whats the difference between red and blue 253

[Calum]

QR prefix would be high comp. Low comp got QS prefix during the years relevant to Sandman production. Holden achieved the different compression by the shape of top of pistons.

Blue 253 will have the prefix WR or VR.

Thanks men 'just for the back of the mind thing' but if its really only piston shape that makes the difference an old rebuilt engine still could be any thing !!

[HK1837]

That is right. Once they are rebuilt they can be anything. Only things that can't really change is the late red and blue engines have longer valley head bolt bosses, and the early reds (pre HJ production) have a neoprene rear main seal.

[Kingsandman]

My bad, its a red block ive just scraped blue paint off and found the original red, the engine no qr588710 casting dates 18j4 , does that eng.no corospond with cast date.cheers andrew.

[Sandaro]

I don't have comprehensive numbers records that others have, but would seem to be fairly right.

[HK1837]

Pretty close, probably an early HJ engine but might just sneak into a very late HQ.

[Big Rob]

Yeah, QR is a HQ 253 high compression.
No way any were painted blue from the factory, it's been recoed and the owner wanted it blue for some reason. (Is the van blue?) It was common back in the Show Van era to paint the motor to match the exterior colour.