View Full Version : 352 Journal speed

03-05-2007, 11:25 AM
Hello From TN:

Being Mr Gimpy I got to sit in the comfy chair at Kroger during a recent trip for groceries. Complimentary coffee, a copy of Hot Rod and I was set. A real Al Bundy (Married with Children show) fantasy was taking place. Doesn't get any better than this. Anyways, here's what I was wondering.

The mag had a short article on Ford 351 engine main journal sizes. It seams one, either Windsor or Cleveland has a large main journal and a shim is now available to shave down the journal diameter for a smaller bearing in an attempt to slow journal speed and decrease bearing wear. This shim is reported to decrease surface journal speed by 10%.

I've been whining to you guys for a long time about this, but I'm just trying to learn more about what happened. I do not have the manual here and I'm not sure of the 352 main journal size, but as I recall the Ford in question was up around 3 inches. Could this be partly to blame for my engines untimely demise? To reiterate, I have an original 32,000 mile engine with trashed (right down to the copper) main bearings. The rod bearings had little to no wear. Seams to me if this is the case that a crank shave down to the minimum diameter would be best for bearing life.


Kevin Edwards


Dick Steinkamp
03-05-2007, 11:51 AM
Interesting. That's the first I've heard about crank journal size determining journal speed and hence bearing wear. It makes a lot of sense. There is obviously a compromise between a big journal crank (strong, but higher speed over the bearings at a given engine RPM), and small (weaker, but slower over the bearings). Probably the usual RPM range of engine being designed is taken into account in determining the journal sizes.

Out of curiosity, I looked up the main journal size on SBC's and the Stude V8.

Prior to the late 60's Chevy used a forged steel crank with 2.3" main journals.

After that, the cranks were cast nodular iron and the main journals moved up to 2.45"

The SBC 400's (cast iron cranks) had a 2.65" main journal.

Studebaker used a 2.5" main journal.

(Not to hijack Kevin's thread, but in checking the Studebaker main journal size in the 59-64 Studebaker Shop Manual, the "crank material" listed is "cast iron". I have been under the impression that Studebaker used forged steel cranks, but under every year (59-64) and for both 259 and 289 engines, the crank material specified in the manual is "cast iron". Maybe forged cranks in the earlier V8's?)

Sorry about the leg. I hope it heals quickly and you get back in the cockpit (it must be driving you nuts to be on the ground so much :().

I hope you can make it to South Bend this year and maybe even bring a Studebaker or two.


03-05-2007, 12:22 PM
351C Ford blocks use a 2.75" Main and the 351W's use a 3" main. The Ford racing 351W blocks also use the cleveland mains. The reason for this is to lower the surface speed of the journal thus reducing the heat generated. This becomes critical on race engines that are expected to turn up to 10.000 rpm for 500 miles. Not as important on your every day street engine.
The Avanti manual says the crank cam gear is cast iron, but in the engine section it shows that cranks are forged.

Butler, PA
63 Avanti R1 R2899

John Kirchhoff
03-05-2007, 12:53 PM
Kevin, I find it interesting that the main bearings were shot while the rod bearings were still ok. I've torn down lots of engines and the only one that ever showed more wear on the crank than the rods was a 585 ci White diesel. I think it has 4" main and 3" rod bearings. I bought the thing used, so I don't know if the rod bearings had been changed before me though. The only thing peculiar to this engine (actually a Minneapolis Moline engine) is that it uses 4 main bearings rather than the normal 7 used on most 6 cylinder diesels.

Do you know the history of your engine and if the rod bearings had ever been changed before? If it were mine, I think I'd be looking for something else before automatically assuming the journal diameter is at fault. If you didn't buy the thing new, you don't know if the previous owner over reved it constantly, if the oil was changed regularly or if some cheap cruddy oil was used. Remember the old oil filters that used a roll of toilet paper? Well they'd sure clean the oil up but they didn't replace important ingrediants like anti-oxidants, anti-scuff, stabilizers and such. I remember the time dad bought a case of recycled (or re-refined as they called it) oil from Sears. It was beautiful oil, slightly golden in color but it ran through engines like cr*p through a tin horn. Something else some people do is rev the engine immediately before shutting it off. They've told me it gets extra oil circulating before they shut it off. Well I figure it also makes the engine coast longer before it comes to a halt and if that's such a good practice, funny I've never seen an operator or shop manual that recommends it. If the engine was previously owned, when the owner started it cold, he may have really reved it before the cold oil ever got circulating. I could very well be wrong, but I figure there's plenty of other things besides journal size that could lead to worn bearings.

03-05-2007, 05:16 PM
1. The Packard V8 has a 2.5 main bearing journal. This is a pretty standard diameter for 1950s V8s with a 3.5 stroke. The main bearing width of .950 is the widest of all V8s, giving Packard 38.6 of main bearing surface area. This is considerably more than average for its size.
2. The Packard V8 has a cast steel crankshaft.
3. The 1955 SBC was designed with a 3.0 stroke and a main bearing diameter of 2.3. When the 350 came along in 1968 with a 3.48 stroke, the main diameter went to 2.45. Finally the 400, with a 3.75 stroke, the main bearings were 2.65.
4. As the crankshaft stroke got longer, above 4 in some of the 400-455 V8s, the main bearings were enlarged to an average of 3 and larger to maintain a minimum overlap and thus strength.
5. The larger diameter main bearings have greater overlap and are thus stronger, but have higher surface speeds at high RPMs. This higher surface speed means more friction and higher oil temperatures. Racers are willing to spend more for forged and billet crankshafts to get smaller diameter main bearings and thus, a bit more horsepower.
6. The 2.5 main bearing diameter of the Packard V8 crankshaft has not been shown to be a definite factor in the main bearing failures regularly experienced. Investigation continues, and here are points for discussion:
a. The Packard cylinder block main bearing webs are relatively thin.
b. There is very little reinforcement up the middle of the cylinder block between the two cylinder banks.
i. The block itself might be insufficiently strong.
ii. The reciprocating assembly; rods, pistons and pins, could be too heavy for the 2.25 rod journals and 2.5 mains.
iii. The OEM main bearing material might not have been of the correct specification
iv. The main bearing bore alignment may not be accurate
v. The specified bearing-to-crankshaft clearances may be insufficient
7. While no one has proven it as the cause, oiling system modifications have been the usual focus for improvement.
a. The Packard engineers made three separate service changes to the oiling system
i. A J-shaped tube to place in the pressure relief plunger bore
ii. A revised cam retainer plate and spacer
iii. A redesigned oil pressure relief system
b. An adapter to mount an Oldsmobile oil pump is now available
c. Modifications and improvements to the Packard oil pump, incorporating the three factory changes, as well as a stronger cover plate and triple the shaft bearing area.

Dick Steinkamp
03-05-2007, 06:24 PM
quote:Originally posted by PackardV8

3. The 1955 SBC was designed with a 3.0 stroke and a main bearing diameter of 2.3. When the 350 came along in 1968 with a 3.48 stroke, the main diameter went to 2.45. Finally the 400, with a 3.75 stroke, the main bearings were 2.65.

Good info. Thanks Pack.

In the SBC case, the change to the 2.45" journal may not be stroke related. Early 327 CID motors (3.25" stroke) had the small journal (2.3") FORGED STEEL cranks. Late 327's (same stroke) had the large journal (2.45") CAST IRON cranks. It sounds like the change to the larger journals may also be related to the change in the crank material.

BTW, I was wrong on the Shop Manual specification for the crank. As Stu63 indicated, it is the CRANK GEAR that is listed as cast iron. The material in the crankshaft is not specified in the shop manual.


John Kirchhoff
03-05-2007, 09:58 PM
Correct me if I'm wrong, but didn't the later Packard engines have a combination oil pump and vacuum pump that was notorious for sucking air and beating up the crank? I also thought I read where the Packard engine used in the Stude application ('56 Golden Hawk) did NOT have the vacuum pump and was therefore more of less unafflicted by the bearing problem. I don't think I dreamed this but read it a long time ago.

03-05-2007, 11:58 PM
Greetings, John,

The '56J Hawk Packard V8 oil pumps originally had a solid bottom cover. The Packards all had the vacuum pump on the bottom of the oil pump. I am not convinced one way or the other as to whether the vacuum pump is the villain. As I mentioned earlier, Packard engineers made three oil system modifications, none dealing with the vacuum pump. It is to be assumed these very experienced engineers would have worked in that area if it were the root cause of the problem.

I have extensively modified the Packard pumps in three additional areas and feel I have eliminated most problems and wear points.

Kevin did not confirm which oil pump his engine had. Like all Studebakers, the '56Js are fifty years old and most are not as built. Many '56Js have engines originally built for Packards in them today.

thnx, jv.


03-06-2007, 09:44 AM
Bet it was the oil:

Dad drove this car last during the summer of 67, then it was cubby
holed in different storage barns around home until he had his own
storage garage in the late 70's. Only movement it saw was when he
moved storage facilities. He would start it 20 minutes at a time in
storage and always say.... "doesn't that sound great"? Car was
maintained sporatically for 35 years, going years between oil changes.
Since I was only a kid when the car was driven last I can't say
weather it had good healthy oil pressure after it was good and hot.

In the first 75 miles in 35 years I stuck and bent a valve. I think
the fresh detergent oil, in concert with a lame stock oil pump had a
lot to do with the bearing failure. When I had the top of the engine
apart for the valve job, I disasembled all the lifters, cleaning them
in kerosene as well as the top of the engine and the lifter bores. I
let the kero run down into the sump and out the drain hole. This was
the start of my oil pressure problems. Yup, I hear all you guys saying
"Bingo, Dumb ass."

I then dropped the pan to pull the oil pump. Joe Hall looked at the
pump and confirmed it was a the weak original pump and needed an
overhaul. I sent it to Packards International for overhaul and

OK, BUT WHY THEN is there not even a scratch on the rod bearings?

My journal speed idea is probably not on target since Jack Vines says
the journal is only 2.5 inches. It sure sounded good though!! Thought
I could cast the blame squarely on the SPC engineers instead of the
guy in the mirror.

I'll pay my stupid tax and get on with fixing it.

Kevin Edwards


03-06-2007, 11:09 AM
Dick: Check page 30 in the engine section of the Avanti Manual. It shows that the cranks in all models are made from heat treated drop forged steel. Langworth's book about the post war Studes said that all v-8s Had forged cranks but I couldn't find any ref in the shop manual til I saw this when I was looking for something else. Seems like I can never find anything till I don't need it.

Butler, PA
63 Avanti R1 R2899

Dick Steinkamp
03-06-2007, 11:21 AM
quote:Originally posted by Stu63

Dick: Check page 30 in the engine section of the Avanti Manual.

I don't have an Avanti manual, but no prob...I take your word for it. :)


03-07-2007, 12:13 AM
Hi, Kevin,

Don't be so hard on yourself. Nothing you did sounds terminally stupid. Most of the Packard V8s I pull down have previously had the crankshaft turned undersize. The few which haven't all show serious main bearing wear.

thnx jv.


02-09-2009, 09:09 PM
FWIW the one Packard engine I've torn down had the 56J oil pump in it, and it was still trashed. The upper bearing had worn out and allowed the gears to wobble, scoring the bottom plate. So there are more problems than just the vacuum pump. That said, the bearings in that engine still looked OK. No idea of mileage, I bought it because it had a 2x4bbl setup and a stickshift bellhousing on it :)


55 Commander Starlight