intake manifold exhaust crossover
I do not have a set of heads to examine. If something was dropped in the left or right exhaust passagway for the intake manifold exhaust crossover that is open on my 68 327/350 intake, would the dropped piece fall into the exhaust pipe or result in possible damage to the exhaust valves?
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Re: intake manifold exhaust crossover
Jim -- all I have handy is this BB aluminum "842" head, but maybe the passage designs are the same, wrt the exhaust X-over. I've threaded a yellow spark plug wire through the channel.
My uneducated guess is that if the piece was small enough (say a bolt or nut) it may slip through a wide open exhaust valve into the combustion chamber where it will cause damage.
I then angled the head on the bench to match what it would be on the block, and dropped a bolt down the heat riser hole; everytime it comes out the exhaust valve hole. So it might just sit on the top of the valve, bouncing around until the exhaust gas velocity is sufficient to blow it up and out the exhaust port of the head into the exhaust manifold. Good chance for damage, either situation.
Luckily, with aluminum heads, you could fish a bolt or nut out with a magnet -- less chance with cast iron.Last edited by Wayne M.; August 13, 2009, 11:40 AM. -
Re: intake manifold exhaust crossover
Jim,
I did just that on my 1967 with 462 heads earlier this year and debated weather to take the intake off to fish the plug out. As it turned out, after removing the manifold, the plug ended up at rest on top of a exhaust valve on the drivers side and a magnet removed it easily.
I shutter to think what would happened if I ran the motor and this small plug fell into the combustion chamber. Pissed and moaned because I had to remove the manifold but
now..
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Re: intake manifold exhaust crossover
You're looking at a 50/50 probability (NOT possibility) of somewhere between minor and major damage (depending on the size of the object and where it ended up) to the engine.
The result could be as minor as a scuffed up passage or damaged valve, all the way up to a busted block and/or head.
If it's in the ex crossover passage, pull the intake and try to fish it out with long forceps or a magnet on a stick. If that doesn't work, pull the head (much cheaper in the long run than replacing a correct block or head).
Even if the object is into the exhaust port, on its way to the exhaust manifold, there is a distinct possibility, due to the reversion effects of transitioning gases, that it could get sucked into the area of an open valve/seat.
If you cannot grasp the object, but were fortunate enough to push it AT LEAST as far as into the ex manifold, then you would probably be safe.
Many years ago, I saw a destroyed engine where a valve failed on one side of the block, and misc parts from that side of the block had ended up in a couple of cylinders on the other side of the block!!!!!! That means they could have only crossed over through the intake manifold passages!Comment
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Re: intake manifold exhaust crossover
Thanks to all for the comments. I am in the process of preventing the flow of renigade exhaust flow into the cavity at the top of my 68's 327/350 intake since I already have the heat riser valve wired open.
I decided since I have the carb off for a renew kit installation thought I would try closing off the flow route for the exhaust heat.
The brass valve seats that came in master cylinder rebuild kits for my 68/70 Corvettes that were not used/required fit the vertical hole snuggly.
These brass valve seats are drilled and tapped for the 1 inch in lengeth bolt that comes in the package with the seats.
I am going to secure a "safety" wire that will connect both bolts and install the bolts into the seats to keep the brass seats from leaving the installed positions.
Request opinions on the above procedure?Comment
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