'Deck Height' on 2.4S

[elflamo]

Hello all,

I'm rebuilding my engine (2.4S 1972), using Waynes book. I'm at the process of measuring the deck height using the solder method.

However, I've performed the test several times and basically, the solder does not crush nor is there any noticable resistance passing TDC. When I look at the solder, I seems it might have crushed a little, but it basically stays very close to 3mm in diameter.

Addtl info:
- heads have been skimmed 0.25mm
- I use one copper base gasket of 0.25mm

Is this normal, maybe because of the lower compression of a 2.4S?

KR

Dennis

[Eagledriver]

I think there is a difference between deck height and cylinder head clearance. The cylinder head clearance can depend on the chamfer of the head and shape of the chamber. The deck height is the distance of the piston edge from the top of the cylinder. I measure this with a depth guage from the top of the cylinder. You can get close with feeler guages and an eyeball. If the piston is more than 1.5 mm from the top of the cylinder then I think you should do something about it. Easiest thing would be to go with no gasket and use some non-hardening sealant. If you are between 1 and 1.5mm on deck height, I wouldn't worry about how much head clearance you have.

-Andy

[elflamo]

Thanks Andy. I think you are correct about the difference you are pointing out. I did some more searching and found that others have been confused by the way the solder method is presented (as an alternative) in Waynes book.

Just from looking at it, there is definitely a lot less real deck height than 3mm. Just wondering how I can easily measure it now that the solder method doesn't really seem to work for me. I'm going to give it another try and see if the solder bit moved towards the center of the pistons, instead of staying put and get squeezed.

Dennis

[piggdekk]

Elfamo,
I don't remeber how this is explained in Wayne's book, but the best way to use solder is make a ring that goes all around the piston diameter. This way it shouldn`t move when You turn the engine over. You may as well roll 2 solder threads so that it is thicker and You can get a proper measurment.
luca

[tom1394racing]

Use a dial gauge on the piston crown to ensure you are at TDC.

Then use the depth measurement on your vernier caliper to measure the distance from the perimeter edge of the piston to the sealing surface of the cylinder.

[elflamo]

Thanks for all the replies.

The thing is that there is no horizontal 'edge' on the piston. The 'dome' starts right where the piston touches the cylinder wall.. That's why I can't take an accurate vernier caliper measurement. (These are brandnew Mahle 2.4S pistons and cylinders).

Now that I think of it, the vernier caliper measurement will show a little less than the actual deck height. I could use that measurement and then make sure that that is right on or just over (higher) the minimal value recommend by people on this board (1.3mm?). The part I wasn't able to measure will be my safety margin.

That said, what is the maximum deck height, I have to make sure that the total is always less than the max. 1.5mm?

Dennis

[Flieger]

Deck height is theoretical. It is from the top rim of the cylinder to the base of the dome- the edge where the piston goes from cylindrical to the dome.