81' dry assembly ???

[flmont]

Well ,.here I go agin..If all my Deck heights are good 160 MM plus on all cylinders...and I have a 20/21 cam on a stk engine. do I have to do the dry fit piston/valve clearance test,..it seems it would pass very easy,..However Iam not sure of the clearance value's yet,.????

TIA,...Frank

[cstreit]

Deck height is the measure of piston top distance to the top of the cylinder head. What is it that you are measuring?

[Rot 911]

I asked the same question when I was doing the reassembly of my stock 3.2 last month. The advice was that it was simple to do and doesn't take much time. They were right, only took me about an hour to do. Not that big of deal for some cheap insurance.

[William Miller]

A little clarification on Deck height please!

On an SC the solder squish test gives you clearance between the piston top and the head. There is also a flat ridge at the edge of the dome arround the piston. (Here you can measure the distance between that flat ridge and the height of the top of the cylinder as it is installed at TDC.
Which is deck height?

On my rebuild, my clearance from piston to head was fine.
My valve to piston clearance was tight with the stock cam timed to US specifications. I re-timed to Euro specifications. This retarded the valve opening and allowed more valve to piston clearance.

Is is possible or probable that the 9.8:1 euro pistons have less clearance requiring the cam timing to be retarded?
This seems logical to me, but I've never seen it written that way.
I've seen it written that US spec were 7deg, ROW 1 deg, and later 84 carerra split the difference at 4 deg.

Could this not really be just a tuning option, but a requirement because of clearance?

In any case it's simple to check and you should do it!

Good luck!

[flmont]

Well... Its been said that if have not made major changes to the engine that you would not really need to do the dry fit,..But what the hell always better to do it while its easy...do ya know the value of the piston/ valve check....Thanks Frank

[William Miller]

I recall 1.5 mm Intake and 2mm exhaust. But you better look it up in Waynes book or do a search here. The correct setup and procedure is as important as the values. You will have to set the cam timing based on the manf. recommendations for their cam. Maybe that can be found on a search as well.

Just a thought, there was a recommendation to do a dry fit without the base gasket. This will also effect valve clearance so I would do the valve clearance check again during final assembly just to be sure.

[flmont]

Thanks alot...Frank

[surflvr911sc]

Frank, I'm a loser, but I haven't forgotten about you!

Great to hear things are still moving along. I can’t wait ‘til you get her on the road.

Thanks again, everything worked great!

[flmont]

Say Dude,..Well Iam glad all went well...is this your dads 1St 911..?? Frank

[surflvr911sc]

Yep, bought it back in August. The bug has really bitten him now.

[cstreit]

I'd still like to hear where a 160mm deck height measurement comes from?!

[William Miller]

Maybe that's 1.6 mm squish test?

[Superman]

Two things. Call WebCam for the proper cam timing for the 20/21 cam. It is different from the stock cam timing.

And finally, you are going to like those cams. Trust me. You're going to like them.

[flmont]

Cstreit,..It comes from my deck height measurment which =1.60 or 0.063 also ,..I did Cyl 5 & 6 they also averaged to 1.60 and 1.67 MM I still need to do Cyl 1,2,and 3 Oddly, when I measured all of my off unit shims for all 6 cyl they all had diffrent shims from .027 to .043 MM which I was very surprized to see..I used all new .025 shims from the gasket kit and still had those numbers after Ollies had clean up my heads by 0.005 ths,..So I can only guess that the factory built it that way,or this engine had been apart in the past..??? Frank

[flmont]

Superman,.I have never driven a 3.0 before, I have only driven the tired 2.7 So Iam looking forward to it for sure...Frank