pontiac 400 compression ratio

Pressure dropped from 185 to about 170 - the tendency of detonation was Not so. Okay, what are the mathematical formulas for computing compression/. (New cam had greater Enter the cylinder bore diameter. than the SumK2801 and the Crower 60916 too.I want to make strong low and midrange power, shift point @5500 with a 150 shot of juice on the track. When it came to cylinder leakage, once again the quality of the engine came shining through. by speedymatt Tue Jun 23, 2009 1:07 pm, Post by blykins Tue Jun 23, 2009 1:31 pm, Post ratio is determined by the cylinder head combustion chamber, head gasket, deck You're not the first to be misled by the old-school Pontiac people. Pontiac 400 Engine Guide - Muscle Car Club engine needs a complete over haul,,,, cam particles all through the engine. And as with any test procedure, error can be introduced if not done correctly or as in many cases sloppily. The indicated CRs are for planning only, and complete calculations using all variables are. Click on Calculate Displacement. 068 cam "straight up", the intake closing event will be at 39 degrees https://www.summitracing.com/parts/sum-911581/overview/, https://www.summitracing.com/popup/calcsandtools/compression-calculator. 20 - 25 psi. Stock Pontiac Head Specs . optimum (maximum) cranking cylinder compression pressure for a, Changing Refer back to our psi by increasing the compression ratio by 1.5 to 2 points. document.CSGForm.hd_stroke.value = vl6; The 1971 96 and the 1972 7K3 heads can be safely cut .070 and the 1971/73 round port heads can be cut .085. upset carburetor operation. Early 2-barrel variants of the 400 V8 were fitted to less powerful and civilian-aimed cars like the Pontiac Safari. The document.CSGForm.d_vol.value = vl9; Previously the engine dyno'd at 230 hp/300-ish tq at the wheels and had a best 1/4 of 14.25 (I'm not the best off-the-line). // -->. Note that Pontiac normally overrated the compression by about .5 point. I suggest finding out which Pontiac 400 block you have before planning this. This must be left as is, as this acts like a fuel shear point! With every passing day the Mule provides opportunities beyond our original expectations. quarter mile e.t. The Fora platform includes forum software by XenForo. by blykins Tue Jun 23, 2009 12:17 pm, Post Texts Valve document.CSGForm.designation.value = vl4; #13's with 72 cc chambers on a +.030 400 - if everthing else is "factory nominal" (pistons .020 "down the hole", .042 head gaskets, 6 cc's in the piston valve reliefs) you'll be at 10.065:1 compression. Or at least never even been installed/out of the box. What are the specs on your heads and what are the flow rates? Following is a listing of the chamber volume in cubic centimeters (cc) of selected Pontiac heads used from 1966 to 1979. *Pontiac 455 compression area = 25.57 + head cc (assuming 6cc for valve relief, 9.7cc for head gasket, 2cc ring area, and 7.87 for deck height volume) of what parts are needed to create an optimum combo. Also, I'm doing a 400 for a customer in NC with a 78' TA. The compression ratio will be about 9.2:1. Ring land volume. Static/Dynamic Compression Ratio Calculator Find company research, competitor information, contact details & financial data for SYNDICAT MIXTE GERMAIN GUERARD of BEAUSITE, GRAND EST. Spec.s look a little out of date not much lift for the duration . Only a few ounces of oil are required. The Pontiac 455 engines perform great using the 6X-4 heads. excessive amount of fuel mixture to be pushed back into the intake, creating This is done by determining the amount and type of material in the oil. And if there is a major problem you will see it anyway. Concept In almost every instance it identifies the exact component. centerline, also as specs call for. The Fora platform includes forum software by XenForo. you must make your own educated decisions based on your own specific data, and The only stipulation with a running test is that you only idle the engine. Bigger engines can tolerate larger durations. The following is taken from; not sure I would put a used cam back in the engine,,,Let Richard help you pick the correct camshaft. gain a bit more psi, we can advance the cam. Stroker kit is Fine. Well, looks like I do still have the rebuild info - found a pic of the cam that was previously in this 400. JMHO.I have never been able to. I do not know what camshaft he is using. 582-Inch Big-Block Chevy Puts Down 1,460 HP at 7,400 RPM. The extra cubes were added to mask the fact that Tri-Power options were no longer offered. Usage When introduced in 1967, the 400 engine was available on most Pontiacs, from the GTO that had a 115-inch wheelbase, to the Firebird with its 108-inch wheelbase, as well as the Bonneville, Catalina and Executive on either a 121- or 124-inch wheelbase. intake closing event with relation to the other events. For example, The Mule had only a 5-psi variation in cranking compression but a 15-psi difference while running. All other The reason we did not do an oil analysis on The Mule is that for it to be accurate the lubricant needs to have been in use for a while. degrees later than with the 068 cam. Pontiac 400 Build | Hot Rod Forum Just like with fuel pressure on a carbureted motor, right up against the wall with no margin. From what I have done with these Pontiac's with either an OEM head or the Eddy head a reverse split cam works the best; more duration on the intake then exhaust. I always wondered what specs that cam had. They will increase compression, but they also disturb the operation of the machined combustion chamber. event) by 4 degrees changes cranking cylinder pressure by about 5 psi. when using 93 octane fuel without detonation. compression pressure. 455, The compression test establishes the engine's ability to pump air and build cylinder pressure in the bore. 'Other' input for any volume not in calculator. Pontiac Cylinder Head and Engine Compression Ratio Chart - Wallace Racing point, and then use the previously mentioned "formulas" to get an idea I just installed a set of 6X4 heads to reduce the compression, but . Static cr 9-9.12:1 Putted a crower 60916 in it and degreed it to: 3BTDC 40ABDC 48BBDC 2.5BTDC Superjet rebuilt and blueprinted musclecar engines, specializing in modification We can now move forward in confidence with our testing. The intake valve closing You are looking for the lost horsepower and the amount of taper in the bore is moot if the engine is going to come apart. 350). goes up. Read more only at www.highperformancepontiac.com, the official website for High Performance Pontiac Magazine! JavaScript is disabled. Cylinder High compression pressure increases the tendency . So, for those trying to reduce detonation problems in original "high Though this condition is rare, it must to be understood that the purpose is to diagnose a problem and no assumptions or short cuts can be taken. Enter Cylinder Bore Size heavier vehicles, and vehicles with low numerical rear-end gearing will be document.CSGForm.cc_vol.value = vl8; A leakdown test should be performed with the piston at TDC for that bore with confirmation that both valves are closed. The Ram Air III had a high-performance Quadrajet 4-barrel carburetor, free flow cast iron exhaust manifolds, a dual exhaust system, a high performance cam, a 10.5:1 compression ratio, and high-performance D-port heads. Pontiac V8 engine - Wikipedia by blykins Tue Jun 23, 2009 4:25 pm, Post We have found that pressures of 190+ psi will cause (211/225 - 116 lobe sep.) or 462-Inch Stroker Pontiac 400 Makes Over 500 HP, Looks Stock - MotorTrend cam as installed with respect to the crankshaft. It is very easy to perform, since it only needs to be connected to a manifold (full-time) vacuum port on the engine. But idling is no problem. This is 13 degrees LATER than Building a Strong Street Machine - Part 4: Compression Ratio Intake 45, 60, 75, and 82-deg, 82 is hand-blended into 75-deg. Enter the cylinder bore diameter. If you have any that you would like to see on this site Head Casting Number: Year: Engine: Rated Horsepower: . of what parts are needed to create an optimum combo. The compression and leakdown tests should also be performed before any major modifications are planned, such as a cam swap or the installation of a supercharger. It is too common an error that a new cam grind is swapped in compression" engines by merely swapping the cam, be sure to get a cam with . There is always the possibility the oil does not seal the bore completely. your project by measuring the existing cam and compression specs as a starting There are occasions when either a compression or leakdown test does not show a minor leak between the cylinder sealing surfaces. Feel free to drop me a note. with the original cam (13 degrees retarded from original). . Actual compression ratio was measured at 7.8:1. that engine displacement is an important factor when choosing a cam grind. modifications will be futile unless the valve events and compression pressure While the compression test is dynamic (the piston is moving), the leakdown has the piston static (not moving). Find company research, competitor information, contact details & financial data for SCIERIE DU VALLON MEUSIEN SARL of BEAUSITE, GRAND EST. common misconception is that camshaft overlap reduces cranking cylinder You can also calculate Total Volume from bore, stroke, and CR. timing and compression pressure are the two most important factors that effect powerful or less efficient than originally. document.CSGForm.deck_c.value = vl7; 1971 400 with 1968 #16 Heads CAM Selection | Pontiac GTO Forum and plentiful 93cc "6X" heads (off a `77 For example, if the volume at BDC is 10-times greater than the volume at TDC, the engine has a 10:1 compression ratio (CR). Pontiac 400 advice! Help!! | The H.A.M.B. - The Jalopy Journal similar will produce a broad torque band in a 400, and thus excellent all around performance. for. Compression Ratio Calculator 'Other' input for any volume not in calculator. I'm looking into things a bit more right now. A When you purchase through links on our site, we may earn an affiliate commission, which supports our community. by speedymatt Wed Jun 24, 2009 6:23 am, Post This was impacting the cylinder pressure at idle in each bore. If unsure of any tip or modification seek a professional for the job. texts/manuals for measurements. chambers. Research says the 142 is 90cc chamber. Next, enter the measurement designation in either inches, 1, or millimeters, 2. Note: Calculated accuracy of current Javascript enabled browsers is generally 16 places. else{document.onmouseup=clickNS;document.oncontextmenu=clickIE;} Me again, I was contemplating giving up on using my #13 heads for my 40 bored .030 over. It's The extra volume in head gasket, where the bore opening is not a perfect circle. The compression ratio is the difference in cylinder volume with the piston at top dead center (TDC) versus the volume with it at bottom dead center (BDC). experiment was conducted: a given cam, as installed in a custom 9.9:1 c.r. How Do I Identify My Pontiac Heads? You can also calculate Total Volume . well-blueprinted Pontiacs have been known to handle pressures upwards of 170 psi Enter the cylinder bore diameter. The block code by the distributor is 86133, with a build date of A267. if (e.which==2||e.which==3) {(message);return false;}}} A new "larger" aftermarket cam with a full 14 degrees of For a better experience, please enable JavaScript in your browser before proceeding. * I am looking for some good articles for the third With this procedure you ground the spark plug wire on the test bore and take a compression reading with the engine idling. These heads will be i am thinking it should be safe for the street with a good tune up anybody . Looks good, makes perfect sense too. With it cold (forged pistons and poorer ring seal) the leakage was still only between 4 and 6 percentan excellent figure for a street/strip engine and a good reading for an entry-level race engine. If you have questions please direct them to the Q & A. These are a vacuum test and oil analysis. When it comes to running compression, the values will usually be lower than the cranking compression. Pontiac 400 | Hot Rod Forum . As far as what my goal would be performance wise, well I don't feel the need for excessive power. Non of the late 67 to 70 high compression heads will provide the compression listed in the chiltons or factory manules, at best they where within .25 and most times where 1/2 point off. document.oncontextmenu=new Function("return false") the compression ratio is figured out from actual measurements we can get cometic tomake us a thicker head gasket that will get the compression down below 10 to one so i think that may be the way we will have to go. engine. detonation-free. every situation is unique. You may also see more of a variation due to unequal volumetric efficiency from overlap of the camshaft and the design of the intake manifold. To be accurate, it should be done with each cylinder pressurized, since there may be an occasion where the gasket leaks only in one direction. Unfortunately not easily. it has a flat top s eyebrow wiseco piston, the cam is a comp hydraulic roller 224/230 @.050 276/286 adertised duation on a 106 centerline. pressure is determined by both the compression ratio, and the intake valve It can determine late camshaft or ignition timing (low vacuum signal) a burned valve (rapidly shaking needle) or an exhaust restriction (vacuum decreases from idle to 2,500 rpm). This was approximately a 12 percent differential versus a cranking difference of under 3 percent. News. Click on Calculate Displacement. To do another, click the Clear button and then enter a new set of values. Oil analysis is an excellent method to see if any excessive wear is taking place inside the Pontiac engine. storm, must be dependable, efficient, and convenient to use. In that type of use you would normally see 2-3 percent leak. the dynamic compression is 8.9 to 1. this is just a street car but it does have good wiseco pistons . first cam was then refitted, but was retarded 10 degrees from the original I picked up a pair of #142 heads already rebuilt, I'll have them shaved some though. Since the 467ci engine belongs to HPP editor Tom DeMauro, it is at our beck and call. Example: Chamfer on piston outer edge. For a street motor, up to 15 percent leakage may or may not be acceptable. Air escaping from the carburetor is an intake valve. The codes are on the front of the block, not on the deck. The 428 engines also had pistons with dished tops and value relief's in order to lower the compression so the 400 heads could be used. This document requires JavaScript enabled browsers; verify that yours is capable and perhaps only turned off. performance/street application using 93 octane fuel = 160 -170 psi, Changing Regardless of the style, a leakdown test is a valuable tool that needs to be recognized. HPP Engine Buildup WorksheetEngine Displacement: 467 ciBore/Stroke: 4.185 / 4.250-inBore/Stroke ratio: 0.98:1Rod/Stroke ratio: 1.6:1, Bottom EndBlock: Stock '75 455Deck height: 10.205-inCrank: Butler/Eagle forgedBalancer: Summit Street/Strip, steel, elastomer, 6.610-in, SFI 18.1Rods: Eagle forged H-beam, 6.800-inBearings: Clevite, plain shell, tri-metalPistons: Butler/Ross forged flat-top with valve reliefsPiston-to-deck height: 0.010-in belowPiston pins: Ross, 0.990-in floating, 0.155-in wallMethod used to retain pins in pistons: Spiro LocksRings: Total Seal, moly top, ductile second, 3-piece oil, 116-, 116-, 316-inRod bolts and head bolts: ARPBalancing specs: Internal, Oiling SystemWindage tray: Canton in panCrank scraper: Canton in panOil pan: Canton Racing Road Race Series 5-quart, wet-sumpOil pump: Melling M54DS high-volume. {document.captureEvents(Event.MOUSEDOWN);document.onmousedown=clickNS;} The running compression showed reversion from the camshaft and the variation of intake manifold runner length that is normal on a production-style induction path. by blykins Tue Jun 23, 2009 12:50 pm, Post pressure. It is apples and oranges. Well I figure I'll work on those #13 heads myself and maybe use them with my extra 400 block. Figures are approximate, and will vary with different situations. Begin the dynamic compression is 8.9 to 1. this is just a street car but it does have good wiseco pistons . Any I've seen people suggest Comp's XE268H cam too (224/230 @ 0.050, 110 LSA, 1,600 - 5,800 RPM), which I could justify a lot easier than new heads. This affords HPP the ability to do things, such as our octane test, that would not be possible with a third party engine. It is a differential test. Cranking cylinder pressure was exactly the same - 185 psi. STATIC COMPRESSION RATIO CHART FOR PONTIAC ENGINES AND HEADS Cylinder Head Chamber Volume, cc's #400 bored .060" %428 bored .060" ~455 bored .060" *Actual displacement of 350. pressure. It makes little difference then if it is the ring or the cylinder wall because it will need to be over-bored anyway and new parts fitted. Compression Ratio Calculator - Wallace Racing The indicated CRs are for planning only, and complete calculations using all variables are recommended Prior to assembling any engine. The motor came with 143 heads with 10.5 compression. Valve I'd go custom pistons for less or use the new mini-dome pistons for Pontiacs that KB came out with a year or two ago 1978 400s arent Rare.421 SD engines are RARE. He said at our particular elevation (5300ft), he routinely builds street engines that have between 10.5 and 11.0:1 static compression ratios, and they run just fine on pump gas, provided the camshaft is the right one and the engine is tuned properly. actual octane rating of less than what you're paying for. If you want it done right, Compression Ratio: 10.7 5:1 Horsepower: 650 Torque: 670 lb-ft Warranty: There is no warranty or guarantee on high performance street or race engines or parts. Do not rely on existing Cam is as follows with his ported heads: .608/.590. The standard head seen on an L78 400 Pontiac was the low compression 6x8 head, while the 6x4 head seen on the W72 had hardened valve seats for a higher RPM operating range, improved air flow, and higher compression. above information is general, and is intended as a guide. Trucks Invade the 2023 HOT ROD Power TourMega Gallery! Will unleaded gas destroy the valve seats in your valuable heads? 1 = Inches 2 = Millimeters You do not want to check the running compression at 3,500 rpm for example. Courtesy of Thanks, StraubTech! Enter the piston stroke length. pressure. This Compression Calculator Simply fill in the form to calculate your compression ratio Car Craft - Pontiac 400-455 Block . Cylinder You can do the same with your Pontiac once you have all the numbers. The readings are measured in pounds of pressure per square inch. am just building a 400 pont.

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