I'am pretty sure with KC the max on the Edelbrock heads 390/428 heads are 330 cfm... As I recall.....and that was @.800" lift.... "I" think....hell its been so long!!

Well good luck with the build!!

 

Hi Russ;

No these were the figures given to me for my heads, stage II by a tech at KC. The 390/428 heads are from the factory 72cc. Depending on what stage you want, Keith opens up the chambers up to 76cc. Ours actually measured 77cc do to the tulip valves. The cores of the 427 head and the 428 head are basically the same, before Edelbrock cuts them for the different chamber and valve sizes(and exhaust bolt patterns). This is what the Edelbrock Tech told me before I purchased the heads, because I was concerned that I would not be able to put the larger valves in the (72cc) 390/428 head. The KC person did give me .700 lift flow numbers, but I did not keep them because I was only concerned with what they flowed at the lift I will be using. He did not say nor did I ask about .800 lift.
My chambers are now the same size as the 427 head size after KC ported them.
BTW:
If you have a 4.13 bore 428, the 1.75 exhaust valves will not clear the cylinder wall using the Edlebrock heads. Our bore is 4.17 so the 1.75 exhaust valves clear.

I found the .700 flow numbers... Intake 335 cfm and exhaust 253. Not much more than the .650 lift.
I think Brian had larger valves... Like 2.25 intakes and I can't remember what his exhausts were.

 

I know I like to compare my stuff with other stuff, so I have a general idea where I fit in. Just in case you are the same way, here are the flow numbers from my Tunnelports and my KCIIIs in your lift range.

TP
.600 294 182
.700 306 182

KCIII
.600 351 236
.700 375 246

-Scouder

 

Ok Lloyd...I know that edelbrock advertise's the 390/428 heads as being a 72cc Chamber ..But I have never ran across any that were...they usually average about 74 to 75cc's... If your running a 1.750" ex valve in those what are you using for an Intake valve?

I did notice one of your posts where you said the valve spring pressure on the nose was 325#s if I recall.... And that doesnt seem right to get a valve float at as you posted 7800rpm's?? Hell the roller cam I just sold Wes was a Mid .600" grind..and I think that was like 500 something on the nose and almost 300 on the seat best I remember...?

Maybe it me just getting to damn many builds stuck in my head...between the 5.0 I was building for a local rod shop..and the Fe's..and Now the Mountain motors..Its a damn wonder I can remember my own name!! LOL...

Ask Glenn !! He'll tell yeah I'am about brain dead with Numbers these days!! LOL

 

Well a blast from the past !! I thought I was close!! LOL... Brian hows the new project coming!! Any updates you care to share with the class ??

 

Russ you are talking about two different engines. Our 428scj had the Crane cam, and the numbers I gave you were right off the cam card.
The Edelbrock rpm heads are new and have never been on an engine. They are still in the box fresh from KC. They will go on the 428cj engine that I am building this winter. The 428cj engine will get a roller cam, so as of yet, I have not purchased the roller cam, springs, lifters, or rocker arms.
Intake valves are 2.19

 

No Lloyd I was talking about your 428 your building...and at a .650" lift with only 300lbs on the nose and a valve float of 7800rpm..just doesnt seem right..when I have used lesser cam "Max" valve float with that much on the seat is all?? I dont think I have your motors crossed ? But maybe I do??

 

What size exhaust valves are you running? If they are the same as mine, then either your exhaust numbers are low or mine are to high, but what I wrote is what I was told.

 

Brian were those tunnelports ported with those numbers? Mine are bone stock and thought they were in the 280 range @ .600.

Thanks!

 

Russ, I have not settled on a cam for the cj engine. The crane cam which has a valve float of 7800 rpm is out of my 428scj that I pulled out of the Falcon. I still have the cam card, and that is what is listed on the cam card for valve float. I never went over 7000 rpm on that engine, and normally shifted at 6800 rpm, and never had a valve float.
fwiw,,, the spring pressure is listed on the cam card as 325 lbs. open.

 

They are 1.75. Isn't that what you have? If they are, taking into consideration the normal margin for error on a flow bench, they look to flow the same, or thereabouts.

-Scouder