Slippery Slope

[HelmetHead]

Well, i've pulled the motor out of my 87' and have started tearing it down as I was noticing persistent smoke, crankcase pressure and low compression numbers. I also noticed worn/pitted camshaft wear when I did the valves a few months ago.

So I got it all torn down to the pistons hanging from the case...I found 4 of 6 pistons with broken rings (top rings) Which to me is a good thing as that was probably the reason for bad compression, smoke, and blow-by.

I have stock p/c's which amazingly enough to the naked eye still look great...good cross hatching on the cylinders and the carbon buildup on pistons is minimal. Problem with the stock pistons are they aren't fully finned... (is this a major issue??) I've heard of using 3.2 mahle's and having them punched to 3.4 and then source some new pistons... this is one of the areas where i'd like to spend some time and $.

The bottom end/case have yet to be split and i'm wondering if I should go ahead with splitting the case since i'm this far along...? In the grand scheme of things probably not a bad idea to check it out for wear and put new main bearings in it and some ARP hardware?

I'm planning to go back with a bit more cam than stock as i'm running a HFS and EFI/motec....any suggestions? I was leaning towards an "SC" cam but haven't done much research into suppliers/cost.

Question is now where do i go from here??? I know most of you have been here done that, but this is my first Porsche engine and I want to do it right the first time without breaking the bank.

Any pointers or suggestions welcome...if you've got some old 3.2 jugs laying around, let me know as I might be interested.

Friday CHEERS!
Einar

[RarlyL8]

Nice looking engine!
964 cams more closely match the characteristics of an HFS. SC cams work better with the 7200.
ARP hardware is cheap insurance. If your in there anyway it's a good idea.

[HelmetHead]

Brian,
Thanks! I bought the car a few months back and almost all the mod's were made by the PO (saved me from having to do it!)
Sorry I wasn't clear...I have a 7200HFS from Kevin and also have a stock 7006 laying around which could be rebuilt. Would the SC's still be better choice with the 7200HFS?

[gsmith660]

Nice looking motor! I was going to pull one or two con rods and look at the con rod bearing wear if I had to pull the heads off from my fiasco and based on that would determine whether I went deeper into the motor I was prepared to do a full rebuild but luckily didn't have to.

[Turboo934]

Oh yes the SLIPPERY SLOPE

[jwasbury]

Good luck on your rebuild. I will be joining you as I plan to drop my engine soon due to ring problem on #6, crankcase pressure, etc.

My plan is to go down to the crank while its apart to be sure all is good (update those rod bolts too). I will be curious to see if my P&Cs are reusable, but have already 'planned' to upgrade to 3.4l (already spent the $ in my mind).

Decisions, decisions.

[RarlyL8]

Both the K27HFS and K27-7006 would benefit more from the 964 cams. SC cams more closely match the characteristics of the K27-7200 as they both come on sooner and fall out after 5500rpm.

[fredmeister]

what is the difference between the k27hfs and the k27s?
is the k27hiflow2 same as the k27s or are these all distinctly different units?
the ultimate motorworks website shows few pictures but the k27hiflow2 looks like pictures i have seen of the k27s turbo.
thanks for any info.

[pkracer21j]

go with a bb turbo.you wont regret it, and your friends will love cruising next to your new learjet

[e170drvr]

Ok, probably a stupid question, but what is high crankcase pressure, and how did you know you have it?

Eric

[NathanUK]

Originally Posted by fredmeister

what is the difference between the k27hfs and the k27s?
is the k27hiflow2 same as the k27s or are these all distinctly different units?
the ultimate motorworks website shows few pictures but the k27hiflow2 looks like pictures i have seen of the k27s turbo.
thanks for any info.

In order of size- K27S, K27HFS, HF2. So, the K27S will spool first and the HF2 can flow the most air.

[A930Rocket]

High is when smoke and oil blow out the oil separator. With a stock air filter housing, it gets sucked in and can cause detonation. At that point though, your rings are probably shot and the cause of your high pressure.

Originally Posted by e170drvr

Ok, probably a stupid question, but what is high crankcase pressure, and how did you know you have it?

Eric

[HelmetHead]

Well, the pistons and cylinders are on the verge of toast and it appears as the 3.4 route will be the direction of my build.
I'm looking for some core 3.2 mahles to punch out and re-nikasil and i'll be running a 7:1 mahle piston unless a set of 3.4's in 7.5:1 or 8:1 comes up for a bargain.
I'm leaning towards the 964 cam for higher RPM power but concerned that lower RPM ranges may suffer with the lower compression pistons. I was considering flame sealing the heads and pistons but don't plan to exceed 1.0bar and the additional cost would hurt the build budget.
If you have any suggestions on where to have my heads "worked" and also who does good cylinder rebuilds let me know..

[David]

You know my recommendation of EBS to handle the head and cylinder work.

From the flame ring thread: Charles Navarro wrote that he didn't think flame rings were needed for a set up like yours. If you're having the heads and cylinders re-worked, you'd have a good, fresh head sealing surface.

Even with the lower compression pistons, I think 964 cams are the way to go.