I recently bought a used 400 to freshen up and put in my ot Nova. Supposedly had rings done at some point. I finally got around to popping one of the heads off tonight to check out the bores and to my surprise I can see the rings around the pistons. I am actually able to slightly wiggle the pistons back and forth in the bore. The pistons appear to be stock bore and there is still some crosshatch and very little ridge. I was hoping to just hone it but I think I may have to have it bored over. I am not completely new to engines though I have never been able to move a piston like that. Any thoughts? If it needs bored would I just be better off using the rotating ***embly in one of the 4 bolt 350 blocks I have and go the 383 route? The pics dont show it well but the rings are visible when looking at it in person. Sent from my XT1635-01 using The H.A.M.B. mobile app
that sounds pretty normal to me for a well used engine. If you can get a dial bore gauge in there and measure the bores....you'll probably think that it needs to be rebored.
That is probably the case. I just hope it will clean up at just 30 over. Probably better in the long run. Those pistons look very detonation prone and new flat tops would bring me right where I want to be with my 70 cc heads. Sent from my XT1635-01 using The H.A.M.B. mobile app
400s were low compression motors for trucks, vans, station wagons, and Monte Carlos. Never intended for performance use, in stock configuration.
The 400 pistons tend to rock in the bores and crack piston pin bosses. Then they sound like loose fit forged piston engines all the time.
With a 400 flat top pistons and good quench will get you 10.5 compression with 70cc heads. To much for a short rod motor on the street.
If you bore it, go with a piston that will work with a 5.7 350 style rod. The stock 400 rods are 5.56
A long rod 400 with flattops with 76 cc heads is a torque monster. We used to run them in dirt track cars that allowed 400 inch motors. We would install the pistons on the rods backwards to take some side load off the bores. It rattled when it was cold ,but quieted down when warmed up.
I think the long rods is the way I'll go. Searching around, Eagle sells a complete long rod rotating ***embly with a new crank for roughly $800. It would save me having to send my crank out to have it turned and balanced so I think I'll do that and save the stock crank for a 350 block for a "someday" project. Sent from my XT1635-01 using The H.A.M.B. mobile app
If you go for the Eagle kit have it balanced. I used an Eagle crank in a 377 a 350 crank with big mains to fit a 400 block it required some heavy metal to balance.
I'm late to the party but what you see with the rings showing is pretty well normal for an engine that had a lot of wear, had the ridges cut out, got honed and had a new set of rings slapped in as Jim said in post 2. The last rering job may not have even been the only rering job as they are usually good for about 60/70K before the rings start going south again. That kit sounds like a cost effective way to go.
I am going to tear it the rest of the way apart and try to get it to the machine shop in the next couple weeks to find out what I've got. I hope it can be cleaned up at 40 over Sent from my XT1635-01 using The H.A.M.B. mobile app
The Jalopy Journal
