427 Cam

[Jeremy Hedges]

What is the correct part number cam for a 1967 L71? And where could I get one? Also where would I find out the specs (lift, duration, etc) for this cam?

Thanks
Jeremy Hedges
#31711

[Joe L.]

Re: 427 Cam

Jeremy------

The cam originally used was a GM #3904362. This cam is GM-discontinued and not reproduced. However, the GM #3863143 is reproduced. It's identical to the 3904362 except that the rear journal is grooved. You can use this cam by slightly modifying the rear cam bearing. Some reproductions of the 3863143 may not even have the groove. This actually makes them a GM #3904362 but they're still sold as reproductions of the GM #3863143 (that part number is more "famous").

Crane and Comp Cams, among others, make reproductions of the 3863143. A Crane-manufactured reproduction in kit form (cam + lifters) is also available from GM under GM #12364057.

[Duke W.]

Re: 427 Cam

Specs? Less than thirty days ago I posted the entire lift, velocity, acceleration, and jerk profile for this cam.

Since this is essentially the blueprint for the lobe you can extract "specs" in any context you want, or take the data to a cam grinder and have it ground.

I don't think anybody had a clue how to interpret the data, and if you can't then specs don't mean anything, anyway.

Search using the part number posted by Joe.

Duke

[Terry F.]

Re: 427 Cam

Joe,

Any chance you can explain the grooved vs. the non-grooved cam thing to me. The transition occured around 67 to 68 in the way the block was machined. Did the cams go from being non-grooved to being grooved from that point? I assume it had something to do with the excessive oil going to the valve train.
Do you know what the correct set up is for my 68 321 block? I am having issues with somewhat minimal oil getting to the rocker arms and I am wondering if my engine builder gaffed me.

Thanks, Terry

[Clem Z.]

Re: 427 Cam

the 65-66 blocks used the grooved rear cam journal and the rear cam bearing had 3 oil holes that must be lined up with the holes in the block. the later years used a block that was grooved under the rear cam bearing to get oil to the lifter gallery and the rear cam bearing had only 1 oil hole. if you use a groved rear journal cam in a later block you need to solder up the larger oil hole in the rear cam bearing and drill a 1/16" hole in its place to prevent a excess internal oil leak

[Terry F.]

Re: 427 Cam

I recall I ordered a factory grind cam for 390hp from crane, I believe it came groved. If the the rear bearing oil orfice was not soldered shut and drilled 1/16th do you think that would be enough to starve the lifters and rockers of oil? Thank you for your responce. Terry

[Clem Z.]

Re: 427 Cam

that i can not answer as i never experienced that problem BUT the oil that leaks out from the rear cam journal being grooved and the large oil supply hole in the bearing COULD cause your problem because the lost oil should be going to the lifter gallery

[Terry F.]

Re: 427 Cam

I am afraid that is my problem. I remember talking to the machinist and he seemed to not be totally familiar with the issue. I really hate the thought of pulling that thing out of there. It is such a tight fit. I will give every other thing the once over but I can't imagine anything else causing the problem. Do you recall if a gasket is used between the oil filter spin on adaptor or is that machine fit? I don't recall seeing one in that region. I will pull that and take a peak. I just think I should pull it out. What a hassle. It is so put back together but hey, what good is it if I can't get good enough oil pressure to the top end. Takes too long and and the front of the engine is getting consistanly less than the back. Oh well, Terry

[Joe L.]

Re: 427 Cam

Terry-----

There is no gasket between the 68+ oil filter adapter and the block.

[Terry F.]

That's what I thought. Thank you, Terry *NM*

[Craig S.]

Re: 427 Cam

Joe - Federal Mogul SpeedPro CS165R has no groove, but explains the cut if required..... Craig

[Craig S.]

Re: 427 Cam

Clem - I have an new 366250 LS6 crate engine I purchased in 1989 for my 74...that has not been installed yet...(another story ) Anyway, it has the 3143 cam from GM....(even though the spec sheet shows 4362). I pulled the cam, and installed a new rear bearing with the soldered shut and redrilled 0.060" hole per the power book discussion. So.....at least in the LS6 crate engine era, GM assembled them wrong......but I am guessing they were assembling engines from parts bins then. I can't attest to if it would have leaked too much or not as I did these before the 2 hours run in it has on the clock....Craig