I've done 3 header installs on lt1s and never had this much trouble. About 6 months ago installed pace setter mids on my bros car and sure enough they started leaking.

So i put the mr.gasket coppers in place of them and every cyl. leaked right away except #7. Then i removed the headers, cleaned surfaces, and made sure the flages were true and reinstalled percy's alum. gaskets with a layer of the copper rtv spread accross them and though they seal up much better then the copper ones, i still have leaks on both banks of the engine besides the usual exhaust ticks i can even see small blue flashes of exhaust coming from under the flanges.

My next step is to try the 1406 felpro with the copper gsket spray i think im gonna order the ARP bolts also, maybe mine have streched and wont torque properly... any other hints on what i might be doing wrong would help.. i sure am getting tired of takin' these damn headers off tho

 

I run these. NO leaks ever

http://www.holley.com/29DA3BERL.asp

 

I use the Fel-Pro 1470s with no RTV and have no leaks. Are you sure you are tightening the bolts enough? You have to really crank them down, and keep at it for a couple weeks to make sure they stay tight.

 

Header flanges can be a huge pain, they get warped and there's really no good way to fix them that I can tell.
Thicker gaskets sometimes work for people.
I've ended up blowing just about every type I've tried with these old Hookers LTs.

Those look interesting, I may see if they have something that will work for my Darts.

 

This needs to be repeated often.

 

Straight flanges, felpro gaskets and arp bolts with occasional tightening. For some reason, I don't trust metal gasket materials with aluminum heads. And it is not unusual to have boogered flanges. JMHO

 

I use the Earles ones too, and they don't leak or come loose. The copper Mr Gasket ones are shaped wrong and leak out the bottom because the header flange shape is different than the head port shape and the sealing bead crosses the openings making a built in leak. You shouldn't have to glue header gaskets on, but a flat flange is helpful. Next gaskets, check the gasket on both surfaces to make sure it really fits. You can see where mine were leaking with my SLP headers in the picture below.

 

i run the felpro 1406's and have had no leaks yet. dont use any rtv either.

However i do have Hooker LT's

 

When I made my headers I used a 3/8 flange. Once they were welded up and
and checked for straightness I milled the area between the bolts that are between the ports .025" or so. This left the sealing directly at the ports. I also used Felpro 1406 gaskets that matched my flange. I checked every couple days to see if they were tight, 1 or 2 seemed to come loose. Took them out and rapped a few layers of teflon tape around them and put them back in. I haven't touched them in over 2 years.

 

I have mac mids I used the fel pro gasket that came in their engine rebuild gasket set. I remember having to (tweak) the bolt holes in the gasket to get a good seal around the header flange. I used ARP header bolts. Its been 1900 miles with no leaks and no loose bolts. It's probably just S#*T luck but it's working

 

Thanks for the input guys, heres the outcome:

Since i already tried the copper, aluminum and reg. paper gaskets i tried the felpro 1406, the ports on em seemed to match up the best. I used fine sand paper on the cyl. head and on the headers so that everything had a ultra clean surface i also put on about 3 coats of the permatex copper spray on the gaskets, torqued everything down and made my own E.G.R pipe gasket out of a graphite gasket, i heat cycled the engine twice and retorqued the bolts and everything sealed up perfect. runs so much smoother with no leaks

 

absolutely.

I used the longer ARP 12-pt bolts with good success. Had to tighten them down 3 times, but it held great.

Absolutely HATE those Percey dead soft aluminum "shims" (I hesitate to call them "gaskets"). Good success with the GM and Felpro gaskets. Don't bother with copper or any exotic crap with header gaskets. KISS.

 

Old thread but o well. Cant seem to get my pacesetter lts and copper gaskets to seal properly. Ive pulled the one side back and cleaned the surface and re installed them. Leak isnt as bad but still pissing me off. Does the engine have to get to operating temp to get them to seal or should they just seal from the get go and cycling needed to insure no leaks? Ive let my car run for a couples minutes but not enought to get it up to temp.

!

 

my pacesetter flanges were totally not straight, the biggest problem area i saw was the area around the bolt holes, some of them were so bad I knew there was no way the port would seal up so i used a file and ground down all the area's around the bolt holes to just under flush compared to the port area. Put them on the first time with felpro's and ultra copper and havent had them off since, that was a couple-3 years ago, also using stock bolts and never have to re-tighten them.

 

arp stainless bolts do not seem to remain tight as the miles (heat cycles) roll by. with my 96 i tighten my slp outside flanges every 3-4k miles. 1985 iroc 3rd gen cast iron heads on the 406 have settled down and need no attention. i think ss bolts are causing trouble.