Hi, i'm rebuilding a 68 350 rocket engine I have rebuilt the bottom end I.e crank, cam and pistons and have installed new bearings and rings. I now think it feels a little tight to turn by hand, it will turn with a 12" wrench but not very freely. I think I'm gonna have to dismantle it and check, anybody got any ideas as to what to look for.

 

is the crank std. or ground? what type of assy. lube did you use on the bearings?

how did the used bearings look? they can tell you a lot if you know what to look for...

 

The crank is std, the old bearing were a little scored but not too badly. I gave everything a light coating of oil as I assembled.

 

It is not going to turn over super easy with the pistons and rings installed. Did you spin the crank while it was installed? How about as you installed each piston assembly? Same with the cam, did it go in easily and turn smoothly? The rings add a lot of tension and drag, even without the compression.

 

Rear main seal will make it drag a bit if not trimmed properly.

 

I would not recommend engine oil as a build lube. you should be using a good name brand assembly lube. If the heads are installed, then even with plugs out you will get some compression resistance.

 

Yes, BUT, to be sure that the crank is turning freely, especially after some machining, it is very useful, and can then be replaced with an appropriate grease.

- Eric

 

My recent 350 build was real tough to turn, but fired right up and all vitals were bang on. I did use plastigauge for all bearings, assembly lube and Brad Penn break in oil for the first 30 min run.

 

if you can rotate the shortblock assy. with a 12" wrench you are probably fine, those rings do add a lot of drag. on the cylinder walls engine oil is fine (you don't want any moly or fancy/funky stuff that will interfere with the rings seating) but it's good to use something with a bit more staying power on the bearings... it'll be fine but if you are going to be rotating it much i'd put the oil pump & pan on it and use an electric drill to prime it up every so often to keep the bearings happy...

 

check the rods i had the same issue when i built mine., turns out i had two bent rods only slightly though but enough to make it really tight. check side clearances on the rod sides thats how i found mine was bent as i tighten it it moved to the side and i had no side clearance i took 6 thousanths off one side and it would still tighten up of course i milled the rod sides knowking i had spares and to know what was going on i had to play with it once i found it it was a simple rod swap. i hope this isnt the issue with yours but in my experience thats what happened. another tip is to loosen the rod caps spin the engine see how free it is when its loose., as you are tightening them back up check to see how it spins as you do one by one thats how i found bent rod number one., number two being the worst was stated earlier

 

Thanks for your advice folks. I checked the rods when they were out and they were fine, thanks coppercutlass. bigD that's very helpfull thanks it does feel as though its the rings dragging that's making it tight. My plan was to run the oil pump with a drill before I fire up. captjim it turned fine until there was a few pistons in and then it started going tighter. Thanks again for all your advice I think I will carry on with my rebuild and hope everything goes ok. Can I blame you all if it dosen't start?

 

Not sure if this helps, but I turned my well running 155K mile 350 over with a wrench (sans plugs) and it felt tight as well (tighter than I would have thought). The rings themselves will give some resistance.

If assembled right, it will start. How how long it runs well afterwards is the question...