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Crank case ventillation hose  Rating:  Rating
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 Posted: 05-15-2013 03:59 pm
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Cac41155
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Reading the blogs on the crank case vent back to the carbs, is there any reason why I couldn't install a catch can off the crank case vent and then vent it to the vacuum port on the intake manifold so I don't have to go through the carbs; when I connect the line to the carbs the engine drops in RPMs and runs rough.

Any comments will be appreciated

Angelo 

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 Posted: 05-15-2013 10:51 pm
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Jim Ketcham
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The original design had the crankcase vent going to the "air box" at it's bottom where heavy vapors could condense and flow back to the crankcase and only light end vapors got sucked through the carbs and burned. I do not know your setup but if you have so much condensate going through your carbs that it affects engine operation you may have other issues going on. I think trying a condensate catch can without hooking to the intake or carbs, just vented to atmosphere with drain back to the crankcase similar to the early 1973 JHs would work.

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 Posted: 05-15-2013 11:07 pm
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Cac41155
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Thanks for the response Jim, I'll try that. Is there a way to tell if the rings are shot, I imagine a compression test won't be conclusive. Is there a normal range of pressure that should be seen on the vent line (inches wc).

Angelo

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 Posted: 05-16-2013 12:31 am
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Jensen Healey
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Before my engine rebuild I fabricated a catch can with 5 or 6 layers of 1/8" screen inside to reduce the amount of oil entering the air box. This didn't work very well due to the volume of blow-by.

I'm sure a better oil separator could be designed.

I have no issues since the rebuild.

Kurt

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 Posted: 05-16-2013 02:22 pm
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Brett Gibson JH5 20497
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To check if the rings are shot you need to do a compression check, make sure though that the carbs are fully open otherwise you may get a bogus reading.

hopefully all the cylinders are better than 100lb's,

Now do a compression check again but sqiurt some engine oil in the cylinder just before doing each one, if the reading is much higher the rings are allowing bypass, (the oil creates a seal) if the reading stay's the same and its low then you have a head issue.

Brett

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 Posted: 05-16-2013 02:58 pm
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Cac41155
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Thanks Brett - I'll give that a try.

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