Grooved Cam for 65-66 425hp Big Block
I opened the box for my TRW TP-165 cam that I have been saving for many many years for my 67 427-435, and it turns out to have a factory groove in the rear journal making it the correct cam for the 65 396 and 66 427-425 engines. The current production of these cams do not have the groove necessary for 65 and 66 oiling. If there are any 65 or 66 owners out there who have a new non-grooved cam and are wondering how to get it grooved, I would be happy to swap it for my new grooved cam.
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Re: Grooved Cam for 65-66 425hp Big Block
The Chevy listings for cam timing do not use the standard .050 checking clearance so it is hard to compare cams specs at .050 clearance to the Chevy Power book. The duration of this cam is 242 degrees intake and exhaust with 114 degree lobe spacing, which is the same as Crane lists for its NHRA legal duplicate of the 143 cam. I will get the exact opening and closing points off the box today. Do you have the Sealed Power specs for comparison?
The cam is dark in color except for the bearing journals so I guess that is parkerizing. TRW was the OE manufacturer of the pistons for SHP 427s, so it is likely the made the OE cams too. It is my understanding that Sealed Power is the successor to the TRW company and they produce many of the same products but off shore rather the in the US today.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
The Chevy Power book says the grooved cam may be used in a 67 engine if you solder the oil hole in the rear cam bearing and redrill it to a smaller .060 size. Since the rest of the short block is already assembled, it is a lot easier to simply use a cam compatible with the cam bearings in the block. Besides, I think NOS grooved cams are pretty rare these days, and I figured one of the 65-66 guys who need grooved cams would be happy to swap it for a common ungrooved cam.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Ok so what would the damage be (exactly) if you used a non-grove cam in a 65-66?
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Re: Grooved Cam for 65-66 425hp Big Block
It would interfere with the oil delivery to the cam, lifters and rocker arms. 1967 and later blocks had an oil passage in the block that earlier blocks did not have. 1965-66 blocks relied on the grooves in the cam and the unique 65-66 rear cam bearing for the vavle train oiling. You are courting disaster to use an ungrooved cam in an early block.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Pat,
There was a post recently on this so the discussion should be in the archives.
If I understand correct, the grooved cam is used in the early big block along with a grooved rear bearing and oil from the main oil gallery goes into this groove and travels through the groove to supply the lifter gallerys and rear main bearing.
In 1967, the groove is machined into the block so it's like a small block where oil travels through the annulas in the block to supply the lifter gallerys. A camshaft with the groove would cause no problems used in the 1967 later block.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Tim: Your description of the parts is acurate. However, my concern is prompted by the following quote from the Chevrolet Power Catalog (6th edition, 1988) a GM publication. "If you are using a camshaft with a grooved rear journal, it is necessary to remove the rear camshaft bearing, solder the bearing oil hole closed, and redrill it to .060-inch diameter. This groove was required for valve lifter oiling, but it creates a major internal oil leak in Mark IV engines produced after 1966."
I am working on the original block of my 67 L-71 with its original grain and stampings intact, and using the TRW 65-66 cam is not worth worrying about a "major internal oil leak."
For those familiar with my earlier post regarding the compatability of an iron cam sprocket wearing against the cam thrust surface of an iron block, I just discovered the following quote in the same Chevrolet Power Catalog.
"Many competition engine builders protect the block's camshaft sprocket thrust face with a brass or roller bearing thrust washer when using a cast iron cam sprocket. This precaution is especially important when using a high-volume oil pump, which increases the load on the thrust face."
I am using the ZL-1 type oil pump with 1.3 inch gears because it came with the correct oil pick-up pre-welded, so I am glad to be using the Cloyes sprocket with a brass thrust washer recommended to me by Clem and Joe in the previous thread. By the way the Comp Cams nylon 202 cam button my machine shop gave me turned out to be for a small block; Comp Cams 205 is the correct part for a big block.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Federal Mogul bought most of TRW's auto parts operations over 20 years ago and incorporated the former TRW products into the Speed Pro and Sealed Power brands.
I have no doubt that the old TRW TP-165 is manufactured to the GM ...143 print, and is the same are the current CS-165R other than the latter does not have the groove.
Previous threads going back a few years stated that Chevrolet rescinded the advise about modifying the rear cam bearing if using a grooved journal cam in a '67 or later block, so it's okay to use a grooved journal cam in a '67-up block, but a grooved journal cam MUST be used in a '65-'66 block.
The description of the surface indicates Parkerizing. After the process is completed the journals are polished to remove the surface treatment from the journals.
DukeComment
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Re: Grooved Cam for 65-66 425hp Big Block
the grooved cam would only be a problem in a later block if you were racing.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Pat,
If it was my engine I would probably go with a camshaft without the groove but I can't understand where the big internal leak could come from. Oil would travel in the groove under pressure but it has to get between the journal and cam bearing to leak out and that clearance is no different than any other engine.Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Tim, you are correct-the others apparently have no experience with big blocks. Using the wrong cam setup will drop the oil pressure to about 10 #'s as soon as warmed up or 10 minutes, give or take. Listen to the GM folks, they're the "experts".Comment
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Re: Grooved Cam for 65-66 425hp Big Block
Sounds like it's the time to re-post the pic from my 396 (3855961 2-bolt, but the '962' 4-bolt would be the same). You can see the hole in the rear cam bearing that shows a bit of the corresponding hole in the block, slightly misaligned. There are three of these holes, at 120 degrees separation.
The orange stuff is Glyptal or equivalent.
yComment
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Re: Grooved Cam for 65-66 425hp Big Block
cam bearings have a lot of clearance .004/,005 and since the grooved cam journal has a open path for the oil to flow thru that groove there is a lot of area around the groove for the oil to flow out fed by 3 large holes in the bearing where the oil is fed into the bearing . the no groove cam bearing journal has only one oil input and that is at the bottom and the cam journal is being pushed downward to seal off that hole where if the journal has a groove there is no resistance to the oil flow. this is why GM says solder up the original 1/4" hole in the bearing and drill a 1/16" hole to act as a restriction to the free flow of the oil into the grooveComment
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