Rb20det Running 5 Cylinders

[rb2?]

hey guys im after a solution for my rb20

we replaced a blown head gasket a few nights ago and placed everything back on the engine, turned it on and all of a sudden its idling weird. We know that the timings out but that can be fixed. We had checked everything before it went back on. The plugs, coils, torque settings, camshaft placement etc, etc. Unfortunately after a quick compression test, my mate found out that the front bore wasnt getting enough compression. What could it be? Has anybody had the same problem before, i cant afford to take it into an mechanic atm? Soo please help

Cheers Tom

[blind_elk]

Hope you haven't bent a valve when clamping the head back down. How much compression is "missing" (compared to other cylinders)?

Have you isolated which cylinder is running crappy? have you checked that you haven't bent a pin in one of the coil pack connections?

[rb2?]

Hope you haven't bent a valve when clamping the head back down. How much compression is "missing" (compared to other cylinders)?

Have you isolated which cylinder is running crappy? have you checked that you haven't bent a pin in one of the coil pack connections?

Thanks for your reply. Um all the coipacks are mint as ae. And its the 1st cylinder from the radiator side.

I did a 'quick compression test' without a compression tester valve by jst feeling how much compression there was in all cylinders by placing my hand over them, and i could definently feel a huge drop in the one cylinder compared to the rest.

It could be a valve, how do i be sure of it though?

Thanks Tom

[blind_elk]

So, you've disconnected each coil and determined that nothing changes when you disconnect #1?

And you need to do a proper compression test, with a gauge. "seat of the pants" measurements are useless as a diagnostic tool.

[Sheriff Wan]

A leakdown test would tell you if its a valve or not...

However, you would need the proper guage to tell you %'s

Basically all you need to do is

- Pressurise the cylinder using an air gun and ensure nothing can get out via the spark plug hole.

- Piston must be at Top Dead Centre this way you will hear the air escape 1 of 3 ways

1. Out the plenum side = intake valve(s)

2. Out the exhaust side = exhaust valve(s)

3. Down past the piston into the crankcase = Rings

I think doing it without the proper guages though could be hard as you wont be able to measure how much or what % is escaping...

My 2 cents

[rb2?]

cheers guys , truly appreciate it. I'll do a proper test, especially see if its leaking on intake or exhaust side.

[rb2?]

hey i did a compression test... and holyf*^#

1st 0psi

2nd 149psi

3rd 139psi

4th 139psi

5th 129psi

6th 122psi

plss help im such a newbie at this stuff

Thanks Tom

[blind_elk]

Best case you've bent a valve. Worst case, you've also punched a hole in #1 piston.

Pull the head back off, tell us what happened.

[Sheriff Wan]

That sounds quite bad, I would be thinking your piston has popped up to see what all the fuss is about an kissed your valves...

Agree with blind elk - you need to get the head off to have a looksie.

Let us know & Good luck

[rb2?]

cheers guys, again.

I will do as soon as i get my tools sorted.

Tom