Neat CNC video.
08-18-2011, 04:59 PM
#61
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^^^ calm down if everyone agreed we wouldnt learn anything. I have a set of sbc TFS 195's converted to lt1 heads that have been decked to 58cc chambers and some bowl and chamber work by CFM can these still get a A.I. Cnc? Or do they have to be virgin casting to work?
08-18-2011, 05:17 PM
#62
.Thanks for your reply - always a pleasure to read your posts.
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?
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.
(Stock spring on right, SR spring w/ damper removed on left. Stock spring almost fits INSIDE of it
)
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.
An exceptionally well made OEM casting like your 200cc offering will wipe the floor with low quality chinese stuff and garbage heads like Edlebrocks and Patriots that don't even outperform stock LT4 stuff. My point is that their are other well made castings though, both OEM and aftermarket, and in some situations they may be a better match for a certain build.
When dealing with all the factors of a modest goal and talking about ease of install, reliability, and price:performance ratio there are not many things that can compete on the same level as your CNC castings.
(continued, too long post LOL...)
08-18-2011, 05:18 PM
#63
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.
. What would be "dated" in my motor, my Supervic? It is proven to be many times better then the stock LT manifold which, sorry to say since I know how often you praise it, is trash. Plenum volume is virtually nonexistant, runners are much too small, the cylinders fight each other for air, and gains by swapping to a single plane on a 7500+ rpm SBC from an LT1 intake are huge. Nothing about my build is archaic or dated, and in fact most parts are modern designs or revisions - lifters, pushrods, shaftmounts, etc.I can't say too much about an engine that has never been ran, but I don't see many stock headed cars besides Abare's 1-off piece making the same power it will.
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
-Phil
We may disagree on a point or two, but I have no ill will towards your products or especially your person. I suggest AI parts more then any other brand, since they cover such a large spectrum of builds...but I feel that they are not the be-all-end-all one size fits all cylinder head that some believe.
08-20-2011, 07:35 AM
#69
On The Tree
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Every time I see that guy, I am reminded of Ellwein. After a successful weekend dyno racing & playing with Aleks' red car down here we all went out and enjoyed a fair quantity of dos equis. Ron was kind enough to abstain & drive, karl was mellow, and the rest of us happily guzzled away after a good day at the track.
