Piston valve clearance, 2.7 CIS

[4sd911]

Looking for the proper height of the head cylinder in relation to the piston on a 2.7 CIS.

The heads were fly cut in ’98, upon assembly the cam didn’t align with the chain box, the machine shop shaved the chain box 1mm (0.040”) to align.

Today I’ve replaced the chain boxes and the cylinder base on the case was shaved by Ollies, they included 0.5mm base gaskets but they did not have the heads so they didn’t know how much they’ve been cut. When mocking up the engine using a 1mm cylinder base gasket the cam does fit the chain box good, the cam is about 0.020” to 0.030” from the crank side of the chain box cam cover. If I try a 1.5mm gasket this moves the cam closer to the other side of the chain box cam cover, this is with using the factory chain box gasket which measures 0.020”, the aftermarket graphite gasket measures 0.040”.

I don’t see any spec in the factory manual or the little spec book on the position of the head in relation to the piston. Is aligning the cam in the chain box good enough? I know with a domed piston you can use clay to check the piston valve clearance. If I use a 1.50mm base gasket to move the assembly out, will this lower the compression to much

Big question is there a spec from the center of the crank to the back of the head or to the center of the cam? Being that parts are machined I’d like to get back to factory height.

[tom1394racing]

It sounds like there was enough machine work done that you'll need to do a prebuild and check deck height, compression ratio and piston to valve clearance.

[4sd911]

Ok, I can't find any info in the manuals on how to check or the spec's. Where do I look for this? Is there a spec for the distance from the sealing surface on the head to the back of the head so I can see how much they've been cut. As to the valve piston clearance since the piston is a CIS type with no cutout for the valve do I just stick some clay on the piston and again I don't see a spec in the manuals for valve clearance.

[tom1394racing]

The procedure is outlined in great detail in Wayne's book.

You can also do a search on this forum under checking deck height, checking compression and checking piston to valve clearance.

[4sd911]

Alright, I've missed some issues. I pulled out the receipt from '98 on the heads, the shop resurfaced the heads approximately .020" - .025". Called Ollies about the cylinder base resurface, they stamped the case the amount removed, .020". So it looks like I need at minimum .040" (1mm) base gasket, this would leave me about .010" short of stock, I could use .060" (1.5mm) at the base and move the head out .010" from stock. Only issue I see is how close can the cam be to the cam cover? With a .040" gasket there is about .020" - .030" between the cover and cam.