440 lo comp rings worn?

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cudaboy 67

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hello there, just a quickie, have a 66 casting 440 lo comp motor in my four speed barracuda, has 906 heads and a real slug,has run hot and overheated due to air leak on inlet manifold, since cured that, runs fluffy up to 2800 pm then clears after that and runs ok,thats a carb prob that being dealt with seperatley lol, two things, first my pal said it needs new rings as "breathing heavy"ie bit of pressure back thro tho oil filler caps however car does not smoke at all or burn oil,secondly after around 20 mins the car feels like it losing somthing, was suggested the vales tightening back into head, ie when ran hot/lean probobally done the seats in.he suggesting full rebuild, i know the cam is worn, i was hoping to pick up a set of worked heads and cam and simply bolt on. could what i am saying make sense? appreciate there are seperate rings doing seperate things on pistons but am not using any oil, cheers in advance, nathan.
 
It's been apart if its a 66 block casting and 906 heads. If you honestly don't know what is going on inside or the history, a tear down is all you can do to find out if something is wrong or right. Could be a lot of things to cause the issues you describe.

Have to put a vacuum gauge on it? Done a compression and leak down test?

If it has one of the plastic toothed "silent" timing chain, that could be an issue as they degrade and fall apart.
 
Unless you have a bore scope that you could run down the cylinders thru the spark plug holes, you'll need to take the heads off for an inspection. This won't tell you anything about the ring seal, but could show scoring of the walls and possibly the condition of the valves. Definitely do the compression leak down test.

I think you'll be heading toward a full tear down and rebuild. Good luck!
 
many thanks, my thoughts werethis, generally the oil scraper rings softer than the compression rings and they be the first to go and possibly cause the engine to smoke, since this is not the case i figured a head swap may help, going to be changing heads either way so if i go and change just them it helps be a result, can see bores same time. who knows as you say only one way to find out!
 
many thanks, my thoughts werethis, generally the oil scraper rings softer than the compression rings and they be the first to go and possibly cause the engine to smoke, since this is not the case i figured a head swap may help, going to be changing heads either way so if i go and change just them it helps be a result, can see bores same time. who knows as you say only one way to find out!

I would run a compression test, a leak down test, verify the oil pressure is good, and see how good of vacuum you have. Does the timing mark dance around when you try and time it? If so you have a bad timing chain, gear or both. I would not spend money on any heads until you know what you have. 906 heads are decent street head if ported and the engine built around them.
 
A compression test and leakdown test will tell you nothing about oil ring condition. Timing dancing around on a big block can be caused by the gear walking(fixed with a lock collar on the dist. shaft) and not the timing chain. I agree I would not spend money on heads until you know the condition of the short block. My thoughts are maybe the oil rings are stuck on the pistons causing the oil at the breathers or the PCV system is inop.
 
A compression test and leakdown test will tell you nothing about oil ring condition. Timing dancing around on a big block can be caused by the gear walking(fixed with a lock collar on the dist. shaft) and not the timing chain. I agree I would not spend money on heads until you know the condition of the short block. My thoughts are maybe the oil rings are stuck on the pistons causing the oil at the breathers or the PCV system is inop.

...and worn out engine is exactly that.
 
hello, many thanks for the input, a pal has loaned me a leakdown kit so will be doing that monday, also the thought of my timing gear being bit @@@ does also make sense! i will be trying a 650 carb on there as the 750 overfueling, yes this will not help a worn engine but i am sure not help the way it behaves! many thanks again, will keep you posted,nathan.
 
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