EQ BBC head porting - zero to hero in 12 days
For my porting school the two heads I focus the students on are BBC and SBC Vortec.
Why these two heads? Because they are challenging. A SBC Vortec head is one of the best stock casting torque generators. There are many folk out there porting these Vortec’s in the manner so often shown in YouTube porting videos. Here then is the news you won’t want to hear. You will have made more negative moves than positive! To make the most of these castings you have to know real porting skills. Even more challenging is the porting of BBC heads. Sure some of the castings are so bad even a guess at what shapes are needed works but that plan of action won’t get you very far if the heads are really good to start with.
In my last porting school I used the iron EQ BBC heads as they are really good right out of the box. To improve on these castings would challenge not only the class attendees but also my capability to pass on what it takes to make real gains on an already well-developed head design.
So how good are these EQ heads? Well let’s look at some numbers here. First the valve and port sizes then the peak flow numbers. In. 2.250 Ex. 1.88. In. port volume (good and bad) 320 cc. Ex. port vol 125. In. cfm 388 @ 0.600, Ex. 247 cfm @0.700.
The exhaust is about typical for a good cast head be it aluminum or iron. The intake though is another story. For a genuine 320 cc port it pretty much matches or even outflows most other heads out there CNC ported or not.
Well flow is one thing but do they make power? I can report here that given the right cam and intake combo they perform really well. I have also heard this from several of my engine builder friends so it’s not a fluke by any means.
Most of my students are either high experience engine builders who do this for their own race efforts or professionals looking to beat their competition in whatever field they specialize in. But for this EQ head class I had one guy who, though an experienced engine builder, had no previous porting skills. (I will leave him as anonymous unless he chooses otherwise). With 10 days of intense schooling the ports he generated went 417 with 330 cc intake (good port) and 298 cfm with 1 150 cc ex port – both at 0.800 lift. This was an excellent figure and, if they got no better, shows the EQ heads in a very good light.
A couple of days back I took a look at the heads and realized they were still equipped with 2.25 intakes rather than the preferred 2.3 and neither intake or exhaust seats had been ‘performance’ cut.
So I cut the seats to suit.
As expected, a super trick seat and a bigger valve pulled some extra flow. These EQ heads were now well into the race flow category with a street port volume and so exhibited good port velocity along with the high flow. I have not quite finished detailing them yet but as soon as I do, I will post the final flow figs.
To summarize I can, with almost certainty say that these heads will really deliver the goods.
I realize that as iron heads they carry a 50 lb. weight penalty. That said there are applications where the extra weight is not a real issue. For instance, a 4500 lb. plus truck is not at any real disadvantage with 50 lbs. extra front-end weight as the EQ heads potential will far outweigh the disadvantage. As a competition set of heads there is at least one area where the extra weight would be an advantage – Bonneville!
Engine(s) for a boat would also not be at a disadvantage as the power potential of these heads far outweighs the weight penalty and of course corrosion in salt water would be far less of a problem compared to aluminum.
I would like to dyno these heads but currently I don’t have a suitable BBC mule that would show them off to their best. The kind of spec where their assets would shine would be a big inch motor. That is of at least 496 inches but preferably a 540 or so right up to 632. On a 632 truck or boat motor they would really be in their element.
Pics – port mold – head- flow curves
If anyone here is thinking of buying a big inch BBC where heads like this would be just what is needed I am prepared to give away the cost of the porting time (at least $2000) cutting these heads to the final spec . What do I expect? I am anticipating about 425-430 CFM with the final intake port volume about 340-345 cc. When I am done with the heads (could be another month yet) I am shipping them up to Terry Walters shop in Roanoke ready for use on an appropriate build. Anyone wanting a set of super trick iron heads where the porting is free might want to call Walters Engines on 540-774-8605.
Wait for final flow data soon.
#1 Here is the raw EQ head before being student reworked.
#2 This is the 417 CFM good port. It does not look anything more than a typical ported BBC head but strong results are in the detail.
#3 Port approach to the bowl and reducing the 'bowl shadow' is the key here and it is easiest achieved with the use of smoke tests, velocity probing, flow balls etc.
#4 here is the EQ BBC flow curves both out of the box (thin lines) and student ported(thick lines)
#5 When you know what to look for the SAE discharge co-efficient is a really good guide towards deciding what the next porting move should be.
#6 Here we have the port velocity before and after. Low port velocity is a big problem with many BBC heads. The EQ is better than most and the mods achieved more velocity on the intake but lost it on the xhaust. Was this that bad - take a look at the port energy graph next in line.
#7 Here is the port energy. Notice that although the exhaust port lost velocity the extra flow totally compensated.
If the concept of 'Port Energy' is new to you then maybe we should do a thread on it.
Last edited by David Vizard; Mar 21st, 19 at 12:51 PM.
Reason: text corection