Hi everybody. I have a '67 FHC, and the paint on the outside of the bonnet is starting to bubble in a small spot due to heat from the exhaust manifold. Is there an insulation kit for the bonnet to prevent this? If not, any suggestions?
Thanks!
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Oy that stinks. Have you Jet Hot’ed the manifolds?
You could also use header wrap, but it’s not easy to get full coverage on those serpentine manifolds. Lastly you could fabricate a heat shield and mount it to manifold studs or to the frame rail.
The manifold is missing most of it’s original coating. I am not ready to pull it and finish it yet. I would like a temporary fix until that day comes. I suppose some self-adhesive heat shield would do the trick. This is a driver, not a show car.
Not sure if self adhesive would last in the heat. I seem to recall this topic discussed previously. Are you sure there isn’t something wrong with your paint?
A single layer of that Al waffleplate stuff is probably enough. All you’d need is to fit 3 “L” shaped brackets along the upper row of exhaust manifold studs, and keep the waffle plate about 1" away from the manifolds.
I use the stuff quite often - not that long ago on a TR3 with tubular headers which glow when the car is doing anything other than idling… and the carbs are immediately above those headers on a TR3.
The “for purpose” self adhesive stuff is good - had it on my XJ6 for nearly two years. Note that there are no vents on an XJ6 - gets prettty warm under there with the old 4.2. I found it at my FLAPS. Paul
try Summit or other race supplies for aluminized stick-on: https://www.summitracing.com/parts/the-13500?seid=srese1&cm_mmc=pla-google--shopping--srese1-_-thermo-tec&gclid=EAIaIQobChMI5Z_z4ZTT2wIVDrXACh3-nwJOEAQYASABEgKqnPD_BwE
you can adapt a heat shield from an XJ6 very easily.
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I was going to suggest that but then thought about where will the heat go if the shield prevents it from going up. Will it cause too much heat to be directed toward the brake bottle heat shield? Probably not but it needs to be considered.
The “fix” for heat-damaged paint is to get it re-painted properly. Properly applied paint will NOT do that. If you look carefully, you will probably find the affected area has a layer of filler, and the filler has lifted from the metal, which is a sure sign of improper application.
Again, properly applied paint will NOT be affected by the exhaust manifold heat.
Regards,
Ray L.
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A valid question. Probably not an issue if the bottle HS is intact. I would curve the waffleplate to follow the headers, and probably put a layer on the bottle HS as well (here it comes in 1x.8m sheets, so there’s always a bit left over for that kind of thing.
The Al foil fiberglass stuff is great, but you need to use the right glue, and it does stick like shit to a wool blanket, so I would be leery of attaching it directly to the underside of the bonnet - unless I was dead certain I wanted it to be permanent.
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Another point that has been mentioned in the past, is the mixture too lean?
Cheers,
LLynn
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This is what I just picked up. I’ll give it a go and see what happens. Thanks for all the feedback and suggestions!
Hmmm, this is all very interesting, and timely – about a month ago I noticed 2 cracks in the paint on the left hand vent, towards the middle of the bonnet and right over the manifold. The paint is 2 years old and other than this I would say was very well applied indeed.
Also…it was idling a bit roughly and I had the mixture leaned out as part of addressing the issue. Weather also much warmer these past couple of months so less ambient heat dissipation.
Like the OP mine is a driver rather than a show car so I was never bothered about the less than perfect manifolds, but if recoating them would stop the paint issue getting worse then I can look at it.
Would a freshly coat on the manifold make that much difference?
I’ve added a strip of the self adhesive insulation to the underside of the bonnet where the heat is building up. We took the car on a jaunt around town in the hot sun, and the temperature of the hood over the manifold felt quite a bit cooler. I decided to swap my flaky and rusty exhaust manifolds for a nice new set of porcelain coated ones, and hope to get the new ones later this week. Normally, I’d pull the old ones and have them coated, but this will be quicker and more convenient. More expensive, too, but I don’t really have a lot of spare time on my hands these days.