Compression

[ReeceGTS-T]

Hello,

I recently purchased a r33 from a person for really low cost knowing that there was bugger all compression in one of the cylinders, i done a compression test all 6 before i payed bugger all anyway just to check.

(i have suspected bent valve or it is not seating correctly 100%)

after pulling apart at the motor for a good day i finally got the head off and checked the valve faces, there was one valve (exhaust) in the cyclinder that had no compression that caught my eye immediatly due to it's colour difference from the rest.

it didn't have an obvouis bend or miss-seat, so i poured some oil down the exhaust exit to see if it will trinkle out the valve, still nothing after 5 mins....i have left the head sitting on it's side with all exhaust exits filled with motor oil to see if any would leak after a few - 24 hours.

am i doing the right thing?

could there be another reason for the problem?

in other words....help!! lol.

and also what is the best valve spring compressor to buy and where do i get it from because it is hard to find one that suits the rb25 bucket like spots where the spring seats......

thanks,

reece.

Edited October 1, 2013 by ReeceGTS-T

[StevenCJR31]

The oil maybe to heavy (or thick)to leak out past the valve seat

When I did this test I used degreaser as its a lot lighter and I wanted to clean the ports anyway

[ReeceGTS-T]

okay i will try that. so even a gap that small then will cause very low close to 0 compression?

[ReeceGTS-T]

okay i will try that. so even a gap that small then will cause very low close to 0 compression?

[blind_elk]

Had an instance many years ago with a L-series engine. One of the rocker arms had a small -ve clearance, ie too tight, which caused 0 compression. Setting the clearance correctly bumped the com,pression to 170 or so.

So, yes, the slightest gap in the valve seat can cause a massive loss of compression.

[ReeceGTS-T]

okay thanks for the advice. since I've got it apart should I put new valves all the way through. I will be doing all the usual suspects like seals and what nots....

[jiffo]

Best to do some sums first.

New valves, seats, resurface, gasket sets........and you haven't looked at the more expensive stuff like ring lands.

Weigh that up against another good running engine, a no brainer.