1965/1966 427 distributor bottom housing.

[Mark F.]

Hello All. New to NCRS and not a computer guy so please excuse me if if I don't reply right back or dont answer right away, it may take me a while to figure it out but I do appreciate all feedback and will get back to you.

Have a 1966 427 L72 (not original to car). Just purchased it about 8 months ago. Was having TI issues and pulled the distributor and saw it does not have the proper housing on the bottom. From the CF the common idea is don't worry about it, but I can't get by the fact that for the 65/66 big block with the groved cam and aft groved bearing it had a special housing on the bottom of the distributor, I believe this housing was for the specific purpose of that groved cam and bearing set up.

Am I wrong on this?

What was this unique lower distributor housing for?

Thanks for all and any comments.

Best Regards. Mark

[Mark M.]

Re: 1965/1966 427 distributor bottom housing.

John Z has explained this best as he always did. Basically the partial grooved distributor was revised to full groove in 67 and no one knows the rational of the 65-66 partial groove. All big block service distributors had full groove for use back to 65. What is important for 65-66 big block and unrelated to the distributor is the grooved rear cam journal and grooved cam bearing with 3 holes lined up correctly. It's required for lifter gallery oil pressure. I would have to double check this but if the 65-66 BB distributor was used and turned in certain clock positions not designed by GM, the oil channeling could be restricted. This may be why they went to a full grove.

[Mark F.]

Re: 1965/1966 427 distributor bottom housing.

John Z has explained this best as he always did. Basically the partial grooved distributor was revised to full groove in 67 and no one knows the rational of the 65-66 partial groove. All big block service distributors had full groove for use back to 65. What is important for 65-66 big block and unrelated to the distributor is the grooved rear cam journal and grooved cam bearing with 3 holes lined up correctly. It's required for lifter gallery oil pressure. I would have to double check this but if the 65-66 BB distributor was used and turned in certain clock positions not designed by GM, the oil channeling could be restricted. This may be why they went to a full grove.

Thanks Mark. I will try to find John Z. article. I was having an oil pressure problem and pulled the TI distributor and thought this full grove could be part of the problem. I have been convinced it is not part of the oil pressure problem. I appreciate your time in reading and responding to my thread. Holiday Cheers. Mark

[Joe L.]

Re: 1965/1966 427 distributor bottom housing.

Hello All. New to NCRS and not a computer guy so please excuse me if if I don't reply right back or dont answer right away, it may take me a while to figure it out but I do appreciate all feedback and will get back to you.

Have a 1966 427 L72 (not original to car). Just purchased it about 8 months ago. Was having TI issues and pulled the distributor and saw it does not have the proper housing on the bottom. From the CF the common idea is don't worry about it, but I can't get by the fact that for the 65/66 big block with the groved cam and aft groved bearing it had a special housing on the bottom of the distributor, I believe this housing was for the specific purpose of that groved cam and bearing set up.

Am I wrong on this?

What was this unique lower distributor housing for?

Thanks for all and any comments.

Best Regards. Mark

Mark------


The "full round" distributor housing replaced the "3/4" round" for SERVICE of all 65-74 big block applications many year ago.

[Mark F.]

Re: 1965/1966 427 distributor bottom housing.

Thanks Mark. I will try to find John Z. article. I was having an oil pressure problem and pulled the TI distributor and thought this full grove could be part of the problem. I have been convinced it is not part of the oil pressure problem. I appreciate your time in reading and responding to my thread. Holiday Cheers. Mark

Hi Mark & Mark and Joe,

You may have located this already, but if not, JohnZ had the following to say in some excerpts from the CF in Posts #41, #61 and #67.

https://www.corvetteforum.com/forums/c1-and-c2-corvettes/2446145-66-427-rear-camshaft-groove-question-4.html

" Starting in 1967, Chevrolet redesigned the oiling path to the lifter galleries. The groove was removed from both the rear cam journal AND from the I.D. of the rear cam bearing, and an annular groove was machined into the rear cam bearing bore in the block instead. With the smooth rear journal and cam bearing surfaces, oil entered the bearing through the same hole in the bottom, but part of it flowed around the outside diameter of the cam bearing, through the groove machined in the bearing bore, and exited through the same two holes in the block at the top that fed the lifter galleries. The cam bearing now had only one hole, at the bottom.

What This Means To You:



"

[Mark M.]

Re: 1965/1966 427 distributor bottom housing.

Something of interest here and important to 67 427 owners is the use of 1966 427 blocks with the 3869942 ground off and 3904351 hand stamped for used in 67s. Do these 66 used in 67 blocks require the grooved parts? When did Chevrolet change for 1967 to the annular groove machined behind the rear cam journal? Did Tonawanda add the 67 machining to the 66 blocks than change it's casting number with a hand stamp? I would check any early big block about to be built. Cheers to all

[Richard M.]

Re: 1965/1966 427 distributor bottom housing.

For reference, the distributor annular ring mating area of a 1967 3904351 block showing the oil passages. I took these years ago when we were having similar discussions here.

Front View
427BB_3904351_Dist_Oil_Port_Front.jpg

Rear View
427BB_3904351_Dist_Oil_Port_Rear.jpg

Photo of a 1967 1111258 TI distributor with 3/4 annular ring(groove). I seem to recall years ago that someone, maybe John, mentioned that the idea behind the 3/4 ring may have been to increase oil flow directly from input to output port in the block. Further research told the engineers this wasn't as effective as was first thought so they abandoned the design. Again this from memory so it may not be accurate.
PC230003.jpg

PC230004.jpg

Also, I also recall being mentioned that re-indexing the plug wires on one of these distributors is not recommended as it could block oil flow.

Rich

[Mark F.]

Re: 1965/1966 427 distributor bottom housing.

Mark------


The "full round" distributor housing replaced the "3/4" round" for SERVICE of all 65-74 big block applications many year ago.

Thanks Joe. I was really concerned this lack of distributor lower housing was part of my oil pressure woes. But apparently not. Thanks and have a good holiday. Mark