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Awesome work! This week I've been able to set the cam timing, rockers, and basically get the long block buttoned up. Today we test fit the engine tin and will get that off to powder coat. It's a great feeling being almost to the finish line.
Nice work, can't wait to see your finished motor! |
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I’m contemplating what system to use for twin plug, and catching up on other projects. I did get the chain tensioners primed and installed and verified valve clearances are still good. http://forums.pelicanparts.com/uploa...1743121162.jpg |
Quick Check for valve clearance’s. 1 and done.
I put in a call with William Marshall, and asked him to help me verify if my valve clearances were good. After a long explanation of what I had been doing he simply said “Go to top dead center”, I said “I’m there”, he then said “go to # 4 and measure the exhaust clearance”. I used my special Icarp magical valve lever (picture below) and noted well over .25’ of travel, I said, “over a quarter of an inch”. He said “one and done, you’re good”.
I thanked him as he had another call coming in and pondered the physics of what had just happened. Most in this forum probably know this, but here’s my thoughts. Check valve clearance at valve overlap for cylinder #4, with the engine at TDC for cylinder #1. Why? Valve overlap for cylinder 4 happens when it reaches TDC during the transition from the exhaust stroke to the intake stroke. The firing order is 1-6-2-4-3-5. Cylinders 1 and 4 are on opposite sides of the engine. When cylinder 1 is at top dead center (TDC) on the intake stroke, cylinder 4 will also be at TDC, but on the exhaust stroke. This is because the two pistons are 360° apart in the four-stroke engine cycle. So, the piston in cylinder 4 will also be at its highest point (TDC), but completing the exhaust stroke, preparing for the intake stroke to follow. Valve overlap occurs at the end of the exhaust stroke and the beginning of the intake stroke. During this phase, both the intake and exhaust valves are slightly open to allow better cylinder scavenging and airflow into the combustion chamber. http://forums.pelicanparts.com/uploa...1743128740.jpg |
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A couple years ago I wrote up about how to check valve clearance at overlap, because that's where the valves get closest to the pistons. You don't need the Stomski tool, although it's handy. Instead, I turn the valve adjusters down to make the valve contact the piston (gently), counting the turns. The adjuster screw pitch is 1mm, so every full turn is 1mm of valve clearance. I check both the #1 and #4 pistons at overlap because I want to be sure there aren't any differences from one side to the other, due to cam timing slipping or some defect in the cams. In my case, using the M1 cam and the Mahle Sport 3.2 "10:1" pistons, my valve clearance at overlap was around .050". I have a tight clearance because the Mahle pistons are domed on one side without valve cutouts, and the M1 cam uses all the available lift and duration with those pistons, and I deleted the copper base gaskets to get a tighter combustion chamber and squish/quench (.030" deck clearance at the edge of the piston/cylinder/head). You had 0.25" of valve clearance because the pistons you used have very deep cutouts. Those pistons are designed for racing engines with high lifts, much higher than what you're running. |
You guys need to be careful here as TDC is not always the point where the piston is closest to the valve on either intake or exhaust sides. If you use a degree wheel to set cam timing you can get a very good picture of the nature of your camshaft(ramps on lifting and closing sides and rate of increase in lift per degree of crank rotation) , and when the valves are the closest to the piston and often it is roughly 10 degrees away from TDC I recall(note book not near me) on the intake side. This is especially true with more aggressive cams as the intake valve opens 20-30-40(or more) degrees BEFORE the piston is up at TDC.
Here is how we check this: Set your cam to desired spec, after you have hopefully found true TDC w a piston stop and a degree wheel as the pulley marks and fan housing's are often not right on, then then run the intake valve in 1mm at at time initially from 0 lash (1 turn is .040" and you can watch this with your micrometer still on) . Turn the engine around 2 revolutions gently as you get towards TDC on firing no . 1 . Back out the exhaust lash to a whole bunch 1st I should note so valves don't tangle. Then go again in 1/4 turn increments or .010" . Keep going until it hits, and you will see it is very very often not at TDC. The intake valve is opening long before TDC getting a head start on the intake stroke at the end of the exhaust stroke. Once done back it off about .005 and you learn your exact clearance within .005" or so. Pro tip- Do this with only one cam timed or you will have to redo both sides if you have to readjust your cam timing because you have inadequate clearance on one valve or the other. We record this info as if we have a problem later, we learn exactly what we can get away w certain cam, valve train spec, springs, retainer, valve weights , spring pressures etc., level of over Rev (from data loggers). We of course have limits we know not to exceed on how close we can get away with, and some clients are much harder on equipment than others, so all this needs to be accounted for, and over revs can exceed what one dreamed was even possible. Then we do the exact same process on the exhaust side, cam still at same timing spec, but now you back off the intake valve rocker several turns from TDC firing NO 1(both valves closed) , and run in the exhaust rocker .040", .060, .080" .100" ...till it hits. Turn the engine slowly 2 turns (all spark plugs out so easier to turn) once you get in to the area where it hits around but not at TDC likely. Then you know almost exactly what you have for clearance. Recall the piston is chasing the Exh valve shut on the exhaust stroke( and this is why a big over rev often breaks a rocker = tags the exhaust valve to piston often -valve float or loss of control- and hopefully doesn't bend the valve ), and the valve doesn't actually close until longer after TDC, 30 degrees on a more racey "cammed" engine. We use this data to then modify our custom piston designs so we don't have one size fits all" giant ass valve pockets" we don't need for next engine like this we do to the same spec(all things equal) . Piston manufacturers commonly make these pockets very deep to avoid come backs from folks having clearance issues, especially off the shelf designs. Streetcar designed pistons have very little valve reliefs so then one cannot fit much additional camshaft, a real bummer. Sometimes there is not enough dome thickness to cut your own valve reliefs, so a different piston or milder cam is required to go forward. This is often why from a new or totally different design or spec standpoint, we end up building an engine 2X, once to chk everything fits", and then the final time after some mod's perhaps. We have had Mahle give us a 3D printed custom piston model to mock up, to make sure the design fits before producing real parts which can waste time and material if a detail missed a bit. Happy engine-ing BeST Kevin GAS Motorsport |
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Great info, yes these pistons have deep pockets, I’m probably going to end up building it again later with twin plug, no base gaskets, higher compression and closer clearances. I did use a piston stop and am using a degree wheel so I have that going for me. My notes show my exhaust valve closes at 15 degrees, I’m going to go back and check. |
Kevin, correct. You should check the valve clearance from 10 degrees before to 10 degrees after TDC to know where the valves are closest. That was in my longer instructions a couple years ago.
In Shane's case, with 1/4" of clearance, he isn't anywhere near having valve contact, no matter how he times the cams. |
Nice project…
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…. now where did I leave those chain housing gaskets? |
To find them, you will have to order new ones. Then you will find the old ones. BTDT.
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Fan fit. http://forums.pelicanparts.com/uploa...1743555884.jpg The tdc line on this fan was 2 degrees off, also the new pully was too close. I took .040” off and used a chisel to punch a new tdc line. http://forums.pelicanparts.com/uploa...1743555884.jpg http://forums.pelicanparts.com/uploa...1743555884.jpg |
Buttoned up.
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Headers and muffler bolted on. Fitting the engine shroud and surrounding bits.
http://forums.pelicanparts.com/uploa...1743828010.jpg |
Dang, you passed me. Waiting for the engine tin to come back from the powder coater, then it's a wrap. Looks great man!
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Build Leak down #s
Dry, cold, fresh build, pre start up, - these #s don't look too bad.
http://forums.pelicanparts.com/uploa...1743874213.jpg http://forums.pelicanparts.com/uploa...1743874213.jpg http://forums.pelicanparts.com/uploa...1743874213.jpg http://forums.pelicanparts.com/uploa...1743874213.jpg http://forums.pelicanparts.com/uploa...1743874213.jpg http://forums.pelicanparts.com/uploa...1743874213.jpg |
Time to fire it up!
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Oil tank, lines and coolers are prepped for installation.
http://forums.pelicanparts.com/uploa...1743986115.jpg |
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