Getting exhaust log to seal???

[JT2Fast4U]

Hi All... Sorry for all the questions lately, but I'm new to all this boating stuff.
I'm tryin to get my aluminum "Hardin Marine" exhaust logs to seal. I have the thick (.043) copper gaskets for it, but it's still not sealing. Is there any kind of sealent that can be put on the gaskets to help it seal? The old gaskets (non-copper) had some kind of black sealer on them & it seemed to work, because it wasn't leaking before I took them off. Also, can these logs be re-surfaced or something at a machine shop? Thanks again everyone for helping me out. It's really appreciated. Thank you...JT2Fast4u

[JetBoatRich]

I had the same problem, put a straight edge across it and you could see the high and low spots.
Took a long flat file and very slowly, was able to smooth it down making sure not to take to much off and we kept checking with a straight edge and feeler guage.
Good luck

[AZKC]

I resurfaced mine and seemed to work great for a while but then they started leaking again. But thats my luck

[Ken F]

I had the same problem with mine on a BBF. Fought it for several years. One solution which seemed to work pretty well, though not for too long, was to take and run a 1/4" bead of orange hi-heat silicone gasket sealer around the flanges on the logs. Let it sit overnight, then put them on. It would work for about a month.
Finally, I ordered a set of Earls header gaskets. Solved the problem.
http://www.racehome.com/productofthemonthjuly.htm
Ken F

[1978 Rogers]

I seal mine as Ken said. I put a small bead of Permatex hi temp sealant on the manafolds. This is what the previous owner had done. I don't have an actual gasket between the head and manifold. I installed my manifold with the bolts hand tight with the sealant wet. This would allow the sealant to adhear to both surfaces. I snuggd them up after 24 hours after it had set up.

[JT2Fast4U]

Thanks for the tips & suggestions so far, I really appreciate it but I'm still having problems getting these things to seal. I had the exhaust logs re-surfaced at a machine shop yesterday, & I went out to the lake today to try it out & the back side of the gasket towards motor ( the part you can't see) of one or two of the exhaust ports were leaking a little bit. Wasen't too bad, but after about 10-15 minutes of running I checked them again & found that all 4 of the exhaust ports (backside of gasket) were leaking, & pretty bad too. Could I have done any damage to the valves, or anything else, by running it with the exhaust leak for this amount of time?
I think I'm going to try using some sealant next time, & hopefully that will help. I thought having the exhaust logs re-surfaced would fix the problem, but it didn't. It like when I start to tighten down the nuts on the exhaust, you can actually see the gaps getting bigger between the exh. manifold & head, & as you tighten the nuts, the bigger the gap gets. This "gap" I'm talking about is the areas on the exhaust manifold that are not right near the mounting studs. It says to torque the nuts to 25 lbs. but I haven't been able to even get them that tight, if I did, I would have a HUGE gap between the head & manifold. Does anyone know what might be causing this? Can alumium "breakdown" in it's hardness or something after time? Because I don't know what to think about this problem... Maybe it's just time to get some kind of other type of exhaust system setup, besides the "Hardin Marine" logs on this motor.
Ken, thanks for the link to "Earlsperformance", for the exhaust gaskets, but the link doesn't work for me, it takes me to some kind of "search" site. I would sure like to try those gaskets too. Could you direct me to where that site is? Thanks & thanks to everyone else that has helped me also. It's very much appreciated. Hopefully I can get this problem solved soon. Thanks again... JT2Fast4u

[mickeyfinn]

Sealant is the way to go. Skip the permatex or any of the other stuff from the parts store. Just trot yourself down to the local chevy dealer and buy a tube of GMS. General Motors Sealant. Never seen anything like it. Stickiest and toughest stuff in the world.

[Jet City]

I redid mine 3 years ago, have been fine since, I filed them flat as mentioned earlier, used Mr Gasket ultra seal gaskets (dry). One thing I noticed, I had to re-tighten them several times for the first few weeks after each outing before they settled in, just the difference in thermal rates between disimilar metals I suppose.

[spectras only]

JT2FAST4U , Harman or Hardin didn't put in gaskets for logs ,and they shouldn't leak at all when torqued properly. Since you've got the logs resurfaced, I suspect the heads maybe the culprit.The high temp copper gasket maker works well if you insist on using a sealant.

[nielly]

I use two sets of BBF Fel Pro gaskets along with high temp sealant. It works great and have not had any problems with leakage.