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Re: roller camshafts
The roller cam is a hydraulic lifter cam. With RPM range of 1200 to 5200. Not a radicle cam and with a smooth idle. I have owned the car for 31 years and don't think I have ever ran it to 6000RPM. The motor was built and prelubed by myself with oil at each rocker. I suspect a problem with the lifter on that lobe, but just a guess.
CORDially MikeComment
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Re: roller camshafts
You didn't say the year, but I assume you understand that '66 and '67 require different rear cam bearings, and '66 engines must use a cam with a grooved rear journal; '67 engines doen't need the rear journal groove, but it will do no harm.
There have been cases reported where the '67 bearing was installed in a '66 block, in which can the lifter galleries and valve train won't get any oil or the cam didn't have the rear groove, which will cause the same lack of oiling even if the rear bearing is correct.
DukeLast edited by Duke W.; February 9, 2011, 09:42 AM.Comment
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Re: roller camshafts
That's unusual for such a mild grind!
If it's a new cam then let F.M. replace it under warranty. Give it another try before you abandon the flat tappets................over the long haul roller tappets are definitely not necessary unless you are looking to enhance your engine's performance. If you just want to "put, put, put" around with your classic Corvette, then there's nothing wrong with the olde fashioned slow, lazy ramp rate camshafts.
The cam oiling is important as was mentioned, and I assume that you noted the configuration prior to reassembly. What some people miss, is that you must use an overly rich suspension of phosphorous compound in break in oil. I'd rather not see you use ZDDP additives with conventional oil. I much prefer to use a fully engineered and compatible formulation. I highly recommend Brad Penn 30 weight break in oil for the run-in and first 100-200 miles:
Use a good based molykote assembly lube and BURNISH the lube into the lifter feet and cam lobes before slathering on the surfaces. Be sure not to get any on the lifter sides as it may partially block oiling holes and even a momentary disruption of oil flow during run in can be fatal!
If the valve springs use inner springs or dampers, then you should remove them during run in. A very wise practice, is to borrow a set of low ratio break in rockers. With a mild cam such as yours, this is not really necessary, but since you had a failure already, then the extra step would be valuable for peace of mind. Look for a set of 1.2:1 - 1.3:1 rocker arms.
Once the cam is run in, it will be trouble free "forever", so long as you use oils that have been recommended here.
If you didn't buy your lifters from Speed Pro, along with the cam, then there are no better lifters on the market, for the price, than these:
Last edited by Joe C.; February 9, 2011, 10:46 AM.Comment
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Re: roller camshafts
before the advent of the EDM holes in the bottom of the lifters i used to grind a .003 deep flat on the side of the lifter from the recessed area in the middle of the lifter down to about 1/8" from the bottom to get extra oil to the interface of the lifter bottom and the cam lobe. pressurized oil would squirt from this area when the lifter was on the heel of the cam lobe and the flat was exposed to the open area below the block in the cam tunnel. NASCAR engines use either 16 jets installed in the cam tunnel pressurized from the main oil gallery squirting on each lobe or they have the bottom of the cam tunnel closed in so the cam runs in a oil bath all the time or a combination of both.That's unusual for such a mild grind!
If it's a new cam then let F.M. replace it under warranty. Give it another try before you abandon the flat tappets................over the long haul roller tappets are definitely not necessary unless you are looking to enhance your engine's performance.
The cam oiling is important as was mentioned, and I assume that you noted the configuration prior to reassembly. What some people miss, is that you must use an overly rich suspension of phosphorous compound in break in oil. I'd rather not see you use ZDDP additives with conventional oil. I much prefer to use a fully engineered and compatible formulation. I highly recommend Brad Penn 30 weight break in oil for the run-in and first 100-200 miles:
Use a good based molykote assembly lube and BURNISH the lube into the lifter feet and cam lobes before slathering on the surfaces. Be sure not to get any on the lifter sides as it may partially block oiling holes and even a momentary disruption of oil flow during run in can be fatal!
If the valve springs use inner springs or dampers, then you should remove them during run in. A very wise practice, is to borrow a set of low ratio break in rockers. With a mild cam such as yours, this is not really necessary, but since you had a failure already, then the extra step would be valuable for peace of mind. Look for a set of 1.2:1 - 1.3:1 rocker arms.
Once the cam is run in, it will be trouble free "forever", so long as you use oils that have been recommended here.
If you didn't buy your lifters from Speed Pro, along with the cam, then there are no better lifters on the market, for the price, than these:
http://www.scorpioncheckout.com/Sear...ts.asp?Cat=173Comment
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Re: roller camshafts
Good illustration of another downside of flat tappets over rollers for squeezing every ounce of performance out of an engine. Roller tappets don't need nearly as much oiling as flat tappets, and although I don't see the necessity of the EDM holes for a well engineered valve train like that found on the 1st gen SBC, the oil splash to the camshaft is much more than ample to keep a SBC camshaft well lubricated. I don't trust the hole, which can be as small as .010" dia, to stay free and clear of debris or varnish/sludge for that matter. I like your ingenious idea better as far as ensuring extra lube to the feet, if you feel the need for it.
A very important modification to a 1st Gen SBC when upgrading to roller tappets, is to install standpipes in the oil gallery drain back holes, to minimize oil splash onto the camshaft, which migrates directly onto the crank, greatly increasing windage losses.Last edited by Joe C.; February 9, 2011, 11:19 AM.Comment
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Re: roller camshafts
ever notice that the cam tunnel in BBC is open on top? this was done so more top end drain back oil would get to the cam. GM must have seen cam lobe wear in development testing.Comment
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Re: roller camshafts
since i was running edge orifice lifters in BBC because i was using full roller rockers and i was getting less oil upstairs i needed more oil to get to the cam lobe interface so i ground the flat on the lifters sides. with piddle valve lifters you got a lot more oil upstairs that had to run back to the sump and that was a problem because in racing the "G" forces in the turns kept the oil from returning to the sump and you could run low in the sump. that is why GM tells new corvette owners who do auto crossing and track days to run a quart over full to prevent oil starvationComment
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Re: roller camshafts
Yes. Valve train durability was never a strong point with Gen 1 BBC and the oddball "porcupine" heads. Pushrods at angles all askew most likely put much more side loading on BBC components than SBC with its beautiful, in-line valves.
SBC's are "elegantly simple"!Last edited by Joe C.; February 9, 2011, 11:55 AM.Comment
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Re: roller camshafts
the original BBC "mystery engines" used in 1963 NASCAR racing did not have the tappet bores on 2 different angles like the "Mark 4" when it came out in 1965 and that was one of the durability problems it had. too much angle on the exhaust push rods. it made lots of HP causing chrysler to come out with the hemi in 1964.
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In Appreciation of John HinckleyComment
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Re: roller camshafts
Joe;
It would be interesting to sit down and recall/record the many different methods/designs used over the years to keep the roller lifters from rotating. I recall the "straddle" design, the "girdles" and several other. guess each one had their advantages and disadvantages.
Stu FoxComment
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Re: roller camshafts
Stu------
As far as aftermarket hydraulic roller lifters go, virtually all, if not all, use a pivoting cross-bar between lifter pairs as the anti-rotation device. I've never seen any exceptions to this, but some may exist.
As far as OEM hydraulic roller lifters go, I know of none that use the above-referenced device. All pretty much use anti-rotation plates which have "flattened" sides that work with a "flattened" upper body of the lifter. The anti-rotation plates are retained by a stamped steel "spider" which is retained by bolts into tapped bosses in the lifter valley.
OEM hydraulic roller lifters will not with a block not designed for roller lifters even if one were to add the anti-rotation plates and the spider retaining bosses. For a non-roller lifter block, aftermarket hydraulic roller lifters and cams must be used.
So, which set-up is best, the aftermarket design or the OEM design? The OEM design is best for a street engine but the aftermarket design is completely adequate.In Appreciation of John HinckleyComment
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Re: roller camshafts
I guess I was looking back to the late 50's and 60's. Believe Isky made one of the early ones with "sraddle" type solid roller lifters, with extensions on the lifter body straddling the cam lobe. This, of course, required machined narrow lobes, and I don't believe the lifter bores were enlarged at all. It probably wasn't too successful.
Stu FoxComment
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