Grooved vs non-grooved cam journals 2 and 4 ?

[66gtafairlane]

We are rebuilding a 1963 427 topoiler and figuring out the cam/ oiling system. It will be a fairly mild flat tappet cam.Why do some FE cams have grooved cam journals in journals 2 & 4 and some cams don´t ?

[blykins]

The typical 352/390/428 block has grooves in the block behind the cam bearings that pass oil to the heads. 

A *side-oiler* 427 block does not have those grooves, so the cam journals are grooved to pass oil around to the secondary hole in the cam bearing that feeds the heads/rockers.

Most of your aftermarket cams will have the grooves.  The cam grinders don't know what block you'll be using the cam in. 

[pbf777]

A 427 block does not have those grooves, . . . . .

     Brent,

     I think you meant: A 427 "Side-Oiler" block. . . . . . .   

     Scott.

[blykins]

Yes sir, thank you.  I'll edit my post.

[frnkeore]

Speaking of #2 & #4, that feed to the rockers comes directly from the main bearing oiling. Even if you restrict the rocker oil to ~.070, your still loosing that oil to the MB and rods.

It's better to block the the oil to the RA's, at the block to head port (3/8 x 16 set screw) and rout internal 1/8 lines, from the center oil gallery to the rocker stands. I know most get away with not doing it but, it will improve oil flow to the crank, in the problematic 2 & 4 position.

[WConley]

Huh??  Frank, can you please explain?  In my book, restricting the flow at the existing 2 and 4 passages will have the same effect as blocking completely and creating new feed lines.  The main oil gallery flow and pressure would be the same in both cases.

Edit - Oh wait, I see it's a Top Oiler.  I still don't see any difference to the main bearing oil feed either way.  I could see how you'd think that taking extra oil at #2 and #4 would create a local pressure drop, but the flow is pretty minimal when properly restricted.  Taking the top end feed off the beginning of the main gallery would evenly distribute the pressure drop, but to me it doesn't seem to be worth the effort.

[frnkeore]

The red X takes oil before it even gets close to the MB, so, 2 & 4 can't get as much oil as all the other MB's because of that, at least .070 leak and if the clearance on 2 & 4 were to increase, for what ever reason it can't get replenished as well as the others, with that leak. 

The way I have modified my blocks is first, I drill the main gallery's (large red box) to 7/16. Then, that leaves the 3 pipe plugs, to come off of, with a line to one of the rocker stands. Of course pluging the oil hole at the top of the block to the rockers, with a 3/8 x 16 set screw.

That gives a fairly large reservoir of oil, to feed everything. If you go one step father, you could increase the annular grooves, under the cam bearing, to .280 x .140 deep and have a bullet proof TO system.

[WConley]

Frank - What you are showing will certainly not hurt anything. 

I don't see a real benefit though.  If you use pipe flow formulas, the 0.070" restricted "leaks" at 2 and 4 are a tiny percentage of the flow in the galleries.  You would see more flow effects from the bearing clearance tolerance.  It's a fun exercise, but I'll put my trust in those old timers who originally designed the FE.  I met some of those guys when I was there, and they were no dummies!

[jayb]

I agree with Bill, it doesn't seem like that modification really makes any significant difference.  Especially with a high volume oil pump, I think there will be plenty of oil to feed the mains with the rockers oiling through the factory passages.

[blykins]

I'll third that motion...

Now granted, I use pushrod oiling a lot more often than not, but I do have some drag race engines out there that are oiling through the heads.  They didn't need anything special as far as oiling. 

I've got one 390 out there, that as of 2023 (looking back at old text messages), it had 6000 street miles and 247 1/4 mile time slips on it, launching at 5500, shifting at 7000, consistent oil pressure throughout the pass.  No internal lines, no drilling out oil galleries.  It's even a hydraulic roller motor, so it has full oil flow going to the lifters. 

Nothing wrong with tinkering, but based off of what I've seen, there is nothing problematic about oiling to the #2 and #4 main bearing because of rocker arm oiling.

[frnkeore]

I do this because it makes since to at least give 2 & 4 the same flow as the rest and to increase the overall flow capacity by 36% by opening the main gallery's.

To me, if a std pump can fill and pressurize a 3/8 galley system, a HV pump, can't push any more oil threw the 3/8 system w/o increasing the pressure, there for a HP pump, should increase volume a little. Where a 7/16 dia system can handle a 36% increase in volume and that HV pump, may be of benefit.

This is another thing to consider on a TO. I don't remember who did the chart but, I think I copied it on this forum.

A 3/8 hole has a area of .1104 and a 7/16 is .1507 (36%). The leakage chart shows that a area of .2584 to fill all the gaps in the engine oiling system WITH a .070 restricter and .0015 M & R clearance. If you open the M to .003 and the R to .0025, that increases the leakage from .2584 to .454. Both more than even a 7/16 area. So, the down stream pressure has to drop off and can only be helped with increased pressure, right?

While the increase in main gallery CSA may not be needed in actual application, it sure should deliver more oil to the overall engine.

Also, there are many things we do on these engines, that they don't actually need but, we do them anyway, right?

[66gtafairlane]

Thanks for everybody`s input, coming back to the original question about the grooves in the camshaft`s bearing journals 2 and 4... still do not quite understand why they are there, and why some cams do not have them ?

I am planning to have a custom mechanical flat tappet cam reground here locally, have a old core which does not have the grooves and was wondering whether they are really needed and should be ground in the journals.

This is a mild street motor ( 1963 topoiler stroked to 456ci already years ago), redline 5800,projected mechanical flat tappet cam to have approximately 238@0.050.

[WConley]

It's very much more complicated than cross-sectional area.  For instance, tribology (the science of lubrication) treats rotating journal bearings as pumps.  Peak pressures can reach thousands of psi at high speeds and loads.  Look up the Reynolds Equation.  What would the flow through the bearing be under those insane pressures?  Clearances around the bearing vary a great deal with load, as does pressure.  There are lots of SAE papers on journal bearing lubrication if you really want to go nuts.

Loads on the rods and mains can be measured in tons at higher rpm and throttle positions.  To convince yourself, do a napkin calculation of how much oil film pressure you need to support even one ton of force on a rod journal.  You'll find it's at least an order of magnitude higher than anything the pump can put out.

[WConley]

Thanks for everybody`s input, coming back to the original question about the grooves in the camshaft`s bearing journals 2 and 4... still do not quite understand why they are there, and why some cams do not have them ?

Ville - Sorry to derail your original post with our arguing!  Since your engine is a 427 Top Oiler, the grooves are already provided in the cam bearing bores of the block (behind the bearing shell).  Therefore you do NOT need grooves at #2 and #4 on your cam.  Your existing cam core should be just fine without the grooves.

The later 427 Sideoiler blocks are machined without the block grooves, so grooves must be provided in the cam journals at #2 and #4 to lubricate the rocker shafts.

[MeanGene]

Yes sir, thank you.  I'll edit my post.

Didn't want to say anything lol