compression on a 400, need help
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compression on a 400, need help
hey, im fixin to test my compression on the 400 that me and my dad has for our project and im going to test the compression on it within the week, whenever school, work, and other activities allow. the thing is though, the compression tester i have tests it in pounds. what is the optimal psi per cylinder on a 400? and how do you change it to the regular ratio, such as 8:5:1 or whatever the compression might be.
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From: Albuquerque
The static ratio is computed solely on the swept and compressed volumes. You can't change it anyway without taking it apart.
To test static compression (p.s.i.) you need to remove all the spark plugs, prop open the carb all the way (disconect the ignition), crank the engine over about 5 times for each cylinder. You can also add a 1/2 teaspoon of oil to each cylinder and try it again. If it goes up significantly your rings are bad.
You will see something like 110 to 130 pounds on a used stockeer. The main thing is that they are all within 10% of each other.
To test static compression (p.s.i.) you need to remove all the spark plugs, prop open the carb all the way (disconect the ignition), crank the engine over about 5 times for each cylinder. You can also add a 1/2 teaspoon of oil to each cylinder and try it again. If it goes up significantly your rings are bad.
You will see something like 110 to 130 pounds on a used stockeer. The main thing is that they are all within 10% of each other.
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yea, man im borrowing the tester with said for me to yank all the plugs and disconnect the ignition then just put the pedal to the floor and crank it 10 times. also told me about the oil idea too. i sure hope that the pressure is good and high and all. so im shottin for somewhere around 130 odd pounds right?
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lilmanMs, hi paul k
can i add alittle something to Big bears advice, look do not misunderstand me. i know Big bear knows this. i think its the constraints of the internet and he speaks fast and strait up. for exp, many guys do not now or have never been told about holding the PLATES OPEN at crankin speed. i rest my case. i stone agree with the light oil test. i KNOW bear is absoutely CORRECT. but if your comp is low, and it does NOT increase after the oil test, SOMETIMES this will indicate leaky valve SEATS, not stems SEATS. but again i support Big Bear 100% he is shootin sguare with you in my nobody op. good luck. paul k. md
can i add alittle something to Big bears advice, look do not misunderstand me. i know Big bear knows this. i think its the constraints of the internet and he speaks fast and strait up. for exp, many guys do not now or have never been told about holding the PLATES OPEN at crankin speed. i rest my case. i stone agree with the light oil test. i KNOW bear is absoutely CORRECT. but if your comp is low, and it does NOT increase after the oil test, SOMETIMES this will indicate leaky valve SEATS, not stems SEATS. but again i support Big Bear 100% he is shootin sguare with you in my nobody op. good luck. paul k. md
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yea, thats how i like it. dont beat around the bush, get to the meat of it ya know. on the first try feller said i dont have to use to oil and if i have low pressure, around the 90 pounds or so, go back with the oil, about 10 cc's, on top of the piston and crank her again and if the oil pressure goes up, means bad piston rings. and said if the pressure of the cylinders are all over the plac,e complete internal rebuilt. so still shootin for the 130 pound range right? or anythin over 110 good?
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mr lms. paul, 1 more point to add, when i said
Big Bear spoke fast and hard i left one last part out, TO THE POINT frankly i like it to. you are right. the deal is I am the one who cant spit it out without writin a book. folks say paul you talk to much, so be it, but i do care and i am always interested always. i done my best for you but again BB is on it and i dont see nothin wrong with sayin so. the man is smart period along with a +++++++++ more on this SITE go with them and you WILL not go wrong. OKAY i always smile and good luk hey stay in touch okay later me, md.
Big Bear spoke fast and hard i left one last part out, TO THE POINT frankly i like it to. you are right. the deal is I am the one who cant spit it out without writin a book. folks say paul you talk to much, so be it, but i do care and i am always interested always. i done my best for you but again BB is on it and i dont see nothin wrong with sayin so. the man is smart period along with a +++++++++ more on this SITE go with them and you WILL not go wrong. OKAY i always smile and good luk hey stay in touch okay later me, md.
