240ZR Posted November 21, 2005 Share Posted November 21, 2005 I haven't worked on problem like this in a few years by myself usually i had my dad double check me, I am pretty sure its just bad timing and before i started messing with it i wanted to check to make sure I wasn't over simplifying something..... help me out here, I have a zz4 (daemon 700 carb) and a 700r4 in my 81 280z when i am on gas or she is still cold she is smooth and sounds like a beast the second she warms up she looses some pep and when in coasting (20-30mph) will lightly misfire, if i hit the hammer hard or am on the freeway (75-100mph) and let off fast it sounds like there is a war in my muffler with pop booms and thwacks, if i ease off the gas seriously like 1lb at a time she is fine, but even then if i left off completely its back firing bad... I've TOUCHED NOTHING since i got it running 3 months ago this was a crate engine, and it ran perfect until about 2 days ago, it was the same day I bottomed out in the desert in one of those "whoops" you know the up and downs you can pull G's in at high speed, was doing 130+ (don't know didn't look until after it happened) car squatted down and there was a rut/groove down the middle of the road bumped the cars suspension just right, also add in the fact i had my friend that weights 300+ lbs and a full tank, i hit the pavement wasn't a really bad hit nothing was harmed (checked it on the lift) but it was a jolt to the car, enough to make me grind my teeth. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 21, 2005 Share Posted November 21, 2005 Backfires in the exhaust can be caused by an exhuast leak. Maybe you cracked an exhaust manifold. Also check that you didn't knock a vacumm hose loose. Quote Link to comment Share on other sites More sharing options...
240ZR Posted November 23, 2005 Author Share Posted November 23, 2005 Ok so i have a faw small cracks i can see... can i fill it? the crack is in the middle of the pipes under the door jam, evidently the hangers stick down about 1/4" more then the reast of the car and when i bottomed out like i did it seems to of creased/tore the metal on the left side one.... do i need to take it to be redone? should i get ovals? can i get somethink to "fill" the cracks? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 23, 2005 Share Posted November 23, 2005 Kind of hard to tell by your description. Cracks can obviously be welded or a new section of pipe installed (the solution I would pursue). If not, auto parts places sell pieces you can clamp over the pipe. If that is not an option because it is too close to the hanger or something, they also sell a glue type stuff that is suppose to fix leaks. Never used that so can't say how well that would work. I would also check very carefully the piping closer to the engine. A hit like that could have jamed the piping back into the engine cracking the manifold. The closer to the exhaust ports the crack is, the more likely it is to affect the running of the engine. A crack under the door jamb sounds pretty far back to me. Good luck Quote Link to comment Share on other sites More sharing options...
BrandonsZ Posted November 23, 2005 Share Posted November 23, 2005 With that much invested you could have bought a welder too, I recommend the Lincoln 180, it's blisssssss.... finally a reasonable estimate of costs. Quote Link to comment Share on other sites More sharing options...
240ZR Posted November 26, 2005 Author Share Posted November 26, 2005 DAMMIT!!! So i examined it much better today on the lift, and I found a CRACK in the Flange and a sheered bolt on the Exhaust manifold, Its warped the metal around the manifold flange a little, I think i might have a problem getting it flush again what do i do? junk it and buy a new one? weld? will this effect performance? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 26, 2005 Share Posted November 26, 2005 Sounds like you will be replacing some exhaust pieces. What exhaust manifolds do you have? Are they factory type cast iron? Cast iron doesn't weld well. Maybe time to upgrade to some block huggers. You definitely don't want exhaust leaks under the hood. Think carbon monoxide. Quote Link to comment Share on other sites More sharing options...
240ZR Posted November 27, 2005 Author Share Posted November 27, 2005 umm they are the spiffy sanderson ones..... with ceramic coat... Quote Link to comment Share on other sites More sharing options...
BrandonsZ Posted November 28, 2005 Share Posted November 28, 2005 ouch! That'll be tough to weld, but not with that Lincoln welder. I think you have a good case for purchase. Not that I sell them or anything, I got mine for $1850 with all the other acc. it came closer to 3k but as you know it's innvaluable to have one on hand. I think it's a 185 not a 180, but close enough. With 100% argon shield and air cooled torch. I just fixed the muffler on my Volvo and replaced the muffler on my Z with a quieter one. On a seperate note, did you have trouble with sealing at the block? I had to install gaskets although these claim to be "gasketless". Quote Link to comment Share on other sites More sharing options...
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