andres1 Posted May 31, 2013 Report Share Posted May 31, 2013 My friend took his shee to another body of his that's a mechanic to do a compression test, to his surprise the guy said that the cylinders had 235 psi on each cylinder which is crazy high for his set up or may be his compression tester wasn't right..... anyways I just would like to know what ur opinions are in this matter. He has a 4 mm with stock bored, 34 mm mikunis, vforce 3, cool head with 20cc domes, and t5.!235 just sound like too much a least that's what I think. Any help will be appreciated thanks. His cylinders are also ported but I don't know what kind of port job he has. Sent from my SAMSUNG-SGH-I717 using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted May 31, 2013 Report Share Posted May 31, 2013 Normally a heavily ported 4mil with 20 cc domes comes in around 175 to 190 static depending on porting style and target for build I would do a squish test on motor and maybe pull domes and make sure they are cut for a 4mill I have seen numerous people purchase stock stroke domes for 4mil set ups not knowing any better Quote Link to comment Share on other sites More sharing options...
rg97 Posted May 31, 2013 Report Share Posted May 31, 2013 I dont think that porting will change your compression any. First of all, those carbs are waaaaay too big. He probably has no low end whatsoever. stockers or 28's would be the best for 4mil stock bore. About the compression, yes that really way to high. not even sure if it would run if it really is that high. 175 psi should be about good, depending on the gas that he runs. Go somewhere else and have it tested Quote Link to comment Share on other sites More sharing options...
jayhawkatv Posted May 31, 2013 Report Share Posted May 31, 2013 My 4 mil was at 230 each cyl when i bought it. Had 18 cc domes for a 350 in it. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted May 31, 2013 Report Share Posted May 31, 2013 I dont think that porting will change your compression any. First of all, those carbs are waaaaay too big. He probably has no low end whatsoever. stockers or 28's would be the best for 4mil stock bore. About the compression, yes that really way to high. not even sure if it would run if it really is that high. 175 psi should be about good, depending on the gas that he runs. Go somewhere else and have it testedPorting most certainly does have an effect on compression. Carbs aren't determined strictly by bore size. You just assume that the 34's are to big with out knowing tha actual intent of the motor. Where do your opinions come from? Quote Link to comment Share on other sites More sharing options...
dozer Posted May 31, 2013 Report Share Posted May 31, 2013 I was thinking porting would affect compression too. Higher timings mean less time for compression to build, or is my thinking wrong? Quote Link to comment Share on other sites More sharing options...
n2otoofast4u Posted May 31, 2013 Report Share Posted May 31, 2013 I dont think that porting will change your compression any. First of all, those carbs are waaaaay too big. He probably has no low end whatsoever. stockers or 28's would be the best for 4mil stock bore. About the compression, yes that really way to high. not even sure if it would run if it really is that high. 175 psi should be about good, depending on the gas that he runs. Go somewhere else and have it tested Just stop posting 1 Quote Link to comment Share on other sites More sharing options...
amado814 Posted May 31, 2013 Report Share Posted May 31, 2013 Just stop posting You crack me up Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted May 31, 2013 Report Share Posted May 31, 2013 I dont think that porting will change your compression any. First of all, those carbs are waaaaay too big. He probably has no low end whatsoever. stockers or 28's would be the best for 4mil stock bore. About the compression, yes that really way to high. not even sure if it would run if it really is that high. 175 psi should be about good, depending on the gas that he runs. Go somewhere else and have it testedHoly shit, another post of you talking out of your ass. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted May 31, 2013 Report Share Posted May 31, 2013 I was thinking porting would affect compression too. Higher timings mean less time for compression to build, or is my thinking wrong? Dozer.....your completely right. With the changed height of the ports, it makes the time that the ports are "open" last longer and does not close off the port until later in the stroke. Thus giving it less room to start compression. And giving it more time to intake air/fuel charge. This is why our site sponsors will tell you that after getting porting done you need to raise the compression back up.....and then some if you want it to run real hard. Quote Link to comment Share on other sites More sharing options...
bansheesandrider Posted May 31, 2013 Report Share Posted May 31, 2013 I dont think that porting will change your compression any. First of all, those carbs are waaaaay too big. He probably has no low end whatsoever. stockers or 28's would be the best for 4mil stock bore. About the compression, yes that really way to high. not even sure if it would run if it really is that high. 175 psi should be about good, depending on the gas that he runs. Go somewhere else and have it tested Another know it all talking out of his ass. He neeeds to just GTFO!!! Quote Link to comment Share on other sites More sharing options...
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