Zero compression on rebuilt engine

and1 · Postby **and1** » Mon Jun 16, 2014 3:18 am

Hey guys. So I finished rebuilding my engine earlier and have only had the chance to attempt to start it recently.

Checked everything beforehand. Spark is good (new plugs), fuel is present and timing seems to be set correctly (I and E set to timing marks on cam gears and camshaft lobes point outwards on cyl 1)

However upon doing a compression test I had nothing show on the gauge. This was consistent across all cylinders. Gauge works as I tested it on another car.

I'm ruling out the piston rings as I gapped each ring to match the bore and then clocked the rings.

I used ARP head studs torqued to around 60 lb-ft.

This leaves the valve seats...

Is a leakdown test the only to check before I pull down the engine again? Might be hard to do this at home without a compressor though...

Thoughts? Tips?

greenMachine · Postby **greenMachine** » Mon Jun 16, 2014 8:02 am

Cam timing. Make sure timing on No1 is TDC on the firing stroke.

:mrgreen:

Sailor · Postby **Sailor** » Mon Jun 16, 2014 11:36 am

Yep agree, almost certainly cam timing

manga_blue · Postby **manga_blue** » Mon Jun 16, 2014 1:04 pm

Cam timing. Crank on top dead centre and cams like this:

Otherwise, are you using HLAs and did you pump them full with oil before you fitted them? If you did then they may be so full of that most of the valves are stuck permanently open. Just leave it overnight and the excess oil will seep out of them and they'll work fine.

Mr Morlock · Postby **Mr Morlock** » Mon Jun 16, 2014 5:15 pm

I was going to post the doubt about it having anything to do with timing- I did a check to see if I was off beam and got " Your timing has nothing to do with the compression in your cylinders. If you have no compression in any of your cylinders the you either have a cracked head,blown head casket, warped head,cracked block between each cylinder." You could look up that and see the full context. It did go on and say that you need to view the valves operating i.e. turning it over and view with cover off. Manga may well be right but would it affect all cylinders?

manga_blue · Postby **manga_blue** » Mon Jun 16, 2014 6:59 pm

Actually Manga is not right because it's an SE. I didn't read that at first. It has solid lifters, not HLAs.

Still, there'd be no compression if cam timing is way way out.

and1 · Postby **and1** » Tue Jun 17, 2014 4:26 am

I'll have to pull covers off to grab a pic of the cam gears however this is how I have it set up. Cyl 1 at TDC (confirmed with screwdriver down spark plug hole).

Intake cam gear has I at the vertical and the E at the timing marks on timing plate. Cyl 1 IN cam lobe points towards intake manifold side of car.
Exhaust cam gear has E at the vertical and the I at the timing marks on timing plate. Cyl 1 EX cam lobe points to exhaust manifold.

My only other concern is perhaps bent or stuck valves, but that wouldn't explain zero compression across all 4 cylinders will it?

sailaholic · Postby **sailaholic** » Tue Jun 17, 2014 7:00 am

If you bent one in each cylinder it would. Most likely culprit is cam timing out. Stick a screw driver down the plug hole and confirm cams are closing and opening at the right times (and hence also check your tdc is actually tdc)

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manga_blue · Postby **manga_blue** » Tue Jun 17, 2014 2:31 pm

You do have clearances between cams and lifters, don't you? It should be 8-9 thou IN, 12-13 thou EX.

Refer P01-10-4/5 in attachment

01-10 MECHANICAL.pdf

Mr Morlock · Postby **Mr Morlock** » Tue Jun 17, 2014 4:48 pm

The man said "Your timing has nothing to do with the compression in your cylinders." If you do some checks on line or go and see a engine builder they will give you are full list of the possible causes. If it were only once cylinder it narrows it down - 4 is a bit different.

manga_blue · Postby **manga_blue** » Tue Jun 17, 2014 5:49 pm

Mr Morlock wrote:The man said "Your timing has nothing to do with the compression in your cylinders."

Whoever said that is talking through his arse. It's easy to set up cams so that the inlets are open on one upstroke and the exhausts are open on the next upstroke - result: zero compression on all 4.

Go back to basics. Firstly you know that the throttle must be fully open for a comp test? Then take off the cam covers, take out the plugs, put a long dowel down into No 1 cylinder and check the cycle on No 1 while you rotate manually:

1st downstroke = intake stroke: inlet valve open
1st upstroke = compression stroke: inlet and exhaust closed
2nd downstroke = firing stroke: inlet and exhaust closed
2nd upstroke = exhaust stroke: exhaust valve open

All cylinders will follow the same cycle. If the cam gear alignment marks are right at TDC but you don't have a proper 4 stroke cycle then you probably have a problem with the way the gears are fitted onto the dowel pins on the ends of the cams. Otherwise you may have incorrectly identified TDC (which may further suggest something wrong with the way the crankshaft pulley is mounted).

Mr Morlock · Postby **Mr Morlock** » Tue Jun 17, 2014 8:02 pm

and1 wll let us know I guess.

Postby **Okibi** » Wed Jun 18, 2014 12:36 am

Fingers crossed he's too busy driving around with a massive smile on his face.

CM sport · Postby **CM sport** » Wed Jun 18, 2014 12:56 am

and1 wrote:I'll have to pull covers off to grab a pic of the cam gears however this is how I have it set up. Cyl 1 at TDC (confirmed with screwdriver down spark plug hole).

Intake cam gear has I at the vertical and the E at the timing marks on timing plate. Cyl 1 IN cam lobe points towards intake manifold side of car.
Exhaust cam gear has E at the vertical and the I at the timing marks on timing plate. Cyl 1 EX cam lobe points to exhaust manifold.

My only other concern is perhaps bent or stuck valves, but that wouldn't explain zero compression across all 4 cylinders will it?

Your timing could be 180deg out and your tdc isn't actually your tdc.

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and1 · Postby **and1** » Wed Jun 18, 2014 3:15 am

CM sport wrote:
and1 wrote:I'll have to pull covers off to grab a pic of the cam gears however this is how I have it set up. Cyl 1 at TDC (confirmed with screwdriver down spark plug hole).

Intake cam gear has I at the vertical and the E at the timing marks on timing plate. Cyl 1 IN cam lobe points towards intake manifold side of car.
Exhaust cam gear has E at the vertical and the I at the timing marks on timing plate. Cyl 1 EX cam lobe points to exhaust manifold.

My only other concern is perhaps bent or stuck valves, but that wouldn't explain zero compression across all 4 cylinders will it?

Your timing could be 180deg out and your tdc isn't actually your tdc.

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Any more info?

I pulled the timing belt to align cyl 1 to TDC. Rotated cams to correct positions before refitting belt. If this is the case then there is only one TDC position.

As for the clearances I will have to double check with some feelers when I pull off the cam cover.