20XE - cylinder head height, piston clearance, multi-layer head gasket?

[Iain]

Measured up my cylinder head, 20XE, and it comes to 135.26mm. Haynes says minimum height is 135.63mm.

Also the guy at Autosprint said XE pistons stick out of the block and sure enough when mine are fitted they do poke out the top - crude measurements are roughly 0.4mm over the block face.

So questions are:

1) Is the head still usable with being ~0.37mm under min height?

2)What's the best way to check the head gasket will give enough clearance when the head is bolted down?

3) Can all solutions be solved with a multi-layer 'Cometic' head gasket? E.g. 1.3mm compressed thickness, so taking head height and piston protusion in to consideration there's an extra 0.5mm clearance?

[burgo]

i cant believe you never listen to me :(, i told you how to check for clearance, yes its a long way but it is the proper way

[Sloth]

put some plastercine on the piston crowns, whang your head on, nip it down, time her up and turn her over by hand a few times, then take the head off and see how thick the plastercine is near the valves etc. if its through to metal its too close.

[burgo]

put some plastercine on the piston crowns, whang your head on, nip it down, time her up and turn her over by hand a few times, then take the head off and see how thick the plastercine is near the valves etc. if its through to metal its too close.shove that up your **** lional :mad:

thats almost word for word what i told him to do

[ste porter]

engineers blue:thumb:

[Sloth]

so i got something right? yay!!!!1

[burgo]

so i got something right? yay!!!!1for once :p

[Iain]

Jesus Burgo calm down lol

The plastecine thing will work for what I've got now, but isn't useful if I want to change the cams in the future is it?

Also doesn't show me if the pistons are going to be very close to the head when the engine is hot - thinking of this rather than valve clearance at the moment.

[blue_peg_16v]

extra clearence will lower the compression tho so you will loose power

[Iain]

It has 'flat top' pistons rather than standard, and a head that's skimmed below Haynes minimum thickness, so I figured a thicker HG would simply make up for the missing cyl head material?

[mowgli]

you could use a curled up bit of solder. it is easier to remove & measure after turning it over..

iain, the thicker the gasket, the more chance of failure.

[ste porter]

peg if the compresion is to high he will suffer from other side afects such as pinking ect aswell as obviously the risk of something meeting something else inside

[burgo]

Jesus Burgo calm down lol

The plastecine thing will work for what I've got now, but isn't useful if I want to change the cams in the future is it?

Also doesn't show me if the pistons are going to be very close to the head when the engine is hot - thinking of this rather than valve clearance at the moment.
well why bludy ask if your just going to dismiss every answer, ive lost count of how many things you have asked me about with this engine and yet you dismiss my answer, go ask a "professional" who just tells you exactly the same as i have! name one thing i have been wrong about

oh and of course the plastercine method will tell you if you have clearance for uprated cams later on, you simperly work out how much extra lift the new cams give and then refer back to the plastercine measurement to see if you have enough clearance for it

[mowgli]

unfortunately, engine building is about 90% measuring. and it does take time.

[Iain]

Well sorry if you've taken offense but I do like to hear other people's opinions and experiences. I've also not asked you about the multilayer/thicker headgaskets so wanted info on those too.

[Stuart]

oh and of course the plastercine method will tell you if you have clearance for uprated cams later on, you simperly work out how much extra lift the new cams give and then refer back to the plastercine measurement to see if you have enough clearance for it


Even then its hard work as you need to plot the cam lift vs timing and work out whaqt lift over what duration you can have at TDC (with space to spare)

[mowgli]

iain, what cr are you trying for, & have you measured all the cc's of the chamber, piston top gasket area etc?

[Iain]

Errrrrmmmmmmm. Yeah. I guess that's the first decision to make.

[Iain]

Right, I've had a go at measuring the volume of everything in order to calculate my CR. Hopefully my measurements aren't too crude to get an estimated figure.

I managed to fill the head chamber with 41.7ml of fluid.
I managed to fill the piston valve cutouts with 0.2-0.3ml of fluid. Seeing as there's four lets say the piston is 1ml (it's flat topped apart from the cutouts).

I have then used this calculator:
http://www.csgnetwork.com/compcalc.html

With the following figures (assumed multilayer headgasket as I know their compressed thickness):

Measurements: MM
Bore size: 87
Piston stroke: 86
Head gasket bore: 88
Compreed gasket thickness: 1.3
Combustion chamber: 41.7cc
Piston dome volume: -1cc
Piston deck clearance: -0.4mm

= 11.6:1 CR

With a 1.9mm thick headgasket this comes down to 10.8.

Please advise if any figures look wrong or if I've messed it up working it out. I have no idea of 11.6:1 is good or bad or what lol

[mowgli]

it would give you impressive power iain, & you should use the good petrol in it.

10.8:1 sounds like a good reliable figure though.

[Iain]

10.5:1 standard 20XE according to Haynes. Was planning on running it on standard injection/dizzy to start with though, how will that handle 10.8 or 11.6?

I guess options are replace the head to use a thinner headgasket, or use a thicker gasket (at least that way I won't worry about piston/head/valve clearance :))

[burgo]

i would use the thicker gasket whilst you've got standard management, and when you go to bodies and after market management go for the thinner gasket for a power hike from the compression raise

[djbrowney]

i have always been led to belive aswel that at higher rpm your valve will travel further into the bore than it will at lower rpm !!! might be worth considering !!!

[Iain]

Hmmkay. Hopefully should be ok on valve clearance thinking about it, as the only thing that has changed since I took it part was deeper-cutout pistons and a head skim. Good thinking Mr Burgo, was thinking of doing that, 1.9mm gasket to get it all up and running and higher compression available with the thinner gasket as and when it's needed.

[burgo]

you will probably have to whip the head off when you go to bodies so you can port match the manifold