Hi Mike, The folks writing here are far more erudite and experienced than I on this whole subject area, so I wonder if I'm missing something to think the direct answer to your question is a little less complicated. If your rebuilder changed the pistons in order to lower the compression, the tops of those new pistons must necessarily ride lower in the cylinder. I wonder if you could simply measure the distance from the top of a spark plug hole down to the top of the piston at TDC and BDC. You can then ask for one of us to do the same on a known-to-be-stock H engine. If your measurements are greater, your pistons must have been changed. If the measurements match, your compression should too. N'est-ce pa? Keith Boonstra - On 11/10/2012 10:14 AM, Michael Moore wrote: > > Thanks Carl, > As a matter of interest, the reason I asked the question initially was > to get an idea as to whether my rebuilder 20 years ago, concerned > about emissions control and loss of premium gasoline, as he prepared > my 300H for a move to California, had installed low compression pistons. > > He had made other mods supporting that goal. I was just looking for a > general idea of what compression readings stock (driver) 300H's ought > to be so I could compare mine and make a judgement about pistons. > Thanks again, Mike > > On Nov 10, 2012, at 6:54 AM, Carlton Schroeder wrote: > > Hello, > This subject appears to be another example of a question being more > complicated than it might first seem. Just on the matter of an engines > compression ratio I thought (and still do) it is just a volume ratio > of the > sum of the cylinder volume the piston moves through + the combustion > chamber > volume divided by the combustion chamber volume. With odd shaped > combustion > chambers, valve tops, the spark plug, head gaskets, and non-flat > piston tops > the exact volume calculations would be complicated. I guess though if you > really wanted to determine a precise CR you could use oil and fill the > volumes (piston at the bottom and piston at the top) and determine the CR > from that data. The valves would have to be closed and to be really > precise > you would have to account for that little additional volume in the spark > plug core. > For another method if the piston was at the bottom and you could make a > pressure and temperature reading then and could also measure the pressure > and temperature in the combustion chamber at the end of the compression > stroke then from gas laws you should be able to calculate the CR. > I hope this understanding is consistent with the rest of the posts > I've been > reading. > Carlton Schroeder > Eagle River, WI > > -----Original Message----- > From: Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com> > [mailto:Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com>] On > Behalf Of RICK AND DEBBIE CLAPHAM > Sent: Saturday, November 10, 2012 7:33 AM > To: larry@xxxxxxxxxx <mailto:larry%40pwbsfo.com>; tfm@xxxxxxxxxxxx > <mailto:tfm%40zippynet.com>; mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>; > flatheadeng@xxxxxxxxxxx <mailto:flatheadeng%40comcast.net>; Rich > Barber; mgoodknight@xxxxxxxx <mailto:mgoodknight%40juno.com> > Cc: chrysler300@xxxxxxxxxxxxxxx <mailto:chrysler300%40yahoogroups.com> > Subject: RE: [Chrysler300] Thermodynamics of a Ram > > Larry, I have been where you are at many times self-inflicted and with > customer's choice. A camshaft change will cure the problem. Actually > Hemispherical combustion chambers can withstand higher dynamic compression > ratios. The chart / tool you have posted will help. I also know finding a > 392 cam is now difficult. Rick > > To: rixpac@xxxxxxx <mailto:rixpac%40msn.com>; tfm@xxxxxxxxxxxx > <mailto:tfm%40zippynet.com>; mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>; > flatheadeng@xxxxxxxxxxx <mailto:flatheadeng%40comcast.net>; > c300@xxxxxxx <mailto:c300%40ez2.net>; mgoodknight@xxxxxxxx > <mailto:mgoodknight%40juno.com> > CC: chrysler300@xxxxxxxxxxxxxxx <mailto:chrysler300%40yahoogroups.com> > From: larry@xxxxxxxxxx <mailto:larry%40pwbsfo.com> > Date: Fri, 9 Nov 2012 21:55:26 -0600 > Subject: RE: [Chrysler300] Thermodynamics of a Ram > > Sorry This has nothing to do about the ram effect but I thought I would > chime in anyway > > The way I understand it is that the 10 to 1 compression is the static > compression ratio which is what you would get when the piston travels from > the bottom of the stroke to the top of the stroke with the valves being > closed at all times > > And to get the real compression ratio or dynamic compression ratio all the > figures as far as stroke, bore, head gasket thickness ect. Would be > the same > for both Accept putting in the degrees ABDC that you have the intake valve > close > > Below is a link that will give you both ratios if you have all the numbers > to put in > > http://kb-silvolite.com/calc.php?action=comp > > 300D 392 > > I used this when I had my engine rebuilt & had the cam designed so we > would > come up with a cam that should be good for the crappy gas we have out here > in CA especially in the Bay Area > > I ended up with a static of 9.1 & a dynamic of 7.6 which supposedly it > perfect for 91 octane > > I think this works for most engines except hemis from the fifties > > After doing all this it still pings under load even by controlling the > total > spark advance to 24 degrees > > The only thing that makes it happy is 96 octane at the race track which > costs about $7.00 a gallon > > If anyone has had this issue of pinging with a 392 and has any solutions I > would like to hear about it > > Thank you > > Larry Jabin > > -----Original Message----- > From: Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com> > [mailto:Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com>] On > Behalf Of RICK AND DEBBIE CLAPHAM > Sent: Friday, November 09, 2012 7:05 PM > To: tfm@xxxxxxxxxxxx <mailto:tfm%40zippynet.com>; mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>; flatheadeng@xxxxxxxxxxx > <mailto:flatheadeng%40comcast.net>; Rich > Barber; mgoodknight@xxxxxxxx <mailto:mgoodknight%40juno.com> > Cc: chrysler300@xxxxxxxxxxxxxxx <mailto:chrysler300%40yahoogroups.com> > Subject: RE: [Chrysler300] Thermodynamics of a Ram > > These explanations are quite adequate on the RAM EFFECT. The camshaft > design > explanation still has me confused. The short ram is basically a 361 > camshaft > with 4 degree retard. I read my fathers papers on cam design and realize > Chrysler had the best labs of any manufactures of the auto industry. They > did know what the wanted and they built it. The bad news is the > compression > has not been effectively used until direct injection. I know we think we > have 10 to 1 compression ratio engines we just do not. The valves open and > close at specific timing and if you figure it out we really never use the > rated compression ratio, Less than half the rated. Here in Colorado we can > drive to the top of Pikes Peak on regular gasoline. Being your effective > compression ratio is effected by altitude. at 5000 foot above sea > level you > lost 20% of the sea level atmosphere. Actually lowering the efective > compression ratio. > > CC: Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com> > To: mmoore8425@xxxxxxx <mailto:mmoore8425%40aol.com>; > flatheadeng@xxxxxxxxxxx <mailto:flatheadeng%40comcast.net>; > c300@xxxxxxx <mailto:c300%40ez2.net>; > mgoodknight@xxxxxxxx <mailto:mgoodknight%40juno.com> > From: tfm@xxxxxxxxxxxx <mailto:tfm%40zippynet.com> > Date: Fri, 9 Nov 2012 20:20:05 -0500 > Subject: Re: [Chrysler300] Thermodynamics of a Ram > > Here's a link to our web site where you'll find the operational theory > behind cross ram induction. Cam timing is *critical* to getting the most > optimal performance from this setup..... > > http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm > > TFM > > Thomas F. Miller > tfm@xxxxxxxxxxxx <mailto:tfm%40zippynet.com> > > '57 300C > '70 440+6 'Cuda > > >>> "Flathead Engineering" <flatheadeng@xxxxxxxxxxx > <mailto:flatheadeng%40comcast.net>> 11/9/2012 6:33 PM > >>>>>> > > My understanding of the ram effect based on fluid dynamics is the when a > traveling wave of pressure meets a boundry condition, closed valve, the > velocity goes to zero and the pressure doubles. The velocity of the > traveling wave and the frequency depend on the geometry of the passage and > the RPM of the engine. The Chrysler ram is long thus tuned to a lower > frequency to complement the large displacement of the engine which turns a > relatively low RPM compared with a race engine. Understanding this you can > see why the wrong camshaft will destroy the ram effect and make for a poor > performing engine. I imagine Chrysler spent a large sum to optimise > the cam > profile and I doubt if some race engine builder can improve on it. > More than > likely they will not understand the principles and put in an inappropriate > cam that works great on a dual plane manifold but is totaly wrong for the > ram effect. > ----- Original Message ----- > From: Rich Barber > To: 'Michael Moore' ; mgoodknight@xxxxxxxx <mailto:mgoodknight%40juno.com> > Cc: Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com> > Sent: Friday, November 09, 2012 3:15 PM > Subject: [Chrysler300] Thermodynamics of a Ram > > Warning: There will be a quiz at the end of this mini-lecture. If > you're not > interested in engine performance and the ram induction effect, tune > out now. > > If the cam allowed some valve opening before TDC on the compression > stroke, > the effective compression could be lower. That would be a real power > robber, > methinks. > > Simply speaking, a 4-stroke cycle engine acts as an air compressor while > being spun by the starter. The compression pressure is measured as the > peak > pressure in the cylinder over a small number of strokes-as PSIG > (Pounds per > square inch-gauge). The Shrader valve in the peak pressure indicator > acts as > a check valve to hold the peak pressure on the gauge until released. > Ideally, the peak pressure can be estimated by the cylinder's compression > ratio. The laws of physics mandate use of absolute units when dealing with > the gas laws, therefore we must use pressures expressed in PSIA > (pounds per > square inch-absolute). PSIA=PSIG plus atmospheric pressure. Differential > pressures are expressed as PSI. > > Examples: > > Sea Level Atmospheric Peak Peak > > Elevation Pressure Compression Pressure Pressure > > Feet PSIA Ratio :1 PSIA > PSIG Engine & Location > > 16 14.69 9.6 141.02 > 126 (My ram K engine at Newark, CA) > > 16 14.69 8.5 124.87 > 110 (My C-300 hemi at Newark, CA) > > 5,280 11.68 9.6 112.13 > 100 (My ram K engine on the first step of State Capitol Building in > Denver) > > 16 17.69 9.6 169.82 > 155 (My ram K engine at Newark with a 3 psi boost from ram induction) > > So the ideal peak pressure depends on elevation and cylinder compression > ratio. Using the same pressure measuring device and techniques in an > engine > at operating temperature and at similar cranking speeds should provide > valid > cylinder-to-cylinder comparisons. Lower peak pressure indicates air > leakage-either/or past the rings, valves, gaskets, pig iron. Adjusting the > valves on a solid-tappet engine before the test makes sense-although > having > them buried below 30" long ram induction intake manifolds makes that a > challenging job. > > BTW, the ram effect is designed to increase the apparent atmospheric > pressure at the intake valve while it is open. The only reference I found > indicated the ram effect could amount to as much as 3 psi at resonant > speed. > As our engines are limited by the amount of air they can inhale (free air > capacity), a 3 psi boost at the inlet could theoretically increase the > engine's power by 20% at sea level. Chrysler only claimed 8.3% (390 HP vs. > 360 for a non-ram K). This suggests a 1.2 psi ram effect. Anyone heard or > measured anything different? > > C-300K'ly > > Rich Barber > > Brentwood, CA (Elevation at my home here in the Bay Area is about 120') > > Ps: Quiz: What is the theoretical peak compression pressure of a > cylinder of > a C-300 hemi engine parked outside the state capitol building at Denver? > (Just before the park police tow the car and arrest the mechanic) Answer: > Scroll down to under Marshall's signature. > > rb > > From: Michael Moore [mailto:mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>] > Sent: Friday, November 09, 2012 5:01 AM > To: mgoodknight@xxxxxxxx <mailto:mgoodknight%40juno.com> > Cc: c300@xxxxxxx <mailto:c300%40ez2.net>; Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com> > Subject: Re: [Chrysler300] Compression pressure , 300H > > Marshall, > > I have been gradually getting my 300H, which I have owned since 1964, back > into a more drivable condition. Some of the major problems which kept me > from driving it much (brakes, steering) are resolved, but the engine > issues, > while better, are still with me. In general, it has suffered from a > lack of > power dating back to the engine rebuild I had done many years ago. The > rebuilder, a highly respected race engine builder, misunderstood > California > (where I was moving to) requirements. He also knew high test was going > away. > Among the mods he made was to lower the compression with a custom Barnes > cam, rejet the carbs with richer needles and install a smog valve. > The car had power, but ran so rich your eyes burned. The carbs were > rebuilt > and rejetted to stock needles and it began to run better. I know it still > does not run as strongly though as it did even in the 90's. > > I obtained a correct 300H camshaft from a member and have a new set of > lifters. My plan is to replace the camshaft with the stock 300H camshaft. > > Recently though, I have been wondering if the rebuilder may have installed > lower compression pistons. If so, now would be the time to replace the > pistons also. > > I also don't fully appreciate how the custom camshaft lowered the > compression ratio other than he adjusted the overlap. > > Thanks, > > Mike Moore > > Morgan Hill, California > > 300H > > On Nov 9, 2012, at 3:44 AM, mgoodknight@xxxxxxxx > <mailto:mgoodknight%40juno.com> wrote: > > Thanks for your research Rich, > > That's a good write-up on compression testing. One might conclude from > that > reading that too much emphasis is often put on the results of compression > testing and that proper (valid) compression testing is not often > accomplished. > > Much can be learned about the condition of an engine from studying the > results of a valid test, but inaccurate diagnostics are more commonly the > main outcome. > > My recommendation is to avoid such a test unless you have strong > evidence of > a problem that can be easily identified by a test. If the engine runs well > and performs properly, don't do the testing. You might see results > that will > cause you undue worries. > > Marshall Goodknight, engine failure analyst > > (Answer: 88 psig-for about a 20% loss in potential power. The C-300 > becomes > a C-240) > > Please note: message attached > > From: "Rich Barber" <c300@xxxxxxx <mailto:c300%40ez2.net>> > To: "'Michael Moore'" <mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>>, "'300'" > <Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com>> > Subject: RE: [Chrysler300] Compression pressure , 300H > Date: Thu, 8 Nov 2012 22:47:28 -0800 > > __________________________________________________________ > 7 foods KILL fat > Surprising foods that boost your metabolism > http://thirdpartyoffers.juno.com/TGL3131/509cecd8c55056cd87e56st01duc > > From: "Rich Barber" <c300@xxxxxxx <mailto:c300%40ez2.net>> > > Subject: RE: [Chrysler300] Compression pressure , 300H > > Date: November 8, 2012 10:47:28 PM PST > > To: "'Michael Moore'" <mmoore8425@xxxxxxx > <mailto:mmoore8425%40aol.com>>, "'300'" > <Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com>> > > Individual compression pressures on a long non-operated, 85,000 mile, > cold, > ram K block ranged from 100 psi to 140 psi. I found this interesting > text on > analyzing compression pressures. According to the 75% criterion, the > engine > failed, although a properly operated and warmed up engine with properly > adjusted solid tappets would have probably tightened the range and > marginally passed. > > C300K'ly, > Rich Barber > > COMPRESSION TESTING > > Note: although this is written primarily for 4cycle gas engine testing, > 2cycle gas and diesel follow pretty much the same sequence of procedures. > Also, many diesel engine companies do not publish specific compression > readings so the values, in the chart, at the end of this section will > be too > low for use with a diesel, you'll have to do the calculation. > > 1. Be sure the crankcase is at the proper level and the battery is > properly > charged. Operate the engine for a minimum of 30 minutes at 1200 rpm, make > sure that the choke has opened, and the engine is at normal operating > temperature. Putting a load on the engine for at least 10 minutes, can > increase the accuracy of your test. Turn the ignition switch off; then > remove all the spark plugs (injectors on the diesel). If the engine has > closed cooling, (green anti-freeze) relieve pressure in the cooling > system. > (carefully) > > 2. Set the throttle plates and choke plate in the wide open position. On 4 > cycle gas engines: Try not to pump raw fuel into the intake with the > accelerator pump. > > 3. Install compression gauge in No. 1 cylinder. > > 4. Install an auxiliary starter switch in the starting circuit. Ground the > coil wire on gas engines. Next, using the auxiliary starter switch, crank > the engine (with the ignition switch off) at least five compression > strokes > and record the highest reading. > > Count the approximate number of compression strokes required to obtain the > highest reading. > > 5. Repeat the test on each cylinder as was required to obtain the highest > reading on the No. 1 cylinder. > > If the readings degrade from front to rear, re-check the battery and > possibly re-run the test starting at cylinder #1. In this way you can > have a > set of two tests to compare an average. > > TEST CONCLUSION > > 2 Cycle Engines: > Your test results need to be within 15 psi range to be considered an > engine > worth using. For example; a 3 cylinder with readings of 130, 135, and 120 > would be considered a good engine. Some might argue that there should > be no > more than 5psi difference between high and low cylinders. But, obviously, > the closer the readings are to each other, the better. > > 4 Cycle Engines: > The indicated compression pressures are considered normal if the lowest > reading cylinder is within 75% of the highest. Refer to the following > example and chart. > > Seventy-five percent of 140, the highest cylinder reading is 105. > Therefore, > cylinder No. 7 being less than 75% of cylinder No. 3 indicates an > improperly > seated valve or worn or broken piston rings. > > If one, or more, cylinders read low, squirt approximately one (1) > tablespoon > of engine oil on top of the pistons in the low reading cylinders. Repeat > compression pressure check on these cylinders. > > 1. If compression improves considerably, the piston rings are at fault. > > 2. If compression does not improve, valves are sticking or seating poorly. > > 3. If two adjacent cylinders indicate low compression pressures and > squirting oil on the pistons does not increase the compression, the cause > may be a cylinder head gasket leak between the cylinders. Engine oil > and/or > coolant in the cylinders could result from this problem. > > Note: An engine compression test is easy to do but, your results need > to be > tempered with the knowledge of testing conditions that reduce the accuracy > of your test. As the battery gets weaker, starter gets hotter, and the > engine cools down, your results from any one cylinder will change. It is > important to do the test a quickly as possible, with as little cranking as > needed to complete the test. > Circumstances arise where a more accurate leak down test should be > utilized > before you start tearing the engine down. Readings that are at the > extremes > of the chart, (meaning over-all very high or very low readings), may > indicate conditions inside the cylinders that a compression test won't > depict properly. > You can do the math yourself but, the following quick reference chart > should > be used when checking cylinder compression pressures. ( to avoid > mathematical errors) The chart (below) has been calculated so that the > lowest reading number is 75% of the highest reading. > Special note: Although the "actual" compression readings are not all that > important, keep in mind that very few engines will run with a compression > under 100 psi. However, there are some engines that will test with > readings > in the 90 psi range on a regular basis. If you're not sure if you have one > of these engines, contact your servicing dealer before you get excited. > > Although 75% range is tolerable for an older motor, keep in mind that most > modern engines are designed at much closer tolerances. Also, on a V8 > engine, > if 7 cylinders test at 150psi and only one tests at 113psi, this is not a > good sign... > > -----Original Message----- > From: Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com> > <mailto:Chrysler300%40yahoogroups.com> > [mailto:Chrysler300@xxxxxxxxxxxxxxx > <mailto:Chrysler300%40yahoogroups.com> > <mailto:Chrysler300%40yahoogroups.com> ] > On Behalf Of Michael Moore > Sent: Thursday, November 08, 2012 11:13 AM > To: 300 > Subject: Re: [Chrysler300] Compression pressure , 300H > > Sorry, that would be engine compression. > > Mike Moore > > On Nov 8, 2012, at 11:00 AM, Michael Moore wrote: > > Does anyone have available the pressure I should read for a stock 300H > when > cranking (with all plugs out) ? > > Thanks, Mike Moore > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] > > ------------------------------------ > > To send a message to this group, send an email to: > Chrysler300@xxxxxxxxxxxxxxx <mailto:Chrysler300%40yahoogroups.com> > <mailto:Chrysler300%40yahoogroups.com> > > To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx > <mailto:bob%40simplexco.com> > <mailto:bob%40simplexco.com> or go to > http://autos.groups.yahoo.com/group/Chrysler300/join and select the "Leave > Group" button > > For list server instructions, go to > http://www.chrysler300club.com/yahoolist/inst.htm > > For archives go to > http://www.forwardlook.net/300-archive/search.htm#querylangYahoo! 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