I was wanting to go to a roller cam in the 230/230 range... most of those hit ridiculous lift numbers, at least compared to my .470-ish cam I have now. The car pulls hard, and it's a lot of fun. Very responsive, but the only time I had it at the track, it trapped at 102, which is okay I guess... but I'd rather hit 105-110. There's not much else I can do to increase the efficiency of what I have without doing internals. Intake an exhaust should give this thing all the flow it can handle.

It's al ong story, I had an original set of heads that I got ripped off on, and found another used set of Vortecs and swapped all my parts over, the only thing I couldn't reuse was the 2.02 intake valves, the margins on em were pretty bad.

This is what I'm working with now:





I've never ported before... how hard is it to do it without damaging the valve seat? is it possible? Or is it one of those things I should just give up on from the start?

 

those exhaust valves will be fine after you get a small 30-degree back cut done to each and every one of them.
a 230/230 cam is wrong, because Vortecs want dual-pattern cams.
If you order an 08-000-8, 3051/3052-112 you should have enough HP to trap about 109 with a stick, or about 107 with a good automatic, and it'll make strong midrange torque, with useable power to 6000 rpm. If you're wanting more rpm, at the expense of midrange torque, then I can spec you something else.

 

You've mentioned several times that Vortec intake lift should be restricted to .480"(+/-). I've seen published results that show the ports stall around that value.
Is it a situation that actually results in LESS cfm as the lift proceeds beyond the mentioned benchmark? Conventional thinking has been that if a port flows well at 'x' lift and you surpass it, then you are actually at 'x' lift for a greater period of time as you pass it on the way up and again on the way back down.
For the record, I wasn't able to find the lobes specified in the above quote. Am I correct in assuming they are around a .480" (on the intake) with duration suited to the application?

 

No, It works like this
the SF1020 showed 238 at 0.475, so I adjusted it on up to 0.500", where it was down to 227. So I watched the readout as I closed the valve, and as I went back past 0.475", the number did NOT climb back up toward 238, not at all.
Maybe spending more time at 227 sounds good to you, but you have to consider what the stalling is doing to the mixture motion, the swirl, and so on.
Next, COMP has an online catalog of all their lobes. Study it. All of these lobes fit the criteria:5201, 5239, 5203, 5241, 5002, 5071,5443, 5085, 3050, 3051, 3052, 3053, 3114, 3310, 3311, 3324, 3326, 3303, 3306, 3307, 3308, 3309.
That's 22 lobes that make good intake lobes for Vortec heads, with duration at 0.050" ranging from 200 degrees, to 246 degrees. Which is too much. But if you can't find something in those 22 choices, then ask me to spec you a cam, I do it well and I do it free.

 

Very interesting.
Prior to my previous posting I had attempted to downlaod the lobe index from Comp. However for whatever reason, the file wouldn't download so I asked my question without the requisite research.
Am enjoying your Vortec porting postings.
Thanks again.
A post edit question. Is your porting done prior to or after a valve job? With an upgrade to 1.6 exhaust valves and the follow up 75 degree bowl hog (as you prescribe), I imagine that the valve job (and possible valve guide repair) would follow the porting.
My apologies if you've posted this info already. I don't have it at my fingertips.

 

I ran into the same problem. Even if you search the lobe index for the lobes he recommended and click pg 429, it goofs up and the picture is of pg 427, which doesnt have those lobes on it. Fantastic...

I'll keep all this in mind for this winter when I get back to it. Been caught up with my dirtbikes this summer.

 

For whatever reason, I was able to access the lobe index list before. I've researched more than a couple of Mr. Funs cam recommendations.
This time around, no such luck.
I'll keep trying.

 

I printed them all, months ago. Saves me a lot of time. I keep the lobe list on top of my computer. It was dog-eared within a month, so I printed a fresh set and had them laminated. I wish Lunati and Crower would do lobe catalogs.
I assumed you guys would all correctly assume that I ran that test twice, then on another head twice more, just to be sure that going above the stall lift always caused the same problem. With SBC Vortecs, it does.
Now, it is possible to port them in such a way that they don't stall until around 0.520", and this sounds great, but it's NOT something an amateur can do. I found it a challenge to get repeatable results, so it'd be virtually impossible to teach.
skinny Z asks: A post edit question. Is your porting done prior to or after a valve job? With an upgrade to 1.6 exhaust valves and the follow up 75 degree bowl hog (as you prescribe), I imagine that the valve job (and possible valve guide repair) would follow the porting.
My answer: When keeping stock valve sizes, if all the desired angles are already present, then the porting happens before the valvejob. But if the existing angles are bad, or if going to larger valves, you are facing 2 valve jobs to get the right results.
If you buy CNC-ported heads, only do what polishing you can do through the header end of the ports.

 

More pics today.

 

 

 

Remember, it's not how it looks, it's how it feels. you're just trying to create about a 15-degree angle chamfer, so that if your intake ports are a little off, there won't be as much turbulence or reversion. At the face, I only removed about 0.010"-0.020" on the top and sides. Again, you can always take more later, you can never put it back. And no wiseacre comments about epoxy.

 

 

well, you just got a sneak preview of stage 3.

 

the hidden bit wasn't finalized. I had to be sure it was both properly shaped, AND looked as correct as possible, since it's extremely sensitive.
Doing the Vortec intake guide bosses is pointless for stages 1 and 2. You'll make things worse.
But when you're ready for stage 3, doing the guide bosses is someting to help utilize 2.02" intake valves.
But if you make any mistake, you'll hurt flow AND swirl.

 

nm

 

nm

 

nm

 

nm

 

nm

 

Awesome information Atilla. I thought there would be much more involved in a stage 3 porting. Or is it still work in progress?

Those Vortecs look to be designed great. No wonder they make so much power.

 

No, that is not all of my stage 3. But the work is on hold. I'll edit this post this weekend to explain better.
Well, that weekend, something came up.
Stage 3 is still on hold until I find funds for getting the seats cut.

 

sorry I do not speak english

continue with your project

advise me on porting chevy bbc 781 heads

I´m learning and I´ll make my head

I´m learning and my head port

thanks teacher

 

thanks, there's really not much to add at the moment.

 

I don't agree with everything in this article: http://www.popularhotrodding.com/eng...ads/index.html

but it's worth looking over.

 

Regarding the article and in particular the small paragraph about Vortec heads, Vizard states, "SB Chevy Vortec. Blending out chamber plug boss with a cutter is the longest job you will need to do on these heads. After that the ports need only be smoothed out with 60 or 80 grit emery rolls to produce a top-notch pair of street heads that will deliver both ends of the rpm scale."
Do you have any examples of what the finished chamber form should look like? By your reckoning, what would this add to the chamber volume in terms of cc's?
I'm also encouraged by what he has to say about the Edelbrock Performer RPM heads (as I now own a new set) although he doesn't make any reference to SBCs, just Fords.
By the way, glad to see you're back.

 

Very observant, but I did specify that I don't agree with everything in there. If you try that, you'll make the iron so thin that it will heat-crack. Also, I've seen Vortecs that do flow well over 270/210 cfm, that haven't had that Vizard mod done to them. So why try it? If you have too much compression, change the pistons or get AFR heads. Or both.
I do advocate polishing the Vortec chambers for most applications, but there is NO reshaping involved. Vizard's trick will also result in a slower burn, and a much greater probability of detonation. That pad is there to help with good combustion.
Vizard is old-school, and he offers NO evidence of that "trick" having ANY merit.

 

If you don't mind me asking, what else do you not agree with in the article?

I understand you are not an advocate of milling heads down more than .030", but are there any other main points that you disagree with?

 

You want me to actually read the whole thing?
All kidding aside, I'll get a notepad and a pen or pencil, and re-read the article.
I thought you liked what I did to your Dart Iron Eagle 200s? Got 'em back on the car yet? And running?

 

No no, I'm quite happy with the work you did to them. Spent a bit of time looking them over and "feeling" the difference once they were milled and cleaned actually, I'm really fascinated by this kinda thing. I've got them back on the motor, all nice and purdy looking now But the motor probably won't be back in the car for a little while, still in the process of cleaning and detailing the engine bay. I'd start the motor now, but my engine stand doesn't have enough room to fit a flywheel, lame.

But I'm confident I'll be pleased when I do finally start it up Should run nicer, with better vacuum, and have more torque and horsepower at pretty much every RPM through 6500 ish I would think between the better matched intake, porting work, increase in compression and a better tune. My timing was off a few degrees, and the spark plugs say I was too rich as well

 

Careful there, advancing the timing will change your plug-reading the same as leaning the carb. Try about 10 degrees initial without vacuum advance, and 32 degrees total centrifugal, all in no sooner than 3000. With the vacuum advance connected, your initial should probably be about 24 degrees. Once you get the dizzy to these specs, clean the plugs, and go for a drive. Then read the plugs, and adjust the fuel accordingly. Actually, you'll need to do ad least 2 plug readings each time. Once after a WOT blast through the top of first gear, to dial in your secondary jeting, and again after sustained 65 mph cruise. Carry a wire brush to clean the plug after each reading.

 

Good again. Problem solved. See:

 

I would assume that this means the vacuum advance is connected to full manifold vacuum as opposed to ported vacuum. I've never understood why anyone would do this.
I can see drivability problems associated with such a setup and have only considered it's use in engines with other issues such as very low vacuum to begin with.
Care to explain the benefit of this arrangement?

 

There is no benefit to ported vacuum. Period.

 

It's the side effects of using UNPORTED vacuum that makes tuning difficult.
However I'll move this discussion to a new thread so as not to mess up this excellent one.

 

Manifold vacuum for the vacuum advance has NO negative side effects. If it gives you difficulties, then you're doing something badly wrong. Ported vacuum is for the EGR.

 

nm

 

Hmmm...What about guides and a valve job?

 

What about 'em? If your seats need cut, have that done before shipping the heads. And if they need cut, you may as well go to bigger valves, except maybe Vortec intakes for most apps.

 

I'm about to make this thread even more definitive. I just did a Vortec exhaust port, to stage 1, but I took 62 pics as I went. So I can break it down into 50 easy steps that anyone should be able to follow.
Actually, I think I'll start posting the pics about 3 in the morning, so noone will interrupt this thread. I have a thing about that. It's a button that smart people just don't push.
This is even better than a video, because you don't have to watch me do the work, and you don't have to wonder when to pause and when not to.
This port required a second round of grinding, because I was too distracted with the pics to grind the area the first time through. Still, I showed that too, all the way to the very end.
You don't have to exactly copy my every move, but it can't hurt.
this port, with a good undercut swirl-polished valve, sporting a 30-degree back-cut, will do 167 cfm at 0.500" at 28"

 

Dammit Atilla, if you weren't living where you are, I'd bring my heads there and WATCH you do the work.
There's a saying in the business world. It's called "sunk cost". If you've already invested in the infrastructure, then it costs nothing to improve, except the development involved. I've owned these Vortecs for years.
I look forward to what you have planed.
My little Vortec headed 350 out performs other 350's with after market aluminum offerings as it stands in stock trim. I would truly like to see what might happen with another 14% on the exhaust (147cfm (w/no pipe) vs. 167 cfm).

 

the flow-bench was freshly calibrated by one of SuperFlow's people, who flew out just to calibrate it and train me. I didn't have any length of header tube. My baseline, after he calibrated it, was 143 cfm at 0.500". so 167/143 is nearly 17% better. That bench always gave low numbers, I suspect that it was our elevation. The bench was about 4250' above sea level.
and I do welcome the enthusiasm. Thanks.
By the way, since you're sunk, go stage 2 and get 181 cfm at 0.600"
And if you're using GM intake valves, changing those to what I like will add 12 cfm at 0.200" without changing the diameter. At 0.300", it adds 11 cfm.

 

I will watch with enthusiam.

 

Watching live wouldn't help you anyway, you wouldn't be able to see for me being in your way.

 

Trust me. Watching counts for quite a bit. It's the opportunity to see technique and other subtilties that only being there can provide. Obviously, the skills will have to be developed with practise as with any other trade.
On that note, why not demonstrate this next project with a few bits of video?

 

i am going to stay up all night. LOL!!!!!!!!!!!!!!!!!!!!!!!

 

z

 

Here's why not: (1) I don't own any electronic device tht will record video, let alone then upload it. (2) Such a device is NOT in my budget. (3) I'm too old to learn how to get any such movie from the device onto StreetFire.net (4) if you just do what my notes say, you'll do fine. Primary above all else is never hold the tool still in any one spot, keep it moving. With each pic I will specify which way the tool should be moved.

 

dang, it takes Photobucket a LONG time to upload 62 pics that are each 2.5 MB. So, I stopped at 20 for now. Step zero is to get ready as described previously.

this is not the lighting I see when I'm porting, but this gives the best pics. You do need lots of light coming through the port, but you also need light overhead. I work in an enclosure with no windows so I can control the lighting. You could build a 48" x 48" plywood box if sun glare is an issue.

I'm not left handed, which is why the camera is in my right hand, and the tool is in my left. But I port right-handed.

 

start with the leading edge of the guide boss. sweep side to side, medium tool speed, medium-slow hand speed.