compression / Psi

[mikeoxford]

right then

building a completely hybrid engine.

what is the maximum PSi compression i can have?

i will be fine with valve clearances and the like ive checked all this, problem i have is i dont know if by fitting a head if it will raise the compression ratio too much, and no one can give me a definite answer as there are too many factors involved, SO

what i propse to do is assemble the engine roughly, and then just compression test the pots to see how much PSi is given.

whats the most PSI i can have.......? before problems will occur or detonation issues or whatever

[Aragorn]

ill shed more light since he aint:

hes fitting a worked 1300 head to a 1600 GTE block :o

a compression test SHOULD give some idea of the comp ratio but what u gorra remember is that once the engine heats up these numbers will all change

i say the only REAL way of working it out is to measure the piston dish and the head's clearance volume and calculate the compression from that

if its been heavily skimmed and u fit it up the compression could be 12 or 13:1 = melted pistons

as ive said my prefered course of action would be to buy a GTE head and inlet manifold for the 40's and use this instead - much safer

also as CP pointed out - running 11:1+ compression ratios on everyday engines is bad due to "wildly varying valve and piston temperatures" caused by the high compression ratio and this will cause more wear than is normal on the engine especially during every day use

[mikeoxford]

as a temporary measure i could always fit 2 head gaskets while my uncle machines me up a nice spacer plate to lower the comp ratio.

also aragorn mate i think it has big valves in it the 1300 head - thats why i want to use it, as well as it having much bigger ports etc etc.........

[Aragorn]

as far as i know the E16SE is about the best flowing head of all

it is VERY similar in design to the lotus designed C14SE head used for the SRi which is about the best standard 8v small block head and im sure its gonna have better flow characteristics than the 1300 head

if its had a LOT of work done then maybe it will match or possibly beat the GTE one but do u know what its had done??

as i said up there

slapping 2 gaskets on aint the solution - u NEED to work out the volume of the head and piston dishes or you wont be able to calculate the thickness of spacer u require

[locky]

Mike, av u tried talking to Bleidenstein or Velos? maybe they can shed some light on the situation!

[mikeoxford]

what is the maximum PSi compression i can have?


:roll: :lol:

anyone?

[Dan]

not sure about max psi/compression but when interpro did a check on mine when engine was warm it went from 230-232psi across all four which as far as i know is quite high

[Aragorn]

dan aint your engine running summat like 11.5:1??

[Dan]

dont know off hand as there aint a way to convert it from one to the other, all i know is the compression i have doesnt harm the car in anyway, at a wild guess which really means f all it 'might' be around 11.1

[rysmee]

i might as well ask while your on the subject as i'm rebuilding a 1.6.
what advantages does the 1.3 head have over the 1.6?just bigger valves or what?

is there an optimum comp ratio to aim for ? i am rebuilding to gain maximum power(but keep it useable for everyday driving) from a 1.6 and prepared to spend ALOT of money.

[Stuart]

as cp has said, and a few otehrs (possibly form him from some other source) a high CR can cause premature wear in an engine that isnt prepared for it.

ir a high CR increases the engines thermal efficiency whic makes it run hotter, so running at full bore will get the pistons good and hot, but then come down to town driving and the pistons will cool rapidly and cause intresting problems lol. but that tends to happen at 13:1 and up

id say stick around 11:1 at the msot for reliability etc.

as for "psi" limit it hits around 500psi when the engines burning fuel at high rpm lol (even reasonably std cars) and the pressure curve will stay similar for most engines since its a fundamental principle