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My official L31DETT RHD thread.


1 fast z

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Yea and I cant just jump into it. I have a P79 that I am working on for a guy, complete port, rebuild, etc. Then I have an order for a custom intake manifold as well, that I need to get done. And I only work on the Z car stuff on weekends and nights, as I have to be a manager and supivisor of all of our employees at our shop during the day. So yea, big headache there. I am just really frusterated over the whole sittuation.

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Sorry to hear about all of it brian.

 

It's been a long road getting the motor to where it's at, and though this incident sucks big ones, just remember the final product. We're all rooting for you here man.

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that sucks man. sorry to hear. I guess Ill be buying all new chains for mine now. Thats not the first KA (head) Ive seen snap the snouts off of the cams. I wonder what it is about these motors (or head I guess) that makes them do that?

 

any plans for further improvement "while youre in there"?

 

You arent going to steal my cams now, are ya? HA ha!

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No I wont be using your cams. I will be sourcing another set hopefully, so I dont have to scavange them out of my complete 26 head I have laying around. I suspect one link broke first, as I could not keep the adjustment tight enough on the upper chain, it just kept getting loser.

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Well, with some really bad news, I snapped a upper timing chain today, snapped off both snouts of the cams, bent two sets of valves. I have learned my lesson to NOT use junkyard timing chains. I had every intention of changing that old KA chain to a new one, because I never knew how many miles were on it, but now I waited too long. So I will now be taking the head off, and replacing a bunch of crap. Just sucks cause there is ALOT of work in those cams, and it is not like they are everywhere. Yea so a pretty bad day actually. Luckely, it was at an idle, so no block damage was done. I just drove over a thousand miles, racing in another state, etc. And it breaks an eight of a mile from my shop at a stop light!!!!!!

 

 

 

-Old mechanic trick, try bending the chain sideways, you can guess the condition of the links and pins that way, the further it bends, the worse it is. I had an old chain from one of my motocross bikes that would damn near go full circle.

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-Old mechanic trick, try bending the chain sideways, you can guess the condition of the links and pins that way, the further it bends, the worse it is. I had an old chain from one of my motocross bikes that would damn near go full circle.

 

I knew this.. Does that mean i'm a "Old mechanic" ?

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Man, shades of Bubbles!

LOL

 

That sucks man. But those corners are sharp, and when you cut em, they BITE HARD!

 

What can you do...live and learn, right? If you're going to have a failure, may as well make it a big one.

 

You forgot your hood...

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  • 2 weeks later...

Ka Heads. Yea, is it doable by someone else? Sure, especially since you have alot of info and pictures here on how to do it. Get ready to do ALOT of RandD work, as you probaby can figure out, I dont post all of my "secrets" of the build. MACK has been trying to build the setup for a couple years now, and he can tell you it is a hassle.

 

 

Since the thread is up, I will tell you all what I have done to the project.

 

Turns out that the CAMS broke first, THEN the chain, for the reason that the wall thickness on the cam snounts are TOO thin for cast iron. I based alot of my cam profiling on KA cams, and I wish I would of known it was a known problem of the cams breaking!

 

So now, I have parted off, the ends of the cams, about half way between the first journal, and the first lobe. I then have brazed on a Peice of 4142HT steel, that will now take 50% more side force, with the same geometry being done on the cam snout. I need to re-index the cams, with new dowell pins yet as well.

 

 

I also am installing 6 new valves, and doing a complete new valve job on ALL 24 valves while I am at it.

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I had my suspicions that the metal was too thin on KA cams, as Ive seen quite a few KA cams in junkyards with snouts broken and yet the timing chain remains whole.

 

Yeah, its been a while, hopefully Ill have mine running this summer. How long ago did you and I start working on that thing? like, 2004 was it? eh, way too long.

 

If I had just stayed in PHX, itd be done, lol oh well.

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I basicly had 1 month in the head and engine, one HARD month. Since they were EDM cut already. LOTS of time, I can attest to that. And if you were to pay a compentent shop to do the job at 100.00 an hour, it ADDS up.

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  • 3 weeks later...

I have a question....

 

Why did you use 3 head sections rather than the rear three cylinders and front three cylinders from two heads? Since an I6 motor is basically two 3 cylinders joined at the middle I'd think that might work a little better.

 

Plus in the middle of the engine you have an extra 2mm to work with for head gasket sealing between sections.

 

Just wondering....It seems simpler to use two sections but maybe there is some interference.

 

Thanks!

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The bore spacing on the center two cylinders is WAY larger than between 1-2 2-3 4-5 5-6. So to maintain the correct bolt patterns, water passages, etc. This was the only way to go.

 

On the L6 or KA24 block? I thought that the bore spacing for the L6 block is 94mm except for the center which is 96mm.

Just clarifying...

Thanks!

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its actually on both blocks. the bore spacing is 96mm between 1&2, 2&3, 4&5, and 5&6 and 98mm between 3&4 2mm extra for the thrust bearing on the L6. on the KA, the bore spacing is 96mm between 1&2 and 3&4, and also 98mm between 2&3 for the thrust bearing also.

 

so, if you were to use 2 chunks of 3, youd get 98mm in three spots instead of 1. the 98mm would end up between 2&3, 3&4 and 4&5. nothing would seal right, including the firing rings and the head would actually be too long.

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"......what's 2mm?"

 

about sixteen ♥♥♥♥-hairs.

 

 

 

perfect, it was censored. I was afraid it was a little too far, but I think anyone can infer what the little hearts stand for, and they aren't over the line at all. :)

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On a technical note, More bad news. I dissasembled the block, to make sure no broken rings, or pistons etc. All of that turned out good, but I was still trying to destinguish how I was loosing water, as the head was sealed up perfectly. I was magnifluxing the block, and found a crack in number two cylinder wall, sonic tester reveals about .135" thickness on that side of the bore, so I am almost thinking water got through somwhere else, and hydrolocked that cylinder. So, I also found a pin-hole in the number two intake port. So looks like I will be sleaving the block to get her back in working order. Should be another three weeks or so, before she gets back on the dyno. I am also converting to a double row, lower timing system, as the single row was stretched. Ill post pics of how I sleeve the block.

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