Rb26 Compression

[Space Goat]

hi ive been thinking of doing a rb26dett conversion for some time now on my r31 series 3 wagon (yes a r31)...

ive found some decent stuff for sale on here to do the conversion... my main worry with buying a halfcut is the state of the engine... ive had the motor compression tested and got 140-150 all round... is this too low for a gtr... ive been reading lately in hpi that a ideal compression is 160psi... is this 140-150 compression too low... should i keep looking... how much range should i allow in the compression (ie say 143 lowest 152 highest for example) is there a percentage that the compression figures should range in???

also on the gtr note... can i use the gtr box to run in rwd and block off the front of the transfer case??? what to do

thanks for your help

Rick

[psybic]

170 from factory.

allow about 12 difference between max and min.

allow minimum of 126

difference of 9? don't do it.

if it were an even 140-150, eg, 144min and 147max, that would be great, imo

[Beer Baron]

difference should be no more than 14psi from best to worst according to the workshop manual. I think anything above 140psi is acceptable as long as they are fairly even.

[T04GTR]

140ish is fine.

iv seen them range from 110-140(not on the same engine.

its also important on the type of tester used. the ones with the long hose give a low reading, the one to use is the push-on type.

you should get the bores inspected with a borescope too.

generaly 10% variation is acceptable.

[blind_elk]

Probably not bad if the engine was cold at the time of the test.

[RB30-POWER]

if the engine is cold as stated above, everything hasn't expanded and isn't offering maximum sealing, so those readings would be fine.

also one of the main things you should look for is even readings across all 6 pots, if one or two pots are out by a significant margin, then its fair to say that something may be a miss inside the engine.

if they are all fairly even across the board then its fair to say its an honest motor.