KA24E compression ratios

[180fan]

Alrighty guys, I know this may have been brought up, but for sure what's the compression ratio on the KA24Es? I've always assumed they were 9.1:1 but some say they were reduced to 8.5:1 after a certain date, and I've even heard of an 11:1 for stock compression ratios. Checking the back of my FSM, it says 9.1:1 but I've also seen a service bulletin saying 8.6:1. So what gives? Anyone have info on the compression ratios with dates or motor model numbers?

[Thee 240sx Owner]

Like my 240.. mine was one of the first 240s made and for the first 6months of their conception... they came with high compression pistons... 9:1:1 but after 6 months they changed the pistions to low compression hencing the 8:6:1... and about the 11:1 compression.. thats from people doing E to DE head swaps....

[180fan]

cool thanks for that bit of info. The first six months of their production, do you happen to know about what time frame that was in? Some local guys are thinking about picking up my old sohc motor but were getting into an argument about what compression it was. The car itself was assembled in august of 88 and not sure if that's within the first six months of the conception of the 240, all I know is that the first owner preordered it like a while before they rolled out to the dealerships..

[Thee 240sx Owner]

yes it is.. mine was made in 8 of 88 as well and i had the highcompression motor so yes it is in the time frame

[:: orion ::]

Easy way to tell: Look for an intake air temp sensor.

When they lowered compression, they added the AIT sensor to the airbox.

The TSB describes all of it...it can be found online.

And there is no 11:1 stock...that'ds attainable if you put the SOHC 8.6:1 pistons into a DOHC motor.

11.7:1 is the result if you use the early 9.1:1 pistons in your DOHC...

- Brian

[Thee 240sx Owner]

[quote=" :: orion :: Easy way to tell: Look for an intake air temp sensor.

When they lowered compression, they added the AIT sensor to the airbox.

The TSB describes all of it...it can be found online.

And there is no 11:1 stock...that'ds attainable if you put the SOHC 8.6:1 pistons into a DOHC motor.

11.7:1 is the result if you use the early 9.1:1 pistons in your DOHC...

- Brian [/quote]

not sure if you saw but i did state that it was from doing the head swaps

[red240ne]

piston swap

[driftaholic]

all it takes is sohc pistons + dohc head.dosen't matter if swap a dohc head onto a sohc block or swap sohc pistons into a dohc block, same result

[sil80drifter]

you cannot swap a DOHC head onto SOHC without SEVERE modifications. Hence piston swap. from SOHC to DOHC.

sil80

[driftaholic]

not saying the head swap is easy, just that it doesn't matter what block you use, as long as it's the sohc pistons and dohc head, cr is the same

[sil80drifter]

point understood. just looked at that post where the guy has been swappin over the DOHC head onto his 1990 engine... hasn't got hsi issues setteled out yet, but he's gettin there. seems really cool so far.

sil80