Radiator seal and under-hood airflow

Forrest Gump

CCCUK regional rep
The gap between the top of the radiator and the underside of the support frame has always been open on my car. You would think with this big gap that l would get cooling issues, but the car seems to manage okay. (The foam strip between top of frame and underside of hood is in place, but somewhat futile with a large gap just below).

I’m still thinking about sealing off this gap however to maximise radiator efficiency. What have others got here? It’s quite a large opening and irregular shape - Is Oem just a large foam strip or some other trim I’m missing?

There’s just one thing I’m wondering though - if by having the gap open as I have at the moment if there is actually any positive benefits, such as a supply of cooler air for engine induction, or generally circulating more air to reduce engine bay temperature.

Theoretically the engine is supposed to draw fresh induction air from the rear of the hood, but I’ve got cooler air rushing in from the front end too so I’ve got no idea of the airflow paths under my hood. I might have to close off the gap over the radiator and see if I notice any difference to temperatures and engine performance.

Any thoughts?

41AC19F8-6726-4421-B38A-F853BDCE78AF.jpegDFD47341-2CE9-420D-A98C-B54FA29FF4F2.jpeg
 

Vetman

CCCUK Member
I doubt that the gaps matter now in the temperate UK. I imagine that for the later C3’s with the forward cold/ram effect inlet that sealing was necessary to induce any cold air to the intake. As you do not have this, nor the intended cowl induction air cleaner arrangement, then some cooler air under the bonnet is probably a good thing. You could also remove the cowl flap to let hot air out at the windscreen, assuming the pressure balance allows this to happen.
 

johng

CCCUK Member
Andy, when I got my car it had a bit of foam in that gap on either side of the air intake as you can just see here.

8821

As the original foam was slightly past it's sell by date I got a replacement kit, but this also had just 2 short lengths, so I bought a separate piece of foam to fill the gap completely. You can just see it in this photo. No idea yet if I actually need it of course!

8822
 

Forrest Gump

CCCUK regional rep
I doubt that the gaps matter now in the temperate UK. I imagine that for the later C3’s with the forward cold/ram effect inlet that sealing was necessary to induce any cold air to the intake. As you do not have this, nor the intended cowl induction air cleaner arrangement, then some cooler air under the bonnet is probably a good thing. You could also remove the cowl flap to let hot air out at the windscreen, assuming the pressure balance allows this to happen.
As you say because the cowl induction parts aren’t there, I could well be robbing cooler air from the engine if I completely close off the gap. I might try just partially blocking the gap.
 

Forrest Gump

CCCUK regional rep
Andy, when I got my car it had a bit of foam in that gap on either side of the air intake as you can just see here.

As the original foam was slightly past it's sell by date I got a replacement kit, but this also had just 2 short lengths, so I bought a separate piece of foam to fill the gap completely. You can just see it in this photo. No idea yet if I actually need it of course!
Thanks John. That’s neat, can’t even see the joint. So you’ve done away with cold air cowl part.
 

Oneball

CCCUK Member
Andy, when I got my car it had a bit of foam in that gap on either side of the air intake as you can just see here.

View attachment 8821

As the original foam was slightly past it's sell by date I got a replacement kit, but this also had just 2 short lengths, so I bought a separate piece of foam to fill the gap completely. You can just see it in this photo. No idea yet if I actually need it of course!

View attachment 8822
What are the spacers you’re holding for?
 

johng

CCCUK Member
Tim, the spacers were under the bonnet hinges (nearly said hood hinges there!), I was making a record of how many went each side.
Andy, you can't see the joint because there isn't one. Given that my engine is such low power anyway I didn't think the cold air would make a significant difference and I fancied an air filter with a bit of bling :) I'm not sure but I might still have the 2 small bits of foam if you want them to block off part of the gap.
 

Roscobbc

Moderator
Earlier C3's would have been totally sealed so that any rubber/sponge sealing/fillet pieces effectively force any air entering the front end to only pass through the radiator - air intake for carb 'pulls' its air from engine compartment. Exception on early C3's would be L88 which has (like later cars) cowl induction.
 

stealthyflatfish

CCCUK regional rep
IMG_20210110_141314_064.jpg
So after also fitting a Champion ally rad, my brass one had a damp patch in lower left corner of the core.
I didn't like the gap on mine either, so hears what I did, got some 2x2 inch ally 90deg angle from B&Q. made a cardboard template, and with the help of a hacksaw and Dremel cut it to the correct tight fit, it just slid in the bottom of the plate butts up squarely to the new rad and the 90 deg angle is perfect, then utilizing the two bolt holes that are already in the radiator surround ( top middle ) I dug out some bolts that fitted and slid some tap washers over the threads, then inserted the bolts into the holes This holds the plate in position, it doesn't rattle and has never moved due to air pressure, a quick polish with Auto-sol it matches the polished Finnish of the rad.
If I run it without the plate in engine runs about 190 deg f
with the plate in engine runs at 180 deg f whilst crusing. Providing the rad is sealed to the support frame. A couple of hours well spent.
 

Forrest Gump

CCCUK regional rep
So after also fitting a Champion ally rad, my brass one had a damp patch in lower left corner of the core.
I didn't like the gap on mine either, so hears what I did, got some 2x2 inch ally 90deg angle from B&Q. made a cardboard template, and with the help of a hacksaw and Dremel cut it to the correct tight fit, it just slid in the bottom of the plate butts up squarely to the new rad and the 90 deg angle is perfect, then utilizing the two bolt holes that are already in the radiator surround ( top middle ) I dug out some bolts that fitted and slid some tap washers over the threads, then inserted the bolts into the holes This holds the plate in position, it doesn't rattle and has never moved due to air pressure, a quick polish with Auto-sol it matches the polished Finnish of the rad.
If I run it without the plate in engine runs about 190 deg f
with the plate in engine runs at 180 deg f whilst crusing. Providing the rad is sealed to the support frame. A couple of hours well spent.
Thanks Stealthy, I like that.
Knocking something up out of Alu plate is probably what I shall do too.

It would be more involved, but I'm also thinking about leaving a gap and then somehow ducting at flow of air back towards my air filter. Maybe a duct on the underside of the hood.

Your radiator looks good too. How many cores is that and did it give you any improvement over the stock brass rad?
 

stealthyflatfish

CCCUK regional rep
Original brass radiator temp was about 205-210f
on a run thought that was a little close for comfort, although that was on the interior guage.
When I originally dropped the ally three core rad Inn
temperature on run dropped to about 190f, doesn't sound a lot but at least it proved the point that ally rads dissipate more heat and at a faster rate.
The ally three core rads are no thicker than the original brass two cores, it's just the cores are thinner and a little lighter. It now runs about 180-185f after my mod, it has twin electric fans which runs automatically off a wet thermal switch, which I believe comes out of a mitsubishi Evo. Fans come on about 210f and off at 185f although they rarely come on out on a cruise.
With regard to your airflow issue, what about using something like kitchen extractor ducting ( the square squashed type ) with the flexible fitting on the end, so when you lift the hood it flexes at that point, don't know if they do a metal construction type ?
Google is your friend.
 

Forrest Gump

CCCUK regional rep
Cheers Stealthy, that’s good info about your champion radiator. I need to wait until my Oem springs a leak before I can justify an Ali rad. The temps you are at now are similar to what I see - It’s manages fine under steady driving but if I lean on the motor for a bit and the temperature goes up, I’m probably a bit marginal. I’m thinking that blanking off the gap will give me a bit more from the radiator. The top half of the radiator must be the area that cools the most so if I can direct more air through the rad and not the gap should help. Not a bad idea re the ducting...painted black 👍
 

stealthyflatfish

CCCUK regional rep
Word of warning to anybody ( and you Forrest ) contemplating buying any sort of alloy radiator for their Vette, make sure you get the type with the chamfered top tanks on both ends, if you get the type with the square end tanks you can run into clearance with the hood issues.
 

Forrest Gump

CCCUK regional rep
Word of warning to anybody ( and you Forrest ) contemplating buying any sort of alloy radiator for their Vette, make sure you get the type with the chamfered top tanks on both ends, if you get the type with the square end tanks you can run into clearance with the hood issues.
Okay cheers - I hope that wasn't your experience, always a worry with any aftermarket part and all the Corvette variants by year etc. Is your rad filler cap remote?
 

stealthyflatfish

CCCUK regional rep
Yes, separate expansion tank mounted over wheel arch on 71 Big Block.
And yes that was my experience as shown in the picture, overcome by striping out the bottom u brackets, making a new bracket to push the bottom of the rad as far forward as possible, so the top of the rad leans back further towards the engine, twas a right PITA and something not to be recommended.
 
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