F22, actually #5 is the closest, I can't even get a finger tip between #5 and the steering box!

The headers I will be getting are headman, here's a link to Jegs;
http://www.jegs.com/i/Hedman/500/68308/10002/-1

 

I have stock manifolds in my 1976 which has a ZZ4 crate engine, and I don't have any cabin heat problems such as you describe. I considered headers, but decided not to try them after reading about the cabin heat problems I read about on various threads. The problem I experienced was heat coming out of the A/C vents which I corrected by sealing the plenum that connects to the passenger's side fender, and sealing where the heater hoses enter the firewall. The heat was such that I could not enjoy riding around on a nice day with the windows down or up, and not use the A/C. I live in central Texas where we typically have triple digit temperature in the summer, and since fixing the heat problem, my cabin stays comfortable even without the A/C. I feel very grateful that I don't have the heat problem you describe.

 

I have the same heads (L98 882 castings, aluminum D-port, same as ZZ4). What stock manifolds, did you go with? Casting #? I'm curious, as I'm contemplating this as well and want that option as well.

 

Looks like they'd work with the aluminum angle plugs head, like mine. I'll check my mew-in-the-box Hedman headers when I get to the Shop, so we can compare notes.

 

I am contemplating stock manifolds which is why I have not pulled the trigger on the headman headers. I'd like to hear from more folks whom are running stock manifolds.

When I had my other 76 back in the early 80's I don't remember the heat like it is now. I was a much younger man then so that may be part of it, and maybe my memory is flawed

 

Me too. BTW, if your memory is flawed from the 70's and 80's, you're not alone!


But seriously, I'd like to see temps and results from the stock manifold crowd too.

 

I currently have the stock manifolds on a ZZ454 and have a lot of heat coming both through the vents and also at my legs. I'll have a look and see if those places need to be sealed up.

I am, however, going for 1 7/8" Hooker headers now. I just can't live with the fact I'm probably losing 60hp or more through the stock manifold, LOL.

When I get my car back I am thinking about getting some corrugated aluminium heat shield to cover the headers...

http://www.thermalvelocity.co.uk/product.asp?P_ID=476
http://www.nimbusmotorsport.com/Prod...=753&CATID=252

I have seen people use it in direct contact with headers, not sure how well it works in that application. That's what we used to use to heat shield the seatback firewall on the rear engined car (which was an inch or less from the headers). With a bit of effort, should be able to form it around the headers. My problem with it, though, if there's so little airflow through the engine bay (and covering things up will only make it worse), it might just get heat saturated and not be overly effective. Or it might not work all that well if it's actually contacting the headers.

 

Wow. I hear you about the contact aspect of it, but is it possible with the corrugation, that you'd have a lot og surface area, both inside the corrugation and outside as pure heat transfer, that it would overcome the small areas (you hope...), where it does contact?

 

That's what I'm thinking. I'm just not getting my hopes up too high in case it fails

 

Just a thought, I've researched that a bit back. Check out the Sign industry, they make the real estate signs out of corrugated aluminum, but not sure if it flexes...

The results, would be another aspect, of how we can possibly fix this, vexing problem!

 

I believe the double layered corrugated aluminium heat shielding is set up in such a way to maintain an air gap between the two layers which helps reduce thermal conductivity, so it should perform better than regular corrugated aluminium.

Maybe several rolls of Reynolds wrap aluminium foil loosely wrapped in 6 or 7 layers would do the same thing, no idea, lol.

EDIT: Actually, don't do that, regular aluminium foil will probably just melt or ignite at the heat your headers get up to, lol.

 

Just to pipe in here again. I have been following along, but have not had any time to drive the 74 lately. Weather is good here tomorrow, so my plan is to drive it to work tomorrow...20 miles each way so I will report my results after I get home. I don't have a IR thermometer, but do have a multimeter with thermocouple.

As you will recall, my car has stock manifolds and will cook you in 45 minutes or so. I just went out and looked, and even the stock manifold is just over an inch away from the steering box. All of you that are thinking of going back to stock manifolds shouldn't bother. It is not the headers that are causing the problem. It is that giant lump of heat generating metal in there with the headers.

If you look at the Chadwick link I posted earlier, he stated an enormous amount of heat was coming in through seams in the plenum on the passenger side. I am thinking that I am going to try that with the windshield sealer in the very near future. The discouraging thing about all of this is that Bob Chadwick spent a huge amount of time and energy trying to resolve this, and stated when I contacted him that he had sold his car because he could not stand the heat and was never able to fully resolve it.

What really has me confused now are that some C3 owners do not appear to have the problem. Maybe we should take a poll of the members to see if it is only certain years that have the issue. I would still like to know if the C2 community has any experience with this as well.

I don't know if there is a way to set up a poll on the forum, but my 74 coupe is basically unbearable after an hour. Is worse at speed with open windows...even worse with the t-tops off. Because of that fact alone, I am convinced that engine compartment heat is flowing in through leaks in the firewall/cowl/floorboards. I will start looking further tomorrow.

John

 

Ludemjo, yeah a poll would be nice to see who or who doesn't have our heat issue and find out different setups.

 

Well, with the T-tops off and the windows down, I don't have a problem with the heat. With just the windows down but the tops on, my legs stay nice and toasty warm but it's not really a problem. With the windows up and the tops on, I'm starting to roast after about 15 minutes on anything other than a frosty morning Even then I'll usually crack a window to stop the windscreen getting fogged up

Yeah, my stock exhaust manifold is really bloody close to the steering as well, though I thought that might just be a BB thing.

The stock exhaust manifolds are a lot thicker and have less surface area, so insulate better, that's part of the reason people like to stick with them.

I'm sure I can resolve the heat problem when I get down to it... I'm just not sure if I can do it without modifying my hood (which I don't want to do at the moment because it has a decent coat of paint on it I don't want to damage and I'm not the most artistic person in the world to go inventing new vents), without adding fans that would sound annoying and put a drain on the electrics, and without adding scoops that make front end lift worse.

I also can't do it while my car is not in my possession I probably won't have time to play with it until Dec or Jan anyway.

 

Just finished the heat shield and it's mounted up! Gotta go and test!

 

45 minutes, including ten or fifteen miles in the canyons, and it was, ahem, spirited driving too. Dropped the steering box by 50 degrees. The corner of the big plate was 167, versus 189, 192 degrees. The inside steering column support dropped 25 degrees to 125 instead of 144. It was warm, but not blazing. The steering column outside was 156, vs 195 yesterday.

Need a longer trip, but so far so good and it got driven hard. Ambient temp was 84 degrees

 

when you can post some pics, I'm interested in seeing how you set them up and attached them, also, did you put any of that kapton on the shields? you readings while not monumental are promising and every bit helps for sure.

 

That sounds like an encouraging start. Would love to see some pics of the shielding you used. Was that sheet aluminium shielding, or did you go with something different?

Big question, did the cabin feel any better? lol

 

I will post pics tomorrow. It felt cooler for longer and while it was pretty warm, it never got blazing, shoe melting hot. I really romped on it hard in the canyons, downshifting for the corners and pulling hard down the straights! Took the temps, at the last stop at the 45 minute mark and that's all the time I had! Thus, the reason I wrung it out. Hopefully the hour and beyond are good.

Tudz, you were right on about the radiation stopping dead at the sheet metal. You can easily feel the difference between the one side of the barrier and the other, with your hand, tho' I can now feel the heat blasting upwards and I'm glad the hood vents are there!

The new shield got a lot of adjustments and repeated retrims! It is crude, but served the purpose. More on that tommorow.

 

Hey John, good stuff! On your test run tomorrow, could you check the inside steering column at the bottom, on the inside? Also the big steel plate on the frontside of the firewall, including the brake booster side as well.