Larger overflow tank needed or not?

[timsmitaruba]

Hi,

Just wanted to get some feedback on the overflow tank. I currently have the long polished thin one that came with my complete kit.
So far I've read a few times that this size might be too small for my engine, which is a 351 stroked to a 427.

I live and will drive in Aruba, where its around 85 degrees throughout the year. Would you advise to get a larger one, and if so do you have any suggestions?
Any pics would be very welcome as well, I am looking for a not too complicated but workable solution.

Thanks in advance,

Tim

[Jeff Kleiner]

The included tank works and I have used it on complete kit builds but I feel the capacity is marginal and because of this it takes a good bit of trial and error to hit the sweet spot of "not too little, not too much". I think it's capacity is around 20 ounces. On base kit builds I have opted for this 52 ounce capacity tank:

http://www.jegs.com/i/RPC/707/R6078X/10002/-1



Jeff

[Big Blocker]

Yup, no question about it, the F5 supplied tank is "marginal" at best.
I had an issue with mine a few years back, tank would fill during spirited driving and then overflow to ground. When the engine cooled, it drew back everything in the tank but was short on full-needed capacity, so drew in air also. That required me to add water/coolant every few drives, about a quart total, to get me back to "full. Changed tank to a larger size and no more adding water - system works perfectly.
Too big is not an issue here when the consequences of too small are air in your system and possible hot spots causing overheating issues.

Doc

[GFX2043mtu]

I didn't even try to use it after looking at it. I went with a Moroso mounted to the F panel.

[boat737]

After reading the threads and notes about the problems with the bigger blocks (351w, 427w), I also went with a bigger tank. Didn't even try the FFR supplied tank, so no input on it's usage good or bad. I went with the Summit 34 oz. tank, which is very similar to the FFR unit, a bit bigger in diameter at 3 in. by 10 in. tall I think. https://www.summitracing.com/parts/sum-300103 I've checked the level after almost every drive, and it seems to be more than sufficient. I fill it to within an inch or two from the top tube when hot (the first few times), and it never gets to within 2 or 3 inches from the bottom tube after cooldown. So far it's fine.

[timsmitaruba]

Thx for the replies guys!

[timsmitaruba]

Hi do you have a picture of the mounted Moroso?

[rrrose]

Hey Tim,

I cannot comment on the tank sent with complete kit. Having read enough of the challenges folks had with the 351W and larger blocks I simply got the 52oz one that seems to be the same as what Jeff uses. Makes it simple for me... it will go in same place as the original its just bigger and just as shiny.

How is your car coming along? You have been silent sense class back in Aug.. I worried the Aruba customs folks had tossed you in a cell for trying to bring in so many tools. That or your spouse had put you in house arrest for all the tools and car parts

Ron

[timsmitaruba]

Hey Tim,

I cannot comment on the tank sent with complete kit. Having read enough of the challenges folks had with the 351W and larger blocks I simply got the 52oz one that seems to be the same as what Jeff uses. Makes it simple for me... it will go in same place as the original its just bigger and just as shiny.

How is your car coming along? You have been silent sense class back in Aug.. I worried the Aruba customs folks had tossed you in a cell for trying to bring in so many tools. That or your spouse had put you in house arrest for all the tools and car parts

Ron

Hey Ron,

Nice to hear from you man! Hope all is well. Haha yeah local customs can be tough (especially that 50% import tax I had to pay on all of it) sometimes but all is good now. My car is actually going very well, most aluminum is in, car rolls and is aligned, 427 engine I bought from Mike Forte is in, wires nearly done, dashboard complete, I am slowly going towards firing it up for the 1st time, plus...I am still married ;-)
My business is doing very well at this time so don't work on the car as much as I would like but since I decided not to give myself a finish dead line I don't stress about it at all, its just a lot of fun and hey, when I do feel like **** I just peak into my little Cobra man cave and I am all smiles again.
Locally lots of folks are following the built and its just a lot of fun, and that's simply what its all about man.

How is your car going by the way? And can you get me a pic of your overflow tank (A Moroso as well?)
Take care amigo, rgds,

Tim

[NAZ]

I calculated the expansion volume of my system to be ~30oz when the coolant is heated from 40F to 200F. My system holds a bit less than 5-gal total. So that may give you a theoretical idea of the size of an overflow tank. Or you could search one of the antifreeze manufacturer's websites for thermal expansion info on their product and do your own calculations.

Or you could use the recovery tank that came with the kit that captures most of your overflow from a full to the brim radiator and leave some airspace in the radiator like we did in the olden days before cars had recovery tanks. Back then the hot tank of the radiator was used as an expansion tank. Remember, the expanded coolant that puked into your recovery tank is doing absolutely nothing to help cool your engine. So don't get too wrapped around the axle over a few ounces of capacity.

[mike223]

Remember, the expanded coolant that puked into your recovery tank is doing absolutely nothing to help cool your engine.

Exactly - if you have a couple inches in the bottom of the overflow when hot - the system is "full".

[GFX2043mtu]

I do thermal transfer professionally and what I can tell you is the exact volume of expansion is tricky as there are a lot of factors that have slight effects on it. What I can say is that NAZ has a good rough figure for a 5 gallon system using a 50/50 mix with distilled water. This system will roughfly expand about 30 oz from 60-220 F. This expansion is proportional for a 4 galon system (24oz). How ever if you change the concentration it will change. This rough figure is accurate enough for small tank sizing. I would avoid not filling the radiator completely This type of practice can result in uneven heat distribution across the heat exchanger. This can cause a noticeable loss of efficiency in the exchanger. And can reduce the heat exchangers life span due to uneven expansion in the cooler. Once again that is why you some times find heat exchangers with side cuts in the end sheets. How ever side cuts are found more often on charge air coolers. One last thing is that for some engines complete deairation of a sysyem might take a few drive cycles, and a system should always be deairated to prevent hot spots. This means the expansion tank must have fluid in it regardless of if its warm or cold. For a stock block 302 the FFR tank might be fine but for a larger motor it is advisable to get a bigger one and do things correctly.

[RR20AC]

I have about 800 miles on my car now and yes, the in and out flow from the system exceeds the tank the way it is set up. I did notice the top of the drain is about 3 inches below the lid of the tank. I added an extension to this so it is right up to the cap. Still need more driving time to see if this extra space is the ticket. I already have a larger tank picked out if needed.

[JRL16]

Sounds like we have the same engine. My FF5 tank was very marginal in this application so I opted for a tank from Canton. Nice thing is it has a sight tube so I know what’s in the tank without taking the cap off. Got it from Summit.

[timsmitaruba]

Thx for all info guys!!

[TexasAviator]

My mustang with decades of use only had an overflow with th 16 # cap, its active expansion and contraction was not using an expansion can but an overflow. With the 180 degree thermostat and good coolant it never expanded past the 3 gallon concentrate water mix. I just installed this same setup on my cobra. The car warmed up to 180, fitech kicked on the fan for the first drive and while letting it run it never expanded past the point of excaping the system. I will have to keep an eye on it as the expansion then will probably let fluid go but not pull it back into the system but it worked on my mustang, i am sure it will work on this.

EDIT: Just so I dont assume too much; I could pull from the bottom of my expansion tank and feed that to the filler neck. Is that a better or more appropriate route? Thanks in advance.


20180303_190204 by Brandon Fertig, on Flickr

[NAZ]

Yes, if you have a cap that has the valve in it you can draw from the bottom of your overflow tank and the coolant that puked into the tank will be drawn back into the radiator when the system cools. Make sure your overflow tank is vented to atmosphere as atmospheric pressure is what provides the motive force to return the coolant back to the cooled down radiator.

[rrrose]

Finally figured out what box and pulled out the original vs the larger size reservoirs.
Ron
MK4 reservoirs 1 sm.jpgMK4 reservoirs 2 sm.jpg

[Rick1916]

I too went with the Canton big one. Not sure of the model but it’s got the sight tube on the side. I really like them in general for what it’s worth.

[jakester888]

The included tank works and I have used it on complete kit builds but I feel the capacity is marginal and because of this it takes a good bit of trial and error to hit the sweet spot of "not too little, not too much". I think it's capacity is around 20 ounces. On base kit builds I have opted for this 52 ounce capacity tank:

http://www.jegs.com/i/RPC/707/R6078X/10002/-1



Jeff

Jeff : do you have the part numbers for those upper hoses?