Compression to high after rebuild?

Hi,
I rebuilded engine and tested it today.
After warming it up I did a compression test.
All cilinders are between 190 and 200 psi.
Standard compression in the manual is 155 psi.
I'm planning on running 1,3 bar.
What now, start over again, new thicker gasket?
Or try running it?
Greets Ive

What machine work was done to block & head face ? what pistons & bore size & HG fitted ?
Is cam timing all correct & pressure guage a good one !
your readings would suggest a comp ratio of around 10:1

Block has never been surfaced, bore is 1 mm oversize.
Head has been surfaced lightly two times.
Head gasket is 1.5mm
Pressure gauge is good, I used to be arround 175psi with this gauge before the rebuild.
I asked for oem compression ratio 8,5 : 1 pistons, but I never checked this so this could be the problem.
Could a bad cam timing give a to high reading, how then?

its more than likely the fact that you have gone for +1mm oversize pistons coupled with the head being skimmed twice now and a 1.5mm hg being fitted will not be enough to bring back down to stock comp ratio of 8.5:1

if you have used new head bolts and are happy that the head is in excellent condition and your clearances with regard to bigend bearings and piston ring end gaps are precise then you could get away with 1.3bar boost but you would need to make sure fuelling is absolutely spot on or it could lead to another build up much sooner than planned, also make sure your ic keeps cylinder temps as low as possible (maybe an aquamist or similar may benefit you in this instance).
if I were you I would back the timing off to around 15-16 degrees as that will at least give you a safeguard and hopefully keep cylinder temps a bit lower then all you can do is see how she goes but always keep an eye on egt and afr readings

Happy to hear that it might still be drivable iff everthing is spot on.
I don't have new headbolts, the rest off the set up is no problem.
I backed off the timing today and now it's also running smoother on idle.

I measured the head gasket where it's sitting just outside the block (at the timing side)
I measured 1.06mm so I think someone fucked me with my head gasket. (ordered 1.5 or 1.7 can't remember)
(MLS head gasket)
So this could be the problem!

Osmax90 wrote:
Could a bad cam timing give a to high reading, how then?

pressure reading you doing is a dynamic test so valve timing can change the actual readings drastically, an engine with a lot of overlap will read far far lower than same engine with less or no overlap .
I personally would look into it further as that static comp ratio looks well too high from results & info mentioned so far, if HG gasket wrong then change it.
One of most important things when building an engine is checking static comp ratio going to be right & tweaking if needs, perhaps simply by HG thickness. other good thing by checking is it reduces drastic f00k ups from wrong parts supplied such as wrong comp ratio pistons or machine shop skimming more than stated .

Ok will double check hg thickness &
Valve cover remove and check cam timing.

Could the chain be one tooth  off on the cranckshaft gear??






I used a feeler gauge to check the distance between head and block. (to know how thick gasket is)
It's 1mm so the gasket is to thin?

I also measured the height off the head = 136,6 mm, so head is 0.4 mm surfaced in total.

Iff the cam timing is correct I will need to install other gasket.

What gasket should I go for?

Also tested compression again 200 psi.

yes your timing is well out
the ex cam needs retarding (turning anticlockwise) one possibly 2 teeth as does the inlet cam

So the chain must be one tooth off on the cranckshaft sprocket?

So I can move the mark on the sprockets 1 tooth anti clockwise on both cams .

Iff this would be the solution to all my problems I would be very

New timing.

Please please check with others I would say it's still out but wait untill others reply

That's defo out now. Your timing before looked correct on the ex cam & inlet cam.
I think the timing is correct on the crank just check cyl1 is at tdc & the woodruff key points up the 12 o'clock on the crank

Ok didn t test yet, will wait till tomorow

this is how it should look if timed up correctly



just sorted the timing position on this one down the workshop to put it at correct marks for you as im a jolly nice chap
if I fitted the chain to this now there would be 11 face links between the 2 marks (including the ones over marks)
easiest way to look at it is all the 4 holes on sprockets, you should see half a hole either side on each sprocket at face level
timing pointer on crank should be at second mark from left just as it is in your first photo.

noticed the crank pulley is not stock so are you sure timing marks are correct on there as you could well be out with the crank pulley marks

Just looked at the pic again now I'm home and the last pic you put up is still a tooth out on both cams so you need to make sure the crank pulley mark is 2nd from the left at the pointer, then turn both cams one more tooth anti-clockwise then that should be correct

Crank pulley is oem but it's machined. I'll adjust it again.
I unnderstand. No problem. Piston 1 at tdc.

Adjusted like your picture, runs smoothly now, 175psi compression.
Thank you everybody for putting the heads togheter and solving my problem.
Without the pictures and quick thinking this wouldn't have been possible.

Bit of luck it was simply timing.
know I think you understand fully how cam timing can drastically change dynamic compression readings :-)
Standard timing is easy using the chain coloured links when initially done (as long chain been put on right way round), distance between marks on cams is 20 chain pins but that don't help without orientating at least one right to start with, can mark them to cover edge which makes it easier see they spot on.
Always worth checking crank pulleys too as they can go out due to being 2 parts & bonded.
Anyone building an engine is best adding a true tdc mark to block/crank & testing the pulley as building it up.

I must have drop the chain a little bit while I was installing the head.
Some extra marks on crank and camsprockets would be nice, will think about that on next rebuild.

^ hope that some way off & you enjoy your rebuilt engine, have fun ...

Should sticky the photos of the cam gears, really good info for anyone rebuilding etc