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11-04-2002, 02:19 PM | #1 |
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Please comment on my speed secret of the day
I just replied to a different thread and said, d a m n, I should share that with all the rest of you Ford Oval Blue Bleeding racers out there.
This is only what I purport it to be, a single and simple speed secret I learned from watching the best and most successful racing legends pull rabbits from their hats. This is not intended to be the "best secret" ever, or even an "important secret." It is just a little thing that may help a few of you pick up a trophy or two. And that is what it is all about. WINNING. So here it is, my very first thread titled "speed secret for today"..... Back in the 70's we used to always buy high dome 12.5 or even 13.5 to1 domed pistons. Then we would machine the valve reliefs for the cam lift and valves sizes we were campaigning, and then we used a dye grinder to totally smooth off the piston top. In some cases companies would sell us the forged domed pistons NON machined on the top, so we could cut only the material we needed for valve clearance and NO MORE. Then we went to work on the piston top with a dye grinder and completely smoothed the entire surface of any ridge or angle that could store heat, glow like a torch and cause pre-detonation at high rpm. We would clean up the combustion chambers too, but you have to know your rule book and what you are allowed to do and not to do for the class you race at. Sometimes we would pocket port heads and polish the combustion chambers and then bead blast or shot peen the ported surface to make it look like stock cast iron. It would pass tech inspection and flow like a DEMON. Getting back to the piston top, we actually wanted to keep the compression to about 11.5 to 12.25 at the upper edge, because we were using extremely high lift, which mimicks the power produced by static compression changes. We cut the dome smooth and removed enough metal to produce a minimum 0.08 quench with the compressed gasket across the entire piston surface other than the wedge of the combustion chamber. Now to keep quench tight on as much of the piston as possible, we wanted to reduce the wedge area just to what was needed to start the flame propogation. In most cases that was about 80% of the stock wedge. In order to reduce the wedge but keep some strength in the head we would angle mill the head, sometimes as much as a quarter inch on one side and by only a few hundredths on the exhaust side. Many people watching the process thought we were trying to increase the static compression ratio, but we were really after having just the 0.08 quench area. If successful, we would have great flame propogation from spark kernal radiating out evenly to the edge of the piston. You will see swirl effects this is good and normal. YOU WANT SWIRL, because it helps pack very dense air fuel charges into the cylinders. That is why the closed chamber Cleveland heads make so much more horsepower than the open chamber 2V heads. You just cannot achieve a tight quench with the open ports and maintain enough air fuel in a tight wedge to create excellent ignition. Do not remove too much of the wedge, because there needs to be a very dense fuel charge around the spark plug to establish the flame propogation. Otherwise you never burn the total fuel that has been compressed. You end up with really stupid, incomplete burns. Expect to have to have a competent machine shop square the head bolt faces on that angle milled head. Plus you will need to counter mill the intake manifold and sometimes dowl fit it to the head to provide proper intake port to head port indexing. Don't be surprised if you don't have to drill your intake manifold bolt holes enlarged, so you can move it forward or back as much as an 1/8 inch to get perfect port match. When piston coatings first came out, we would coat both the entire surface of the piston and the entire top of the dome. We tried coating the back of the intake and exhaust valves found it did nothing to affect HP or torque. Running the coatings allowed us to bump up static compression by 1/2 to 1 point. When you take a 383 from 11.25 to 12.25 compression ration you get an additional 30 horsepower or so at the rear wheels. This is not insignificant. Often it was the coating that provided the extra compression ratio, so if the rule book said you had to use a stock piston, and 11.5 was all you had, the coating would put you at 12 or 12.25 compression!!!! This is a good secret to share with you guys. Run a dished piston with less quench when you are building for torque, like an off road truck or boat engine. Run a very tight quench when you are after higher horsepower. I do not know all the physics on flame travel under velocity and compressed combustion, but to keep things simple the flame travel is broader, slower, and the fuel burns more complete when you keep the quench area really tight. I learned that from watching a Smokey Yunick engine being torn down after winning its bracket at the Winternationals. I wish I could have taken pictures of that combustion chamber and piston top for you to see. The burn pattern was perfect from the spark kernal to the extreme edge of the piston tops and there was no area of any piston that showed combustion generated turbulence. In fact, the flame pattern indicated the effect of the intake charge swirl that Smokey was famous for. All of our modern heads have strong engineering provisions to generate enhanced intake swirl, but it is up to you to build a piston top that reduces quench to the optimum amount. Just as a historical asside, Smokey Yunick worked for FORD for almost two years during the time Bunkie brought over Shinoda from GM to design the 69, 70, and 71 models. Smokey helped sort out the 302 Boss engines for track racing. That is why you see a 780 CFM holley strapped on to those engines. It was the same carb he used to get the 396 to 425 HP. He helped get the 302 BOSS set up for the new trans am races. Bet you CHEVY guys never knew that, and I bet you FORD guys never knew a CHEVY guy was responsible for our DOMINATION in trans am racing. Smokey was a true genius when it came to making horsepower. I hope this helps all of you realize just how complicated and exciting quench can be! Go quench safely out there and take home some trophies for all your hard earned money and effort!
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-04-2002, 02:44 PM | #2 |
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I read your entire post and found it to be interesting.
I think you would have to really know your stuff in order to apply your tip though. I shutter at the thought of me taking a die grinder to a piston. Later,
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92' LX-Big brakes, Lots and lots of suspension, GT40X heads, Ported cobra intake, stock cam, Vortech SC trim. 00' Lightning-Stock 88'CRX-13 second ego killer |
11-04-2002, 02:50 PM | #3 |
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Cool tip, Jim! Just a dumb question though. Was your quench .08, or .008?
Andy
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11-04-2002, 02:52 PM | #4 |
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Interesting stuff I have read one of Smokeys books on the SBC and picked up allot of that stuff in there.
One thing I don't understand- Less Quench= more torque I don't see how that is possible. The whole point of having a small quench area it to get the a/f mixture to mix better, and swirl which creates a more potent and controled combustion. That right there will give you more hp and torque. Not to mention.. less quench is more prone to detonate.
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79 Hatch: NA 347, Stage 2 Canfield Heads, Victor JR. Intake, Blueprinted Holley 750 HP, Solid Roller Cam, Shooting for 10's on motor 93 LX: Tremec, dual friction clutch, fms flywheel, Hedman shorties, O/R H-pipe Ricer hater's club member #49 |
11-04-2002, 04:05 PM | #5 |
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Here is some very good reading (although a little technical) concerning quench and dished pistons etc. The article is related to Keith Black Hyperutectic pistons but a good deal of it relates to any type or brand piston and just general engine design.
http://www.kb-silvolite.com/page07.htm |
11-04-2002, 04:08 PM | #6 |
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Wads56 is out there thinking.
Love ya man.... That is what this post was intended to do. YES AND NO WADS56. I should have said that a factory torque engine builds torque in a certain and silly way. Not what a racer like you or I would do to make efficient torque. For a factory engine built for trucks and off road or marine use, the factory will reduce the compression ratio due to the load it expects the engine to run against during its life cycle. So they reduce the compression by enlarging the cc of the wedge, and by adding dishes to the pistons. This is the cheapest way for them to lower the static compression ration. However, this just eliminates the quench all together. Still the engines build great torque. Why? Because the factory correctly made the wedge larger allowing a large dense mixture to ignite properly with reduced compression ratio. Did you know ignition events are always EASIER as you increase compression? So as you decrease compression you need more fuel in that wedge just to get it to burn at all. Less quench means the initial flame propogation will be faster and more downward thrust will be produced from the rapidly burning mixture. If you look at the combustion at say 10 degrees after top dead center, the combustion event has collapsed due to the lack of quench. So alot of fuel remains unburned or partially burnt. That is why most street engines require smog control systems. On a properly built street engine, you could control smog by just running a CAT alone. Now here is another zinger for you all. As RPM increases in an engine the volume of intake charge is reduced in the cylinder. That is why torque engines fall off in power so quickly. They are efficient at low rpms where the vacume pulls sufficient volumes of air and fuel for the combustion. But as RPM goes up, the short duration of the valve events works against the vacumes ability to pull the intake mixture into the cylinder. In order to regain the power in higher rpms we need more valve event, and more overlap. Overlap will be another issue all together. YES YOU ARE RIGHT, it is still important to have tight quench at the edges of the piston or that fuel will not burn. Just as an aside, FORD did build one engine that had great low end torque and really good horsepower. This was the 351 Cleveland 2 barrel. It made 275 horsepower, got 18 mpg and pulled a 3250 lb car to 60 mph in only 7.5 seconds. The head and the piston top look very much like a Chrysler Hemi head. The flame travel is extremely fast and strong rather than slow and complete so it never built the same horsepower as a 4V head. Just for grins, I can tell you we ran many a 2V engine at 400 hp without any detonation problems even with the whacky open chambers. Most of the pinging engines I come across are of the wedge combustion chamber variety. They have little to no swirl, have low compression by big wedges and piston dishing. Their quench is NON EXISTANT. THIS IS WHAT YOU POINTED OUT. But this is what the factory does to save money. Yes it is back a s s w a r d. That is why we need to correct their mistakes when we put together a performance piece. Now I hope others out there correctly think this through as WADS56 has done. Wad, you know your stuff. You and I can build a high torque engine with small quench. Absolutely. All my tow vehicle engines run tight quench to eliminate detonation. JUST AS YOU POINTED OUT. Man I love how many of you really know your stuff out there. I am glad no one is letting me get away easy. You are all going to learn some great things over the coming weeks. NOW AS FOR THE COMMON GUY NOT GETTING MUCH OUT OF THIS... Humph...... It costs about 75 bucks to have a shop angle mill the heads. Another 75 bucks for the shop to correct your intake's angle. It costs 50 bucks to have them enlarge the intake bolt holes and square the head bolt bosses. So for 200 bucks you can now build a 10-11 to 1 ratio engine, pick up 30-35 horsepower, and have a chance at trophy. $200.00 bucks. This is half the price of the forged pistons I run. This is less than a tenth of the price of cranks that are built for 8 second brackets. NOW AS FOR I WOULD NEVER TAKE A DYE GRINDER TO A PISTON TOP, then use a sanding wheel, belt sander, what ever you need. Do just one, and ask the shop to cnc the other 7 to match, then clean them up so they are all the same. I would never hand prepare 8 pistons anymore. The cnc machine takes only a few minutes to program and will do all 7 so precisely it makes me ill to think about all the time it took to build a 9 second car in the 70's and 80's.
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-04-2002, 05:05 PM | #7 | |
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Re: Please comment on my speed secret of the day
Quote:
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X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear |
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11-04-2002, 06:59 PM | #8 |
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interesting
this might be a dumb question (but it's smarter then not asking) i got kinda lost cause i was having trouble understanding the definition of quench.....is this the chamber area of the head, ???or how the piston pop up fills the chamber i'm still pretty amuature ,but i'm interested in learning
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the "not so old",old guy 87 Mustang GT T-top >hanlon t-5, pro 5.0, centerforce clutch ,adj. cable/quatrant ,3.27s ,full 2 1/2 ex(off road H) adj. reg. ,e-cam ,70mm TB, cobra intake ,1.7rr ,ported/milled e7ets w/crane springs ,306 balaced/decked short block w/speed pro forged flat top pistons ...257rwhp/302rwt best et 13.7@102 (4/11 ) '80 Capri (future project,currently collecting parts for 351 moter) |
11-04-2002, 07:19 PM | #9 |
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quench area= on the compression stroke when the piston reaches tdc the a/f mixture is forced into the combustion chamber of the head rather then the whole cilinder. When this happens it squeezes the mixture to the chamber causing it to atomize (sp) more which will make it more combustable and efficent. This is where combustion chamber designs play a big role in engine blueprinting.
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79 Hatch: NA 347, Stage 2 Canfield Heads, Victor JR. Intake, Blueprinted Holley 750 HP, Solid Roller Cam, Shooting for 10's on motor 93 LX: Tremec, dual friction clutch, fms flywheel, Hedman shorties, O/R H-pipe Ricer hater's club member #49 |
11-04-2002, 07:41 PM | #10 |
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Andy I did not mean to ignore you.
I hate to give away all my secrets. I should probably send you a personal email, but since I have openned up the can of worms I might as well see if they are tasty. You typically have some type of deck heightwith every block out there. This is not accidental. As you rev up, and as the combustion temperature rises the pistons and the rods grow. So the deck height is calculated to absorb that growth, and any slop that happens as your main and rod bearings wear. For instance on my street rod 358, my deck height is .017 inches and my compressed gasket is .039. So my quench area would appear to be ideal at around .056. Very close to the minimum .080 quench I reported. BUT I OVERSIMPLIFIED TO SEE IF ANYONE COULD CATCH THIS, and you may have figured it out in a roundabout fashion. Good job! On my 9.2 et bracket engine, I reduced the deck and gasket quench to .044. I couldn't make it tighter, just trust me on this. It is way too complicated to explain how we determined the bare minimum for this response. If you are running aluminum or titanium rods, these grow much longer than forged steel rods. You need to take all this into account. I try to get the dome of the piston to fill as much of the wedge as I can, as I start the process of shaping the piston top. The valve reliefs make you do some strange contortions to keep the piston top smooth. That is why I like to use blanks, and cut exactly what I need to get my piston to valve clearance handled. Then you have to measure. Check with clay or displacement media. My favorite was a type of silly putty they use for stroke patients to stregthen the peoples grip. When I take my first measurements my compression starts at about 13.75 to 14.25 compression. Way high for my tastes unless you are running Alcohol. Then 14 to 1 is perfect. You can stop right there. Since I like to polish my combustion chambers I often work the chamber a bit to get the reduction in compression ratio and work to establish that .080 space from the dome to the wedge. Polished combustion chambers NEVER make more horsepower or torque. I could just remove all the rough goobers and that would be fine but NO. I have to be anal retentive about it and polish the thing. I am a NUT. I admit it. Everyone who knows me well would agree. I try to give myself a generous wedge area at least 1 inch surrounding the spark plug tip. 1 1/4 to 1 1/2 is great. So I take the 0.10 measurement as the most gap around that 1 1/2 inch wedge and then taper it gradually reducing to the .044 quench at the deck. There you have another secret. Keep things open around your plug, and tight at the piston edges. So Andy has in a round about fashion, found one of my trick points I was using to test you. I figured someone would say if .080 is ideal, why wouldn't .050 be even better..... Why not run it ultra tight, remember that the air fuel charge has to be very dense and thick right around the spark plug or the mixture will not ignite properly and the flame will not propogate smoothly across the piston like you need. So you need that wedge effect going for you at the plug and you need to go from wide to thin as you move away from the piston center. Then I go for the dang longest rod that can be shoe horned into that cylinder. I have had journals cut down to weirdest sizes just to get an extra .10 to .30 rod length. If you minimize your quench, have a smooth surface to burn across, and sit the piston at top dead center as long as you can keep it there, your torque will be a brute. Anyone ever own or race a 455 Stage Ior Stage II Olds engine?. They ran 475 hp and roughly 575 ft pounds of torque. These were factory long rod engines that you could buy, drive to the strip and take home your trophy. It took us a while with 390 Ford engines to keep up with these. Actually it took a 427 side oiler or a 428 to do one in. When the 429 SCJ hit the market, the Olds guys really got left in the shade. You were running a massaged Rat a Wedge or Hemi Crysler or a 428 or 429 CJ. The others took a back seat. If you can get away with it, and you have to be really careful, you should see if you can reduce the overall deck quench to about .044 on your engine running a quality Rod. Add some clearance if you are running aluminum or titanium. So leave yourself some clearance for rod growth and bearing wear on the mains and the rods. So who will find my other tests....... The race is on!
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-04-2002, 09:40 PM | #11 |
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ok ,thats what i was thinking ,thanks andy
let me make sure i'm on the right page ..... quench=the area the air/gas mix is sqeezed into on compression stroke...... wedge =the amount space occupied by the the pop up on the piston as it fits into the heads chamber ?? when you say .080=measurement of space between the top of the piston wedge and heads chamber am i lost .......(he he, i know...engine building egronomics for dummies here) jim.......now if .080 is ideal ,then isn't .056 a smaller tighter area ?? i'm kinda interested in this coversation cause i'm planning on a short block rebuild next month .......i'm not going real radical and i'm planing to keep most of my combo the same (stock cam stock heads)......i'm kinda trying to get some ideas for a few tricks to give her a little bit of an edge on a buget i had plans on tinkering with the cumbstion chamber on my heads , but i wasn't going to do anything but mild polishing (knocking off the casting bumps and such) i want to bump my compression up a bit ,but i havn't ordered pistons and i'm still open to learing a bit before i start spending hard earned money
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the "not so old",old guy 87 Mustang GT T-top >hanlon t-5, pro 5.0, centerforce clutch ,adj. cable/quatrant ,3.27s ,full 2 1/2 ex(off road H) adj. reg. ,e-cam ,70mm TB, cobra intake ,1.7rr ,ported/milled e7ets w/crane springs ,306 balaced/decked short block w/speed pro forged flat top pistons ...257rwhp/302rwt best et 13.7@102 (4/11 ) '80 Capri (future project,currently collecting parts for 351 moter) Last edited by Old Guy with 87 GT; 11-04-2002 at 09:48 PM.. |
11-04-2002, 11:17 PM | #12 |
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Jim, I almost edited my post after I reread yours. I forgot we were talking about domed pistons. I have never built a domed engine so I dont know jack about the squish distances on them. .08 seemed like alot though. My flattop motor (and several friends motors') is at .037. My pistons are .010 out of the hole and I use a .047 copper head gasket. People have different theories on whether to bring the piston out, or leave it flush. After talking with another friend (a local Super Stock builder) I am almost sure that my next motor will be zero decked.
Another thing that struck me as odd was your piston coatings. You picked up close to a point by coating them? Isnt that roughly equivalent to 10cc's? I really wish we could change the topic so it relates to flattops! hehhe Andy
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11-04-2002, 11:22 PM | #13 |
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When you think of an engine, remember it is simply an air pump that pulls air fuel mixtures into the cylinder. Compresses them into the combustion chamber. Ignites the mixture. And makes grown men beg for more.
Now say you are displacing 302 cubic inches. With a stock length rod of 5.09 inches and a crank stroke of 3.00 inches you will be compressing 37.75 cubic inches of swept space into the space that exists between the piston's top surface and the top of the block at top dead center. Also figured in is the volume of space created by the compressed head gasket and finally you add in the volume of the combustion chamber. Dividing the total combustion area by the swept rea plus the combustion area give you the static compression rate. On a street engine you want 9.3 for Iron heads and 10.0 for Aluminum heads. So the quench area equals the space between the piston top and the head surface (including the wedge). The tighter the quench, the better the fuel burns plus it burns slow and evenly. The looser the quench the easier it is for the air and fuel to be unevenly mixed and you will have pockets of burning fuel plus areas of exploded fuel and unburned fuel that disrupt the flame propogation. At the wedge around the spark plug I leave it unfilled so there is a walnut of space where the fuel can be properly ignited by the spark. This preignition then becomes a wave front. This is what we mean by flame propogation. There needs to be ignition of the fuel, and then it needs to propogate from the center of the cylinder to the edges as evenly and as controlled as possible. When an engine pings, the fuel is literally exploding and the force pushes down on the piston which cannot control the force and the piston "knocks in the bore" This beats up you cylinder walls, your piston skirts, hammers your rings, and will destroy your valve guides. Most Chevy racers worth a darn will not build an engine with over 0.10 quench. The engine will run flat. They will shave the block deck, run high compression pistons and shave down the surface, what ever it takes. So tight quench allows a slow, long, controlled burn. This builds HORSEPOWER. Torque is a separate issue I will discuss at another time. s Now say you want 370 hp from your 302. Your goal is to put 300 hp to your rear wheels. What do you do. Do not look at my idea as where to go. That would be foolish. Why would you want to buy 500 dollars worth of pop up piston blanks, work them for 20 hours, measure and sweat the details and bolt it all up to get a few extra 2 or 3 horsepower at 10 to 1 compression. Use a good quality flat top 11 to 1 compression piston. Verify the valve reliefs are adequate to your cams lift and duration and valve size. Then use a carbide cutter on a dye grinder to completely smooth the valve reliefs so there are no edges or ridges of any sort. Chamfer the piston edges so they are round not square but NOT OVERLY ROUND. Don't go overboard on me here. Just no edges to store heat, glow orange and predetonate the mixture as your RPM climbs. I would run a solid roller lifter/roller cam/roller rocker arm set up on stock ported or aluminum heads. Once you have the piston relieved to 10 to 1 compression, run a cam like this. Comp cam solid roller lifter, roller cam with Intake specs of 225 duration at .050 lift and .550 lift. Exhaust valve should be 235 duration at .050 lift and .570 duration. Port the stock heads to fit felpro 1250 gaskets, or buy some Trick Flow heads like mine. I LOVE THEM. So easy to use and enjoy. If you have a little extra money go with a 331 or 347 stroker kit. This cam, good heads, and a long rod set up will get you 390 horsepower fairly easily. You will get 14 mpg on a carb or 17 mpg on fuel injection. Now you just need 3.73 to 4.10 gears and a transmission and clutch that can take the power. You will have a great mild car. The mods I outlined are for 6,7,8 and 9 second ET bracklets depending on rules of the class. I like to do this mod on NOS engines because they really respond to a smooth combustion chamber surface without ridges and irregularities. Hope this helps. Look for further speed secrets as they pop up. I think I will discuss torque tomorrow. You will want to read this and try to find where I am looking for people to challenge me. I am using this as a way to get people thinking about the physics going on in their engines. This is the way to build a good engine that will deliver the results you are looking for.
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-04-2002, 11:31 PM | #14 |
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ABSOLUTELY RIGHT.
You get a prize my friend. If I were answering my post I would say Jim ol boy, we are not recommending pop up pistons any longer. We build an efficient wedge combustion chamber that swirls good, we get the spark plug as near the center of the cylinder as humanly possible and we run flat tops to get the best flame propogation. This is all current motor building theory 102. Old racers like me used pop ups because we were convinced that reducing the area between the piston top and the combustion chamber would make for a better more powerful burn and it does. Racers went to flat tops because they did not want to take the time and effort to smooth the pop up top so the flame could travel without bumping, dodging, or skipping. This is why my race engines won trophies. Because I did not buy into engine building 102, I improved the burn cycle of 101. Now for a zero deck height, that is fine with a copper gasket with .049 compressed thickness with forged steel rods and aluminum pistons you are good to go. Play with a piston or two as I described and see if you want to try it. It is easy enough to switch pistons during a season to test what delivers the best ET's. I promise you mine will do better in a NOS classification. But you try it and tell me what you find out.....
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-04-2002, 11:36 PM | #15 |
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I'd love to run a set of domed pistons, Jim. Only trouble is tech wouldnt much care for it. Class rules stipulate a flattop and a minimum squish of .035. The highest static that I can calculate with a 58cc head, is 10.2:1.
Andy
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11-04-2002, 11:41 PM | #16 |
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Yer Funny
Now that i'll be 44 on DEC 10 . I have to agree with you on small aspects of your posts ! I bought a 1965 Mustang coupe (Black ,Red interior. 4 speed Muncie) this was the thinking in 1974. But not now . Sorry , It's Just a defferent deal now! I have a almost stock 1991 Coupe Mustang . That runs 12.00 all day and needs Computer control to do it . So now I need quench !
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11-04-2002, 11:55 PM | #17 |
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thanks for the tips
the specs you mentioned are close to an e cams specs(w/1.7 rockers) ......i've been debating using an e cam but ,....since i'm running speed density efi its a little trickier for tuning on a daily driver i was thinking along the lines of flat tops too ,i was hoping bring a flat top closer to the deck to bump my compression up to around 10-1 .....right now i'm running stock heads with a mild port job and .020 milled off em witch should have it around 9.3- 1....... i'm probly going to go to a 306 so i'll probly have to buy pistons (engines got over 200k on the clock)............what i might do now is buy flat tops with no reliefes and a higher deck clearance then have my engine builder do the reliefes (at a minimum needed tolerance)and talk to him about smoothing out the sharp edges a little ps..... i do have plans for lower gears but i'm not going real low (3.27s)cause i want the car to maintian good highway cruising ability.......thats why i'm interested in torgue and bumping my compression up a bit thanks for the input .....been interesting reading (even for us 13sec guys )
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the "not so old",old guy 87 Mustang GT T-top >hanlon t-5, pro 5.0, centerforce clutch ,adj. cable/quatrant ,3.27s ,full 2 1/2 ex(off road H) adj. reg. ,e-cam ,70mm TB, cobra intake ,1.7rr ,ported/milled e7ets w/crane springs ,306 balaced/decked short block w/speed pro forged flat top pistons ...257rwhp/302rwt best et 13.7@102 (4/11 ) '80 Capri (future project,currently collecting parts for 351 moter) |
11-05-2002, 01:34 AM | #18 |
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Posts: 247
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Good point Andy, and I have said it a half dozen times today. Check your rule book for the bracket you want to run.
See if you can angle mill the head to reduce chamber volume, then take that material out around the valve pockets to make a little bit of a dish. I am not sure from your comments if the class stipulates flat top unmodified, or a maximum static ratio given the stock class you are running. Man I wish I had a current rule book. Mine is way far old. I just street race and grunge race now, so everything is straight up on the tree. I just do not have the desire to bracket race this street rod. It is built to autocross, not knock the snot out of the thing.... If they allow angle milling, and they allow you any stock piston, then you can usually find a ford forged or hypereutectic piston with a dish. just make sure you also remove all the edges ridges etc as long as the rules allow smoothing contours. Most rule books allow this if the combustion volume remains stock. So the angle mill reduces the quench area significantly, and the dish is just to smooth the valve reliefs and nothing more. USE ZERO GAPPED rings if they are allowed. I like child and alberts because it is a slider style and holds up to mild abuse pretty darn well. This will reduce the leak down on the rings from 31 cubic inches per rotation to just 16 cubic inches per rotation. That equals A LOT of cylinder pressure that could have been converted to torque. If you have to use stock rings. Take a file to fit set and do what child and albert does with their sliding overlap. We did this all the time on the Hemi's to keep the cylinder pressure high during the power stroke. High cylinder pressure made for a more efficient exhaust cycle and the additional scavanging would net us an additional 8-12 hp over a standard ring set on a static dyno run and almost 30 hp on a dynamic dyno run. Someone asked how I got an extra point of static compression with coatings. I did the angle milling on the heads first to reduce the wedge volume, then added that volume back by evenly removing material across the entire face of the piston. The coating was a standard brand at the time, to which I added a high silicate ceramic substrate that my buddy at Northrup developed for heat shields on space craft. It was really cool of him to lend me some material to test at 1400 degrees. So my coatings were especially thick, but legal because they were a single coat. Almost resembled "aluminizing" if any of you are old enough to remember that process. My buddy helped me glue together a persimmon golf driver too. That thing is still holding up 21 years later. Wish I could run out and buy epoxy that good.......
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-05-2002, 01:49 AM | #19 |
Registered Member
Join Date: Apr 2002
Location: Portland Oregon
Posts: 247
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Hey my street rod ran 13.9's with badly damaged valve guides.
The new 358 should hit high 12's or early 13's. That is based on Don Garlits time with his 358 and similar cams. I am running better heads. But he ran a better carb. Don always knew how to tune a carb better than me. Talk to J&E pistons. They will custom build whatever you want. You can go zero deck, just go with a very thick gasket. I like Ross and Probe pistonstoo, but J&E is really a top notch company in my dealings. They are superb.
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1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi |
11-05-2002, 02:04 PM | #20 |
NX dealer-man
Join Date: Sep 1998
Location: Peoria, Illinois
Posts: 977
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Jim, you sound like my old man, LOL! My dad talks about most all of the individuals you've mentioned from back in the day... another thing, btw, he did my heads and just happend to mirror polish the chambers... you made me think of him when you mentioned your doing so.
Thanks for sharing some of your 'speed secrets' with us... In fact, keep 'em coming... BTW, you familiar with the names Racer Brown or Jim Naramore? |
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