Looking for 3925535 cam

[Jon S.]

I'm looking for an NOS 3925535 camshaft for a '69 L88. It is my understanding that the service replacements have a grooved rear journal, and that if I use this in my L88 block I need to do a rear bearing modification in order to avoid internal oil leaks. I would prefer to find an original cam that does not have the groove if I can. Any leads would be appreciated.

Thanks in advance,
Jonstr
NCRS #10673

[Joe L.]

Re: Looking for 3925535 cam

John-----

The GM #3925535 camshaft was discontinued in September, 1996. There might still be a few around, but I don't know where. They "pop up" every now-and-then on eBay.

As far as using a reproduction of this camshaft, I don't know why the reproductions would come with the rear journal circumferential groove----I don't think that the original camshaft ever had one inasmuch as no L-88 ever needed one. Notwithstanding that, the groove, if present, will cause no problem, whatsoever, in engines not requiring the groove.

You can purchase Crane-manuafctured reproduction of this camshaft in a camshaft and lifter kit available under GM #12364058.

[Jon S.]

Re: Looking for 3925535 cam

Thanks for the info, Joe. I'm a little fuzzy on the details, but sounds like the service replacement for the 535 cam can be used in big blocks from 65-69, although it was ground to L88 specs. The grooved journal was for the earlier non-L88 blocks. Another member sent me this from the 5th Edition Chevrolet Power Manual:

"In the event you use a camshaft which has a groove in the rear camshaft journal, remove the rear camshaft bearing, solder up the hole, and redrill it to .060" (Figure 26). A grooved rear journal was required for valve lifter oiling in 1965-66, but creates a major internal oil leak in later engines which can affect oiling system performance."

Jon
NCRS #10673

[Joe L.]

Re: Looking for 3925535 cam

John-----

GM for years sold the GM #3863143 camshaft (the SHP mechanical lifter camshaft) to SERVICE all 1965-71 big blocks with SHP engines, although the 3863143 was likely only used in PRODUCTION for 65-66 engines. The 3863143 has the rear journal groove. I am not aware of any instructions that came with this camshaft regarding the need to modify the rear cam bearing when using this camshaft with 1967 or later engines. It's possible, though, that such instructions were included and, if so, I stand corrected on this point. The February, 1988 SERVICE replacement for the 3863143, known as the GM #3904362 and likely the camshaft used in PRODUCTION for 1967+ SHP big blocks, did not have the rear groove and did come with instructions that if it was to be used for 65-66 applications, then the groove had to be added to the rear journal.

As far as the 3925535 camshaft goes, I am not aware that any GM examples of it have the groove. This camshaft was never originally used in an engine that required the rear journal groove, so I don't know why the specs for the part would have called for such a groove, especially if the presence of the groove were detrimental to 67+ engines or required modification of the rear cam bearing. I can't see the addition of the groove even for SERVICE examples of the part, but it's possible that a change was made. I don't have any examples of the cam in the collection to use for reference. Also, I don't know what the rear journal configuration is for this camshaft with respect to the Crane-manufactured reproduction available in kit form under the GM part number I previously provided. To find out for sure, you could call Crane at 386-258-6174 and asking them about this feature for their camshaft part number 968561. This is their part number for reproduction GM #3925535 camshaft and I feel quite sure that it's the same one supplied with the GM kit. If you do, let us know what you find out; I'm curious, too.

[Jon S.]

Re: Looking for 3925535 cam

Thanks again, Joe. I will contact Crane and find out, and post their response here.

As for a 3925535 cam with the grooved rear journal, there is an advertisement for one in the current Driveline. I don't have a copy handy (pg. 34 or 54 stick in my memory), but the ad was for a "nearly new" 3925535 cam. I called the seller and he pulled the cam out of the box while I was on the phone and found that it had the grooved journal. Now, of course I didn't see it myself, and I don't know if the part number appears on the cam (as opposed to just being on the box - which may not be the original box), so take that for what it's worth. :-) However, the seller (a very nice guy who's name escapes me at the moment) seemed pretty sure of the origins of the cam.

The search continues...

Thanks again,
Jon #10673

[Joe L.]

Re: Looking for 3925535 cam

Jon-----

I'll be looking forward to what you find out from Crane; I'm interested.

As far as the GM #3925535 cam goes, a GM piece should have the number "3925536" or a number close to that between the journals/lobes.

[Joe L.]

Addendum

Jon-----

Having researched this matter a little more, I've come up with some conflicting information. Here's what I've found:

The 1966 through 1968 L-88 camshaft was GM #3879605. Although no 1966 L-88s were built for PRODUCTION, parts for it were designed and manufactured that early. The part number is generally consistent with a 1966-issued part. In that case, the 3879605 would definitely have had the rear groove.

In August, 1968, the 3879605 was discontinued from SERVICE and replaced, for SERVICE, by the GM #3925535. That number is generally consistent with a 1968-issued part. Although some references show the 3925535 as being the PRODUCTION 1967 camshaft, I don't think that it could have been for 2 reasons. First, the part number is not consistent with a 1967-issued part. It's possible, of course, but highly unlikely, in my opinion. Second, as far as I can tell, the 3879605 was the 1967 L-88 camshaft.

The 1968-69 L-88 PRODUCTION camshaft is shown by some references as being GM #3928909. I can't confirm this, but I think that it's very likely that this is the correct PRODUCTION part number for the L-88 cam. This part was NEVER available in SERVICE, however. For L-88 SERVICE, the only cam available since the outset of the 1969 model year is the 3925535. This camshaft also SERVICES 1967-68 L-88s.

I think that it's possible that the GM #3925535 camshaft was a SERVICE-only piece designed to SERVICE all 66-69 L-88 applications. As such and if it does, indeed, have the rear journal groove, that would explain why it does. However, if it has the rear journal groove and if the information found in the Chevrolet Power Manual, which information I have been aware of for years, is accurate, then this camshaft would have to have been supplied with instructions regarding modifying the rear cam bearing for 68-69 applications.

[Jon S.]

Re: Addendum

Thanks again, Joe.

According to Crane's Tech Line, their 968561 cam does not have a grooved rear journal. It looks like this might be a possible alternative to finding a NOS 535 cam. Thanks for the info!

Jon

[Clem Z.]

Re: Addendum

joe the 535 came in over the counter engines because i have taken them out and sold them. that was so long ago i do not remember if they had grooves or not. the 605 camshaft was available in 66 as kit #3887175 which was the 605 cam,613 retainer and seal,608 valve spring and damper and 612 rocker arm ball

[Craig S.]

Re: Addendum

I have a new 1989 vintage crate LS6 engine...it supposedly has the 4362 cam per the spec sheet, but it definitely does have the groove, I had it out and performed the solder action on the rear cam bearing and drilled out per the power book. Based on Joe's comments that the 4362 doesn't have a groove like the 3143, I am now wondering if I really have a 3143 leftover in the crate engine.....Craig

[Clem Z.]

Re: Addendum

the cam number should be stamped on the back end of the cam and if you pop out the rear expansion plug you should be able to see the number

[Craig S.]

Re: Addendum

Thx Clem - maybe I will do that...it is still on a stand....Craig

[Frank H.]

Re: blueprint cam

I have a crane blueprint cam/lifter kit,it isn't grooved,it is for sale,and was used for an hour and a half on a dyno test of five cams,I bought three of the cams tested,been saving this,its dated 1992,Crane claims it has inhanced timing to the original,but actually they gave you 0.20 more lift to make up for that lost on lash.One in my car is same part number but is listed as NHRA legal version less lift .500 not .520

cam and specs listed at link below




crane street mechanical cam