Porting 96 heads a few early flow test results
 

Hi everybody. I am but a novice in the world of porting heads. I am reading Jim Hands book and trying to pick up what I can here and there. I am wondering if I will pick up what I lost in the low lift area with a proper valve job? We are experimenting with some 4x heads assuming what works on them we can use on the 96 heads.

The bowls have been cut only. No blending yet at all.

I also was hoping to re use the valves, that being said shooting for a 1.6 installed height is getting difficult with 125-130 lbs closed valve spring 320-350lbs open. So I could always cut the valve seat .100 to make up for that problem? If I have to replace valves for longer ones do they make non dished valves as my rough estimate with a .030 over 455 and 96 heads makes like 9.37 comp with a .030 head gasket. Hate to lose any more compression with the dished valves.

First off are you shooting for more peak flow with those 4X heads than that 218 that you have attained already?

You have picked up high lift flow and gave up some low lift flow because all you have done with your work is open up the throat of the valve bowl, and that mainly controls the total air mass that can make its way to the back side of the valve, but your work has also changed the relationship between that throat size and the curves / angles that form the rest of the valve bowl shape, that being the factory 60 degree bottom cut and the as cast 75 degree walls of the rest of the valve bowl.
I assume you have also blended the radius of the short turn, yes?

Have you done a valve job yet that takes the 30 degree seat OD out to 2.095” yet?

Here’s a early on flow test for a project for a friend I have been helping him with.

His request was to not loose any throttle response, yet to pick up a good chunk of HP for a street 400 cid motor.

I set a goal of 230 cfm @ ,500” for his project and have since got there.
The Head is a 6X-4 tested with its stock 2.11” valve with a 30 seat.
Stock these heads flow very similar to the 96 casting .

Here’s flow test number 8 out of the 12 that where done to get to that 230 cfm number, and the throat at this point is 1.66” up from the stock 1.60”

I can post up current pictures if you like that might offer you some help.


Flow @ 28”
.100”. 78

.200”. 145.7

.300”. 185.5

.400”. 212.2

.450”. 221.2

.500”. 223

.550”. 225.8

No grinding work or blending at all yet. I would very much appreciate the photos.

A) How much HP are you looking to make out of these 96 castings and B) How much valve lift are you willing to run?

How much does the car weigh?

What rear gear does the car have, or will have in the future?

There are not issues cutting the spring seats .1” deeper if you need to. If you used a small shim, the Crower 68404 springs should work for the spring pressure suggested with stock length valves.

The new replacement valves like ferrea and Manley do not have much dish and really loose very little cc’s against stock. I would replace the stock 2 piece OEM valves if that is what is in the head yet. Especially the intakes. It is never worth the time to regrind a set of 2 piece valves that have a bunch of miles on them, they can break the valve head off and destroy the engine. Replace them with a one piece.

If this is an econo build street engine I would not get wrapped up and a bunch of little mods like a .030” thick head gasket and the small 7* dish in aftermarket valves. A .030” gaskets would probably be a cometic, they require a glass like surface to seal up correctly. If your trying to save money that means more machine work. Jmho… If your ported heads, you will find more power in the heads than a couple tenths of compression.

Generally low lift flows are found working on the ceiling with the bowl smaller, and higher lift flows come more from working on the short side radius with the bowl opened up more. You could likely get the low flows back close to what they were with some work on the ceiling. Common for 45* valves loose flow against the 30* up to .3” lift. Maybe I read wrong, but looked like the 4x have 45*?

this is what i was thinking as well.