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Cylinder Head Porting

7K views 33 replies 8 participants last post by  prostcelica 
#1 ·
#2 ·
Hard to say. Who wrote it? What are the persons references?
It doesnt say whether the author builds or races.
I am a sceptic so dont be offended. Not busting your chops here by any means.
I would rather talk to some of the guys here and get tips from them, talk to the machine shop guys who build engines for local racers.
Every town has a shop that does speed shop work for competition. I would trust there word over some E Bay DVD of which I knew nothing of the author. But thats just me, like I said , I am a sceptic.
On another note , it would be interesting to see what it says in detail. Maybe it is worth the cha ching. Only one way to know for sure. :thumbup:
 
#3 ·
Hey Latech. No offence taken at all. I appreciate the reply and all the things you stated ran through my mind. I figured for 12$ plus shipping it was worth taking a look. I will deffinatly be looking for advise on the forum as it is apparent that there is a lot of knowlege here. I also thought that I would read the book David Vazard wrote or if there is another book that someone here would recomend.
 
#4 ·
I take it your porting estreet heads from your previous post, im porting a set of them myself right now. I talked to a local speed shop that has done a lot of estreets he said to blend the intake port opening they are very rough that being done alone will give you huge gains.
 
#5 ·
Thanks italian. I have never ported a set of heads before but am a welder by trade and also did a stint in an auto resto shop so I'm no green horn on a die grinder. I plan to do plenty of research before I start. How bout you?? Any tips you could throw my way would be great.
 
#6 · (Edited)
I'm a diesel mechanic by trade. I ported a set of camel humps 10 years ago in high school shop and they rocked was a good build. I'm no expert by all means, the guy at the speed shop told me to blend the intake port at the roof, and just smooth out the rest of the runner, and to stay away from the floor just smooth it out a bit. I blended the bowls and cleaned up the exhaust port a little bit also, i didnt get too agressive. I hope this helped ya out a bit.
 
#8 ·
I don't know anything about that video, but I can tell you from experience that it's tough for any video to cover more than the basics. Every head is different on what works best, and can't say what works for one does the same for all.
I've also found that a little is better, so don't go crazy porting your heads, or you risk having them not work better, or even ruining them.
Gasket matching is good, and cleaning up imperfections is also good. Some factory heads have a reputation for having the same imperfections in the same places, so if you know someone who's done much with your type heads, talk to them and see where the bad spots are. I know the newer SBC smog heads have some horrible looking casting flaws hanging into the intake runners when compared to aftermarket, or older better heads.
Stay away from the bosses around the valve guide areas in the runners! You can easily ruin heads grinding around that area! Get some machinist bluing and you can mark out the intake gasket to match them, and then just gradually blend, and not go too far. If you have an intake already, check it also against whatever gasket you will use, and match it to the same.
On the exhaust side I usually just clean things up, as I haven't found as much increase in performance with a lot of exhaust port work, where intake work seems to garner more for me.
Should do all your work with the heads disassembled too! Don't take a chance on damaging a valve stem, or getting grit in places you don't want it. I do all my porting on stripped heads, before any valve job or assembly is done.
 
#11 ·
Thanks for the great info 1971bb427. My paln in not to remove to much metal as I don't want to lose port velocity. I think I will port match and blend intake runnes, smooth out short side radius, polish up runners to 40G. Do the same on exhaust side minus the port match and polish up to a finer grit. Polish up combustion chambers, de shrould exhaust valves (if needed) and do some clean up in the bowl area. If you guys see any flaws in my plan please speak up. Any info would be great!!......the one questuon I have is when I'm finished can I just reasemble the heads with out valve job?? I'm buying them assembled so pretty sure I don't need to worry about that but not 100% sure. Thanks in advance guys.
 
#12 ·
When you are done get a 3 angle valve job done. If you can find a shop and the heads have the material in the right place, get a 5 angle job done.
Cleaning casting flash,port matching, smoothing the short turn radius ...all good ideas. So is not going overboard.:thumbup:
 
#15 ·
If these are new Estreet heads then you wont need another valve job. They come with a good valve job. I'd be careful not to do anythin more than polishing in the chambers. Start unshrouding valves and you'll change the CC size of the chambers, and also creat differences between chambers that result in differences in compression ration from one to the others. If you don't know how to CC a chamber to match them all, you should only polish them lightly.
 
#17 ·
Unless the video IS by someone notable, I would put much more "salt" in Mr. Vizard's book. Misconception is among the most common areas of ruining heads when trying to "port". A "litttle" IS better unless you're shooting for super-high revs and don't care about low-end.

Also be careful comparing heads using runner volumes. Not all ports are "equal", even when they're the same "size". Extensive use of "inside" and "outside" calipers (dividers) is necessary. Cross-section MUST be maintained up to the "venturi". Use a smaller OD valve as a "gage" for the bowl/throat work.

Although the video is not using Chevy heads, Pete McCarthy has an excellent video porting Pontiac heads. The majority of the fundementals are the same. THAT video might offer some insight giving you an advantage. For those not familiar with Pete and his work, he's one of the guys responsible for the "Angeles-McCarthy" '68 Firebird C/SSA that has been a class and race winner at NHRA events over the last 15 years, sporting a 400 Pontiac and running in the low 9s with a Q-Jet. He knows what he's doing... Pete's getting on" these days, but his books and videos are stilling selling well.

Jim
 
#22 ·
To add to what Timo says, we too, have seen pretty shoddy seat grinds coming out of most aftermarket head suppliers. There's nearly ALWAYS improvements to be made.

We also advise our customers, if supplying heads for us to build, buy them "bare". The hardware various aftermarket companies use, including Edelbrock, "meet" minimum requirements. They don't "exceed" them, and in a performance build, EVERYTHING shoulld exceed requirements for durability.

Jim
 
#25 ·
Traditionally, the term "three angle valve job" refers to three separate angles on the seat. Most already know this, but I'm going through the "exercise" for those that may not be clear. The "top" angle is 30 deg. The "seat" is 45 and the "throat", 60. As a youngster in machine shops, that's the way we were taught. The primary purpose of the distinct angles is to insure the seat angle is concentric and of equal width all the way "around". The intake seat isn't as crucial regarding the width of the seat for longevity. The exhaust is very important, as that's how the heat dissapates from the valve. Heat is like electricity. It follows the path of least resistance. A "thnner" portion will transfer heat in a more concentrated manner, "burning" either the seat or the valve.

Today, we use a little different rationale on the angles. The seat angle of a typical small block will always be 45 deg. But by changing the top and throat, we can improve flow. A 15-17 deg. top and 70 deg throat will significantly increase flow "across the lift range". To the tune of 5-7 CFM. The intake is more "reactive". A top of 10, blended to a 30, a seat of 45, .060" wide and a 70 deg throat will improve mid- and high-lift flow. A wider seat and "more" 30 will improve low-lift flow. For a lower revving street engine, low-lift flow is important for torque production.

All that said, the "provided" valve seats will seal the cylinders and allow the engine to run properly. They are, by no means, "optimum". Some of the Dart and Brodix stuff I've seen delivered "ready to run" had really nice radius seats.

That brings us to modern "high performance" or "competition" valve grinds. Most shops today use stones only for "stock" valve jobs or "truing" the seat angles after the cutters do their "stuff". We have carbide cutters in various "profiles" for different applications, operating in a heavy machine. Very accurate. A true radius (exhaust) will obviously flow much better than anything with abrupt changes. Many builders use a full radius cutter on small blocks for drags. We use one that has a 15 degree "top" angle included in the profile for accurately limiting the OD. We also have a method of creating a "venturi" seat. Pontiacs REALLY "like" that one...

One last thing. Most engine families have cylinder heads based on different principles and applications. No two respond the same to the same seat profiles. Even some within the same family will respond differently to similar modifications. There are NO "absolutes".

This is strictly about the seats. There are some things that can be done with the valves, as well. That's a "story" for another day.

FWIW

Jim
 
#29 ·
The how to Port and Flow Test heads is about a waste of $. It's full of graphs and pictures of aftermarket heads that have been done and CNC'd. Plus a bunch of overly technical stuff that won't apply to most hot rodders, like wet flow analysis. It doesn't show how to do anything. Vizard's book on budget sbc is good tho.
 
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