Genuine 5k. 3k/4k head will still seal on it. Mines still holding together some 12 months later now! :S

Righto - I'll be honest, I've skim read most of the thread, sorry for that oversight (12 pages - crazy) so you're dead on, you probably won't bend a valve.

 

Nonetheless, you don't look to have a lot of room in there though.

 

That head looks a lot like a 5K head to me. If you get a volume measurement, if its around 18cc it's a 5K head. I'm running 9cc dish on my pistons as well, but you seem to have even less than that.

Hm ok ill get a 5K, even though my bore is larger

 

We will see how it goes, I'm not too confident

Hm ok ill get a 5K, even though my bore is larger

 

Huh? Are they oversize 4age pistons. You're really starting to loose me now! :S

Ok my bad, i just re measured using verniers and the bore is 81mm, I guess that 0.5mm is not a big issue?

 

The Genuine gasket is coming on Friday, it should be all good

Cool. :S yeah if its just a stock sized bore 5k block then use a 5k HG.

Good stuff.

 

Have you CC'd the combustion chambers? I'd do that to verify the CR before bolting it all back together. Not hard to do with a bit of clear perspex with a hole drilled in the center and a syringe.

 

• Turn head upside down and level. Some grease around the outside of the combustion chamber, stick perspex down.
  

• Fill syringe with water and proceed to fill combustion chamber. Keep track of how many ml (1 ml = 1 cc) you pump in to get level with bottom of center hole in perspex.
  

• Work out compression ratio. Off the top of my head the head gasket volume is about 5 cc. Won't be quite spot on with the valve cutouts in your pistons, but better than later on discovering you have a hot running motor that pings its' head off, due to too much compression.
  

 

Oh yea, if you don't want suss looks when you go to the chemist, just tell them you don't want the needles to go with the syringes.

 

A syringe with a bit of vacuum hose on the end of it is a great tool to keep in your toolbox. Great for sucking water out of those sparkplug tubes after degreasing a K series motor. Also good for sucking some fuel out of a fuelcan and squirting it down the throat of a carb to start a motor that has been sitting around a while.

Edited November 11, 200916 yr by Felix

There's a whole bunch of measurements you should get that all impact your Compression ratio. These are the specs I sent to my engine builder at his request after I bolted the motor together and he confirmed the CR for me with some software package. It's in Inches but you at least get an idea of what ineeds to be considered:

 

Bore Diameter: 3.248 inches

Stroke: 2.874in

Cylinders: 4

Combustion Volume: 18cc

Crown-Deck distance: -0.0118in

Piston Valve Relief: 0

Compressed Gasket Thk: Uncertain of this, you mentioned they are usually 5 thou.

Gasket Bore Diameter: 3.268in

Piston Dish Volume: 8cc

Outer diameter of piston at crown: 3.177in

Piston crown to rind land distance: 0.276in

Edited November 11, 200916 yr by philbey

yea but guys, the engine builder who shaved and cleaned up my head has already shaved the head down to 10.7:1 comp ratio, that was with me telling them most of those details! And they are a reputable engine shop called L W Parry, i do trust that they have done the head work correctly! He said he had information of all the piston cc etc.

Compressed gasket is about 1.3mm thick but in this pic pistons seem to be taller than the block or is it

just an illution..

 

 

As mentioned before the front left corner of the piston, where it looks slightly darker seems to come out the tiniest bit

Put a straight edge across it! A plastic ruler, your drivers license, the razor you use to cut lines of cocaine will tell you immediately if it's higher than the deck.

 

As per my previous post, my pistons are half a millimetre below the deck and my engine is running a shitload of static compression, 11.8:1.

 

I'm skeptical about your 10.7:1 CR, especially if you have less than .5 mm.

There is nothing wrong with the pistons slightly protuding from the deck of the block. So long as at high revs any rod stretch isn't allowing piston to head contact.

 

Personally I'm thinking the old headgasket was a 3/4k item and the piston was contacting the firing ring of the HG.

Use kero or turps when measuring combustion chambers, they don't suffer from surface tension bubbles like water.

 

You should be able to put the head on using four bolts and without a headgasket, assemble the rockers on one cylinder and turn the motor over with no trouble.

 

If your pistons hit a valve without a gasket it means you have no safety factor for stretch/heat expansion/valve bounce and you will bend valves sooner or later anyway.

 

If you can turn it without a gasket then all your problems must be in that gasket size and will hopefully be solved over the weekend!

If you can turn it without a gasket then all your problems must be in that gasket size and will hopefully be solved over the weekend!

 

If his pistons protrude above the block deck height, this won't work, and the motor will not turn over.

 

Piston protrusion is a tuning trick to increase squish and provide added detonation resistance.