Discussion in 'Street/strip 400/430/455' started by Christopher Spouse Drew, Jul 25, 2018.
Alright good to know Steve, thanks!
Came up with these. Thoughts?
Thanks Matt, this is a very good visual! I just got all my burrs in today and im gonna start porting Monday.
Before you spin up even a polishing roll no less a cutting Burr you need to access the port to figure out why it flows the way it does, where the port choke is and try to figure out where the air wants to go , not where you want it to go!
At low lift up to about .300" the air is taking the path of least resistance just like water would.
Most times Intake wise the air is following the center line of the port to the center back of the Intake valve.
So this means the shape of the valve bowl , the valve job and the shape of the back side of the valve is are all what's controlling this level of air flow.
The air that does pass into the chamber.
Keeping a Venturi shape in either valve bowl , or making a Venturi shape better needs to be kept paramount in mind when you do a bowl blend!
One short fall in this regard on some Buick heads is the short turn as it's shaped for good high lift flow above .400" which leaves a lot of what could had at lower lifts otherwise on the table!
Never forget that even if you run a Cam lift of .550" way more then 50% of the open time for the valve is spent at or below 275" lift where the shape of the valve bowl is controlling flow, NOT the overall size of the port!
The kind and shape of the short turn that for example Matt shows in his pictures is one of the best reasons for stepping up to a bigger valve.
.This should be your first move along with a proper valve job before any porting work is done from my point of view, especially if you need new valves anyway which if your heads have more the 45K miles on them you need new valves anyway because there stems have more then .001" ware on them I promise you, and that's too much !
Remember you dealing with a round valve stem and a round guide hole, this means that .001" of ware translates into .003" of excess guide clearance!
As Bruce Lee would say “be like water my friend”. Lol. I like the idea of thinking about how water would flow rather than trying to force the flow somewhere else. Us humans are really bad at trying to force solutions!
I'm getting my stage 1 valves soon and im getting the valve seats cut with a 3 angle valve job. So I will do that first like you recommend.
Lets talk about porting the side walls. I want each port to be uniform, so I was thinking ill find the smallest pinch point and widest point after measuring each port of the head. If the smallest pinch point of the head and the widest point of the head is not excessively far apart that im not scared of hitting water I'm going to open up each port to that widest point. That's how im going to start my side to side porting. Maybe ill gasket match it after that point if its not too much material.
The port roof and port floor I will do something similar, ill measure pinch point of each port and instead of opening up to the widest point, I'm going to only clean up the port floor, and take any other material I need to take off the roof. Now I will be only measuring and taking material off up to the crown(pictured above in matts post).
I still need to study the head to see how the flow travels for the short turn radius so i dont have a game plan on that and the bowl blend, but when the valve seats increase ill do what matts post suggest and open it up to 86-89% of my new stage 1 valve for the throat. I will cut the valve support down considerably, idk how much yet.
Thats my thoughts right now, tell me what you think Steve. And if you dont mind I would like to call you before i start doing any work on the heads.
Probably just get the heads roughed in just in case you cutter slips which they do so you don't mess up your brand new valve job.
Yeah you're right, I didn't think of messing up the valve job. Hmmm maybe ill put a few layers of tape over the valve seats so if i hit it ill be okay.
Okay so I looked over my heads tonight to really study the head and remember things we were discussing on here. I understand looking at the head that its easy to hit water, they have pretty thin walls. Looking at this im going to take off as little material as possible. I'm going to make every port uniform with one another and be done with that, no gasket matching. The valve guide boss is such a restriction so ill take that down quite a bit.
Im still trying to understand the bowl area and short turn, so ill read through each of the post again and try to get a game plan. but first step is, get these filthy heads to the machine shop for a hot tank or pellet blasting on tuesday.
The port walls are atleast .160" thick if the motor has been run with antifreeze all its life so you need to do a good bunch of heavy handed grinding to bust through!
If you call me some evening I can tell you how to make 2 simple templates to 1) evaluate the port as is, and 2) guide your porting to make things better!
914 420 4356 EST
Okay Steve that would be great, I'll call you next week for sure, probably Tuesday.
That evening will be fine!
Chris should you call tonight try to have these things on hand,.
A compass for drawing circles .
A dial caliper.
Inside snap gauges.
And one head.
Okay Steve, I have all those items, is 7pm tonight alright? That's when I take my break from class for an hour.
I just finished reading through this thread, lots of great info. I'm looking at potentially doing some port work on some heads that I have. Any updates on how it went?
Steve gave me some great information. I was redoing systems one at a time and when I'm finished with my suspension it will be on to the engine! So I didn't port yet, but I got all the tools to port and made templates.
Did you get an electrical grinding unit or air? What type did you get?
Electric grinder with variable speed.
What made you choose that one? Price? Availability? Features?