90 roller

[stepson]

Originally Posted by JK McDonald

Hey Rufrob - It is never a good sign to open up the water pump cavity to find it's impeller broken into pieces. A serious high temp cycle can cause all sorts of problems for an aluminum 928 engine. The problem now is to assess the usable status of everything. Especially whether the unsleeved, silicon alloy engine block can be saved. I've read about a special process to over bore and re-etch the Alusil cylinders to bring the silicon crystals back out as a wear surface again. There are much more experienced engine builders here that can probably make some recommendations to help you decide on your options at this point.

Good Luck, Michael

JK, I know you meant Alusil, so I fixed for you for posterity.

[JK McDonald]

Hey Stepson - Thanks for the correction. There is nothing worse than recommending the wrong repair procedure- ha Do you think the rings will be able to seal up at the top of the corroded cylinders in Rufrob's block ?

Thanks again - Michael

[honerboys]

i redid a 944 years ago - someone on that forum suggested a scotch brite pad, some valve grinding compound and a cylinder hone to brighten up the cylinders - their blocks are the same as these (minus 4 cylinders) - i tried it and re-ringed the engine - compression was fine and car ran very strong - until my sister totaled it - anybody on here tried that on a 928 (i mean buffing up the cylinders... not totaling it)

[stepson]

Originally Posted by JK McDonald

Hey Stepson - Thanks for the correction. There is nothing worse than recommending the wrong repair procedure- ha Do you think the rings will be able to seal up at the top of the corroded cylinders in Rufrob's block ?

Thanks again - Michael

JK,

Sometimes I will be thinking one thing and then something else pops in my head just as I am posting something and then I find that I posted the thing that popped in my head briefly and not what I was thinking the whole time. I knew what you were thinking, but I didn't want someone else down the road to get the wrong idea.

Re Rufrob's cylinders: I can't discern how deep those pits at the top really are, but it certainly doesn't appear that the rings could seal at the top of the stroke.

[rufrob]

There wasn’t much carbon at the top of the cylinders. Rub with a shop rag removed it. The intake valves were pretty easy to clean but the exhaust valves had a caked on white stuff. Drill and sand paper got most of it off. Those valve keepers were a pita. Took 3 hours.
Right bank done. Tomorrow I tackle the left.


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[rufrob]

GF’s away so what else should a single guy do in Tokyo on the Saturday night of a 3 day weekend?
Valve seals baby. 16 in 4 hours. My legs are cramped.







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[JK McDonald]

Hey Rufrob - You are making great progress - How did the upper rim of your cylinders come out after the cleanup ? If lucky, any corrosion along the top cylinder edge will be above the wear point of the piston compression rings. You should really have an experienced machinist who is familiar with the 928 take a close look at any questionable surface areas. His opinion on how the rings are going to seal can save you a lot of grief.

Also just a word of caution, don't scrimp on a good valve job. With all the time and expense involved in the assembly of your motor, there is not much more discouraging than building a smoker.

Please keep us posted -

Good Luck, Michael

[ClausGraf]

Good job!

[rufrob]

I know how important valve jobs are but I simply can’t afford it know. I’ll spend all sorts of money on the 930 but for now I’ll be happy to get the 928 running smoothly. With 80,000km on the odometer I can’t see it needing more that a clean up.they seeded flush into the head so unfortunately that’s all they are going to get for now.
Typhoon 24 cancelled my summer vacation to Okinawa and slowed any work I could do on the car. Man, you guys with your own garage are so fortunate. During a break in the rain I managed to change the front crank seal and strip the top of the original motor. Surprised how dirty it got in the couple of months I put it together.



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[rufrob]

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[Mal81]

I see some of your engine work is done indoors. I hope your g/f isn’t like my “hurricane in all kinds of weather” wife is. Lol.

[JK McDonald]

Hey Rufrob - If you don't plan on having a machinist perform a valve job, you might at least hand lap in the valves, assemble the heads, flip them over and then fill each cylinder cavity with kerosene. Inspect the intake/exhaust ports for any sign of seepage.

In a pinch - This should give you an idea if you'll be "initially" running on all cylinders.

Good Luck, Michael

[rufrob]

While cleaning I did fill the ports. No leakage.



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[rufrob]

The engine hoist didn’t materialize, so- thank God for good weather and a 3’day weekend.
I don’t remember taking out 944 engine was so difficult.
Is standing an engine on it flywheel so bad?

No end play motor ready to go in




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[rufrob]

Sometimes I amaze myself


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[Mal81]

Originally Posted by rufrob

I know how important valve jobs are but I simply can’t afford it know. I’ll spend all sorts of money on the 930 but for now I’ll be happy to get the 928 running



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Rufrob, you might be pleasantly surprised at how little an independent machine shop will charge to do a valve job for you. Maybe I'm just lucky to live where I do, but my local machinist only charges me $150US per head plus parts. He's an honest guy, so he doesn't charge me to replace parts that I don't need. When he did my Trooper, for example, he said everything was within spec, and only charged me for his shop time..3 years, and 50k miles later, it's still running like a watch.

[honerboys]

"The engine hoist didn’t materialize, so- thank God for good weather and a 3’day weekend."

so rufrob - no hoist? - how big are you?

[rufrob]

I’m not as young as I used to be. I’m so sore.
Especially after wrestling the engine into position and torquing the LCA. Ill be 50 soon and I’ve always been slight in build but high in motivation.



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[honerboys]

well good on you - motivation moves mountains - i'm 62 now so i know from whence you speak - soreness is a way of life now - great job

[stepson]

Originally Posted by rufrob

Rufrob,

Do your neighbors talk bad about you due to the overgrown condition of your bonzai tree shown in the picture?

J/K

Seriously, Good work getting the engine out and the new one in?