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Hi, about 2 months ago we purchased a '68 427/435 vert - after working with the 16 year owner (and previous 11 year owner) for several months sharing info, pics, etc. The car and I are still 'getting to know each other' but I'm very pleased so far. All the numbers (VIN, block, heads, intake, carbs, trans, rear, etc.) all check out. I've been going thru mostly cosmetic stuff underhood and under car. It's pretty hot here right now, and will be for a bit, so I have some questions on cooling.
There are no leaks from radiator, hoses, etc. On 90+ degree days it'll run just under 212 according to the gauge - gets just a bit cooler while moving, and right at 212 when idling in traffic. I'm going to change out hoses and such, but want to make sure that before I do I get some good intel from the experts on whether there are other changes that I should make at the same time to keep it running a bit cooler and not have to worry about it.
For additional background, I'd like to keep it stock looking underhood, but I'm not afraid to swap out to a new radiator if that would help.
I'm putting in some pics. Can those in the know help with these questions?
* Is this the stock radiator? I don't really know how to tell for sure.
* It appears to be missing a few items around the overflow tank - what am I missing? It's over 50 years old so I expect to have to replace some stuff. :-)
* Would it be worth it to change out to one of the expensive aluminum radiators? If this is the stock unit, I'd just store it........
* What Tstat should I run - I'll change it out when I change hoses, fluid.
* Any other advice to keep these things cool without going to electric fans?
* Any other observations?
Hi, about 2 months ago we purchased a '68 427/435 vert - after working with the 16 year owner (and previous 11 year owner) for several months sharing info, pics, etc. The car and I are still 'getting to know each other' but I'm very pleased so far. All the numbers (VIN, block, heads, intake, carbs, trans, rear, etc.) all check out. I've been going thru mostly cosmetic stuff underhood and under car. It's pretty hot here right now, and will be for a bit, so I have some questions on cooling.
There are no leaks from radiator, hoses, etc. On 90+ degree days it'll run just under 212 according to the gauge - gets just a bit cooler while moving, and right at 212 when idling in traffic. I'm going to change out hoses and such, but want to make sure that before I do I get some good intel from the experts on whether there are other changes that I should make at the same time to keep it running a bit cooler and not have to worry about it.
For additional background, I'd like to keep it stock looking underhood, but I'm not afraid to swap out to a new radiator if that would help.
I'm putting in some pics. Can those in the know help with these questions?
* Is this the stock radiator? I don't really know how to tell for sure. Not the original radiator. The original radiator won't have a cap on the radiator itself.
* It appears to be missing a few items around the overflow tank - what am I missing? It's over 50 years old so I expect to have to replace some stuff. :-) Hoses appear to be routed wrong. Get new repro hoses and re-plumb.
* Would it be worth it to change out to one of the expensive aluminum radiators? If this is the stock unit, I'd just store it........You can get a Dewitts factory appearing/painted radiator that cools great and looks stock.
* What Tstat should I run - I'll change it out when I change hoses, fluid. If you are in a hot climate, I'd run a 160* myself... most will recommend a 180*. Cooler the better in my mind for many reasons. Cooler temps, less detonation probability.
* Any other advice to keep these things cool without going to electric fans? You can run the Hayden #2799 extreme fan clutch on your stock 7 blade fan. That may help your temps at idle, but will eat up some HP.
* Any other observations? Honestly, your temps are not that bad if its stable at 212*….that's about what they ran from the factory, I probably wouldn't worry about it unless the temp is climbing higher then that. You do need to verify what the temp actually is though, try an IR temp gun on the water neck. Gauges are notoriously off. It its not puking over when you shut it off, its not likely that hot.
You are missing your overflow hose that runs towards the front of the car. If you did have any coolant puke out you would shoot it straight into your engine bay.
212 degrees honestly doesn't seem out of line to me with a stock setup, but I'm not an expert. I do see you are at the very least missing the seal at the top of the radiator frame to the radiator. You want all of the seals in place to force as much air as possible through the radiator.
I am running the Dewitt's radiator and dual electric fan setup on my L88 and the setup is a beast. Once it hits 195 degrees the fans kick on and and they drain the heat away.
That small hose coming off the small tank should run to an outlet soldered near the top of the right side rad. tank. If it isn't connected to anything it will most likely be blocked ,look for a ball bearing or similar pushed into the hose.
Should have no cap on the radiator.
Looks like the foam rubber seals are missing from between rad. frame and rad. itself.
My 427 was running around what yours is and putting a dewits radiator was the best solution to the high temps ,Tried flushing old radiator, flushing engine ,new seals ,hoses and water pump still ran hot so put the dewits in and job done.
with ajrothm's comments but would go with a 180* tstat to ensure the oil is at an optimum temperature. Also, stuff in the biggest aluminium rad you can find.
I really appreciate the insights and guidance. I'm going to get a Dewits. Does anyone have a pic of the hose routings, including any pics of the area around the overflow tank? Much appreciated!
Your cooling system has been modified from stock. Your radiator looks correct but it has been re cored. A 68 L71 would not have an external expansion tank. The expansion tank was built into the radiator. You are missing the lower fan shroud extension. This would help pull a little bit more air through the radiator if added it back.
If you are getting a temperature gauge reading of 212 on a 90 degree day I think your doing pretty good. When I lived in Phoenix the temp gauge on my 68 L71 was always near the 212 mark regardless of what the out side temperature was. Prolonged city driving would raise it just a little and cool days lower it maybe 5 degrees. I live in Wisconsin now and it still hovers at 212 when I drive. I know that is a temperature that freaks most people out thinking it is high but I think it is just the nature of the beast. I consider it normal for a stock L71. If that is to high for you add a Dewitt's aluminum radiator.
Hi John, I thought that might be the case - expansion tank and all - I didn't think it was 'supposed' to be there. The car spent quite a bit of its life in S CA, and 2 owners ago (I've spoken with him) did whatever he thought best to keep it running a bit cooler and, although I didn't ask, I'll bet he added the tank and whatever he thought useful.
I had it out yesterday - 96 degrees out. When idling it ran up a bit over the 212 mark. Although it seems like it might be okay, I still wonder what will happen on the 100+ degree days we get. So, I'll probably go with the proper looking 'restoration radiator' from Dewitts and remove the overflow tank? I have the AIM, but it's a bit hard to see how the hoses, etc. route. Do you (or anyone else reading this) have any pics of how the radiator, heater hoses, etc. are 'supposed' to look?
A pic from a 1968 issue of Car & Driver. Note presence of radiator cap and no expansion tank.
But unless originality is important to you, I would add an overflow bottle like this guy did. It expands the capacity of your cooling system by eliminating air in your radiator.
Hi Brad, really appreciate your insights and pics. (beautiful car, btw!)
The good news is that, after spending several months talking with the last two owners (covering 1/2 the cars life), having sufficient remnants of the tank sticker, and checking all dates, codes, etc. on the block, heads, carbs, intake, exhaust manifolds, trans, rear, I'm confident this is the real deal. That said, over the years I know previous owners made a few changes including cooling, removing the smog, and removing the TI (I got the distributor, shielded plug wires, and other stuff with the car, the mounting holes are there, etc.).
When I get a 'new' old car like this, I always go thru the stuff that can leave you stranded, and cooling is one I'm taking on now. We're now in the mid-90s every day, and we'll have several 100+ degree days. I want to be able to use the car without worrying about overheating. I knew the expansion tank 'shouldn't' be there and was added somewhere along the way. My sort of dilemma is that I want the car to look stock but also be as usable as possible (this car was ordered with 4.11 gears, so it will never be a 'highway cruiser'). So, for your input (and any other forum members who have some experience here) if you would, I think I'm down to three options:
1) Replace the current radiator with a Dewitts 'restoration radiator'; remove the added expansion tank.
2) Leave the current radiator that I now understand has be recored, and remove the expansion tank
3) Recore the current radiator using the Harrison tanks (is there a way to see if these tanks are the originals? I didn't bother checking this because I figured the radiator was not 'stock'); remove the expansion tank.
Whichever option I use, I have new heater and radiator hoses, and will replace the stat.
From what I can see, yes, those are original Harrison tanks. Many people have purchased repro radiators only to find that they have difficulty getting the hoses to line up without rubbing as the aftermarket inlet and outlet hose necks are significantly different in shape. Notice your top neck is a precise, sharp 90 degree bend. GM did not spend all the extra money to have those made that way if a much cheaper to produce simple curved extrusion would work. What people never realize is GM literally spent millions and millions fine tuning the cooling systems to be able to tame the 427 monsters for everyday street usage. I have been inside the wind tunnels at testing facilities at the Harrison Lockport NY plant several times over the last 40 years. People think a $200 radiator from china is going to do the job of cooling are making a huge mistake.
You have the correct 1968 fan shroud, you will need to add all of the foam seals around the core support and shroud to make sure air is being forced through the radiator and not going around it. (Air acts like water and will take the path of least resistance. Its easier to go around the radiator than through it). You appear to have a correct fan blade, and need to make sure your fan clutch is working properly (locking up at higher temperatures), and definitely toss that radiator cap and get a Delco 15lb. Even if it is a part store one, not 100% original big ear 1968 one, a proper cap is a critical component to properly raising the boiling point of the coolant so the car does not overheat.
Pics of the tubes inside the radiator looking in through the filler neck (Cap hole) will help me tell you the condition of the internal radiator.
Dont give in to most internet experts that will tell you to put in a champion radiator and ford taurus electric fans. You have a nice car, let me help you make it better
p.s. join us at 1968 Corvette owners group on FB
BigRedBrad
Last edited by bigredbrad; 07-03-2019 at 01:22 PM.
Hopper12, sorry about the bad info I gave you on the 68' radiator with the cap/no cap and the expansion tank. Our 67' 427/435 has a cap and no tank, and then our 69' 427/400 has no cap and does have the expansion tank. I thought the 68' was the same as the 69'.
I'm glad Brad came in and got all of the 68' info straight. As he mentioned, if your tanks are original, you may as well just have the radiator re-cored and it will likely cool fine. Honestly, it seems like yours has already been re-cored, you may not get much temp reduction if you redo it. Also as mentioned, 212* on a 96* day is not bad as long as its stable there out on the road. If its heating up at slow speeds, I'd be looking at the fan clutch. However you can never go wrong with a Dewitts resto/direct fit. I have one in our 65' 396/425hp and it runs around 185-190* most of the time on the road on a 95* day, however, idling it WILL heat up. On one extreme scenario, we saw 240* idling in a toll booth for 15 mins after an hour at highway speeds, that was with a 7 blade fan and extreme duty clutch... Pretty scary..
^^^^ No worries at all. I'm just thankful for the many forum members like yourself who are willing to take the time to share, help, etc. I do when I can help - more knowledgeable on C7s but I'm coming up to speed fast on C3s.
I think, based on your and Brad's comments, that I may be on option #4: evaluate current radiator guts; if they look ok (I'm going to get a pic later this afternoon) then verify fan clutch is good, take off fan/pulley/etc. and clean them up/repaint; replace hoses/clamps/belts; replace stat; replace antifreeze because I really don't know how long it's been in there; replace the seals (on order); and let it ride for a bit.
Also, from Brad's picture, I'm guessing that the water outlet on the intake should not be painted? I'm sure the engine rebuilder from about 15 years ago did that. :-)
The present radiator is an aluminum unit. With the temps you presently run, I wouldn't consider swapping it, just yet. When the rad swap was made, it appears that the radiator seals were omitted from the process. Investigate this and compare what you have with what is called out in the A.I.M. Installing the seals will help improve the cooling capabilities of the radiator 'system'.
Go with a 180* stat, if the one presently installed is 195*F. That may not lower final operating temps; but if you have the 195*F stat in there, it could help.
If doing those things get you down below 200*F, leave it alone. Just make sure you have a good pressure cap on the expansion tank and a 50/50 mix of antifreeze and distilled water in the system.
I disagree with 7T1 vette, but you can tell us Hopper if the radiator is aluminum or copper/brass. I have never seen aluminum tanks with the factory sharp 90 degree necks before and there is no way to connect the brass tanks onto an aluminum core. Maybe Im missing something in the photo that shows it is an aluminum replacement. No problem. Either way, I agree that inspecting the inside of the radiator with pics of the tubes looking in through the filler neck would be helpful for me to help diagnose your issues. I also agree that adding all the factory foam seals will help, usually 10 degrees or so depending on condition. There should be ones between the core support and the radiator tanks, at the bottom of the radiator to the lower core support, in two places at the top of the radiator to the fan shroud and the core support. ALSO, there is supposed to be a rubber one at the top of the core support - It is a metal piece that screws to the core support and has a 1/8 piece of rubber that seals the top of the core support to the hood. This keeps air from going over the radiator.
I drove mine in a 30 minute parade at 90 degrees, 85% humidity, idling at 2 mph and it never got over 200. As soon as I left and got the rpms up and pulled a little air through, right back to 185.
I truly appreciate the thoughts and advice. I'm going to drain a bit of coolant from the radiator so I can see if it's brass or aluminum (due to the overflow tank the radiator was completely full and I couldn't really tell) and I'll take a pic and post it.
This is why I find this forum so useful - lots of fellow enthusiasts willing to share their ideas. I will say that I had it out again yesterday while it was mid-upper 80s and it never went over 210........
07-01-2019, 03:54 PM
'68 427/435 cooling questions
with ajrothm's comments but would go with a 180* tstat to ensure the oil is at an optimum temperature. Also, stuff in the biggest aluminium rad you can find.
