Sorry for the following rant. I think PHR has been pretty awesome recently, yet I have a hard time handling all the strong statements made in Vizard's recent write-ups that oversimplify what is really happening and can be misleading.

In the May PHR, Vizard has a couple articles - one about how to win the EMC and another about a 408/350 build. I learned the ropes with my "How to Rebuild Your Small-Block Chevy" and think Vizard really knows a lot about engines. As I learn more, I seem to be having more issues with his writing style. He gives the impression he knows everything, when the truth is "The more you know, the more you know you know nothing." Car engines seem relatively simple, yet theory and design can be pretty complicated.

He is always pushing for tight LSAs as displacement goes up. I followed his advice with a 108 LSA in my 383 chevy, which ran pretty good but had no chance of vacuum for power brakes. We recently put together 2 427 sbc motors, almost identical except one had a 110 and one had a 112 LSA. The difference is hard to tell, except the 110 idles a little meaner (rougher). Everyone says fuel injection is why GM gets away with huge LSAs and short durations in their LS motors, but this also seems to work with many carb setups too. I wondered why the Viz doesn't enter the EMC. Maybe he thinks it would be unfair because he would dominate too much.

Here's my beef with the 408 from 350 article - who says RPM Air Gaps don't work over 530hp? There was a recent article on intake manifold porting that showed the RPM AG pretty capable right up to the 600hp number. It also showed the importance of intake/head combo flow, which was higher for the AG with the head than alone. Also, little to no tweaking was done to optimize the dual plane setup and it still almost hit 550 hp. The 427s I talked about earlier are about 2 mph different in the quarter, and the 110 LSA one has a Victor Jr and the 112 LSA one has an Air Gap (and is 300 lbs heavier).  

Vizard likes to say, "I don't have an opinion, I have a dyno." To that point, he approaches everything with a good dose of skepticism, and never lays out an "opinion" without substantial dyno data to back it up. That said, a tight lobe angle has been proven to produce better average power numbers, but yes, there is some sacrifice in the way of engine vacuum. If engine vacuum is a priority, your best bet is to tell your cam grinder that this is so. You'll get something really liveable on the street, but that will give up something on the drag strip or front straighaway.  

Thanks for the reply. I really don't care at all about vacuum (manual brakes, all electric actuators for the AC), but I'd like the broadest torque curve with the best 3500-6500 avg torque possible with 92/93 octane. We had one 427 sbc dyno'd at 630hp/6300rpm and 590ftlbs/5200rpm. It was 10.7 CR, used 3318/3319 (248/254 deg @ 0.050 0.6/0.619 lift) comp hyd roller lobes on a 110 LSA installed at at 106 LCA, 210 AFR heads with full CNC, and Victor Jr intake (tested with no accessories and the dyno shop's electric water pump). I wish I had the 112 LSA motor dyno'd, but couldn't rationalize the cost.

I struggled with Vizard's cam advice that I interpreted to mean I need something like a 106/108 LSA with a relatively short duration (but my heads wanted more lift than I could readily get with enough available hyd roller lift). I built another motor, same specs except with the AFR Eliminator versions, 112 LSA and 108 LCA, and RPM Air Gap, and this motor doesn't feel as peaky as the 110 LSA combo but crashes the 6800 rpm rev limiter a bit harder. This combo is only 2 mph slower (although 300 lbs heavier), but handles the peddle to the floor a lot better (although you can't floor 1st anywhere except at the track with reduced tire pressure).

It's not easy to get a read on people based on what they write. I maybe wrongly criticized Vizard, but I still think his conclusions based on his dyno experiences sometimes oversimplify what's going on to make certain points to your general reader population.  

I don't think that Vizard's conclusions regarding LSA are his alone.  If you look at the cam spec trends among the EMC competitors' engines you might find that a good portion of them (especially in the mid sized engines that most build) are in the 106-108 range.  We've found like he has that it builds a greater amount of cylinder pressure and torque throughout the usable RPM range instead of being a more peaky, high rpm engine.  You also have to look at what your duration is doing.  Someone once said 'lobe separation is just a byproduct of the valve timing events' and if you look at it that way it totally makes sense.  Don't think in terms of LSA or overlap but in terms of the valve timing events themselves and the LSA will tell the story of how the two lobes interact.

I have to laugh a little because my friend always made fun of me whenever a new Vizard article came out.  You see my buddy first came to me and wanted me to do the 'Vizard 30 degree valve job' on a set of heads for his hot rod.  I kept telling him it wouldn't flow any air or make any power in an engine with more than about .450 lift or 210@.050 duration.  Had to do it though and it just killed the heads.  A new set of valves and new valve job later we picked it right back up.  Since then he pokes and prods me for being a Vizard-hater.  I'm not at all, I just don't think that one valve job works.  Vizard is one of the best out there for empirically testing engines and components and until you run the test yourself and find different results, I would always recommend following his advice.  

Revolutionary: I'm just curious.  When you did the 30 degree valve job for your friend, did you up-size the valves?  In Vizard's "How to Build Max Performance Chevy Small Blocks on a Buget" he says this is a necessity where a 45 seat is being machined to a 30 or the seat will sink too far into the head and flow will suffer.  I am very inexperienced when it comes to engine building and would like the luxury of taking everything Vizard says to heart.  So I'm just trying to get my head around the reason for your experience.  In this book, Vizard seems to be pushing his 30 degree seat for all SBC applications regardless of lift or duration.

I just realized the age of this thread.  oops.  Oh well, the question still stands.