Cracked Exhaust

[zoom240]

I cranked the 260Z up this morning to do a bit of tinkering & I heard exhaust sounds in the engine bay. I'd wrapped the exhaust with a heat blanket a couple of weeks ago to reduce the heat in the engine bay. Now I have a crack along one wing of the manifold (picture).:dead: Anyone seen this before? It's a first for me.

I'd had overheating problems for most of the time I'd owned the car. New water pump, new fan, system drained, radiator removed & cleaned, replaced the exhaust manifold gasket, all leaks fixed -- still some heat. So, I'd added the blanket. It did reduce the engine temperature a bit ... but it looks like it overheated the exhaust manifold -- or maybe I got it in a bind when I replaced the gaskets?

So, what exhaust system should I replace it with? I'm thinking of just ordering the Motorsports headers. The car is a very nice dailiy driver - I use it for commuting, but I like to romp on it every now & then. Suggestions on exhaust?

Thanks!

[2ManyZs]

Could have been heat, stress, or just plain old age or corrosion that cause it to crack like that. You could have it welded, but you will need to find someone that can weld cast iron. Cast is one of the hardest things to weld correctly. You might be better off either finding another manifold, should be quite a few up for grabs since so many people have already replaced them with headers. It would probably end up being much cheaper in the long run if you replaced it with another used manifold as the cracks are so large.

The MSA headers are fairly good if you want to go that route, it's all up to you and how much you want to spend. I've used them in the past with good results. If you do get one, I would suggest going the extra expense of the Jet Hot coating as it not only will prevent it from corrosion, but it helps control the heat to a certain extent as well. Rust is one of the biggest enemies of a header as the tubes are fairly thin wall steel.

Try hooking up a mechanical water temp gauge temporarily to get a more accurate reading on your engine temps if you are still relying on the stock electrical gauge. The stock gauges are notorious for not being very acurrate, the same as the oil pressure guage. You can pick up a cheap one at most any auto parts store and just run it through the firewall and lay it on the console while you drive it a bit, you might not have as bad a tamp problem as you think, considering all you have done previously to correct it.

[Mike]

Originally posted by zoom240

So, what exhaust system should I replace it with? I'm thinking of just ordering the Motorsports headers. The car is a very nice dailiy driver - I use it for commuting, but I like to romp on it every now & then. Suggestions on exhaust?

Go with a 6 to 1 header. Motorsport sells a decent one. Don't, I repeat, DON'T buy an exhaust piping kit. Buy, the header and take the car down to your local custom exhaust shop. They'll install new pipe that is much better quality. Go with a 2.25" or 2.5" exhaust.

[zoom240]

Thanks for the advice & vote of confidence on the MSA headers. I might look for a used exhaust manifold temporarily, as I can't drive it without exhaust & Xmas has left the Z fund lower than normal, but headers are what I'll go for next.

On the temp, when we were trouble shooting it, a mechanic shot the block & mfld with a heat gun and it was running much hotter than normal. I don't know why. When I bought the car, the PO was running almost straight water & the radiator was pretty crudded up. The cooling tube through the carbs was packed with crud too. I'm a bit worried that the water jackets in the block are packed. No matter what I do, it runs hotter than my previous Z, which had 2x as many miles.

If I just change out the exhaust mfld with a replacement, do I need to get another gasket, or can I cheat and reuse this one do? -- I had just replaced it, had to order it from Nissan.

Also... my mechanic had advised me to wait on the headers until I redid the engine & had a chance to mill the exhaust flat... is it that big a deal?

Thanks!

[2ManyZs]

As far as milling the intake/exhaust port side of the head, it probably isn't necessary. But, when you get your header, make sure there are no pieces of welding slag in the ports of the header, and using a large flat file, make sure the flanges around the port of the header are flat. If you do a search here, you should find a number of posts dealing with header gasket leaks. You might get away with re-using the gasket, but I would recommend getting another new one. No sense in finding out you have a leak because you re-used the old one to save a little money and have to tear it apart all over again.

As far as the coolant passages et al, if you haven't already done it, try using a good block cleaner and flush it out again. If you don't use one of the caustic cleaners that you circulate throught the block and radiator you really will never know if the block is clean. A simple flush with straight water will never truly clean anything. I believe Prestone and a few others make a good flush kit that might make a bit of difference. Not very expensive and it's always worth a try. It might get some of the crud out on the first try, and if it does, you could always do it again to see how much better you can make it. All you do is dump out the antifreeze mix, re-fill with straight water, run the car till it gets hot, add the flush mix, run the car for 15-30 minutes and flush it out with plain water and then re-fill it with your antifreeze mix.

Next idea is, have you tried a lower temp thermostat? If you can find a 160 degree thermostat, try it and see if it makes a difference.

[Mike]

Originally posted by zoom240

Thanks for the advice & vote of confidence on the MSA headers. I might look for a used exhaust manifold temporarily, as I can't drive it without exhaust & Xmas has left the Z fund lower than normal, but headers are what I'll go for next.

Zoom...

Post a message in the wanted area of our forums. Ask to see if anyone will DONATE a stock manifold to you. I don't think these are very hard to come by and should be laying around somewhere. Man, I remember throwing away at least 2-3 of those a few years ago.

[Daniel]

Been there' Ruined that!! Once upon a time I wrapped my header tubes with a blanket type stuff also. Same results. Seems keeping that heat in is not good.Mine was done in an effort to stop vapor lock.As best as I can recall it worked ---except for that one small drawback---holes blown out of the header!!! Oh yeah in case you're following my footsteps-you can't sandblast headers either. Have fun!! Daniel

[zoom240]

Thanks Daniel. I thought it might have been the blanket. Think I'm just going to park it till after Xmas & then look into getting the header. Means I'll have to sort out the temperature problem as well! Good advice all...

[Daniel]

I noticed that while throwing parts at your temp issue you said fan but not fan clutch.Are you using one? If so did you test it?Also I have a stock exhaust manifold available if you're interested. Daniel

[59ghia]

Since you'll be pulling the intake/exhaust , and you mentioned heavy crud, I'd pull a couple of freeze plugs and have a look inside.

Good luck,

Dave

[zoom240]

Daniel,

Thanks for the offer on the exhaust mfld. I can't get to it till after January anyway -- I'm out of town for weeks after Xmas. By that time, I'll probably just put headers on it -- that's what I was planning on. Just sooner now than later. I did replace the fan clutch (not the clutch as I mentioned).

59Ghia... I'll look into pulling the freeze plugs when I change out the mfld. I'm curious -- can't think of anything else I can do to drop the temperature... something's got to be crudded up.

Thanks all.

[JEFF]

Zoom - If you want to reduce under hood temps. & are

going to buy a header - buy one with a ceramic

coating - The ceramic does not transfer heat very

well - sending it out the back. try this , hold a 6"

square of floor tile in the palm of your hand, then

blast the top side with a tourch - you will hardly

feel the heat and not enough to drop the tile!!

The ceramic coating looks GREAT for ever!! Never

have to look at a rusty header again!

One brand is ' Armor Coat' another is 'Jet Hot'

Jet Hot is the coating that comes factory on

Dodge Viper exhaust systems - they were having

a floor board temp. problem - fixed it.

- Jeff