How much fluid is in a 350 block?

[ryan_289]

Ive been working on the temp sending units and such on my 78 C20. The coolant ive drained out has been pretty brown and dirty. Before I put a thermostat back in I thought it would be a good idea to run water through the block and drain it out several times until I get cleaner water. When I get finished I figure I will be pretty close to straight water in the block. How much will that be so that I can put the correct amount of anitifreeze in the radiator to get a 50/50 mix?

 

[1987 GMC Jimmy]

Ive been working on the temp sending units and such on my 78 C20. The coolant ive drained out has been pretty brown and dirty. Before I put a thermostat back in I thought it would be a good idea to run water through the block and drain it out several times until I get cleaner water. When I get finished I figure I will be pretty close to straight water in the block. How much will that be so that I can put the correct amount of anitifreeze in the radiator to get a 50/50 mix?

Are you using the little three dollar Prestone flush kit? That'll flush your heater core, block, and radiator with some pressure. Good little tool. As far as capacity goes, I'm not sure. Bone dry, I would say mix three gallons of straight coolant and three gallons of water in a bucket and just start pouring. You won't be able to get all the water out, though, so that's a hard number to put out there.

 

[vkh]

If you're worried about the ratio get one of those antifreeze testers. Fill your radiator 50/50 mix until about 3/4, run it abit to mix it all. Then test your fluid to see if it's where you want it freezing point wise. Then adjust from there by adding antifreeze or water.

 

[CSFJ]

another point to consider, is that it's fine to use tap water for the flush operation, but when you do the final fill,try to drain as much of the flush water out and use distilled water when you mix with the coolant.

 

[HotRodPC]

If you bought 2 gallons of Coolant, you'll have better than a 50/50 ratio. I hope you do know, you don't pay for water and buy 50/50 mix.

Unless of course you can find it on sale for $4.99 a gallon like it is at Napa this month. It's $4.99 for a gallon of 50/50 right now. That's equal to $10 for a gallon of full strength so I'd do that, but I just won't pay $11.99 for 50/50 when full strength is usually $1 more. That makes for expensive water.

 

[HotRodPC]

IIRC, it seems my 454 with a 4 core takes about 3.5 gallons. I usually put a gallon of Coolant, gallon of water, gallon of coolant and it never took another full gallon of water so I know it was better than 50/50.

 

[ryan_289]

I wasn't planning on using a flush kit, just running a few cycles of water through. Right now there is no thermostat so it should cycle through quickly.

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[chengny]

Ive been working on the temp sending units and such on my 78 C20. The coolant ive drained out has been pretty brown and dirty. Before I put a thermostat back in I thought it would be a good idea to run water through the block and drain it out several times until I get cleaner water. When I get finished I figure I will be pretty close to straight water in the block. How much will that be so that I can put the correct amount of anitifreeze in the radiator to get a 50/50 mix?

I hope you're planning to do one of the final flushes using Prestone Super Flush - and then flush again several times with fresh water.

But that aside, rather than leaving the water in the block - after your final flush - wouldn't it make sense to just dump the system until empty? Then, instead of trying to dial in the 50/50 mix by adding straight glycol to the leftover flush water, you could start with a blank slate. Premix the glycol and water (at a 1:1 ratio) in a bucket/old coolant bottle and then simply fill the system with your blend.

 

[ryan_289]

I hope you're planning to do one of the final flushes using Prestone Super Flush - and then flush again several times with fresh water.

But that aside, rather than leaving the water in the block - after your final flush - wouldn't it make sense to just dump the system until empty? Then, instead of trying to dial in the 50/50 mix by adding straight glycol to the leftover flush water, you could start with a blank slate. Premix the glycol and water (at a 1:1 ratio) in a bucket/old coolant bottle and then simply fill the system with your blend.

Are there drain plugs in the block to get the water out of the block?

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[74 Shortbed]

Are there drain plugs in the block to get the water out of the block?

Yep, one on each side, pipe plug just above the [an rail.

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[chengny]

Are there drain plugs in the block to get the water out of the block?

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Yes, there are two block drains - sealed with 1/4" NPT pipe plugs. I wasn't going to get into this because it sounded like you wanted to do this flush quickly, but since you asked:


If you pull those plugs, it is almost a sure thing that no coolant will drain out. With the plug removed, if you look into the coolant passage behind it, you will see it is packed solid with 40 years of sediment. Just to get a trickle to flow will require that you use a small screwdriver, a pick or whatever to chip the deposits out.

Once you get some flow, you would need to thread nipples into the tapped holes and backflush the block. I would flush bottom up and let the water flow out of the t-stat housing.

Actually, I flush using a solution made with ZEP Heavy Duty Calcium Lime & Rust Remover and water. The solution works best when moving, so I use a small utility pump to recirculate the flushing liquid.

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[HotRodPC]

I kind of like that cheap Prestone flush kit too. I'd still do the Chemical flush too, but then I'd prefer the backflush T in the Prestone kit. It not only gets the heater core since you're using a heater hose, but it pushes the water backwards through the system. At least so I think it does. It would seem to make more sense to me to push crap backwards out of the holes instead of trying to cram it on through and possibly wedge the junk in the tubes.

 

[HotRodPC]

BTW, for those who are interested in the backflush kit, it's at Wally's for $3.44 with 2 day shipping available. Maybe available in the store or for store pick up same day.

https://www.walmart.com/ip/Prestone...75035&wl11=online&wl12=16817507&wl13=&veh=sem

 

[1987 GMC Jimmy]

I just pluck mine of the shelf at the Walmart TLE. Those things seem to sell like hotcakes at my local store. I like it. It's always there if you want to flush it again, and it gives it some oomph to clean it out good. The chemical flush is a good idea. I've never used it because neither of mine were that gnarly when I got them, but they were definitely dirty. I attach a section of old garden hose to the spout and drain it into an old cooler so I can see the carnage. It's not messy, either.

 

[HotRodPC]

I just pluck mine of the shelf at the Walmart TLE. Those things seem to sell like hotcakes at my local store. I like it. It's always there if you want to flush it again, and it gives it some oomph to clean it out good. The chemical flush is a good idea. I've never used it because neither of mine were that gnarly when I got them, but they were definitely dirty. I attach a section of old garden hose to the spout and drain it into an old cooler so I can see the carnage. It's not messy, either.

Agreed. I use the hose too. I've bought one of these kits just for the radiator spill out spout and the hose adapter. As far as the T that you put inline to a heater hose, I've collected a few of those from Pull A Part so I had spares in my parts bin. Get a new to me truck and I decide to to do the flush, I go to the part bin and install it and use the same hose adapter and spill spout that I keep in my tool chest in the specialty tools drawer.