I'm working on installing the cooling system of my 1987, LS427 swapped IROC as seen in my signature. I have a brand new Cold Case 2 X 1.25" aluminum radiator and a new, parallel flow AC condensor. I want my electric fan to pull the maximum amount of air through both of them and that will require sealing up all gaps. I need some type of temperature resistant foam to seal the gaps up.

I think that most (maybe all) of the AC sealing foam at Lowes/Home Depot is low temperature stuff that probably won't handle 220F. Does anyone have any recommendations on what I can use to seal things up so that all the air pulled by the fan will flow through the condensor and radiator and not through gaps between the two?

 

I'm using the Home Depot type stuff on mine and it seems to be doing ok.

 

It's standing up to the high temperatures? I assumed that the Home Depot AC sealing foams would melt at car radiator coolant temperatures.

 

Technically I dont run mine to 220.... but it'll hit 200 on really hot days

 

The first summer, 2024, that I had my LS376/480 swapped Mustang (see signature) on the road, I didn't have my C7 Corvette, PWM fan dialed in quite right and I saw 220F, extended idling with the AC on. I got it dialed in better for summer, 2025 and I never saw temps higher than 210F, AC on, in Houston heat during extended idling. I could probably get in the Holley Dominator and command the fan on at a little higher speed and I think that I could get those temps down further but people say that even 220F is no issue for an LS engine. Kinda makes me uncomfortable, though.

Here is a picture of some of the Home Depot foams that I have on hand:


The blue packages are lightweight, open cell foam. The black tubing is more dense, closed cell foam for hot water pipes.


ULTM8Z, are any of these foams the same as what you used?

 

This is what I'm using. It's been 2 years & 10k miles. Hasn't melted or changed. You can cut it thinner but goo builds up on sciccors/utility knife. You have to remove the goo, brake clean or something. but it can be done.

https://www.menards.com/main/hardwar...172-c-3624.htm

 

Thank you for posting your experience with this Menard's foam. It looks similar to my blue packages Frost King foam. Mine doesn't have adhesive, though. We don't have Menards around where I live but I know that I can buy something similar at either Ace Hardware, HD, Lowes or McCoys that are all near me.

I'm getting the fealing that I underestimated the high temperature capabilities of this home AC sealing foam.

 

Frost King... yeah, that's what I"m using.

 

AWESOME! Thank you for confirming this!!

 

I have mine stuffed with the frost king stuff as well, no issues.

 

This is great news. I just ***assumed*** that this foam couldn't handle high temperatures and I'm really happy that I was wrong. It looks like the Frost King foam should be really easy to work with and it should seal everything up real nice forcing all the air to flow through the condenser and then the radiator itself. This will really help air conditioning performance which is a must here in the Houston area,

 

I know it's not an option for everyone, but I did it while the fascia was off. That was I could stuff it in all the way down to the core support along with next to the radiator. I don't have the scoop the V8 cars have, it's all open so I wanted to make sure air had no choice but to go through the condenser/radiator.

 

I use the rigid plastic edging for flower beds and walk ways. It last for years unlike foam. A lot of the newer vehicles also use rigid plastic air guides to help funnel airflow through the cooling stack.