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b84 MC 470 Compression Range

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a1nowell

Contributing Member
I have been all through the Se

I have been all through the Seloc Manuel and cannot find the compression range that is acceptable. Does anyone have these spec's and would you please send them to me.
 
Larry
Some say 15% others say

Larry
Some say 15% others say 20%. Myself I go with the 15% difference.
Bert
 
"Bert,
What are the actual po

"Bert,
What are the actual pounds of compression per cylinder I should be looking for? 130 lbs, 150 lbs, 180 lbs etc?

Thanks
Larry"
 
"Larry
It's not the compr

"Larry
It's not the compression that is that important but the range the cylinders are with each other. So if they are all within 15% of the highest one then the engine is viable.
Some one else here on the board may have the actual spec on a newly built engine. I'd say somewhere between 120 and 140 psi would put you in the ball park, then go from there with each number compared to the highest.
Hope this helps. What are you getting for readings?
Bert"
 
"Bert is on the money. If it h

"Bert is on the money. If it helps, when I tested mine they were all about 130 all within 5 lbs. I was happy with that. The motor had at the time 700 hours."
 
"Bert & PugetSounder,
Her

"Bert & PugetSounder,
Here are my compression number. I would like to know what you think.
#1 170 lbs
#2 135 lbs
#3 165 lbs
#4 140 lbs.

Quite a range."
 
"Larry
You appear to be withi

"Larry
You appear to be within the 20% range. Keep in mind the ratio I mentioned. One also has to consider the state of the compression tester and if it has been certified as accurate. Was the test done on a warm engine, were the throttle plates opened wide,was the test done wet or dry?
Myself with numbers like that I'd go fishing and check it again at the end of the fishing season,
Bert"
 
As long as it runs good and sm

As long as it runs good and smooth I'm with Bert. Go out and have fun. You don't really have a "Low" compression cylinder to worry about but they are at the 20% (difference 170 and 135 is stretching 20%) so I would check the engine warm and dry test first to see if it changes. How many hours on the engine?
 
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