Compression test results

Id say a valve job.     but, how many miles on it?  Reason I ask, is if its high miles and hasnt been rebuilt, the rings may leak after a valve job.  been there..

"Thinking it may be time to find a rebuilt 360 long block.  What do you all think?"

You will have to take the engine out to properly replace the rear main seal. That's cheap money, but having the heads rebuilt is not (around $300-$400 per head). I rebuilt my 304 myself, but had the heads and block done at a machine shop. A reconditioned 360 is an option, probably around $1,200-$1,500 without delivery. It should fit right in with no other changes. In my case, I live in Canada where rebuilt AMC motors are not so easy to come by. Also many people consider a 304 that needs rebuilding to have no resale value, so for me, selling it and getting a 360 did not make a lot of sense. Besides, rebuilding an engine yourself is not that hard and I enjoyed learning how to do it.

Doing the heads can cause the rings to leak, but it shouldn't be any worse than when the heads were leaking... just might not be much or any better. Of course there will be blow-by through the crankcase if they leak real bad, but that's not usually the case. So you should be able to get another year or two out of the engine with rebuilding the heads. Helps spread costs out a bit if needed. If you have the time and budget may as well pull it and rebuild, or look for a 360 (or even another 304 if you prefer) to rebuild and drive this as is until ready to swap. 

one bad rambler wrote: Smitty52 wrote: OK I did a leak down test and figure I might just live with it for now.  The good news is that there was hardly any leaks past the rings as the oil fill tube was quiet for each cylinder.  Cyl #! had the highest leakage as might be expected.  The rear main seal leaks a quart every 150 miles so my plan was to replace that.  If I can find a way to do that without pulling the engine then I will leave the heads alone for now.  However, if the engine has to come out then the head work is easy when it is on a stand.  On Cyl 8 I do not think I had it at TDC.  I pulled the valve covers off (and it looks super super clean) and rotated the engine until both rocker arms were free of tension before I tested a cylinder but 8 may have been a little off.  I will recheck just for my own peace of mind. So, any tricks to replacing the rear seal without pulling the engine??? Closed throttle Open throttle Leak rate area Cyl dry wet dry wet 1 110 122 105 118 25% E 2 120 125 140 145 15% 3 140 152 150 170 17% I 4 120 130 152 160 17% I 5 140 170 153 173 10% 6 125 150 135 147 15% I 7 130 160 153 175 18% I 8 125 165 170 180 20% E You can see by the result`s all 8 cyl.`s went up wet (Rings) and 6 had valve leakage..plus a rear main seal leak (Pos. bearings)...But what does not make sense to me is 25% cyl 1 105lb compared to cyl 8 with 20% @ 170lb  That`s a 65lb loose at only 5% add`ll leakage

Smitty52 wrote: So, any tricks to replacing the rear seal without pulling the engine???

Edited by Red Devil - Jan/22/2017 at 8:45pm