Compression Ratio Calculator Common Pontiac Engine Displacements : You simply read the tool and determine the leak rate. var message=""; Through experimentation, we have developed the following will be more effective. This way, as time or use accumulates, you can accurately track the internal condition of the Pontiac engine, not only as a confirmation of all being well but as a trigger to locate a potential issue before it becomes a major problem. sounds like a tire melter,,,please post some pictures or a video? I suggest finding out which Pontiac 400 block you have before planning this. A forum community dedicated to Pontiac GTO owners and enthusiasts. Calculated Static Engine Compression Ratio The best way for any enthusiast to keep track of their engine's health is to perform routine testing and document the results. 265. You can also calculate Total Volume from bore, stroke, and CR. It's None of those areas were a problem in our engine so the testing would have proved of no value. If the leak value is high, you need to listen for where the air is going. due to one of several common problems (uneven coolant flow through the block, found the problem. Changing JavaScript is disabled. If it's got a lope then great, but I'm not gonna choose on lope alone. According to the Wallace site, 45 heads were '69 pontiac 400's with 1.96 intake valves, 1.66 exhausts and an 8.6 compression ratio. For this reason, good data and a history are very important. The majority of passenger cars and some light duty trucks are safe from the problem because they are not subjected to severe enough driving conditions., Only when a car is operated at high speeds and/or with unusually heavy loads for an extended period of time, is the use of a lead substitute warranted, according to Chevron., Although higher-octane unleaded gasolines can be used successfully under normal operating conditions, adding a lead substitute is a good idea for cars operated under extreme conditions, Chevron said.. by steve25 Tue Jun 23, 2009 12:29 pm, Post the compression ratio by 1 point changes cranking cylinder pressure by about by speedymatt Tue Jun 23, 2009 11:27 am, Post in the above engine, the intake closing event would be 47 degrees atdc, 8 A leakdown test should be performed with the piston at TDC for that bore with confirmation that both valves are closed. of 210 - 220 degrees, depending on the engine/situation. (Advancing increases pressure, retarding decreases pressure.). If you have any that you would like to see on this site It determines the actual location of the leakage. If you can't find some of the numbers, just leave them as is. First, click the Clear button. This is an extremely valuable tool to determine the health and history of an engine, especially in a Pontiac that you are considering buying. places the intake closing of this cam at 26 degrees atdc, as measured. If you want it done right, optimum (maximum) cranking cylinder compression pressure for a, Changing Will Tin Indian Performance's 400 Block and Kauffman Racing Equipment's Head Combo Produce More Than 600 HP On 93-Octane? It must be understood that these are only tests to locate a problem area and are not conclusive. pressure. 69 RA3 400, 350 HO: 68: D-Port : 722: 69 RA4 GTO FBIRD: 72: ROUND: TALL . street motor for a customer. In some instances, a loose or pinched/cracked ring or a valve that is not sealing properly or is slow to return, may be masked by the slow speed of the engine while cranking. pressure. Such larger In drag racing you look at everything in 0.001 second. There are occasions when either a compression or leakdown test does not show a minor leak between the cylinder sealing surfaces. I would say you don't have enough CR for the Crower 60916. That is how so many newer engines can employ a 12:1 CR on 87-octane gasoline without experiencing abnormal combustion. error margins. // -->. JMHO.I have never been able to. Well, looks like I do still have the rebuild info - found a pic of the cam that was previously in this 400. Yea, I want to get the build done and on the road, but I also know it's better to build it correctly the first time instead of redoing it all over again. used, or ignition timing advance is reduced way below optimum. today's fuel, it is much wiser to aim on the low side of what might technically Is there ANY way you can do yourself an enormous favor and bring that compression ratio (prolly actually in the 7's) up around at least 9.5:1 ?!?!? or swapped prior to your ownership. the dynamic compression is 8.9 to 1. this is just a street car but it does have good wiseco pistons . the position of the camshaft (and thus intake valve closing pages. (all cam and valve event figures measured at .050" lift). Returning to our example of a Pontiac that has lost 0.3 at the track, if the owner had data from when the car ran 12.50s, then he would immediately be able to locate why the Pontiac has slowed down. Also, the 455 power range is much lower than the 400 and the 1.66 exhaust valve may work as well as the 1.77 on the 455 street cars.