right done a search and couldent find anything is the pm billet head anygood ? the one that sits under the original skull cap not the gold one i mean as wann keep everything on the downlow ? thankyou steve if anyone knows what the cimpression ratio would be on it that would be brilliant 55mm crank 172 kit with a 2mm gasket i believe thanks again
if you cant work out the compression ratio yourself why do you need to know it exactly? there higher compression but still ofset plug. the malossi head really is a big ol peice of misshaped rubbish made to produce torque and keep engines happy for a long time. a different combustion shape is only any good if your engine can actually do anything with the higher compression. usually upping compression in an enigne for no reason reduces power as you gain pumping losses. ie, your wasting power squeezing a mixture into a density it cant even combust at the correct speed for. in short, yes there good to bolt on. the reasons behind this run alot deeper than a single line explination.. plus, compression on a 2t is dependant on the exhaust port timing. the compression ratio you would be asking for would be the static compression (ie the volume of the head compaird to the volume of the cylinder with the piston at bdc) in other words.. if the head has a vol of 17.2ml then the static compression on a 172 is 10:1... again, your exhaust port is open half the stroke almost so the compression go's up and down as the pressure rises and drops inside the exhaust. bolt the thing on and do a compression test. psi is more important than a mathmatical figure. heads and exhausts go verrymuch hand in hand
hi thanks for the reply and yes static compression ratio is what i was after i cant calculate the compression ratio myself as i dont have a head to mesure the volume ? or a bore kit for diameter crank well i guess thats a 55mm stroke lol but again with the gaskets at 2mm i need to allow for squeeze on that etc i was trying to conjure up a medium beetween a road engine and a race engine and if the static cr is more than 12.5 it really is gonna need 98 99 ron as a minimum by my standards. and about the exhaust part thanks very much i sometimes forget on 2ts the piston is the valves aswell lol im used to 4t tuning so essentialy enlarging the exhaust port is gonna give more time were compression is dropping yet i can chick more in at the same time hmmmmmmm right im off to have a little read. when i get a crank and bore kit i can cc and mesure comp on them then decide if i want a head aswell thankyou steve
by your guessing this AINT A 4T ENGINE?!?!?!?! i hate people treating them the same, totally different. its like compairing meat to fish. bell up pm, they make em. ask THEM what cc there head is... fairly easy to work out from that. as for your guestimations about compression ratio's, they are based on 4t tunning and of no use to you.. try road fuel, if you know the symptoms of detonation/blowout/slow burn then you know WHY to ajust the fuel, rather than blindly fgollowing "above 12:1 means 98ron fuel) you can only buy 97 ron.. you will need 97 ron with any pm head, i use it with any 172.. you cant buy or use anything higher on the road legally and octain boosters strip 2t from parts so your using 97 ron or 97 ron.... so again, your question is pritty irelevent.... again, bell pm if you want information on THERE parts.
ok thnaks again and to add shell sell 98 ron some tescos do a 99 and im not guessing this aint a 4t i know the difference im just not as familiar with 2ts as i am with 4ts i build low comp motors for boost and have only worked on normal cylinder heads. and when boosting for the motors i build it is simply bigger is better. from what ive read and been told 2ts are very different when it comes to the port work etc and again exhaust design. thanks again steve
exhaust is everything.... the static compression is variable on how well the pipe "scavenges" at any given rpm... you can almost double the compression inside an engine with the correct pipe. stick with the usual 10:1 compression static, anything above this just eats pistons really, anything under and your missing out on power. again tho the actual compression isnt the factor, the pipe, the squish area and the shape of the head are more important than its physical volume. the pm head's used to be claimed at 12:1 i belive... altho dont quote me, best to ask them to be honest. definatly too much for an unported malossi kit, whatever is gained is simply lost to pumping losses.
cheers mate i will ask them but there advice is from a sales point of view so everything they make will be brilliant acording to them cheers
well, ask to talk to one of there so say tunners... according to them they weld the pipes up there, cnc out all there own heads, cast there own cylinders LOL there should be 20+ people there making things so i dont see the problem one of them comming to the phone to talk to you about the bits they sell. unless of course they have one mechanic, a sales team and a whole load of box's from china
