Exhaust Heat

[Dellb]

Hi All
A couple of years ago I posted a thread about the amount of heat generated by my headers, and the effect it was having on the starter and cabling etc. As a result I converted to manifolds, and the problem went away.
However the change in performance and exhaust note was noticeable.

I have therefore decided to refit the headers, and as I write they are being blasted and ceramic coated. I then intend to wrap them before fitting. Has anyone had experience of this and can recommend a good wrap.

Rods. Delb

 

[Steven Smith]

I used exhaust wrap from Funk Motorsport on my C4, not all the exhaust just near the starter motor and suspension bushes to protect them from the heat.

 

[Biff.bailey]

I have a pair of block hugger headers on my 78....I've wrapped the headers and down pipes , also, I have amini starter fitted and have wrapped a heat blanket around the trans cooler lines as they're close to the headers

 

[Roscobbc]

Hi Dellb.......you won't want to hear this but there is a significant down-side to using exhaust wrap on headers, especially ceramic coated ones. Enbrittlement of the header material and welds can result in cracks and weld failures with the headers operating at higher than design temperatures. Couple that with the potential of the wrap to absorb damp and condensation if stored in a cold/damp garage or outside. OEM ceramic headers are usually coated internally and externally and really work very well in reducing heat and noise.

 

[teamzr1]

Hi All
A couple of years ago I posted a thread about the amount of heat generated by my headers, and the effect it was having on the starter and cabling etc. As a result I converted to manifolds, and the problem went away.
However the change in performance and exhaust note was noticeable.

I have therefore decided to refit the headers, and as I write they are being blasted and ceramic coated. I then intend to wrap them before fitting. Has anyone had experience of this and can recommend a good wrap.

Rods. Delb

You did not mention if your headers are stainless steel or mild steel ?

If stainless, all that is needed is heat coating
Wrapping causes trapped heat can crack the welds

Mild steel is worse as the welds are thicker than the pipe and due to trapped wrapped heat and expanding / contracting different rate than the thinner pipe can cause welds to pop

So coating is best but do not wrap whole system
Instead wrap like starter, or other parts likes slave for car with clutch, etc

 

[Dellb]

Thanks Guys

Rob your advice is heeded, and I will have a re-think on wrapping. If my memory serves me correctly, your C3 is a 500+ bhp big block beast. With even less room under the bonnet how have you managed the heat.

Delb

 

[Mad4slalom]

Hi All
A couple of years ago I posted a thread about the amount of heat generated by my headers, and the effect it was having on the starter and cabling etc. As a result I converted to manifolds, and the problem went away.
However the change in performance and exhaust note was noticeable.

I have therefore decided to refit the headers, and as I write they are being blasted and ceramic coated. I then intend to wrap them before fitting. Has anyone had experience of this and can recommend a good wrap.

Rods. Delb

Would it be worth trying a set of LT1 Rams horn manifolds ? which I think are larger internally than the stock base rams horn( or did they just connect to a 2.5” exhaust?), in my younger days I would have gone with headers 100% but now I really prefer the look of rams over headers , funny how things change when you become an old duffer !

 

[Forrest Gump]

Hi All
A couple of years ago I posted a thread about the amount of heat generated by my headers, and the effect it was having on the starter and cabling etc. As a result I converted to manifolds, and the problem went away.
However the change in performance and exhaust note was noticeable.

I have therefore decided to refit the headers, and as I write they are being blasted and ceramic coated. I then intend to wrap them before fitting. Has anyone had experience of this and can recommend a good wrap.

Rods. Delb

I’ve got ceramic coated headers (no wrapping) and a mini starter and don’t get any problems with heat (With a performance 383, driven hard).
I used to get problems when I had a stock starter. If you’ve still got a stock starter I would recommend changing to a mini.

 

[Roscobbc]

Theoretically I have the worst possible combination -
1. a modified big block.
2. same thing in an early C3 body (later C3's had better underhood air mnovement.
3. headers.
4 stock starter motor.
Yes, during very hot weather if caught in stationary traffic despite a DeWitt ally radiator it gets hot, very hot, unbelieveably hot, so hot that when you appear to see a mirage forming over the frontal view over the hood.......when you do eventually drive off the heat blasting under the dash is sufficient to make your eyes water for a few minutes under excess heat is vented-off........but it dosen't overheat as such.....hot yes, but generally below 210 degrees.
Yes, starter motor is 'wrapped' and often struggles to operate fast enough to start theengine......couple that with a small degree of carb/inlet manifold 'percolation' and usually leaving for a few seconds/minute or so and it will re-start.
Note
When I first bought the car installation of headers surprisingly helped the engine to run cooler and reduced the underhood temperatures

 

[Mad4slalom]

Theoretically I have the worst possible combination -
1. a modified big block.
2. same thing in an early C3 body (later C3's had better underhood air mnovement.
3. headers.
4 stock starter motor.
Yes, during very hot weather if caught in stationary traffic despite a DeWitt ally radiator it gets hot, very hot, unbelieveably hot, so hot that when you appear to see a mirage forming over the frontal view over the hood.......when you do eventually drive off the heat blasting under the dash is sufficient to make your eyes water for a few minutes under excess heat is vented-off........but it dosen't overheat as such.....hot yes, but generally below 210 degrees.
Yes, starter motor is 'wrapped' and often struggles to operate fast enough to start theengine......couple that with a small degree of carb/inlet manifold 'percolation' and usually leaving for a few seconds/minute or so and it will re-start.
Note
When I first bought the car installation of headers surprisingly helped the engine to run cooler and reduced the underhood temperatures

Do you worry about the paint on your hood ? When I get back from a run and put the 72 in the garage I always open the hood to let all that heat out. And mine according to the gauge runs super cool for a vette, only a small block tho, never here her “ticking” down when hot as you do with some engines.

 

[Roscobbc]

Not worried about paint on hood.....it's only some poorly applied crap satin black.......but still open up hood when it goes back in garage to dissipate the heat. Oddly this is the first year where I haven't stowed the T roofs and rear window away permanently for the summer season.

 

[CaptainK]

I have a 68, so same issues Ross says (earl C3, headers, stock starter) - BUT only a tiny 327 small block. When I got the car, the starter was weak, so I had it rebuilt. Not had any issues since, except for fuel percolation, which I solved with a thermal gasket between the inlet and carb to limit the heat transfer to carb, and thus stop the fuel boiling off. It used to be really bad for percolating before I did that.

 

[Roscobbc]

As has been mentioned briefly (I recall) on another thread there seems on C3's the apparant random OEM use of a 'recirculating' fueling system depending on what carb/engine combination was originally fitted. There perhaps is zero logic in whether used exclusively on big block/small block/Rochester or Holley equipped Vettes?
Mine (with its OEM fitted L36 427 and Quadrajet) fed the gas from the mechanical pump to a small metal canister filter placed in front of the passenger side cylinder head.
The filter has two outlets - one to the carb - the other, smaller one is the smaller diameter return feed to the fuel tank. Not 100% sure how other engine/carb combo's do it.
Logic/common sense says this is a good idea with the benefit of cooler fuel from the tank in constant circulation. I'm guessing however this would perhaps have limited benefits if travelling longer distances or with low fuel levels on extremely hot days as the ambient temperature of fuel in the tank presumably will gradually increase over the journey.
With the OEM fuel feed line clipped to the top of the passenger side chassis (and immediately underneath the exhaust manifolds/headers) one can see why on a hot day the fuel line will heat-up and possibly 'boil-off' (percolate) creating running issues.
These problems are made even worse with any V8 engine layout when the engine is turned off. Without coolant circulation (and a closed hood) remaining heat within the engine will rise-up through the engine block........straight into the inlet manifold and carb.
If, after a hot run, on a high temperature day try opening the hood, remove the air filter, then watch/listen over the top of the carb as the fuel in the feed line/carb 'boils-off', pressurises the fuel line and carb and raw fuel bubbles in to the carb, often through the accelerator pump outlets. You'll see how fuel fuel can 'puddle' inside the manifold.