aventari

Today I worked on my 89 951.
I installed my cylinder head. It was rebuilt by Lindsey Racing and o-ringed. I'm using a stock head gasket kit (maybe widefire? i forget I ordered it 9 mos ago). Brand new washers.

I installed the head and was reading along in the factory manual and read the 'Preloading cylinder head gasket steps'

So I torqued all of my nuts to 20 Nm in sequence, then 50 Nm in sequence, then 90 Nm in sequence. The 90 Nm step was very tight. I continue to install cam and everything and only then do I read the next page in the factory manual of "20 Nm then 90 degree sequence and then another 90 degree sequence".

**** -- I did the preloading sequence, not the actual torquing sequence and I don't even know what the 'preloading sequence' is.

So I read up on Clarks garage and the archives here about the torque sequence. It seems according to Clark that the old spec for the 944 (without 12mm high nuts) is the actual the pre-loading sequence. [http://www.clarks-garage.com/shop-manual/cyl-03.htm]


So I'm loathe to remove all of that stuff again and get a new head gasket. I've done cylinder heads on other motors at least 10 times before so I know how to feel how tight a head bolt/stud should be and the amount of force to tighten it with. The amount I put on felt about right (which means it gets scary as you're tightening it because just as you're imagining something snapping--the torque wrench clicks and yay you're done.)

I'm planning on running it like it is and if the head gasket goes, oh well I'm not any further behind than I am now because I'll have to tear it down anyway and put a new gasket on.


Has anyone run a car after they did the incorrect "preload" torque sequence?

What about loosening the nuts and retorquing to the proper 20Nm-90-90 sequence? If the head gasket is already compressed isn't that a terrible idea?

thanks, and yeah I know: completely before you start a job.

Mikes3.0cabturbo

I was chatting to Markus951 who as you may be aware runs high HP engine, I think he ran 110Nm on stock studs...maybe ask him direct?

TF

Raceware recomends a sequencve on thier head studs of 35ft/lbs 50ft/lbs then 65ft/lbs which equates to about 90Nm. I went to 75 ft/lbs or 100 Nm on my 986 with no problems.

Tom

hosrom_951

Once you loosen the cylinder head nuts, the head gasket MUST be replaced, unless you are using a copper head gasket.

xsboost90

when i did my n/a head gasket i found the ft/lb conversion and it was something like 35lbs, 48lbs then 67.?? lbs. When i did my turbo i just went to 70lbs for the final step.

aventari

ok sweet, thanks again people.

I will run it just like it is right now then and it should be fine

INURGRL951

How is the head gasket holding on this car for the past year?????

Kool

With 120 posts I am saying we will never know.