How much cylinder head flow needed to feed 535CI?
 

This is going to be very vague I know but approximately/roughly how much cylinder CFM flow would be required to feed a naturally aspirated 535 CI Pontiac bracket engine? I'm pretty confident my 290cfm heads will fall well short.

Assumed Variables: my 78 Trans Am below, Northwind 4500 intake, necessary size Dominator, appropriate size solid roller cam. E-85 fuel

Playing on the KRE website, it looks like I can have my KRE 290 D-port heads and Northwind opened up to 340cfm. Of course I'd probably have to find some round port adapters so I could run bigger round port headers.

Thanks,
John

I would say 380 at minimum depending on cam. Northwind should be ok with a worked over 1050. I run 2-1/8 -2-1/4 headers on my HiPorts with no mods to the heads.

I had the Hedman adapters on my D ports and you could run 2" on those, I bought matching stubs and built a set that were 1 7/8 stepped to 2" , they were still a d port header, not round port. I think Darby runs 350+ cfm d ports on his 505 and runs 9.50s. So depends on how fast you want to go. He would have to chime in on his tube size.

What RPM target would you want peak HP?

Do you have a suitable cam now?

The question is how much power do you want to make and at what rpm do you want peak torque and hp to be attained at?

Basically with any motor when where talking airflow levels at a 28" depression you will need 4 Intake cfm for every 1 hp you want to make per cylinder.

Really well worked out and thought out combos can make 1 hp per cylinder with just 3.59 cfm at the rpm of peak hp.

Also you need a certain amount of minimum port area also to hit your rpm goals of peak torque and hp and the Cam you pick and it's centerline and overlap also is a big factor in this.

For entertainment....

http://www.wallaceracing.com/calc-cfm-head.php

http://www.wallaceracing.com/flow-rpm.php

http://www.wallaceracing.com/head-flow-ratio.php


.

For interest, and related to the intake runner volume ? And the RPM involved.

The larger stroke engine will be sensitive to under-flowing heads. To illustrate, grab a bicycle tire pump some time, and first try to operate it as quickly as you can. Then, slow down the pumping action. You will notice that it is far easier to move the pump handle slowly. Your engine is no different- slow down the piston, and the engine has less work to do. Again, this situation is aggravated by high RPM conditions. The important thing to remember is that no matter how fast or slow the piston goes, the engine moves exactly the same amount of gasses during the same number of crank degrees. This situation could be improved by using the longest rods possible, which would increase the rod ratio and somewhat alleviate the angularity problem.
by Phil Parsons


.

May i ask where you got 3.59cfm from? That's 100hp shy of what mine made. Guess i have never seen this cfm per hp per cylinder before.
But anyway, i agree with target hp and target rpm need to be know. Imo screw cfm, if you get the correct size port for the ci and rpm then usually the rest falls into place somewhat

In my experiences, 200-210cfm is enough for about 400'ish HP, 300cfm ~ 600hp, etc. About 2HP/CFM on pump gas street/strip motors V-8's. E85 will make a bit more. well built/tuned examples will make more, more average examples will be less.

As for headers, I have Steve C.'s old BIG D-ports I'm not likely to ever use. Part number 35145, 1-7/8" primaries, 3.5" collectors. They have an adapter flange that bolts to the head, then the header flange bolts to it (wider bolt pattern).
https://www.hedman.com/product-detail/35145 Coated inside/out, with a higher quality coating than I've seen on most other headers.

I think I paid Steve about $370 for them?? Maybe he remembers :-)

Thank you gentlemen for all your replies. If I could make this a consistent 11.05 car (I only have a rollbar) at the high elevation tracks I race at (Pueblo 4913ft, Bandimere 5814ft) I would be quite thrilled. I'd even be glad to put a big honkin SFT cam in it to chill it out. As for heads I imagine it would be easiest to go with the KRE's on the current motor but I could also go with my Edelbrock D-ports that would need some serious/excessive porting as they are as cast.

Another gentleman and I are in deep negotiations for his unassembled 535 short block which is what brought up my question. I have a 1200hp rated PG and a 9in Ford housing that was modified for a 2nd Gen F-body if you 35 spline 12 bolt isn't up to the task.

Thank you soo much Lee, if this pans out you will be the first person I contact for those headers.

Lee, I have no clue what I paid for those headers. They were last used on my 600+ HP 462 with d-port heads that was completed and dyno tested 22 years ago :)


.

I think you can run 10.00 with a bar as long as the floor is not altered

I will add more detail to what I posted, that being for a street motor with 10 to 1 comp it will take between 3.8 and 4.2 cfm to make 1 hp per cylinder.

Just rough balling it.

3600 # w driver to run 11.0 @ 122 = 520 HP

Racing at 4200 feet altitude that would be about 610 Corrected HP.

A 535 ci with 340 CFM intake track flow should make the needed HP.

Will the car run the numbers and show that HP?

Stan

... so 8 hp ?? ... :Peace:

... i would tell you this, the CV-1 head out of the box goes 350's as cast on a small bore, so open the chamber to big bore stuff and you'll get even more without porting the head, excellent starting point for sure ...

Thanks for the tip, unfortunately this 535 option didn't pan out.

Johnny406 do u have a 9 in ford for sale?

I have a 9" housing and a incomplete 3rd member with trashed 5.38 gears that came out of a 2nd Gen Camaro race car.