John92LT1

O.K., she did it to me again. I have had the right header welded twice, but it just cracked again. :banghead: My searches show that intact, original 1981 headers are hard to find (i.e.: $$$$$). Can you all suggest anything? I am not against aftermarket headers, as long as they don't cost an arm & leg, and maintain the correct emission fittings. Oh yeah, the motor is bone (dog-slow) stock, and will remain that way for a few more years.

Thanks for the help.

rcastor426

ok, when you say header do you mean header or are you speaking of the stock exhaust manifold? if it is the manifold, there is valve just below it, make sure that the linkage is hooked up and working.... and if you are cracking headers, you have a most probalby have hanger problem and try the same for the manifold, the pipe should bolt to the manifold with out any pressure at all. the ones on my 78 fit perfect without having to move the pipe around at all

John92LT1

1981 marked the first year that GM used stainless steel tubular exhaust headers on the Corvette, instead of the cast iron exhaust manifolds they used on all previous years. They are known to crack (I am guessing that it is chloride stress cracking, but who knows...).

So, I am talking about the exhaust header that bolts to the head. Your comment on binding raises an interesting question, though, and I will examine the condition of the motor mounts, in case they are allowing too much movement. If things are true to form of other parts of this car... there will be problems. The first time that I worked on the rear suspension, I found that, of the three bolts holding the spring to the diff, one was gone, one was broken-off in the differential housing, and only one (gulp!) was holding the spring in place!

Gordonm

My neighbor has an 81 and while I was working on it I noticed a cracked header also. A good set of headers is worth the money. When you have future plans for more HP the headers will already be there. My vote is for a set of good headers. They won't be to cheap due to emission fittings but how much will repair or replacement of the stock one cost?

geezer

If you decide to get it welded again, try this. At the ends of each crack drill a small (1/8" or less) hole. This hole may stop the crack from spreading as the part is being welded. Use a new, sharp bit and drill slow, what you want is a nice machined hole. I know it works for cast iron. It could be that the SS is so brittle that any amount of high, localized heat is causing the crack to run.
P.S. This trick also prevents a crack in plexiglass from running.

adam

When did you work on my differential?

Must have come from the same owner! :D

Sorry, can't help you with the exhausts - mine aren't cracked...

bertmeister

I picked up a used set of 81 stock headers here on the forum for 75.00. If you want to stay with the stock headers, check ebay, I've seen them there occasionally.
:cheers:

UKPaul

I fitted a set of Dynomax ceramic coated Headers to my '81. They fit perfectly, but obviously you'll have to modify the exhausts to clamp up to them. Summit sell reducers (3" to 2 1/2") which have provision for an O2 sensor. My O2 sensor is now in the reducer on the d.side header & I haven't noticed any problems due to the sensor not getting hot enough. Don't know if Dynomax Headers are available with the AIR fittings if you're still running it. I think the support for the A/C compressor will need to be modified (took mine off so couldn't say what's involved).
I used copper Header to Head gaskets & chucked the supplied Header bolts away. I used stainless allen head screws that were 1/4"(?) longer than the supplied bolts. No loose Header bolts & no leaks either. Who needs locking Header bolts? Just get some allen heads & tighten the crap outta them! I used the cheapo supplied collector gaskets & they don't leak either. I think you've just got to be careful not to overtighten them. No problems with plug wires getting cooked, but they are in the stock position (down the side of the block.... & what a PITA it is changing those little darlings :( ).
One thing you'll definately need to do if you go for Headers is to fit a cheapo heat shield for the starter motor. I didn't & fried the motor. That was a laugh :rolleyes: Also, the carb will run weak on the secondaries. You should have CH rods fitted as stock & will need to change them to DA (available from GM). Lars told me the size to use & I trust his advice (not done any high speed runs to test them due to grim weather).
If Headers aren't the way you want to go, will earlier cast manifolds bolt into the system OK?
If you get a set of stock manifolds try to get some for an '82. I've heard that the '82 ones were 2 1/2", whereas the '81 were 2", & another 1/2" isn't a bad thing :) Personally I'm glad that I fitted the Headers. Not for any performance gains (honest!) but because there's no more phut phut phut sounds from leaking gaskets or cracked stock tubular manifolds. One year after being fitted the ceramic coating looks as good as when the mailman delivered them.
:cheers:

markdtn

Get some stock C4 TPI "header" manifoilds. You can maintain full emissions and they would bolt right on. Only issue will be that they have a true 2 1/2" outlet. You could modify your exhaust right there and deal with that.

USA SHARK

Saw these on ebay. The price is right so far. Good luck

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2467487265

:seeya

weendoggy

Those are not stock '81 headers. They are missing the air tubes, which are welded to the headers. Those look more like an '80 or some that have been "modified".