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Take a look at these Manifolds

winter

winter

Active member
Just got a nice set of gently used EMI Thunder BB manifolds, but upon inspection, i found traces of what appears to be calcium deposits in most of the runners, mainly where the runners meet the exhaust port on the head. Is this a sign of an internal crack between the water jacket and manifold?

PC142009.png
 
Mr. Buss said:
the white stuff kinda looks like race gas residue.. does it rub off with your finger?? its it gritty?
Click to expand...

It doesn't rub off, it flakes off. and yeah, it's pretty much all the ports, some worse than others. I'll def. pressure test them, just wondering what everyones thoughts were.
 
I was told by my cam guy that the early models of EMI Thunder manifolds were prone to reversion issues. I would venture to guess that might cause the residue.
 
teamhart2 said:
I was half expecting this thread to be pictures of attractive women :drool:
Click to expand...

That was worth a laugh...


to the op, can you give the guy you got them from a shout/ surely he would know if he was having reversion issues - the heads would look like crap.

My first impression was octane boost, race gas, etc.. like mentioned above, and second if it was tougher to rub off would be aluminum oxide (very common aluminum corrosion). even if you have some corrosion, it can be from condensation - doesn't necessarily mean a leak. Also, the probability of both sides leaking, just enough to cause that, at the same time... seems pretty low to me. If they were wet from reversion, surely the heads would tell that story as soon as the manifolds came off.

From your picture it also looks like there is more of it where the exhaust gases aere hitting the surface... leans a bit toward residue from additives... do they all look like that?

Either way, I would pressure test ANY manifold or riser that I didn't buy new before using it. only takes one good leak before you're looking for an engine... just my two cents...
 
reversion is an issue

I have two sets of these, one with short aluminum risers on a stock 502mpi, we added threaded ports to install an O2 sensor. with the plugs out of the O2 locations and the corsa quick and quiet open through the hull, this will revert water and we get it spitting out of the hole and changing idle quality. close the QnQ an the prblem goes away. STRANGE.

the other I had issues with was with a poorly designed cam, Im sure that made the problem even worse. I even ran nearly dry, long tube with no QNQ then they ran dry (and loud).

I have no idea what the version of the exhaust this is, I bought them both used also.
 
As i studied them tonight, how does one go about pressure testing these? Would sending them to EMI be the smartest move? I'm having a pretty sweet motor built and want to ensure all will be happy when i fire it up! :eyecrazy:
 
boatn70 said:
I have two sets of these, one with short aluminum risers on a stock 502mpi, we added threaded ports to install an O2 sensor. with the plugs out of the O2 locations and the corsa quick and quiet open through the hull, this will revert water and we get it spitting out of the hole and changing idle quality. close the QnQ an the prblem goes away. STRANGE.

the other I had issues with was with a poorly designed cam, Im sure that made the problem even worse. I even ran nearly dry, long tube with no QNQ then they ran dry (and loud).

I have no idea what the version of the exhaust this is, I bought them both used also.
Click to expand...
Winter
I agree with this water reversion from the wrong cam , and low risers ,the old style Gil's had the same problem on the hp engines. If all ports on both manifold show this I would say there is no cracks. A good combination will be coco brown to black in color.
depending on what engine you have alot of stock of mercs. 454,502 cams have a wide lobe separation to help prevent this, like 115 L.C.

The QnQ closed the water would have to travel more vertical to revert from the prop. Gavity was working for you there it drained better.
There are exhaust manifolds I recommend for high performance use but they are more expensive then the units you have.

MKHammer
 
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