Compression Issues Options

[deloreandude86]

Alright guys, we've been working on this for a while now and I'm starting to wonder just what the hell. A few weeks ago I checked the compression getting readings like 36, 42, 46, etc. so we tore the engine down, honed the cylinders checked the valves, rings, gaskets and everthing else, put it all back together and we're still getting the same readings, given it does have a little more power than it did before, as far as compression goes, its the same. Now this engine is intresting because during the rebuild we found out that it was originally a 72 1.7L. However, the bore is 94mm? could this have an effect on compression? and if so are my readings close to what they should be? Also is there a special technique to doing a compression check on the 914 that differs from a standard engine?

Thanks

[nathansnathan]

I'd try verifying the readings with another gauge.

[flash914]

Normaly it's 3 compression strokes for a full test. Are you only doing one? This I think allows the hose on the gauge to "bleed" Kind of like getting the air out of a brake system. The other thing I would question, would be your compression ratio.
If it has 94 mm slugs and a 1.7 crank. ??? Heads over cut to the point that to much chamber. Also cam timing could be off allowing the valves to shut late. Don't know just things to check. Flash (IMG:style_emoticons/default/driving.gif)

[VaccaRabite]

When you do a compression test you need to make sure of a few things.
1) Valves must be set properly.
2) make sure the throttle is wide open.
3) the engine must be warm.
4) crank the engine until the tester does not go any higher. Don't worry so much about the number of cranks.

If the valves are off, the engine is cold, o the throttle is closed - eash of these things could cause poor compression.

My engine was a 1.7 that was turned into a 2056. The heads were cut to accept 2.0 cylinders, and those cylinders were cut to 96mm.

My last compression test was 165psi.

A properly built engine will have killer compression.

Zach

[914Mels]

Somethings not right with your testing. I would suspect a bad compression gauge, with compression under 50 pounds on all your cylinders, your engine wouldn't even start.

[Cap'n Krusty]

Normaly it's 3 compression strokes for a full test. Are you only doing one? This I think allows the hose on the gauge to "bleed" Kind of like getting the air out of a brake system. The other thing I would question, would be your compression ratio.
If it has 94 mm slugs and a 1.7 crank. ??? Heads over cut to the point that to much chamber. Also cam timing could be off allowing the valves to shut late. Don't know just things to check. Flash (IMG:style_emoticons/default/driving.gif)

Three? Try eight compression strokes, paying extra attention to the first two or three and the last two. This is done AFTER a valve adjustment and with the engine at normal operating temperature with all the spark plugs removed and the ignition disabled.

The Cap'n

[somd914]

Somethings not right with your testing. I would suspect a bad compression gauge, with compression under 50 pounds on all your cylinders, your engine wouldn't even start.

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