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Subject: 8n ring seating

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Michael    Posted 10-20-2018 at 14:57:28 [URL] [DELETE]        [Reply] [Email]  
  • 8n ring seating

  • I have a 1951 8n that has a rebuilt engine. New pistons, rings, sleeves, valves ( valves were lapped) , bearings, etc. the problem is I have low compression (~85 per each cylinder). And the engine runs a little rough. Will hesitate on take off. I have checked all the electrical (at least to my knowledge) and can find no reason for the rough running except the low compression maybe. I have spark to all plugs. Timing is correct. Can mark is lined up with crank mark. Wires, coil etc are good. It does not burn oil and I see no smoke from tailpipe and no exhaust gases from oil breather. I'm at my wits end. Could it be that the rings are not seating ?? What could I do to get them to seat if this is possibly the problem. Thanks

    K.LaRue-VA    Posted 10-21-2018 at 11:21:59 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n ring seating
  • Low compression in one or in two adjacent cylinders might be a cracked head, warped head, blown head gasket, or valve problems. If more than one compression gauge shows low compression in all cylinders (cranking with a good battery and all spark plugs out) the quality of the engine work is about all it could be. I'm wondering how/if the sleeves were finished and if the pistons and rings were properly fitted in each cylinder. New parts won't work as good as the old parts if not properly finished and fitted. Lapping of valves is the final step after the seats have been properly machined. Was that work done well?

    R Geiger    Posted 10-20-2018 at 16:14:35 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n ring seating
  • Did you do a wet check and a dry compression check?

    Michael    Posted 10-20-2018 at 16:21:23 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n ring seating
  • Yes. The wet check was about 5lbs more than the dry.

    r geiger    Posted 10-20-2018 at 17:50:41 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n ring seating
  • no more difference than that I would suspect a valve problem, assume you set the lifter clearances correctly.

    Michael    Posted 10-20-2018 at 18:08:03 [URL] [DELETE]        [Reply] [Email]  
  • Re: 8n ring seating
  • Yes. I originally thought it was the valves. So I took the head off and lapped the valves and seats. Put back together and set the lifter clearances and still same problem. Sounds like it's missing and hesitates on take off. Almost cuts off if I don't play with the clutch a little. I put some wd40 on the top of the valves and left overnight and it did not leak down. So I thought the seats and valves were ok. But I'm really not sure at this point.

    R Geiger    Posted 10-20-2018 at 20:55:00 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n ring seating
  • In that case I wold try a different compression gauge. just to be sure.

    Tony C    Posted 10-20-2018 at 21:34:59 [URL] [DELETE]        [Reply] [No Email]  
  • Re: 8n ring seating
  • Could be a carburetion problem, especially since it is hesitating upon acceleration.

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