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Debbie Harris's 1969 Grand Prix

2022 September
of the Month

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Flushing engine block

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The water/coolent in the engine is really rusty and $hit brown from sitting a long time. I want to isolate and flush the block by itself. Meaning I dont want to flush that ugly brown water into heater core and rad. (I'll do those seperately as well). The water that came out of the rad. is clean looking so no need to run rusty water thru it Im thinking.

My thoughts are to attach hose barbs to heater hose at the rear of the engine and the hose at the water pump. Screw two garden hoses to the ends and connect one to a faucet and the other to the drain. I think I only need to pull the lower rad. hose and plug as the upper has the thermostat which should be shut .

Does this sound right?

And which way should I make the water to flow? Does it matter?

After it comes clear I will flush with a Gunk Rad. rust remover product.

Any thoughts or advice on this would be appreciated.

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Sounds like you have a good plan. Flush engine, rad and heater core separately.

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I trust you're aware that flushing a block this way is a good way of knocking crud loose to plug up small passages, and flushing compound has a habit of doing too good a job and leaving you with pin hole leaks. Of course, if that happens, it was going to happen sooner or later anyhow. Just be aware that immediately after flushing (100 miles or so) aren't the time to go for a long drive or to sit in traffic. Personally, I'm not a fan of flushing a block without opening the top end. If it's bad enough to need a flush, odds are your head gasket (and sometimes intake) have taken similar punishment.

The thermostat should be pulled and replaced at any rate. If the water jacket is that nasty, the thermostat's been bathing in that same crud.

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Thanks Prof.

I'm hoping it knocks all the crud loose and shoots it out the discharge hose...then maybe reverse the flow a couple of times. PIN HOLE LEAKS! Now ur starting to scare me! lol I will indeed replace the thermostat.

Thanks for the heads-up..And I'm hoping for the best but preparing for the worst.

Much appreciated..

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Well I flushed the heater core, rad. and block using a power flusher (air/water) and everything came out real clear after good flushing. No chunks or heavy setiment was observed.

I did, however manage to blow out the seal in the H2o pump, better in the garage than out on the road, right?.

Thanks to all for the advice and I'll be back for more. I'm off to price a water pump now...any suggestions or references?

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Is the water pump shot or just the gasket? If it looks really crudy, then definitely replace it to be safe. Remember which bolts come from which position/bolt hole since they are varying lengths.

I prefer a Mr. Gasket wide-mouth thermostat just help flow more coolant when the thermostat is open. Obviously don't put the new one in upside down.

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Thanks Frosty,

I pulled the water pump off last night and low and behold crud galore! Alot was built up around the ports, mud and kind of like clumps of white looking crystals probably from the anti-freeze broken down. The area under the thermostat has got alot of crap aswell which leads me to believe the whole engine is full of crap.

Geez part of me wants to dig deeper and rip the intake and heads off, but the other the part of me wants to get this thing started.

I think it was the gaskets leaking but there is signs of rust at the weep hole. And btw I've bought a new pump but the plate that sits behind the pump looks like it was hit with a shotgun.

Where do I find one of these?

I gotta figure out what route to take on this engine.

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But aren't you glad you took the time to address this instead of just turning the key and hoping for the best? Good instincts there.

But if you've found this ... you need to find the rest. You know it's there now.

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OK Its gone from BAD to WORSE now! It looks like I need a timing chain cover too. Corrosion has eatin thru the housing.

Wheres a good source for parts anyone?

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For the record ... it's hasn't gone from bad to worse at all. It was already worse (you just didn't know it) and now it's getting steadily better.

Have you mentioned where you are and what engine it's for? Probably someone here has one lying about. While you've got it off, may as well finish the job. New timing chain and gears ... heck, since you're in that far, what more is it to remove the rocker covers and intake, pull the push rods and lifters, ease out that cam shaft and see how those bearings are. If they're good, odds are good the bottom end is ok. If not ... well, better to know now than when you fire it up.

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yeah you people that responded were a little more realistic about this than I was. I guess thats the route I should take..start digging in to it.

I'm located in WI.

I've located an old '70 350 long block (instate) for $55, if the timing chain cover is still good its cheaper than a new one.

Plus I have a new Cam thats better suited to this engine, just need to invest in the matching valvetrain components.

I was just hoping I didnt have go this route right out the gate...Like I mentioned in an earlier post, I wanted instant gratification.

We dont always get what we want do we?

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... but we get what we need.

Good attitude. Yeah, it sucks. But that's what we choose when we haul an old carcass out of a field instead of heading to the dealership. And if it wasn't such work ... it wouldn't be so damn satisfying when you do turn that key and hear the beast roar.

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