Noddle Posted March 30, 2009 Share Posted March 30, 2009 As some you may know, this topic came up before in 2005 he's a link http://forums.hybridz.org/showthread.php?t=98988&highlight=spark+plug at the bottom their is a link to a '.pdf' off some testing that was done, Nigel Quote Link to comment Share on other sites More sharing options...
rsicard Posted April 1, 2009 Share Posted April 1, 2009 As some you may know, this topic came up before in 2005 he's a link http://forums.hybridz.org/showthread.php?t=98988&highlight=spark+plug at the bottom their is a link to a '.pdf' off some testing that was done, Nigel Noddle: Thanks ever so much for this link. It adds to what I already know about grooves and one of the fellows on Turbobrick I have already run into on other forums. He is very knowledgeable about grooves and brings experience with him. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 1, 2009 Share Posted April 1, 2009 Gentlemen: This is the issue that I would like answered by Mr. Sing himself. What Jon says I believe to be true. I am building a 383 Gen 1 SBC and it has been decked to 9.005" deck height or .005 piston down in the cylinder at TDC. I have purchased AFR 195 heads and they have been tested to deliver the most power (best velocity and swirl on the market) for this displacement. I would like to go with a .028" compressed thickness head gasket which yields .033" quench/squish clearance. The bottom end is TOTALLY forged. I do this because it should generate the greatest in cylinder turbulence and thus fast burn. (still reading the thread but) I have to point out that .033" is a VERY wide piston-to-head clearance for a quench pad... .024-.021 is what I hear is the sweet spot. As for "Ever put a screen under your carb/" this is true also. The leader in MAF sensors will tell you that taking off the screen ahead of the MAF sensor screws up the MAF sensor characteristics. The screen straightenes and evens out the flow of air. Okay, the screen on a MAF is there to straighten the airflow and reduce stability..... because turbulent air moves in more directions than one, and will cool the hotwire of the MAF off more rapidly than straight laminar flow. this totally alters the signal that the MAF sends to the ECU; TonyD (I *think*) told a story about boggling his little daughters' mind by opening up his engine and "blowing out the fire" simply by blowing on the MAF element. Most of the time OEM manufacturers take great pains to place the MAF after a fairly long straight run of air piping, because many autos have experienced bucking and surgign issues that were literally wind-based due to overexposed MAF elements; its the single greatest drawback to a MAF-based system IMHO (but that is an opinion I have lately been wondering if I need more education to leave behind; I may be "wrong" but I will still say I prefer MAF based over MAP until I learn more about MAP) So, how does the screen help a carburetor?? I would have thought it would be a gathering spot for gasoline to separate out of suspension onto... I had posted something else here, but somehow it got clobbered into browser javascript gobbledygook. In short, i said I was posting largely to subscribe because I am interested in this idea and happen to have a pile o' L-6 heads so, you never know. So, don't take much offense or read any aggressive condescension into my quoting above. I caught the gobbledygook when I came back to recommend that John Coffey read the pdf file that was linked to earlier in the thread, http://www.herningg.com/singh/Engine%20Running%20Tests%20Analysis.pdf I didn't read it through in depth but it appears to be a thorough, documented analysis of this idea. I am going to look into it further after I get further caught up on my normal internet prowling; my wireless card has been out for the last two weeks. Quote Link to comment Share on other sites More sharing options...
UR50SLO Posted April 1, 2009 Share Posted April 1, 2009 Okay, the screen on a MAF is there to straighten the airflow and reduce stability..... because turbulent air moves in more directions than one, and will cool the hotwire of the MAF off more rapidly than straight laminar flow. this totally alters the signal that the MAF sends to the ECU; TonyD (I *think*) told a story about boggling his little daughters' mind by opening up his engine and "blowing out the fire" simply by blowing on the MAF element. Most of the time OEM manufacturers take great pains to place the MAF after a fairly long straight run of air piping, because many autos have experienced bucking and surgign issues that were literally wind-based due to overexposed MAF elements; its the single greatest drawback to a MAF-based system IMHO (but that is an opinion I have lately been wondering if I need more education to leave behind; I may be "wrong" but I will still say I prefer MAF based over MAP until I learn more about MAP) Absolutly right... I had a guy with a turbo Maxima bring it over because it would not idle right.. kind of like a huge cam in it.. AFR's all over. I took the maf out of the charged side (right by a bend) and stuck it on the inlet side where the air filter was and it was glas smooth. MAF cars are VERY Sensitive in deed. So, how does the screen help a carburetor?? I would have thought it would be a gathering spot for gasoline to separate out of suspension onto... Well.. first off carbs are junk.. Lol.. but if you take a squirt bottle and put it in a streem pattern (not mist) and go spray it.. big drops right? Go over to a screen door and spray it through the screen... it breaks up the droplets into a mist for you! Imagine that with high velocisty going through it... It's not fuel injection mind you but it helps atomize the fuel..... Since liquid fuel won't burn. ~Scott Quote Link to comment Share on other sites More sharing options...
rsicard Posted April 1, 2009 Share Posted April 1, 2009 Daeron: Where does "I have to point out that .033" is a VERY wide piston-to-head clearance for a quench pad... .024-.021 is what I hear is the sweet spot." come from? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted April 1, 2009 Share Posted April 1, 2009 It comes from a couple guys here who are building their engines with very tight piston/head clearances. Daeron probably got his info from them and thought that this was the "normal" way it is done, and it isn't. Here is the latest example: http://forums.hybridz.org/showthread.php?t=145256 Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 2, 2009 Share Posted April 2, 2009 It comes from a couple guys here who are building their engines with very tight piston/head clearances. Daeron probably got his info from them and thought that this was the "normal" way it is done, and it isn't. Here is the latest example: http://forums.hybridz.org/showthread.php?t=145256 Well, in a nutshell it comes from never having seen anyone gainsay brian (1fastz) in quoting that range. I have read other numbers quoted in articles (such as the Vizard popular hotrodding article linked somewhere above) but most of those guys are using SBCs as their "example" engines, and I suppose I presumed a difference in engines may as well account for the difference in head to piston tolerance needed. Since this IS the L-6 subforum, I reached for the only/best/most common datum available to me that directly references high-quench L-6 cylinder heads. (Query: is the difference between presumption and assumption the fact that I only made an ass out of myself?) So, jmortensen, rsicard et al, what sort of piston-to-quench pad clearances would you recommend running on a p-90/e-31/welded closed chambered L head? Understand, I am asking, not goading. UR50SLO: If I spray a sprayer at a screen door that is turned to mist, and not to stream, the mist tends to group up on the screen and half of it dribbles down. That was the effect I was wondering. If theres a thousand tons of anecdotal evidence saying that screening underneath a four barrel is a good thing, so be it.. that is far from my forte, I was just asking. I am all for air straightening within the intake tract, so I was curious about the matter. Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted April 2, 2009 Share Posted April 2, 2009 UR50SLO: If I spray a sprayer at a screen door that is turned to mist, and not to stream, the mist tends to group up on the screen and half of it dribbles down. That was the effect I was wondering. If theres a thousand tons of anecdotal evidence saying that screening underneath a four barrel is a good thing, so be it.. that is far from my forte, I was just asking. I think I can solve that one! Spray a stream at a screen door, and it's in still air, Spray a stream at a screen with a big ass leaf blower funnelling a load of air through the screen, then the stream is pushed through the screen instead of dribbling down. whats the velocity of air through a carb? There's probably plenty there to pull the fuel through the mesh all nicely atomised even at idle speeds. Quote Link to comment Share on other sites More sharing options...
johnc Posted April 2, 2009 Share Posted April 2, 2009 I don't understand how a screen under a carburetor proves that grooves in a cylinder head make more power. Why are we discussing the screen under the carb in this context? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted April 2, 2009 Share Posted April 2, 2009 So, jmortensen, rsicard et al, what sort of piston-to-quench pad clearances would you recommend running on a p-90/e-31/welded closed chambered L head? Understand, I am asking, not goading. The "standard" numbers I've heard are usually .035" to .055". Some examples of this: http://www.chevyhiperformance.com/techarticles/94138_piston_head_clearance_guide/index.html http://www.302w.com/Forums/forums/thread/1752.aspx http://blogs.hotrod.com/6252212/editorials/hot-rod-engine-tech/index.html http://www.oldspower.com/VB/archive/index.php?t-36898.html EDIT--I wouldn't necessarily recommend these clearances. I didn't read and thought that you were asking what would "normally" be recommended. I like the idea of the smaller gap, assuming that the pistons don't contact the head. I think piston rock is one of the limiting factors here and I think a lot of the conventional wisdom comes from V8 engines which have large bores and would therefore need larger tolerances due to piston rock. Quote Link to comment Share on other sites More sharing options...
rsicard Posted April 2, 2009 Share Posted April 2, 2009 I don't understand how a screen under a carburetor proves that grooves in a cylinder head make more power. Why are we discussing the screen under the carb in this context? John: I don't believe there was any association between grooves and a screen under the carb. As for the grooves, I cannot substantiate that they INCREASE power. They MAY improve combustion chamber turbulence and therefore MAY INCREASE fast or more complete burn. Quote Link to comment Share on other sites More sharing options...
Mack Posted April 2, 2009 Share Posted April 2, 2009 I run my high quench set up with a MN47 head, stock L28 flat top (which pop out of the bore about .005") and a fail-pro head gasket (although it has never failed on me in 30,000 miles of 11.5:1 hard driving.) which gives me a final piston to quench clearance of around .027". fail pros have a compressed height of .8mm or .032". On the grooves thing.... I can see how the turbulence they created as the piston came up to the head on a high quench/low clearance application would cause a lot of swirl and turbulence in a combustion chamber promoting a more complete and faster burn. On the screen note, there was acutallly a gasket kit you could buy for SBCs that had a screen or mesh type of material built INTO the intake mani-to-head gasket, right before the port. I cant remember who made it. Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 2, 2009 Share Posted April 2, 2009 My F54 flat pistons, MN47, and felpro gasket was a no-no with the pistons hitting the flat part of the chamber just above the spark-plug. Really almost nothing yet a direct contact on all cylinders! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted April 2, 2009 Share Posted April 2, 2009 My F54 flat pistons, MN47, and felpro gasket was a no-no with the pistons hitting the flat part of the chamber just above the spark-plug. Really almost nothing yet a direct contact on all cylinders! That doesn't make sense, unless you had the wrong pistons in there. The Fel Pro is .040" thick (1mm) out of the box. Quote Link to comment Share on other sites More sharing options...
Mack Posted April 2, 2009 Share Posted April 2, 2009 running L24 rods?? something isnt right there. Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 3, 2009 Share Posted April 3, 2009 Just a fact At first I had what I thought was valves noise... I set them, and again, and re check... still lotta noise from the head! I rechecked the towers, head bolts, springs, tappets... still noisy! I used my TDC finder but one part of the tool fall into the cylinder So no choice but to take the head out... and I had instant explanation. A print on the piston and and the head. I changed the head gasket and no more noise! The bottom is rebuilt with std parts, std pistons, the head is MN47... It's an Euro spec engine, but I don't think there is any difference in the bottom end. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 3, 2009 Share Posted April 3, 2009 I don't understand how a screen under a carburetor proves that grooves in a cylinder head make more power. Why are we discussing the screen under the carb in this context? Largely because (I guess) the idea seemed counter intuitive; if its old hat I'll STFU. I think I can solve that one! Spray a stream at a screen door, and it's in still air, Spray a stream at a screen with a big ass leaf blower funnelling a load of air through the screen, then the stream is pushed through the screen instead of dribbling down. whats the velocity of air through a carb? There's probably plenty there to pull the fuel through the mesh all nicely atomised even at idle speeds. Like I said before, I suppose its one of those things I'll just accept despite my intuition... straightener before the carb I can see, just seeems like anything afterwards would net a loss. Thanks for explaining. The "standard" numbers I've heard are usually .035" to .055". Some examples of this: http://www.chevyhiperformance.com/techarticles/94138_piston_head_clearance_guide/index.html http://www.302w.com/Forums/forums/thread/1752.aspx http://blogs.hotrod.com/6252212/editorials/hot-rod-engine-tech/index.html http://www.oldspower.com/VB/archive/index.php?t-36898.html EDIT--I wouldn't necessarily recommend these clearances. I didn't read and thought that you were asking what would "normally" be recommended. I like the idea of the smaller gap, assuming that the pistons don't contact the head. I think piston rock is one of the limiting factors here and I think a lot of the conventional wisdom comes from V8 engines which have large bores and would therefore need larger tolerances due to piston rock. Well, like I said, *I* was under the impression that a gap that broad was limiting it, to say the least. Apparently it isn't as important to get as ever-loving tight as I had imagine, rather there IS an aspect of "the closer you could get, the better.." Obviously compression increases, but as it does so minutely, the squishing action of the "fluid" in the chamber is giving you more agitation and "white noise" movement to grant an octane-offset from the comp increase. One issue that I have an immense amount of trouble with is the simple fact that I don't think well in fractions of an inch; I have always preferred metric measurement and "since its Japanese anyway" I pretty well have failed to get a good sense of my conversion factors in decimal places. What sort of depth would a standard L28 dished piston have if it's volume is around 10cc? I plugged ".055inches to mm" into google and it came back at almost 1.5mm, which is about what I had thought and that STILL seems a long ways away. It just makes me wonder just how flat a set of stocker dished pistons might be grindable........ Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 4, 2009 Share Posted April 4, 2009 How about concentric grooves in the valves? This guy machines grooves on the backside of the intake valves. He also actively modifies heads with the Somender Singh (or whatever they were) grooves on the combustion chambers. A few other things as well. http://www.allpar.com/fix/holler/valve-prepping.html Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 4, 2009 Share Posted April 4, 2009 If you go direct injection, would turbulence be needed? I always figured turbulence was to better atomize fuel that was in too large droplets. Direct injection allows lexus to run 11.8 to 1 compression ratio in their direct injection V6. Quote Link to comment Share on other sites More sharing options...
Mack Posted April 4, 2009 Share Posted April 4, 2009 turbulence is also needed to homogonize the air/fuel mixture. but on the other hand, there is this thing called stratified charge engines. google it. Quote Link to comment Share on other sites More sharing options...
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