|08-21-2012 08:19 PM|
|prostcelica||Verdicts in boys.......save your money. He didnt tell me anything I didnt know already.......and I dont know much|
|08-16-2012 09:16 PM|
|6426yy||Yes, so does the old book How to hot rod Small block chevys. it's from the 70's but a lot of the info applies to all the old style wedge chambered heads.|
|08-16-2012 12:17 AM|
|justahoby||x2 on any Vizards book. I don't agree 100% with everything he says, but he is one damn good book teacher, and knows what he is talking about. He also has a book on Chevrolet heads, no mater what you own, alot applies. Also a couple good PHR articles by David on porting, i found them online, about as good as the damn book! study , throw off fear , pursue confidence , pull out die grinder, make it less scary than it is,excecute! gets experience|
|08-15-2012 10:51 PM|
|prostcelica||Thanks Italian. Will do. 6426yy: Thanks for the heads up on Vizards book. Does the "sbc on a budget" talk about porting ??|
|08-15-2012 08:23 PM|
|theitalian||Yes sir another tip for you...change out the studs they are junk.... i ran the estreets on my camaro last year and bent a few of them, caused rocker arm binding and wiped out my cam.|
|08-15-2012 05:24 PM|
|6426yy||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.|
|08-13-2012 06:29 PM|
|prostcelica||Thanks Timofinn. Im deffinatly going to buy Vizards porting book.|
|08-13-2012 11:11 AM|
and to celica, buy that David Vizard`s book or books
I have a several of his books and they are good and informative with good pictures in them
take a look here:
Amazon.com: David Vizard: Books
|08-09-2012 09:12 PM|
|1971BB427||That's very good information Jim for everyone, regardless of their expertise!|
|08-09-2012 07:54 PM|
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.
|08-09-2012 03:39 PM|
|08-09-2012 01:16 PM|
|prostcelica||Thanks guys. These heads have a 3 angle valve job but not sure on the quality of the vavle job as heads are still assembled. What am I looking for in a bad valve job?? Is it something that can be corrected when I port and polish ??|
|08-09-2012 08:22 AM|
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.
|08-09-2012 01:24 AM|
|08-08-2012 09:50 PM|
|prostcelica||My new heads arrived today. I see what you were saying about blending the intake port roof Italian, deffinatly a pretty big ridge there.|
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