Exhaust Manifold - Crack??

[CDAHDAH]

Hey guys - I just rebuilt my 1984 Supra Chevy 350 motor. I posted a thread a while ago about water somehow getting into my cylinders. Well I ended up taking the motor apart, and noticed that the piston rings were seized/locked due to water infiltration. Pretty nasty stuff...

Good news is that I have a BEAUTIFUL rebuilt engine that I can say I did 100% myself. I'm afraid of having the same thing happen again.

My question is the machine told me my heads weren't warped, the intake manifold looks good, and the block was not cracked. So where could water possibly come from, the exhaust manifolds perhaps??

I keep hearing that you can pressure check exhaust manifolds, but no machine shop I contacted is able to do it. With my exhaust manifolds off, I stuck a garden hose on the elbow/water inlet of the exhaust manifold, and watched water flow out the 2.5" outlet portion. This looks good.
When I place my hand over the 2.5" outlet, the water fills up in the exhaust manifold and begins to exit out of the exhaust ports where it bolts to the engine.

The first pic shows just the exhaust manifold. The second pic shows my filling it with water and plugging the back with my hand. You'll see that water flows out from the exhaust ports.

Is this normal? Should water never come back out the exhaust ports? I got the same results from both of the exhaust manifolds.

[sybrmike]

Perfectly normal under that test. You've got two pieces of the exhaust - the manifold and the riser. In the manifold, water passages are cast around the exhaust ports to cool the manifold and exhaust gases. The water jackets combine into a common water outlet at the top of the manifold. The exhaust ports also combine into a common gas outlet. The riser (top part of assembly) has a divider plate cast in that keeps the water and gas separated until the flow is directed downward. Then the divider ends, allowing the liquid and gas to combine at the outlet of the riser.

You may have a leaky manifold/riser gasket. Use lots of PB Blaster on the bolts before breaking them loose - they can rust in pretty good & have a tendency to snap the bolt heads. Gaskets are cheap - skidim.com. Good luck.

[CDAHDAH]

Mike, Thank you for the quick reply.

Glad to hear that's normal, and I assumed that they had a common meeting point towards the end which resulted in water coming out of the exhaust ports when plugged.

I guess this leads to my next question, at what point will they need to be replaced and how can you determine that somewhat accurately? When I run a garden hose through with the manifold upright, the water exists fine. Do I need to take my riser off and check inside the manifold for cracks or will that not be possible?

If anything, I hope all you guys out there put some effort into checking your exhaust manifolds for leaks. It definitely develops into a costly repair and trust me, you don't want to go there.

[Okie Boarder]

Hmmm, this makes me wonder something. I see a little bit of evidence of water leaking where the riser and manifold mee. It is never really wet, but has some staining on it. Maybe I'll take a picture and post it. Should I consider replacing those gaskets to prevent a problem?

[wotan2525]

I really don't think that exhaust manifolds/risers like these would ever crack. They're just sooo big and heavy. They seem really over engineered.

How were your head gaskets when you yanked the engine? Were any of them a little questionable?

FelPro exhaust manifold gaskets are cheap and easy to do. You can actually do them without actually removing the bolts... There are 4 short bolts and 4 long ones... remove the short ones, loosen the long ones and the exhaust manifold will pull out far enough to wiggle the gaskets out. Wiggle the new ones in and torque all the bolts back down with a dab of high temp silicone and you should be good to go.

[Okie Boarder]

wotan, was the head gasket question for me?

[CDAHDAH]

Wotan - I don't remember how they looked when I got the gaskets off, but they did look pretty cheap. That's a very good point, it could have easily been them.

I guess would it be a good idea to put my exhaust manifolds back on, and run the boat until i break my new seals in and new camshaft. The only thing that I didn't replace in the rebuild was my crankshaft, block, head and piston rods. Everything else is brand new, marine grade where possible.

Once doing so, I can take the spark plugs out and feel around/look into the cylinders as much as possible and check for any water infiltration. Would that be a logical thing to do to test out my exhaust manifolds? I'm just really nervous with the first start-up.

[beast 496]

PCM manifolds along with all other manifolds will break and do break if not winterized properly. To test, manifold: Remove risor assy. scrape old gasket from manifold. Manufactur a flat 1/4 to 3/8" plate with bolt holes that are exactly the same alignment as risor. Bolt plate onto manifold utilizing the gasket as well. This will seal the exaust and water jacket area. Pressure test with water or air. You can use the plugs in the manifold and fitting for the water hose if you chose. The manifold should hold 40lbs pressure with no leaks. I would replace the risors if you have any doughts, much cheaper than another engine overhaul. After 30 years it is probably time to replace anyway. Al

[brack]

i second that about any doubt about the risers.....i ended up with with a melted hose coming off the riser ( due to peices of rust blocking my water flow ) and having to cut out the back floor of the boat this weekend to inspect / replace the other damage to the exhaust system

[CDAHDAH]

Beast, that sounds like the right way to test it. Everything makes sense, but how do you block the water flow at the exiting side of the manifold to test it. I looked at where the water exists, and that water jacket opening is about a 1.5" round hole, unthreaded and a little mishaped. I can't think of a tool that would plug that hole? Any suggestions?