[Lear35A]

When we last left this intrepid doityourselfer, I was happy with the way my Darton wet sleeved engine was running. Hah.

First sign of trouble was a clicking noise. Lifters? I pulled the cams and the lifters all looked great. Rod bearing? I pulled the pan (huge pita job), and they all looked great. I checked compression and, oops, #1, 2 and 3 were all close to 200 followed "closely" by #4 at 15. A leakdown test showed that 1, 2 and 3 weren't all that great and #4 had a huge leak down. Running the car in the shop I also noticed oil smoke coming out of the oil filler pipe.



I stuck a boroscope in the cylinders and could see vertical scoring on both sides of the #4 bore. So off with the head. It was not pretty. The walls of #4 were a mess and I could see signs of similar problems starting in the other 3. First picture shows this scoring. So out came the engine for about the fourth time.



The next picture shows the #4 piston. The top compression ring was literally welded into the ring land. Ugly.



So what was the problem? With my concurrence my shop honed the bores of the sleeves to the factory spec clearance. This is actually less than 0.001" which is a very tight clearance. And it may work well with an aluminum piston in an aluminum non-sleeved block. But it sure isn't enough for an aluminum piston in a ductile iron sleeve. This is especially true of a boosted engine. The piston's at temperature diameter matched or exceeded the bore diameter galling the piston and wall badly.



I could give up, but what fun is that. The goal was to save this block, and I'm still not ready to quit. After a lot of research and discussion I decided on a clearance of .0045". I also decided to stick with stock pistons. I custom ordered rings and I will also use larger ring gaps. Last night the honing was completed (picture 3). I can now start yet another assembly.



Many thanks to Flash, Andy, Pete, Mike of Lindsey Racing and other resources. All have been tremendously helpful to me in working through this.



...to be continued

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[Cloud9...68]

If there were an award for perseverance...



At least you have a firm handle on what went wrong, so hopefully the fifth time will be the charm.

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[Lear35A]

I see post 1 is late December. It is now late February, and the car is running again. I think this is the 4th complete rebuild with the head off a couple of times in between in the last few years. However, this time I may actually have it. Main difference is a lot more piston to wall clearance and bigger piston ring gaps.

The engine started almost instantly and idled with nice high oil pressures. This was yesterday. I drove it a few miles just to check for leaks and loose stuff. All seemed well.

Today I took it on the highway for a few miles and took it to about 6,000rpm a few times. With the stage 3 DS1 supercharger this thing has balls. Oil pressure, water temp and fuel pressure AOK. This was running with the hood off. I need to scrape up some helpers to get it back on.

After the hood's on, I need an alignment and then I'll put all the suspension stuff back on. I've got a new windshield in the box waiting as well.

If the thing stays together, the car should be in quite nice shape in about a month more.

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[DaveN]

That's awesome! I hope to get the balls into my engine next month. I think my wife will let me borrow them for the summer anyway; then they go back into the box <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

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[flash]

very glad it's running again. i can't wait to hear what you think when it's all buttoned up.

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[KRAG50]

Looks like the by-pass hose is kinked?

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[Lear35A]

It is a bit. Couldn't see a way to avoid it. I'm very open to ideas to avoid this.

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[MB968]

I'd have been really pissed with the shop. They should have known better than to use the OEM clearance. Surely they must have experience with a lot of engines that have iron liners cast in the aluminum block. It is fairly common. My Mazda KL engine which comes from the factory with an iron liner cast in the aluminum block has a nominal piston/bore clearance of .0017". When the KL engine is boosted, this clearance is typically set in the range of .004 - 006" (for an 84.5 - 87 mm bore). Significantly larger bores require larger clearance as thermal expansion is a per inch issue. If the pistons are hypereutectic, their thermal expansion will be less, in which case a smaller gap can be set. If the 968 pistons are forged, I'm pretty sure they can't be hypereutectic aluminum which I believe is always cast.



Any good shop should know all this stuff. Can't believe they let you set it this tight.

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[KRAG50]

A one inch OD diameter light duty spring about eight inches long inserted inside.

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[flash]

as long as we are going to critique the install:



the 3" hose is cocked to the side. that needs to be rotated toward the driver side. if it is too long, then shorten it on the supercharger end. this will help better align the blowoff hose.



the MAF extension cable needs to be run where it is supposed to be run, per the instructions, and not along the charge pipe. the charge pipe can get to over 200 degrees, and the housing over the wires will melt.



the supercharger oil hose should run UNDERNEATH the supercharger, not above it, and be zip tied to the blowoff hose. this allows them to be as cool as possible.



where is the belt cover???



here is the correct orientation and routing:

   

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[DaveN]

My 2cents as to the kink. I just put a Jubilee clamp over the kink and tightened it just enough to force the hose back to round.

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[flash]

that works. so does cutting the hose back a couple of inches and installing a 90 degree elbow.



i've have yet to have one that i could not get straight though, by merely properly orienting the large hose and elbow. it takes some fiddling, but i've gotten it every time.

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[KRAG50]

Yup, you can get it without a kink by playing with it, except now that it has had the kink it will always re kink in that spot, so a 90 elbow, a internal spring or a couple of hose clamps needed, or a new piece of hose?

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[flash]

or just reverse the hose

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[KRAG50]

That'll work.

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[DaveN]

But the air will go the wrong way ;-)

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[Lear35A]

Ok. Ok. I'll fix the darn hose.

Seriously I do appreciate the suggestions.

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[flash]

lol - what can i say? i'm anal about my stuff. seriously though, once you fiddle with the 3" hose, everything will line up better and fit better, and you won't have the problems with the kinking.



frankly though i'm more worried about the MAF wiring. the plastic housing is not up to high temps, and will start softening at 180 degrees, and melt not far beyond that. that charge pipe can easily see 200 degrees at full boost in the summer. if you really want to run the harness there, i would replace the jacket with something that can withstand the heat. i'd hate to see those wires melt and short out.

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[Lear35A]

Thanks for the observations. I'm in Dominican Republic today, but when I'm back I'll start working on these details. For sure I haven't run this enough to even warm up the charge pipe. The covering is fine. Should be easy to move the oil hose on the SC. I'll do wht is necessary to get the kink out of the blow off hose.

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[flash]

yeah - i'm all about having things work long term. that's why i did everything i did, exactly how i did it. i looked at all of the potential issues, and put things where they are for a reason.



you would be amazed at how hot the air in the charge pipe gets. without even going on boost, it will be about 130 degrees in the summer. the compressor will add 50-60 degrees to ambient temp at normal running, and more on boost. on boost, you'll regularly see 160 degrees, and can see temps as high as 210 in 100 degree weather. most things in the engine bay get to 200 degrees on an average summer day. the pvc has a melting point beginning just over 190 degrees. this isn't a problem if the routing is such that it gets cooling air over it, or it isn't making direct contact with much of anything.



that sleeving making direct contact with a hot part is a bad idea. everywhere you have a zip tie, it makes for a hot spot. i would definitely either re-route it like shown in the instructions, or change out the sleeving to something more heat resistant. come summer you could have a problem if you don't



lol - besides that, it's ugly.

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