Compression Test Results

[axe s]

Well long story short,

My step father is putting an RB30E+T into his EH holden,

Long process, finally got it going, took it for a bit of a drive to set the boost controller...

Pulled up to check where the tyres were rubbing, and noticed a miss, took it back to the house... did all the normal checks, couldn't find anything...

Next day my step father checked it over and found milky oil on the dipstick and in the rocker covers,

Did a compression test 140psi on 1,2,4,5 and about 125 on the 3 and 6

Motor was rebuilt about 10 years ago and done bugger all K's since, was in another EH that was a weekender...

What's do u's reckons wrong?? we're in the process of removing the head as we're leaning toward head gasket...

[GT-RZ]

looks like that due to the oil colour. maybe the gasket is fine and when the rebuild was done the head was slightly warped and not re faced?? Generally i think most alu heads need a skim.

maybe if you know details of the build?

[axe s]

by the sounds of it he would have... he's sending him an email at the moment,

it's was also blowing steam out the exhaust... that was our main reason for thinking gasket...

also radiator lost fluid and pressurized with gas...

inside exhaust was also wet...

Edited July 1, 2009 by axe s

[Mattee]

sounds like a head gasket to me. Also, I'm assuming the motor was originally from a VL, Holden in all there wisdom decided to get the heads for that motor made from there own supplier because it was "cheaper", and it was, in every sense of the word, hence VL's had a problem with the heads cracking when the engine was over heated

[axe s]

mmm... That's something i didn't know...

I didn't overheat, it was only a short drive and we were watching coolant temps...

[Mattee]

yes, but it's something that may have been overlooked when the engine was rebuilt....

[GT-RZ]

I always was led to believe the heads in VL's cracked due to radiator placement and air getting trapped in the head causing hot spots...

[Mattee]

that's true, the radiator sits lower than the head, which makes them hard to bleed properly, and causes them to overheat.

but the cheaper materials used also made the head crack instead of just blowing the gasket

[axe s]

well, we'll find out tomorrow... lol...

anyone know a good place to get a head gasket... we're thinking of going a bit thicker to lower the the compression a bit...

[Jmaac]

+1 for a headgasket. nissan sohc heads are fine, they do not crack because they're made of a 'cheaper' material-they're all made from the same standard grade, its its all about process, both before the casting is made and operating conditions after. Anyway as above, the heads would only warp/crack if the cooling system wasnt bled correctly (most people either still dont know they have to do this or still cant do it correctly (2 top bleeders))

Genuine Nissan headgaskets are the best to go by in my book, even Supercheap ones are up to the task. I wouldnt try lowering the compression... as far as I recall the rb30et compression ratio is already pretty low at 7.8:1. Skim the head, and gain some response unless you want to run huge boost.

[axe s]

Yeah it was bleed properly... checked 3 times,

It's not an RB30ET, it's an RB30E+T... so it'll have higher compression, thats why we want to lower it a bit

We're looking at a cometic 1.88mm/0.074 gasket..

[axe s]

Found out the pistons are Hypatecs

i can only find a little bit of info, but looks like the range form 7.5:1 - 8.3:1

My guess would be that it's got the 8.3:1

Don't know what size gasket to use now...