930 (3.3L) Deck Height Q
 

Just installed a fresh (new) set of Mahle 3.3L on my 930. After measuring my deck height using the crushed solder method I look to have a strong 1.5-1.6 MM of clearance. Struck me as somewhat surprising and maybe too great?

I installed the cylinders using the .25 mm (I believe) black coated cylinder gaskets that came in my pelican rebuild kit. Tried it on both cylinder 1 and 3 and after torquing down the heads, the solder was barely touched. Really had to search to try and find some indication that it even came into contact with the head!

Your thoughts and experiences are appreciated as always.

Thanks,

Just pulled one of the cylinders up far enough to gra a measurement on the gasket. Looks to be closer to 0.4mm than 0.25. Probably explains the high height measurements.

How much is too much for a deck height on a 930?

Any thoughts guys? What's the maximum deckheight that you'd want to go with to avoid detonation on a 930?

Thanks

For me, .040" is max. I usually shoot for something slightly less, depending on each application.

I agree it sounds like too much.

What cylinders are you using?

Brand new Mahle 3.3L P&Cs.

Duh, me. Sorry.

You have a couple options:
1) Don't run base gaskets. Use Curil-T only. This is what you would do in a pinch, kind of thing.

2) Mill the cylinders down (and at the correct angle), and cut the sealing ring groove appropriately deeper. [Make the cylinder shorter.] I would only use a top machine shop for this.

3) Have the connecting rod small bushing replaced and bored 'offset', lengthening the connecting rod.

My personal leanings would be towards #2 as the best overall combination. If your cylinders are too short in the future, it is easy to get thicker base gaskets. As you're finding out, it is difficult to go the other way. PM me if you want a reco for a machine shop.

That's what I kind of figured my options were. Somewhat surprised that I have too much deck height given that the heads had be cut slightly and these are new factory P&Cs. Rods had been re-bushed already and I'm not about to crack that case open again.

I was guessing that's pretty much the situation. Cutting the heads doesn't really change the deck height, because the deck moves away just as fast as you planing off material. I'm honestly not that surprised, most factory new stuff is set up a bit "big" like this.

Although a 'dry' build is time-consuming, your cheapest, best and simplest option if you had everything apart would be #3 - Modifying the rods.

Okay I guess the noob in me is showing through again... seems that it pays to use spacers and really tighten down the cylinders before taking the deck height measurements.

Went to HD today to find some appropriate spacer material, washers and nuts (M10 x 1.25 - as I'm using the Supertec studs and didn't want to monkey around with the final hardware).

Went one-by-one and made sure each piston was at TDC and took measurements from each end of the wrist pins as well as perpendicular to them just to satisfy my curiosity. The average of each pair of measurements was generally right around 1.1 MM. I'm pretty happy with that. Took multiple measurements each time with the caliper to try and be sure to get repeadable numbers before moving on.

Thanks for the suggestions. Guess I jumped the gun.

Using the crushed solder method doesn't measure deck height. It measures cylinder head clearance. Deck height is measured from the top of the cylinder, as you are doing with your vernier calipers in the last post.

-Andy