tfuno

I have a 77 that needs shorty headers with AIR. I want to lower the car and long tube headers hang too low and present a clearance problem.

Has anyone in CA used the OEM tubular exhaust manifold with AIR from an 81-82 Vette?

OldCarBum

I just finished an '83 GMC pickup. All I can suggest is that before you purchase any parts, do the research and make sure the parts are 50 state CARB legal. Check through Summit Racing Equipment. There are actually a lot of performance options available. Good luck.

tfuno

Thanks OldCarBum, I have sent emails to ARB asking for clarification. I have read the guidelines on their Web site. Since the 81 and 82 tubular exhaust are considered exhaust manifold as oppose to headers. My question is can these be used on an earlier Vette. One of the conditions is that all the existing smog must be able to connect and remain basically unchanged. The tubular exhaust is far less restrictive than the cast iron ones.

I did check with Hedman and they legal long tube headers with the EO plate. These hang too low.

McJacks sells the 82 tubular exhaust which fits all C3s. They make the oem replacement. It costs just under $700. I definitely will wait for the answers before buying.

Thanks again for your advice.

Big2Bird

I have an 81 with all the emissions.
I have the 81 headers in my garage.
I have rams horns in the car with the air tubes. (79-80)
The rams horns flow every bit as good, just heavier, and don't crack.
I have looked at the Mc Jacks headers at their shop. They say GM. All he does is buy used headers, and have them ceramic coated.
As long as you have either with nozzles, they will just do a visual. There is not ONE TECH that knows any better. The ones that would know are retired.
My tech told me I could change cam, heads, and as long as it passed visual and the sniffer, it would pass. All the check is timing, whether it has all the equipment that should be there, the fuel cap test, and the sniffer.

Shark Racer

Legal? No.
Likelihood it would pass a smog check? Very very high.

I've been driving my 78 with long tube headers for 13 years. The headers don't hang significantly lower than the exhaust where it splits to the mufflers near the diff. You can get more HP and have a legal pair of headers.

I highly recommend going with long tubes.

Big2Bird

Dammit. Now you have me thinking about those Hedmans.

61308 has the AIR tubes and the oxygen sensor bung.They also have the CARB cert. $835.00

ddawson

Got to pay for that CARB number some how.

mrvette

Them nitwits would have a COW with my '72 vert......nothing stock, nothing, stem to stern, wheels through roof....nothing.....

Big2Bird

Your car would be exempt Gene.

Shark Racer

HED-68301 comes in at $362 on Summit's website...

Big2Bird

I show 652.97

carriljc

numbers are similar -

https://www.summitracing.com/parts/hed-68301

https://www.summitracing.com/parts/hed-61308

And, there are other choices, see below where I attached the CARB EO document from the summit website FYI.

It would be better if they attach actual images of the product since some of these do not show the A.I.R. injection tubes and just a generic header.

I used to have the 68301's and they fit quite well.

Big2Bird

Hedman is 35 minutes from here. I think I will cruise up there and look at one.

Shark Racer

Here's a picture that demonstrates their height relative to the trans bellhousing.

tfuno

I have long tube headers right now. The prior owner welded AIR tubes but I wanted to lower the car and the long tube hangs too low. I have a 1970 LT1 block in my 77. So my goal is to get a legal shorty that breathes better than the stock manifold. I was under the impression the later C3 with tubular manifolds would flow better.

Thank you Big2Bird for reaffirming. Now I just need to find a good used pair of tubular shorty's which is getting harder to find.

Shark Racer

Big2Bird claimed he didn't think the tubular exhaust would flow any better in his post.

Personally, I'd guess that the tubular manifolds flow a fair bit better than the rams horns do. I have no data to substantiate this claim, but I'd love to see a 3-way comparison between ram's horns, tubular manifolds and a set of headers on an L-48 and/or L-82.

tfuno

I saw photos of an old tubular manifold and it looks like there is room to clean up with a porting bit. My block is a 1970 lt1 block with 300 hp. It's has a mild cam. I plan to get it ready for spring.

Big2Bird

I have no hard data as well. I do not like the choke point of the collector on the GM tubular manifold. Dimension wise, its identical. However, the rams horn is fully open all the way. The tubular is lighter by a bunch.

tfuno

Yeah, there is a fair amount to clean up to improve flow. I plan to find a good used set, then port and ceramic coat. I'll post a pic when done.

Big2Bird

My exhaust is 3" higher than that. The bottom is level with the 700R pan.