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update on what the %#&@


smooth as glass

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Finally found my issue....cracked head. After changing riser gaskets, pulled port head and found crack. The water jacket was clogged in a couple places with river trash. Don't know if that was enough to over heat or what. Temp has never read more than 165 and it's never been frozen so guess just age and hours (1700). I don't get why there is not a strainer of some sort on the intake, I note my buddys Nautique has one. I will install one when this repair is done. I've been told I should just go ahead and replace both heads, so they match. Sounds reasonable. Is that a a good call? other one seems sound. Mike

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If the other one is sound, assuming you can get a 100% matching head, you could probably get away with the old one as long as you rebuild the old head.

The rework of the head is what will allow the compression to be the same (roughly) on both sides, you will want to check the cost of reworking the old head against the replacement cost of a new one. Your goal in this is to have good compression on both sides of the motor.

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"I've been told I should just go ahead and replace both heads, so they match. Sounds reasonable. Is that a a good call?"

With 1700 hours.

:plus1:

Can you get a get some money back if you use your good head as a core ... or as NB said have it rebuild.

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If the water jacket is clogged with river trash, and the clog is not near the temp sensor, is it possible to overheat one or two cylinders and not the whole engine, resulting in a cracked head without the engine temp gauge reading hot??

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If the water jacket is clogged with river trash, and the clog is not near the temp sensor, is it possible to overheat one or two cylinders and not the whole engine, resulting in a cracked head without the engine temp gauge reading hot??

My guess it this is exactly what happened. There's lot's of strainers on the way to the engine. The hull strainer, the impellar acts as a strainer and the tranny cooler.

I'm wondering if it was a combination of things...mineral deposits, maybe low water pressure because of old circulating pump, or weak impellar.

Where was the crack? Allowing water into piston? Or lifter valley? Or both? Or just into exhaust port?

Steve B.

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Hi, Smooth.

If you're interested, I just posted a bit of info on the strainer (and flushing point) installation I did on my 2005 RLXi. It's in the 'how-to' section under 'Strainer installation'. It hasn't been approved and made accessible as I write so I haven't checked how it looks - don't even know if I've done the post properly but hopefully it might help you or someone else...

(Good sign-off, too!)

Steve G.

Edited by GreenMan
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I would rebuild the other head. If you can the block would be a good idea it sound like you are a do it your self kind of guy so for the most part it is easy. Let the shop do the head and check the cylinders and change the cam bearings. Just an idea. If you did and need some help just ask.

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It is easy to locally overheat a cylinder head, particularly since you had trash buildup in the head. You will want to examine and check the other head for similar issues. The temp sensor reads the water temp coming out of the heads and this is pretty much an "average" of all the flow, so you probably had one head supplying most of the water being measured. A strainer will help, but you will need to check it consistently.

You can easily replace the cracked head and get a duplicate, so if the other head is sound, no need to replace. The vortec came out in 1996. I would certainly check the other head, before you pull it I would recommend a leak down test. Once removed, I would check flatness and valve and seat integrity. I would do a valve job on the "good" one at a minimum. For the cracked head, you could buy a bare head and transfer all the valves/springs from the cracked one. That would be the most economical way to go.

Edited by Woodski
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Thanks for all the input fellas....... Pistol, I did consider a new block but hoping to economize, and the Clymers has been by my side thus far. To match heads sounds like my best route. I've been told new castings are better made since 2000. so going with 2 new and transfer parts, I live for peace of mind. I'd sure like to get another 1700 hours. Boz, the crack was right in the middle top by the valve valley, the water jacket was plugged at the stern cylinder. Related? who knows. Bradley I may take you up on help. My concern now is Can I just put these new heads back without having taken them off at TDC???? Is there a procedsure?bout now I'm wondering if I'm in to deep :unsure: thanks again for support and input. Mike

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Just something to throw out there, I do have a set of used Indmar cylinder heads (standard and GM Performance Fastburn heads)

Replacing heads is pretty involved, there are multiple torque passes for the heads. Adjusting the valves is the tough part, Indmar has their heads adjusted to 1/2 a turn pass zero lash with the lifters pumped up. If you have a service manual it will help. Check out the resource library on Bake's Online and you should hopefully be able to find a manual to help you out.

(I just noticed our server is down, CRIPES!) I will work on getting this back up asap.

-Paul

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Thanks Paul, already got new ones from Racing Tech? My xmas vacation is already planned! Should be fun! :thumbup::crazy: And thanks Wildcat, would like that!

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Is the motor open now? The one thing I might do if it was me, would be to mark the exact position of the distributor in relation to the intake manifold where they meet, as far as timing goes.

If you didn't do it, you'll have to "time" the engine. No big deal, you would have probably had to anyway. I dont think there's a need to think about TDC if you are lucky.

These engines use hydraulic valve lifter's dont they? If they do, that will make valve adjustment a breeze.

Keep up posted,

Steve B.

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  • 4 months later...

Is there anything that could have been done to prevent this? I'm freakishly paranoid about engine temp as that seems to be the one thing that can really F up an engine quickly. My temp was holding steady 163 under power (no ballast) and dropping down to 150 or so when throttling down. It was completely backwards from what I would expect if there was a clog, or debris in the line.

I haven't pulled the tranny cooler to check the screen, nor the impeller, but that is on the list to do this weekend. Can you backflush the cooling lines to help clean out debris? Or is that a one-way tube so to speak?

The engine warms up to about 170 before starting to drop after launch, but that has kind of been SOP, so I don't think too much of that other than the thermostat is a bit sticky until it opens up the first time.

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