Ok, knowing that the valves spend most of the time at mid lift numbers, what would be the optimal mid range flow numbers on a set of ported stock LT1 heads to achieve the best powerband?

 

That would depend a lot on your cam configuration. A cam with more lift and duration will need higher flowing heads to push the air through...and a head with big ports will sacrifice velocity at lower lift, so it's a toss up.

 

Well, I'll ask this question with the CC305 specs, considering that's what I'm going with. 220/230@.050, .544/.544

 

Sorry to jump in on your thread but, could someone give good head flow numbers for a xe230/236??

thanks

 

My Impala has the iron heads which have been ported. Here are the flow numbers:

FLOW @ 28" H2O

Lift -- Intake -- Exhaust
0.100 -- 68.8 -- 51.6 -- 75%
0.200 -- 135.0 -- 112.1 -- 83%
0.300 -- 198.1 -- 160.8 -- 81%
0.400 -- 240.0 -- 178.6 -- 74%
0.500 -- 250.7 -- 184.5 -- 74%
0.600 -- 253.9 -- 188.3 -- 74%

With these flow numbers, and a 224/236 Comp Xtreme Energy, I was able to run 107mph in my 4400lb car. This should equate to around 114mph in a 3700lb car.

 

Wow!! That seems like a pretty good trap speed for those heads.

My head porter told me that he could get mine to flow upper 290's/lower200's with appropriate low lift numbers as well. I would like to run those heads with a xe 230/236. Do you think i could trap higher than 114??

thomas

 

I look at it like this... cam can only make so much power on x shortblock. You need x amt of air to make x power.. necessitating x min crossectional area... so.. there's our MCA & it flows what it flows after that

vague enough? :P

 

I run the XE 230/236.

Here are my head flow numbers:
Int. Exh
.200 151 139

.300 202 172

.400 233 192

.500 250 205

yep the numbers aren't BIG like all like to talk about but, Check my times in the sig!


Looking for an 11 here soon with a little tweakin

Ken

 

d'oh.. not to be a *****, but your I/E is fuct, and using 2.055's in an lt1 is 'tardified and whatnot =P

quick, but not fass

 

it works for me! How many stock bottom end LT1's ya see running 12.0.

But thanks for your constructive criticism amd positive feedback!

Ken

 

Hey, wasnt tryin to be a ****, but im not gonna sugarcoat stuff either. Its "tech," an i felt inclined to mention something technical.

It doesnt take big HP to be quick, yer quick. Nice times though, im not trying to take anything away from it. *shrug* whaddever

 

Skarodom: What would be good heads flow numbers all the way across the band for a xe 230/236.

Thanks phil

thomas

 

Why dont yiou get the heads done 1st like you should an dthen taylor the cam around the heads,drivetrain,compression,intended rpm afterwards..Shelf cams are for idiots who think there is a universal ansewer to make power..

For a street car keep your intakes around 190-200CC max (your porter should be able to make a mold to tell you the exact spec when he is done)..On a strong 355 around 240 CFM would be enough to get 400+ HP without killing velocity.

Your on the right track by not worrying about the big #s..But look at the mid lift area and you want the heads to be in or almost in by 350 or so..When your bench testing is done be sure the porter records the #s every 50 not 100..That will give you a better idea on how they will act..200 CFM at .300 lift intake is great..Stray away from the big valves too, it will kill your velocity too much..Try to make best do with the stock 1.94 intake valve and pay attention to the valve job..I had a post the other week disscussing this..55* angles i havent treid yet due to the move but its worth a shot along with a 5 angle valve job..Almost a nessecity in my eyes for a street car..Ferrera valves since the heads are contoured and give 5 cfm or so apart from the enck in the port are a good choice..There you will gain some flow without altering velocity much..Also make sure all your rocker stud holes are filled in with some sorta epoxy or filled and welded over..Filling is cheaper just make sure the epoxy used has been proven..That alone is worth a few cfm and lot less turbulence..Wich in turn will promote more velocity..

But in the end by the cam last and never never take an off the shelf cam..One of the rerasons i dont use Comp often..Crower is more willing to work with customers on custom grinds..

 

Who would be able to help me match a "custom" cam to my head flow numbers??

Comp cams??

 

I had my heads ported specifically to the cam I selected.

It was a custom grind from Comp Cams using their lobe catalog. The trick to any cam is to get the highest possible ramp acceleration with the shortest possible duration.

As far as a cam after the heads are done, first you need to find the lift at which the heads stall, then tailor you maximum lift to that. Adjust lobe separation angle to account for things such as MAP requirements of the PCM, if any. If you intend on using nitrous, you need to have a decent amount of advance ground into the cam, at least 5 to 6 degrees (also makes it sound really cool ).