Need Help- Porting Heads for beginners

Chris if your working on them now or during the day before 9 pm, then just call me.
I just sent you a pm with my number.

 

My question was exactly that,...an attempt to "add" a different dynamic to the thread and learn,...by asking a question,....I understand the theory behind it just fine,..but you obviously have a deep grasp on the subject,... so I asked how much of this applies to a large cid engine. Not sure why you took it personally?

 

Steve I’m going to give you a call after I get off work at 4 and we can formulate a plan of attack for these heads and I appreciate you taking the time for all your postings and to speak to me.

 

Sounds like a plan!

 

Hugger I am sorry , but with printed works it’s hard to judge a persons tone at times that’s really all I ment to say!

How large a cid motor are we talking about in terms of your question?

 

464~494in 10.75 to 1
240ish duration
625 lift roller
Single plane
950~1050 carb

3800~4200stall
373~410 gear 28in tire
3700lbs

How much concern should there be on throat ratios,..pinch points,..port velocity/cross section and such?

With a milder combo with street gearing and or more weight,..I can see where getting carried away with bowl size and and criss section will hurt performance without a doubt

Ive been going back and forth for months on heads for my Z06,....because of this

 

Thanks for the info!
Some questions now.
What heads are you thinking of going with, and how much power are you looking to make at a minimum?
Also how will the car be driven most of the time?

 

Hugger I did some math for you last night once I figured out the Bore and stroke of the two motors you posted about.
Assuming the heads you run use a 2.130" valve with a 11/32" stem then that area would be 3.328 sq inches at most since this does not take into account that the true sq inch Area would be less by some 10% due to the need to have a valve seat under the head of the valve.

With a 2.130" valve and a 464 cid motor, and assuming a ideal port area on back up the port from the valve the peak port velocity at 6000 rpm would be 460 fps.
This is good since if you top 690 fps then air flow is in effect blocked off due to high pumping losses.

In terms of a 464 cid motor at 6000 rpm you would need a overall port area of 2.266 sq inches to not top 690 fps.
A 494 cid motor needs 2.41 sq inches of overall port area to not top 690 fps at 6000 rpm.

To spin a 494 to 7000 rpm and not top 690 fps you need 2.770 sq inches of port area.

These fps numbers are all based off of the type of Cam that it seems your running , and the Cam has a big effect on what rpm peak air speed and peak hp get made at!

If you want to see what the numbers would be like for a 464 cid motor then times these 494 numbers by 6.5% and minus that out.
By the way a 240@ .050" Cam is on the small side for 494 cid!

In terms of port volume I do not know how many CCs the TA heads are to kinda do a comparison, but if you want to compare stock a 455 heads Intake port at 186 CCs to for instance the Edelbrock heads at 215 CCs which are 15 percent bigger then just bolting on the Edelbrock heads will raise the rpm of peak torque and hp by that same 15 percent alone, assuming the intake manifold is not a restriction port area wise!
If a stock non stage 1 455 made peak hp at 5500 rpm then that would change to 6300 rpm with a 215 CC port .

Note that these assessments are kind of general since exact minimum dimensions would have to looked at between both of these heads I am talking about.

I hope this helps somewhat!

 

Steve, I want to give you a call around 4 if that’s an available time for you?
I measured my throat again for the intake and exhaust and it’s basically around that 85% of the valve.

 

That works, talk to ya then!

 

Hi all!
I keep forgetting to post back this info.

Aftetmarket heads with there far deeper valve bowls and in turn higher short turns make it far less likely when doing valve bowl work of loosing air flow numbers then in the reworking of stock non stage 2 iron heads.

For example, the very shallow stock exh ports in these heads is a classic example when you look at the cut away pictures posted earlier in this thread!

If you took that stock exh port and kept its same dimensions, but just made it a overall 1/4” deeper you would have 8 to 10 more cfm of high lift flow taking place, with no loss of low lift flow!