Compression Test

[hispeedimports]

Hi,

I did a compression test with engine cold, because I can get it to start.

Results: #1 on - 165, 170, 190, 180, 180 & 165.

The manual recommend between 142-156 psi with the engine hot,

are these numbers ok taking in consideration that the engine was cold?

Thanks in advance, Mario

[jlevie]

There is more spread than desirable. but the lowest numbers are good. The high numbers could well be carbon in the head, which suggests a problem with the engine management, system, fuel system, or injectors.

[Quinthirty]

What if it reads something like this?

100
120
125
140
140
150

Noticed that the PO welded two hex bolts with nuts at the heads as I assumed that the heads were "rounded." I'm assuming that the head bolts weren't in the correct torque because of that. Could possibly contribute to these numbers?

I'm thinking of:
1. checking of the head if its warped due to PO's cheap solution, or
2. do you think that a head bolt swap would just fine?

[jlevie]

Those numbers would tend to make me think that, a) the rings/cylinders on the first three cylinders are bad, b) the head is in serious need or a rebuild, c) both of those. A leak down test will give a better idea of where the problems are.

[Quinthirty]

Thanks Jim. The welded bolts are actually on that side of the head, that is why I was thinking that the bolts are not on torque. I say this because the car is not smoking and pumping oil both on idle nor high RPMs. Plugs are not oily either. Having said that, would it be safe to assume that the rings are fine?

I agree that my head may need rebuilding. And if rebuilding, we mean:

1. shave head (if warped). But would a thicker head gasket be a good solution if warpage is minimal? What is considered tolerable warpage?
2. replace valve guides, etc.
3. re-seat, re-grind or replace valves, seals, springs, etc?

Thanks again!

[jlevie]

In addition to that work on the head, have the cam profiled to see if it needs to be (or can be) reground or replaced.

You don't fix head warp with a thicker gasket. You fix it by making the head flat.

[jeffnhiscars]

Before pulling the head you may want to do a wet compression test as well which will give you better info on your rings.

[Quinthirty]

Jim, thanks again. We'll do the recommendations.

Jeff, I'll ask the mechanic if he did a wet compression test. Thanks!