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HEADERS


profaqualung
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I feel certain someone out there has put headers on their Avanti II, and I would really appreciate some help to point me in the right direction, as there is only one speed shop around here, and they have not been very helpful.

Would prefer something a little longer than 'block huggers'. I have a mechanic that has a mandrel tubing bender, but it would be easier if I could find something from another vehicle that would fit.

Thanks in advance.

Thomas

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I feel certain someone out there has put headers on their Avanti II, and I would really appreciate some help to point me in the right direction, as there is only one speed shop around here, and they have not been very helpful.

Would prefer something a little longer than 'block huggers'. I have a mechanic that has a mandrel tubing bender, but it would be easier if I could find something from another vehicle that would fit.

Thanks in advance.

Thomas

I haven't done it, nor do I know of anyone that has, but here's some thoughts....

I'm pretty certain the stock cast iron manifolds are from a Corvette, so "shorty" headers that

would fit a 63-67 Corvette would likely fit the Avanti. I doubt they'd make a lot of improvement

in the power department, though, and they'll transmit much more exhaust noise than cast iron.

Probably the only thing they'd add is chrome bling, aside from a weight savings. If it's a weight

savings you're after, check out later model Corvettes with lighter weight manifolds (but they'll

have air injection fittings on them, too)... I'm not certain what year they started using tube manifolds,

but I think perhaps with the C4 in 1984, and for sure by 1995.

I doubt you can even find aftermarket "shorty" headers for a 63-67 Corvette, perhaps for the

reason I stated... the stock exhaust manifolds work just fine.

As for longer (full length) headers, they are available for Corvettes, but chances are slim to none

they'd fit an Avanti because the routing and outlets won't be correct. And, be aware that

the routing of the exhaust on the driver's side is especially tricky, in that the pipes have to avoid the

steering box & column as well as allow access to the oil filter... if you've ever changed the filter you

know what I mean (I may still have some wrist burn scars); long individual-port header pipes will only exacerbate the problem, it would be near impossible to fit 4 pipes through there, not to mention the

difficulty of accessing the oil filter and #7 spark plug if you did shoehorn them in.

You are also going to face some issues with the heat riser, and the alternator mount.

Sorry to be negative, but not really worth doing, in my opinion... I'd spend that money on more

fruitful engine mods.

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I agree. Without sending your car to a custom header builder, I doubt if you're going to find long-tube headers to fit. That would not be cost effective.

On my '70, the speed shop that installed the new crate engine added ceramic coated Sanderson headers of the block hugger design. They fit great, look great, and leave plenty of space for plug wires, steering components, etc. Sanderson also has the thickest flanges I've ever seen on headers to keep the bolts from backing out and creating leaks.

The original exhaust manifolds used on the earlier Avanti II's is the standard "Ram's Horn" manifolds. They can be found in junk yards and also as new reproductions through the Corvette restoration catalogs. The repros are somewhat expensive, so again, I think the header options would be more cost effective.

If you want to see photos of the installation of mine, I have a photo album of mine on the Avanti Yahoo group under RQB1574 reconstruction. You can see what it looks like before the body was re-mated to the frame.

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We reused the GM 305 HO cast iron exhaust manifold. The speed shop doing the work didn't think any headers that would fit in the available space would be a significant improvement. We ended up mounting the oil filter remotely with excellent results.

350sbLeft.jpg

Bruce, are these the "ram's horn" manifolds?

Joe M in WV

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Yeah Joe...they are. They're supposed to be about as good as it gets for cast iron manifolds. My understanding is they're hard to improve on without going to tuned long-tube headers.

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Here are the coated block hugger headers from Sanderson in the stainless Avanti chassis.

IRPB30Qdx6eOSLIT7aFZIvyDNq9om1l-01E0.jpg

If you like the idea of the Chevrolet rams horns, Speedway Motors sells these for street rodders, and they are available in cast iron, stainless steel, or polished stainless.

9300302_L.jpg

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Gentlemen -

Thank you for all the helpful info.

The reason I asked the question in the first place, is because I am running Flowmaster mufflers with stainless 2 1/2 inch exhaust from the mufflers to the rear. Just thought it would be nice having headers and 2 1/2 going into the mufflers.

The Sandersons [or similar block huggers] appear to be the way to go. We did some measuring with the block huggers on my El Camino [DYNOMAX], and concluded they would work, but we are going to extend the tubes and reposition the 4 into 1 collector. Then send them to Jet Hot for some basic 'black'.

Thank goodness for a friend /mechanic who likes a challenge - though I had to pass on his idea of bending me up a set of 'Cobra' [thru the body] style side-pipes.

Thanks again.

Thomas

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  • 1 year later...

Friends,

I once had a '65 Chevrolet Caprice, 396/325 with single exhaust. I changed it over to a dual exhaust and was amazed at how much better the engine breathed. A buddy of mine gave me his cast iron exhausts from his '66 Impala w/427. I was again amazed at the difference. It was similar to going from a single to dual exhaust. When I put some actual headers on, I couldn't tell the difference from the 427 iron manifolds - the difference may have been there but masked by the additional noise. My point is the difference in going from the tiny little mouse motor manifolds to ANYTHING that might breathe better.

Cheers!

E Coloney

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  • 2 months later...
On my '70, the speed shop that installed the new crate engine added ceramic coated Sanderson headers of the block hugger design. They fit great, look great, and leave plenty of space for plug wires, steering components, etc. Sanderson also has the thickest flanges I've ever seen on headers to keep the bolts from backing out and creating leaks.

Gunslinger, what model # of Sanderson headers did you choose? I have never used Sanderson but have heard a lot of good things about them. The only negative that i have heard is in show quality finishing. I am not into show cars just for the show aspect of having a car so it doesnt really matter to me.

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Gunslinger, what model # of Sanderson headers did you choose? I have never used Sanderson but have heard a lot of good things about them. The only negative that i have heard is in show quality finishing. I am not into show cars just for the show aspect of having a car so it doesnt really matter to me.

I can't find the invoice for them, but I believe they're #CC-1 block huggers. Mine are ceramic coated which looked like they were highly polished when new, but after being run they have a more frosted appearance. All headers will change appearance after being run...painted units will blister and rust, chromed will discolor and turn blue, cast iron will rust...not a lot you can do to change it outside of get coated headers and that's more for heat reduction than anything.

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