This ought to be interesting...

 

Definitely. I mean this site is only used for his entertainment therefore it ought to be a smash.

 

In for some tech.

 

^^^who isn't?

 

Dare I say , someone is gonna get served?

 

Back from the second page. I want to make sure that this issue is adequately addressed. Many of us including myself, might deem an articulated response to AI's referral, valuable information.

 

I think we will get one.

 

I am highly disappointed no explanation has been given from Puck's POV. Perhaps the sources supplying said information cannot be reached at this time?

 

When talking about builds in that small percentage that should be looking for aftermarket heads, there are clearly reasons to NOT go with stock castings that either cannot be fixed, or would cost too much money to be a logical choice. Off the top of my head i can point to deck thickness, weak exhaust ports, heavy thick stemmed valves, cannot clear thick pushrods without hacking them up, spring pockets need heavy machining to clear large springs, and geometry that limits the maximum you can port them. A lot of that can be fixed, but that is expensive considering the killer aftermarket heads you can get these days. Have you seen the newer economy line AirWolfs? $1,500 for a reported 325cfm is a STEAL, even if they flowed closer to 310 when benched. I understand that is overkill for a lot of people, but if you are building something big how can a stock casting compare to that kind of value?

Stuff like that may not be an issue for the people content with a 400-425 rwhp street car, but it makes no sense to even consider stock castings for an aggressive build unless you just want a trophy show piece "just to say you did". Your LT1 CNC heads may be the best stock castings available, and they are more then potent enough for a large majority of customers, but you can't say with a straight face that they can hold a candle to any of the big brand aftermarket castings that have for the most part eliminated many of the drawbacks of the ancient SBC cylinder head design.

Apologies for not living on LS1Tech - I forgot about this thread until I just saw it pop up on top of page 1 again.

 

I may have missed it but what are the geometry problems that you stated they have in a previous post?

Also the highest trapping t-56 lt1 is running stock castings so it would seem that they are pretty strong.

 

Apology accepted. I have read where you've frequented this site most every day. No big.

I may be wrong, however my best guess would be pushrods not aligning well to the rocker? If this is the case most everyone knows it's nothing more than a nuisance, not worth complaining about because it can be easily remedied.

 

I'll respond point by point...

This is a talking point that is often repeated online. It isn't exactly a surprise to find that the people who mention it typically aren't able to even venture a guess as to what thickness is required for various applications. Furthermore, the internal structure of the head ensures that the areas where the deck is thinnest is not where the clamping force is applied. Where that force is applied, even the thinnest OEM casting is sufficiently thick to seal the overwhelming majority of applications without issue. We have many OEM headed guys making 700-1000rwhp in power adder applications without issue. My questions to you would then be:

1. Do you know how thick the deck of the OEM GM LT head is in various areas?
2. Do you know how thick the deck of your AFR's are in various areas?
3. If we just assume thicker is better, is there a corresponding trade off beyond the obvious weight issue? Cooling perhaps?

You'll have to forgive me, I don't follow - how are they weak? What is different about the aftermarket casting that alleviates the issue?

Valve mass is an interesting discussion. People online have been (mis)led to believe that valve stem diameter somehow equates directly and proportionally to mass. That is not the case. For instance, many of the aftermarket 8mm stem LS valves are actually heavier than the OEM GM LT1 11/32" stem valves. The custom valves we designed for our CNC'd GM LT heads are not only lighter than many 8mm stem diameter valves, but lighter than the OEM LT1 valves as well.


We have very many guys out there running 3/8" pushrods on our CNC'd GM heads, without added clearance. It is possible to put together combinations, and have core shift such that there is little to no clearance, but nothing that requires any real work to clearance. We have more machine work generating clearance for 3/8" pushrods in aftermarket heads than OEM GM LT heads.


No, they do not. Actually, they require significantly less work in many cases than aftermarket castings. Some of the most time consuming spring pad work is machining AFR's to clear larger springs.


We are talking about OEM 23deg heads vs. Aftermarket 23deg heads that must both utilize the same manifolds, headers, and valve train. Could you share a specific example of the limiting geometry of the OEM head, and what was done on an aftermarket 23deg head to improve that?


The flow # claimed does not indicate potential performance. More importantly, it is the machine work applied to the casting that dictates performance potential since all of these castings are roughly similar insofar as layout and mating components go. So, an OEM casting as a base with vastly superior machine work, better components, far less weight, better port designs, and a much lower probability of fitment issues (it is after all an OEM GM part) is clearly the better value for the overwhelming majority building 400-500rwhp LT engines.


I realize that earlier you added the vague qualification "when talking about builds in that small percentage that should be looking for aftermarket heads." It seems the above quote defines that line as 400-425rwhp, or ~450-500hp flywheel. That is an interesting position to take, when we repatedly manage 100-150hp above these "limits" with the OEM castings. It isn't exactly a recent occurrance either.

Insofar as "eliminating" the drawbacks of the "ancient" SBC head design is concerned, I'd refer first to the points above. Secondly, consider that you are actually asserting that designs that are far older than the OEM LT head have somehow eliminated "drawbacks" of their descendant - the OEM GM LT head. The aftermarket heads you mention are, in some cases, decades older designs than the GM LT head. The engine you're building is a great example - you would have a difficult time coming up with a more dated setup. While it may end up running OK, in the end, it is improbable that it will outperform what we do with boring regularity using the OEM GM LT head. Of course that stands to reason - the OEM head is not only a newer design, but had the SBC masters design it - GM themselves.

Thanks for taking the time to clarify. I do understand you'll probably not like this, but the reality is that this serves as an excellent example of just how perilous taking advice from public forums can be. The overwhelming majority of assertions tend to be questionable, and in many cases 180deg opposed to reality like those above. If you answer my other Q's I'll try and take the time to respond to those as well. In the meantime, if you'd like to learn about the history of the head you are using, try and look up the now defunct Brownfield head company. I think it will be enlightening for head design era comparisons.

-Phil

 

 

You mess with the bull, boy, you're gonna get the horns!

Nice reply. Not expecting a response to the battle of wits here - some people are just unarmed, and some just regurgitate bad internet information.

 

So your telling me a OEM casting will get you as much power on an all out N/A set up vs an aftermarket casting??? seems like a far fetched idea to me or EVERYONE who runs the solid roller set ups would be running OEM castings

How about a youtube special on the history of the LT1 heads?? I mean they were SOOOOO good they lasted what 8 years? before the LS series came out that makes the LT1 look dismal in design

 

Oh, sweet Jesus. LSx point - irrelevant, and the LTx head was based on the latest cylinder head that had been around, and has been making great power when properly prepped, since the 1950's. The LSx is a significant change in cylinder head architecture - we're talking about 23* castings here.

 

reminds me of the cz28.com days circa 2002 with Phil's response

 

I'll try to get back on the topic of post #1 with a CNC machine story:

I went to flow my home ported heads Tuesday after work. I was told we were going to someone's house and I was expecting a cheap shop-vac flow bench. This was a small residential house in a bad area of town after all. I was suprised to find a "Superflow" bench (forget the model #, 600 I think). After talking with this guy I learned he's been porting heads (under the radar nationally, but known in this area by many) for 15+ years and he is very knowledgable. He took one look at my heads and felt the intake ports and made his prediction that they wouldn't increase flow after .500 -.550 lift because of the short side radius. I'm getting off track here, but the point is he was right on. The graph climbed all the way to 253cfm at .550 and flat lined to .650. I was impressed by his prediction, but I haven't met many head "experts" personally. (Don't bash me for chosing to port my own heads or my flow numbers, I did it for the experience and I'm glad I did. Every good head porter had to start with a 1st set of heads, but that's not the point of the story here.)

Moving on....He said he wanted to take us next door to show us something cool. I was amazed to find that this guy had a 5-axis CNC machine as shown in the photos below. He's had it for 4 months but is keeping it quiet because he is still programming and experimenting, and he doesn't seem to be a big advertiser anyway.

I know Phil mentions Centroid as a lower end machine, but I never thought I would see one of these machines in action with my own eyes, and I sure as hell wasn't expecting it in a shed in a guy's backyard in a neighborhood you don't want get caught in after dark. Especially not this night.

I left there fascinated and impressed with this guy and his achievements. He might not be the best porter in the country, or have the best most expensive cnc machine, but he started from nothing with a passion for racing and has made a living to support his family who appears to be following in his footsteps, so I have much respect for this guy.

Did I mention he was in a WHEELCHAIR and hasn't had the use of his legs for 18 years? He said he spent many years with a grinder on his back porch in the heat and cold, with gnats and mosquitos, before he built his little head porting shack with a window a/c. Now he has a 3 room head/motor shop, a brand new "shed" with a CNC machine, a nice 1969ish Mach 1 Mustang fastback, new 2011 5.0 mustang (ya he's a ford guy), but still drives his 90s model F150 single cab truck to get around. All of his vehicles have the handicap hand controls. He wants to design and make new controls with his new machine.

The video in the OP is cool, but to see it in person and see the digital 3D imagining and the products that come out of it is truly amazing. At least for me anyway.

I was inspired by the whole experience and I thought I would share it here in this CNC thread.

 

You guys needs to go to IMTS in Chicago (International Machining and Tool Show) which is every 2 years. They have HUNDREDS (if not thousands) of CNC machines there, and I'm always amazed at them - and this coming from a guy who runs a Mazak Integrex 300 6-axis, which is a nice machine as well.

 

Those people who don't have direct, first-hand experience with the products that Phil produces should simply shut the hell up.