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Compression question

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super_silent

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Discussion starter · #1 ·
I did a compression test on my 67 Camaro, 327 275HP
These are the readings:

cyl. 1) 160 -
2) 170 -
3) 160 -
4) 169 -
5) 170 -
6) 160 -
7) 200 -
8) 160 -

I don't understand why # 7 is so much higher. I pulled the intake manifold today and also pulled out the cam but eveyrthing looks fairly new. A few members in another forum suggested the cam lobes for # 7 may be worn and a few others said it may be carbon buildup in # 7. I now know it's not the cam. Anyone have any other suggestions ?

Thanks
 
#4 ·
Well, there is a fork in the road now. Decision to put it back the way it was or re-ring it, depending on how many miles you have on it. I would check tolerances and see if you can get away with re-ring and bearings, unless you want more out of motor. If you do go new rings, think about going .005 over size and file to fit the rings to your cly. Use a glaze breaker to rough up cly for better sealing. Check the lobes on the bottom of each lifter and make sure the go back into the same hole. Your call.
 
Discussion starter · #5 ·
I was planning on doing the top end, I bought a new cam, lifters timing chain set etc... The odometer reads 82000 miles, I was told it was original and assumed the motor hadn't had any work done but after opening it up today I discovered a new cam, lifters & timing set, the frost plugs also look new which makes me believe the whole motor may have been rebuilt. The compression readings seem acceptable except for # 7
I put 3 squirts of oil into the cylinders with the lower readings but no change so I'm guessing a valve job is in order but I'm stumped with #7.
 
Discussion starter · #7 ·
correct me if I'm wrong but I don't think it's a leakage problem, my problem is that one cyl., #7 has too much compression for some reason.
A few members in another forum suggested it may be a carbon build up.
That would have to be alot of carbon though wouldn't it ??
 
#8 ·
super_silent said:
correct me if I'm wrong but I don't think it's a leakage problem, my problem is that one cyl., #7 has too much compression for some reason.
A few members in another forum suggested it may be a carbon build up.
That would have to be alot of carbon though wouldn't it ??
Click to expand...

#7 could be sealing better than rest?
 
#9 ·
Could be alot of things:
Check the depth of #7 and compare to the rest.
Check the seated height of the #7 valves compared to others.
Smaller combustion chamber in the head.
Cylinder wall surface for #7 is a mirror compared to the others.

If carbon build-up is suspected, there would have to be considerably more than other cylinders.

I agree with Don, #7 is sealing better, you did the oil trick to others and no difference.
 
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super_silent
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