392 problems

vbdig · #1 (**permalink**) 03-12-2004, 05:02 PM

I have 3 problems I need feedback on, I replaced a 351 crate motor with a 392 crate motor. All of the accesories stayed the same, ( 6al msd, 670 street avenger, etc.) The problems are as follows:
1. Oil pressure is lower than first engine. 4 bar (60psi) at cruise speed, 1 1/2 bar at hot idle. It seems low to me, old engine rarely dropped below 45 psi at idle. Using 20-50 oil, no oil cooler.
2. Bad vibration in shift lever at 4500 rpms and above under hard acceleration. Free reving seems not to be the same, just under hard acceleration.
3. Missing. The engine seems to miss at 3000 rpm. Plugs read good except #7 and #8 which seem to be reading rich. I can hear the right side exhast stutter about that rpm under partial acceleration. I have tried jetting up and down, but problem remains. Now I'm wondering if the hard vibration I feel is a cylinder or two cutting out. This engine has so much more acceleration than the last one I'm not sure if the missing is occuring all of the time and I just can't hear it. If so, what would cause 1 or 2 cylinders to cut out. I did weld on the frame without disconnecting the msd, could I have a problem there?

G.R. · #2 (**permalink**) 03-12-2004, 07:33 PM

I'm not a mechanic-- but in my other car ,an SPF, I had a 392 and it always seemed to hold about 60psi, hot or cold, hot idle it would drop if I had had been driving it for awhile and was in heavy stop and go traffic to around 45-50, may have been the gauge because I really don't know.
As for your miss I suspect that it could be due to the MSD--I read the manual and vaguely remember it cautioning about disconnecting it before doing any type of electrical work or welding. I do know a welder in proximty to "live" electronics can mess them up---can you borrow a MSD and temporarily hook it up to see if that is indeed the problem? I maybe way out of the ball park here.

NMattison · #3 (**permalink**) 03-13-2004, 02:40 AM

hi i would also check your msd for the miss but the vibration, has this always vibrated? i was wondering are you using a manual trans? if so did u balance the engine i have the tremec with stock 5.0 flywheel and i had to have the wheel drilled. so as it would be balanced with the engine. if not drilled it will cause a vibration hope this might help for my .02

Cobra20646 · #4 (**permalink**) 03-13-2004, 04:30 AM

Vibration.... was there a pilot bearing in the new motors crank?

vbdig · #5 (**permalink**) 03-13-2004, 08:08 AM

The engine came with flywheel, I assume it was balanced, as the engine was test run at ford. I did remove flywheel to install the steel backing plate for the bellhousing, but it seems that the flywheel can only go on one way. Is this correct? a pilot bearing was included in this package.

Cal Metal · #6 (**permalink**) 03-13-2004, 09:41 AM

If the pilot bearing was missing, you most likely would be grinding going into reverse at idle. The misalignment from not having the pilot bearing would manifest itself in this way.

niles · #7 (**permalink**) 03-13-2004, 04:07 PM

Speaking of pilot bearings.
How do you remove a dinged up bearing?
gn

Lowell W · #8 (**permalink**) 03-13-2004, 06:01 PM

To remove a pilot bearing:

Locate (or turn on the lathe or have someone do it for you) a rod which will just slip into the pilot bearing. Pack the bearing with grease, push the rod in as far as you can, then give it a few whacks with a hammer. The grease will push the bearing out. Never had to remove one that was badly dinged up on the inside, but I suppose you could drill it out to the next common size, then just use that size rod to extract it. Or, if the pilot bearing is an odd size, I guess you could drill it out to whatever size you have a rod to match, rather than go through the trouble of making a rod to match the bearing.