Turbo build running problem possible headgasket or Pistons - help please

[djx11b]

I had a running Saxo vts turbo build (see my build thread). I wanted more power so I purchased a j4 bottom end forged engine with the following spec

Engine Spec - standard 16v block with wossner forged low comp pistons, standard rods, ARP rod bolts, new bearings everywhere, and been professionally board out 0.2mm.

I fitted my fully rebuilt jp4 head on to the forged engine block that I got rebuilt myself by a local company and it was on the original engine for 2000/3000 miles and had no issues.

I got the new engine fitted in with the recommended jp4 headgasket and it ran off boost for 50 miles no issues but it then started to ideal rough and run awful sounded like it was running on 3 cylinders.

I checked spark plugs, coilpack and injectors. Coilpack was ok. All injectors were ok and swapped them over to double check. One spark plug was wet and the others were dry. After removing the spark plugs I noticed that one Pistons was gleaming clean like new and the other three were blacker and carbon up.

Could the headgasket have failed and let water in to this piston or have I possibly got a issue with the bottom end ?

I pulled the head of this afternoon please see the photos .

Any advice would be great, looking online people are saying if water got in would steam clean the piston. Was very smoky but gasket looked ok no holes but it was wet looking when removed.







Picture shows valves above the piston that was shiny clean

[djx11b]

Bump ... anyone that's built a engine can give some help ?

[Beaniemoo]

Have you done a compression test or a cylinder leakage test?
If not
You could level the Pistons in the bores, put say 5mm of oil in each bore, leave over night, then see if any one has considerably less or no oil in it?
Also turn the head upside down, all valves closed, fill each dome in the head for each cylinder with petrol, see if any one leaks out quickly or more quickly than the others

That will let you know if there is a mechanical issue

Did you check injectors weren't leaking when pressurised?
If not you could plumb in the fuel rail but not fit it into the inlet manifold, activate the fuel pump and see if any injector leaks at all.

[djx11b]

I did a compression test all showed 100 psi and with oil stayed the same thinking the tester may be faulty so ordered a new one as even with low compression Pistons seemed low.

Every piston showed the same 100 psi no difference.

The injectors I took out and tested all were ok and no leaks only fitted recently and genuine pico injectors that were bench tested and all were fine.

I'll try the oil test in the Pistons and see what happens.

The head was fully rebuilt an tested less than 2000 miles ago and was all ok with no issues.

I'm thinking the headgasket and bolts may have failed when rebuilding or the rings have went but leaning more towards the headgasket at the moment.

[djx11b]

Braved the cold and snow today and checked the Pistons and head out.

The Pistons seem fine put same amount of oil in each cylinder and left them while I moved on to the head. They all stayed at the same level and nothing dropped.

The head I removed the manifold and filled up each side both the inlet and outlet with petrol. No leaks from either side all the valves seem fine which I thought they should have been with it only just being fully rebuilt.

I'm going to order a new headgasket and set of head bolts. Clean up the head and block then refit it all back on and do a new compression test with the new tester.

It looks like it was the head gasket that has failed with the others tests all checking out ok.

[BLAKEYBONUS]

What is the arp conrod bolts part number?

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[Johnjourno]

I remember doing the missus head gasket and the head bolts packaging had the torque settings on, which also stated they need slackening and re-torquing after a period, can't remember what that was though. Defective gasket? No signs of gasket separation? Next thing would be checking your head and block with a flat edge and feeler gauge, could always take the head for a pressure test, probably £20, and that rules out cracks in the head/valve seats.

[Johnjourno]

100PSI is slightly low, but being a turbo, with low compression pistons etc, is that normal for the build? On a non turbo I'd look for 120-150PSI.

[Chipwizards]

There's an awful lot of oil around, especially in the bore with the clean piston. Was it not smoking heavily?
The deposits on the other pistons look very heavy for the mileage covered too, were the ring gaps set properly?