I thought I would summarize what I have learned about hydraulic lifters and fancy adjustments and aftermarket anti-pump up lifters. Thus far what I have learned is that a standard stock lifter with factory adjustments is probly good till about 6000 RPM in many applications that allow for hydraulic lifters. Bigger cams and higher RPM's would require other things (probably why engines with higher red line settings used a solid lifter). That is about it in a nut shell. Anti-pump up lifters are probably best for engines in the 6000-7000 RPM range. How often do corvettes driven (safely) on the street do that?? I will keep working on gathering more information but for the most part, I feel confident that form my application a stock or good quality stock replacement hydraulic lifter will find a home in my engine. Thanks to everyone that contributed to that thread down below! Terry
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Re: Hydraulic lifters.........:)
The limiting RPM of hydraulic lifters is a function of lobe dynamics and valve spring characteristics, and more spring force than necessary or an aggressive lobe that requires high spring force is a recipe for lobe flattening in typical street use.
Unless you have the detailed engineering lobe data, you know virtually nothing about the lobe's dynamics, so selection of valve train parts is nothing more than a wide as... guess.
You are fortunate that Chevrolet had a very good handle on valve train dynamics beginning in the early sixties, and all subsequent OE cam designs allowed the engines to rev about 10 percent above their actual power peaks, but peak power revs will increase with head massaging.
Careful attention to valve spring setup is important to achieving maximum revs and the OE springs should be set up to yield about .090-.100" margin to coil bind (assuming a 1.44:1 rocker ratio on SBs) on a street engine, but you can go to .050", if necessary. This means that different lobe lifts require different installed heights, and a lower lift lobe such as on the "300 HP" SB cam should have the valve spring installed height set lower than the L-79 lobe if a 300 HP lobe is being used in a hi-rev application. These lobes have very similar lobe dynamics, but the 300 HP cam lobes need lower installed valve spring height to achieve the same spring restoring force at peak lift.
OE or OE equivalent parts will work extremely well with OE reliability on any reasonable street engine application.
Getting the most out of an OE configuration is all in the details - head prep, selection and attainment of a suitable compression ratio for the installed camshaft, and attention to all assembly details such as installed valve spring height.
With proper setup of the OE valvesprings OE hydraulic SB lobes will go to about 6500 and SB mechanical lifter lobes are good to 7200.
The lesson here is that OE or OE equivalent valvetrain parts will rev to the upper useable limit of the power bandwidth if proper attention is paid to up front system engineering and assembly detail.
Duke -
i have used GM part# 3927142 springs on
every SBC i ever built using the stock GM cams.i also used GM part# 3970627 springs on all BBC using stock GM cams.Comment
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Re: i have used GM part# 3927142 springs on
The 3927142 is the over-the-counter "off-road" spring originally designed for the "140" off-road cam. It's way more than needed for a road engine with a production cam, but it will extend the range of the production cams if that's necessary, like for racing. For typical vintage car use (lots or idling and low speed driving), they are going to increase the chance of wiping a lobe, and the additional revs they allow will likely break the weak OE 327 rods.
The peak SB revs I mentioned for both hydraulic and mechanical lifter cams are with the production 3911068 springs that were in your grandmother's 283 two-barrel and virtually all production SBs from '67-up, and to achieve these revs without the risk of breaking a rod and holing an original 870 block I absolutely recommend better than OE connecting rods.
DukeComment
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i used them because if you miss a gear during
a fast shift there is less chance of floating the valves and smacking a piston. back then there was not another choice besides the stock springs.Comment
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Weak OE 327 rods
Duke,
What rods would you recommend in place of the OE small journal rod?
Thanks.Comment
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Re: Hydraulic lifters.........:)
Hey Terry I responded to your earlier post on this subject and have been following later postings with interest.I'm not sure what 'vette you have but if it's a C$4(thats a typo but I'll leave it!!) it's going to cut out at 5400 rpm.Perhaps you have been a naughty boy and played with the computer.
I first noticed this with my 383 Lingenfelter when my nose was pressed to the windshield having exceeded the rpm limit around 80mph. Engine braking is far more effective than the anchors the factory fitted!!Comment
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Re: Weak OE 327 rods
I like the Crower Sportsmans because they are only marginally heavier than the OE rods, but they are only available on special order. There have been some group buys in the past that cut the price to about $450 per set.
Better rods are available off the shelf, but most are significantly heavier than OE, which complicates engine balancing.
The weakest rods are the pre-'66 type, which I would only trust up to 5500 if they pass Magnaflux, but even then I think they are iffy, and they are a disaster waiting to happen on a mechanical lifter engine.
The '66-'67 rods are okay to 6000 if they pass Magnaflux. These can be IDed by the little hump of material adjacent to the bolt seats. This is absent on the earlier rods, and that's where they break.
DukeComment
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Re: Hydraulic lifters.........:)
Dave, my car is a 68 427/390hp. No engine brakes that I know of.. TerryComment
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Re: Weak OE 327 rods
Thanks! I saw another recommendation for Crower Sportsman but they didn't give the weight.Comment
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Re: Weak OE 327 rods
By the way, what is the weight of an OE 327 rod?Comment
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About 570 grams *NM*
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Re: Weak OE 327 rods
i worked on and ran a lot of these older 327 SBC in circle track and drag race cars and i never broke a rod.these engine back them were just blueprinted stock parts with maybe a cam change. we abused the hell out of these engines with no rod failures.Comment
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Re: Weak OE 327 rods
clem-----
I agree with you. The 327 rods will hold up fine in the vast, vast majority of the cases and certainly for street applications. Notwithstanding that, though, if I had a 327, would I use the stock rods? Not a chance. The cost difference between having an original set of rods magna-flux-inspected, re-sized + new rod bolts versus a new set of high quality aftermarket rods is just not great enough to "shift the equation" towards using the original rods. Sure, you also have to have the engine re-balanced after changing rods, but you're going to need to do that, anyway, if you want everything to come out right.
Plus, as I understand it, these days there is a fanatical obsession with "original numbers", especially as it relates to the BLOCK. As you know, blocks can be seriously affected by failed connecting rods. So, why take a chance, as small as it may be, using original rods just to save a few hundred dollars? In fact, even if I had a 66-67 327 with the 3864881 rods, I'd still "dump" them in favor of aftermarket rods.
Of course, I'm not a "327 guy" so I don't expect to ever have this problem on my hands. For "350 guys" like me, the choice is REAL EASY. Buy a set of forged, powder metal connecting rods from GM under GM #12495071. This includes a set of eight rods of GM #10108688. GM list is $326 and one can easily buy a set for about $275. I doubt that one could even get a set of original rods magna flux inspected, re-sized and new rod bolts fitted for very much less than that.
Plus, the forged, powder metal rods are NEW, more than TWICE as strong as the original LT-1 "pink rods" and extremely weight-consistent. This is a total "no brainer". I JUST LOVE IT when I see these nuts on eBay pay $1,000 in a bidding frenzy over an NOS set of "pink" rods.In Appreciation of John HinckleyComment
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Re: Weak OE 327 rods
I have mixed feelings on the insane prices on eBay. First, I find it insane that the price is so high and think the guy desires to be ripped off. Of course, some are victims, not knowing, only that this "xxxxx" is the one the shop/restorer/judging manual/etc says I need.
Second, I am upset with the insane prices. This drives many parts to be above what many of us can afford for our hobby. If it were our business, fine, but as a hobby, it shouldn't be dipping this heavy into the household account. And if the price of "xxxxx" goes that high, then the "yyyyy" and the "zzzzz" will also begin to go higher as they are "just as rare" or something to that extent.Comment
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