Jump to content
SAU Community

Recommended Posts

Hello, after engine rebuild(new cylinder liners and piston rings, arp headstuds, metal cometic tripple layer gasket, all new main/rod bearings) and roughly 100km made I did measure compression and it’s (1-6) - 80, 60, 90, 120, 110, 135. It’s rb25det series 1 - hydraulic lifters. Measured on cold engine. Didn’t check on hot due to overall car problems such as broken 3rd gear, idle issues, misfire etc. I did smoke test only on 2nd and 5th cylinder bcs soldering iron used with this method broke itself. So after setting cams to side - side 90 left/right angle I can see smoke coming off from intake manifold and turbo exhaust flange. 5th didn’t notice any smoke. Shop did head, valve etc job but I assemble it by myself. So I thinking about lifters. I don’t remember if they were soft or not it was long time ago. In my opinion I didn’t bleed them and they can be opened more than they should be. Can it be more likely possible? Or timing can be off by 1 teeth and can cause such weird compression? But if timing would be out wouldn’t it be like such big difference across all cylinders? Please help I’m so sad it happened. 

Link to comment
https://www.sau.com.au/forums/topic/486230-weird-compression-after-rebuild/
Share on other sites

More likely you didn't bed the rings in correctly and have glazed the bores. Running with misfires on a fresh build is somewhat of a no-no.

Surely no-one "smoke tests" the combustion chamber? That's what a leakdown test is for. Smoke testing is, um, a bit of a wank at best, and only really useful for external pipework.

 

But if I smoke test 5th cylinder it’s all ok, no leaks 

when I try with 2nd it’s leaking exhaust and intake, it doesn’t come from oil dip stick. 
 

so maybe when car was running poorly, rich or sth. Spark plugs were black and covered in charcoal or sth lookalike. could potential contamination make valves not seal properly?

is there also a possibility that rb’s don’t have equal performing cooling passages  meaning back of the engine will be hotter than front. Can this cause improper wear if engine was running under load for short time? Or carbon build up could just burnt from 4-6 and is still on 1-3?

 

I out of my head like really. Timing is as manual crank-exhaust 47, exhaust-intake 38

at this point I thinking about give it a try and make another 500-1000km and check if anything change, if not I will most likely disassemble engine head /or whole engine and send it back to rebuild. It’s killing me 
 

 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Yep, there's a very minor drift left that happens a few seconds after letting go of the steering wheel, but not enough to bother me. Enjoying the car still!
    • Got you mate. Check your email!
    • I see you've never had to push start your own car... You could save some weight right now...
    • Sounds good.  I don't 100% understand what your getting at here. When you say, "I keep seeing YouTube videos where people have new paint and primer land on the old clearcoat that isn't even dulled down" do you mean this - there is a panel with factory paint, without any prep work, they paint the entire panel with primer, then colour then clear?  If that's what you mean, sure it will "stick" for a year, 2 years, maybe 3 years? Who knows. But at some stage it will flake off and when it does it's going to come off in huge chunks and look horrific.  Of course read your technical data sheet for your paint, but generally speaking, you can apply primer to a scuffed/prepped clear coat. Generally speaking, I wouldn't do this. I would scuff/prep the clear and then lay colour then clear. Adding the primer to these steps just adds cost and time. It will stick to the clear coat provided it has been appropriately scuffed/prepped first.  When you say, "but the new paint is landing on the old clearcoat" I am imagining someone not masking up the car and just letting overspray go wherever it wants. Surely this isn't what you mean?  So I'll assume the following scenario - there is a small scratch. The person manages to somehow fill the scratch and now has a perfectly flat surface. They then spray colour and clear over this small masked off section of the car. Is this what you mean? If this is the case, yes the new paint will eventually flake off in X number of years time.  The easy solution is to scuff/prep all of the paint that hasn't been masked off in the repair area then lay the paint.  So you want to prep the surface, lay primer, then lay filler, then lay primer, then colour, then clear?  Life seems so much simpler if you prep, fill, primer, colour then clear.  There are very few reasons to go to bare metal. Chasing rust is a good example of why you'd go to bare metal.  A simple dent, there is no way in hell I'm going to bare metal for that repair. I've got enough on my plate without creating extra work for myself lol. 
×
×
  • Create New...