Camshaft oil groove

[Craig S.]

Re: I think so.

Clem - I did the solder trick on my 1989 vintage crate LS6 that GM shipped new with the 3864362 cam with a groove, couldn't believe they sent it that way, so I performed the solder and drill process per the Chevy power book. Also, my 66 427 is a 942 block casting and it has the ungrooved rear bearing support in #5 cam support, so I will be grooving my Federal Mogul (Speed Pro) blueprint 3143 cam. I also plan to use the LS7 oil pump with 1.3" gears, leaving the pressure spring in for standard pressure....Craig

[Craig S.]

Re: Camshaft oil groove

I bought a set of their Howards Cam melonited black valves for my 66 L72, probably way more valve than I will ever need the way I will run it, but they were first rate items....albeit costly (but not as much as buying chevy valves through the parts system)....Craig

[Craig S.]

Re: Camshaft oil groove

Clem and Terry - I have a still new LS6 crate engine I bought in 1989 with a June 30 1989 casting date, I think the block carries 286 as the last three digits. It has the 4362 mechanical cam, with the groove in the back. I know this because I pulled and inspected the cam before fire up, althougn it had been factory test fired on natural gas I assume. There was evidence it has run a small amount, since it came with a Chevelle oil pan etc I had the pan off. This mill definitely DID NOT have the soldered shut oil hole, it had the standard large 3/16-1/4" or whatever hole. Since I did have the power book, and had read about the large internal leak using a grooved cam in the newer blocks, I bought a new bearing and soldered it shut, and drilled the 0.062" hole to control oil bleed off into the groove. I was surprised GM sent a crate engine out this way....ugh. I pulled the inner valve springs and ran it in for 30 minutes at 2200- 2500 rpm, varying the rpm. I pulled the intake, and inspected all the lifters. They all broke in well but one, cylinder 6 (I don't recall if it was intake or exhaust, but was the 3rd lifter from the back on the RH bank) shows an hourglass burnish pattern versus the expected rotational pattern. I had 5 new GM mech lifters, so I replaced that one hoping the lifter versus lobe was at fault, the lobe seemed good, and all measure equal lift with a dial guage on magnetic base. I reassembled, and ran it in for 2 more hours with outer only springs using the 627 springs. I am also using a Cloyes Hexajust timing set, dialed in the cam, and have comp cams pro magnum roller rockers under the standard steel dripper covers, with L89 D port heads. I pulled the 3163 manifold, and have a 67 tripower going on (just cause I love them). This engine is going in my 74 coupe, with the original L82 stored. Now I am wondering what that one lifter will look like when I pull it to inspect...haven't got around to it for the last several years with all the time going into the 66 lately. If that lobe is gone, I blame GM on the test fire not the way I went to every trouble to break it in right, including preoiling, filling the carb bowls with gas, instant fire up and correct run in on an engine stand... Anyway, I can absolutely confirm that the 1989 crate LS6 engines built in mid summer had the new bearings with the old groove cam. I suspect they were just building them from parts bins to use up the parts before they dropped this engine...and I am sure they didn't really think about customizing the bearings per the power book since that would be a very nonstandard operation for the line.....Craig

[Clem Z.]

Re: Camshaft oil groove

i built 2 or 3 engines where i soldered up the rear cam bearing when using a grooved cam in later blocks and never had any problems. the grooved cams were sold at chevy and the aftermarket long after the block oiling was changed. if the crate engines came with the grooved cam and the large oil hole bearing i still can not understand why as terry stated changing to a non grooved cam would cause a problem unless the bearing had the small hole not allowing enought oil to the lifter galleries but this would only happen in a block that there was no groove behind the cam bearing. in the non grooved block a grooved cam bearing journal was required because this is how the oil got to the lifters. with a non grooved cam the fact that the cam journal rests on the oil hole limiting the amout of oil that get thru with the large hole and with the grooved cam lots of oil would leak out around the rear cam bearing inside the engine. one of the mysteries of engine building.

[Craig S.]

Re: Camshaft oil groove

Clem - I agree with you completely, to me, the small hole in the bearing with no groove would not cause any limitation to the top end oiling at all due to the groove in the block, but may starve that cam bearing adequate oil. This leaves no explanation whay Terry saw the top end problems. By the way, my block did indeed have the groove, no surprise there, being a 1989 block. I read in one of the other books on the market (I think it was the dated version of how to hotrod your BB chevy, or may have been Tom Wilson's how to rebuild your BB chevy) that the grooved journal with larger hole bearing was not a problem. But the GM power book made a big deal of it, so I did it. The one thing I did worry some about was the grooved block shaving the cam bearing backside as it is installed, resulting in some metal filings in the oil channel back there. I flushed as best I could with brake cleaner through all the oil passages. The other thing I have done, is drill 0.060" holes in the pipe plugs in the front oil channels behind the cam gear, allowing oil flow onto the cam gear/chain, eliminating any air pocket areas in teh lifter galleries, and with the 1.3" pump gears, should not be a pressure loss issue. I am thinking of doing the same on my 66 L72 when I assemble....Craig

[Clem Z.]

Re: Camshaft oil groove

i drilled all my BBC lifter gallery front plugs to put extra oil on the timing chain but i used .030 holes

[Craig S.]

Re: Camshaft oil groove

Clem - I think that's what I used too, it was in the power book, maybe it was an number 60 drill bit size....Craig

[Craig S.]

Re: Camshaft oil groove

I found the text I was remembering and it was the 0.030" as you mention, and was not in the power book but the How to rebuild a BBC book...I must have been remembering a number 60 drill...Craig

[Terry M.]

Re: Camshaft oil groove *TL*

Craig,

At least one edition of the Chevrolet Power Book quotes a drill size of 0.060 inch.

In case 1 the hole in the rear cam bearing is a lot larger than 0.060. I just got the tool to take the cam bearings out, but haven't used it yet. I want to see if there is a groove behind the rear cam bearing. There better be because there is not enough holes in the bearing to get oil to the lifter galleries if the oil has to travel through the cam groove.

[Craig S.]

Re: Camshaft oil groove

Terry - I think we are now talking about different things. Earlier in the thread, we were talking about the 0.060" hole being drilled out after soldering shut the cam bearing from the larger 3/16" or 1/4" hole to contol the bleed off loss through the groove in the rear cam journal. The holes Clem and I are now discussing are the air bleed and lube squirter holes in the pipe plugs in the front of the two lifter oil galleries that spray on the cam sproket. I will be very interested in what you find.....my LS6 definitely has the annular groove in the block behind the rear bearing, plus the grooved cam, which is why I added the bearing with the hole soldered shut and redrilled. Now, my 66 block has no groove in the block, plus the 3 holes in the cam bearing, and of course I need the groove (in this case, the Speed Pro CS165R blueprint cam for the GM 3143 is not grooved, so I have to pass it through my metal lathe to cut the correct groove for my usage in the 66 block).....Craig

[Terry M.]

Re: Camshaft oil groove *TL*

Sorry Craig - I thought the thread went back to the solder and drill of the cam bearing.
As far as I can see there is only one hole in the rear cam bearing, so I can't imagine that the groove in the rear cam journal had any useful purpose, but since the cam bearings are coming out anyway it will be interesting to see what is there.

[Joe L.]

Re: Camshaft oil groove

Terry-----

All 1967+ Chevrolet big block blocks should have the groove behind the rear cam bearing. I will be AMAZED if you find anything else.

[Joe L.]

Re: Camshaft oil groove

Craig------

If the "blueprint" GM #3863143 cam that you have does not have the groove on the rear journal, then it's not an exact reproduction and it's not made to the "blueprint". The original 3863143 cam DID have the groove. Even though this camshaft was used in PRODUCTION in some 67+ big blocks and specified as the SERVICE cam for many years for most 65-71 SHP big blocks, it had the groove. Grooved cams can be used in 67+ big blocks.

The GM #3904362 which came into use in 1967 for some SHP big block applications and became the SERVICE cam for all 65-71 SHP big block applications after the 3863143 was discontinued does not have the rear journal groove. When the 3904362 is used for 65-66 SERVICE, the groove has to be added.

[Terry M.]

Re: Camshaft oil groove *TL*

I too will be surprised if the groove is not in the case. He hasn't pushed the bearing out yet, but I can see that there is only one hole in the rear cam bearing.
It occurs to me how fortunate we are who work with original components. In this case we are struggling with the uncertainty of what may have been done by others who have been in there before.

[Craig S.]

Re: Camshaft oil groove

Thx Joe - hmmmm, well, according to the parts breakdown on my 1989 vintage LS6 engine, GM says it has a 3904362 cam, but it definitely has the groove, and had the right ID info on the cam itself (but I can't remember what it was now, seems like OMO something). It also was color coded with paint ID. Maybe it was an old left over 3143, but hard to believe as the engine was built in July of 1989. The Speed Pro CS165R is listed by Speed Pro (FM) as a "blueprint" grind of the 3143 in thier catalog, but it definitely doesn't have the groove. I do have a sheet from my machine shop from Isky cams with the measurement point and depth of the groove when you add it yourself. Sooo, sounds like there are a lot differences out there in the aftermarket world on the way the GM street mechanical cams were configured. I am really curious what was different between the 3143 and 4362 cams from GM....was it just the removal of the groove? and if so, I am still mystified by the inclusion of the groove in my 1989 crate engine. I am very interested in what your thoughts on this are, and your point about the groove removal makes total sense to me since I think the lobe grinds, base circle, and lobe separation are all the same on these two cams....Craig