I was told back in the 60's it had something to do with the design of the ramps. Old mechanics back then said no one builds a cam with .030" lash clearance and wouldn't believe it.
The ‘097 is the only one that was known as the Duntov grind. It was designed by Zora to be used to enhance the performance and image of Chevrolet in the eyes of hot rodders and build a following. By ‘64 the need for a different grind was seen and the result was the 30-30 that had more lift and duration. AFAIK Duntov had nothing to do with that cam, instead asking Denny Davis, one of the engineers in the group to design it. The ‘097 cam was in 1957 270 horse dual quad 283’s, naturally the’57 283-283 fuel injection engines and then it was used all the way to the ‘63 327 Hi-Perf 340 four barrel and 360 FI Corvettes. The 1964 30-30 cammed engines raised the HP to 365 and 375 for the FI Corvette, all else being equal. In 1967 the new 302-290 horse Z-28 used the 30-30 and the later 1970 350-370 LT-1 had a different solid lifter cam. There were even different Hi-Perf hydraulics for small blocks. The favorite is the ‘151 or L-79 grind used in the 327-350 horse engines while the later 350-350 L-46 had a revised grind, a touch more duration and lift.
Damn right, when I ran it in my .060 over 327 It would occasionally sling the belts off even with deep groove alt pulley. It was a bit lazy till about 4K but when it got up on the pipe she pulled hard. If you run this cam I’d strongly suggest nice rollers and a good girdle. That said I’m sure there are even newer grinds and even better roller cams that will out perform the 294s magnum. Still my favorite flat tapper I’ve ever ran on the street.
I’m doing a similar build. Mine is 67 small journal 327 0.40 dome pistons Forged rods 65 camel hump heads Roller rockers 3x2 Holley 94 setup Comp Cam XE268H CR 10.35 Should be around the 300-350bhp
I don't think it has anything to do with "needs", I think, it has to do with tuning a solid lifter cam. changing the lash can change the reaction of the valve. I knew a guy with a "big" cam that would run it loose to drive it daily and make adjustments at the track.
If you have more of a CR, it opens the possibilities quite a bit, also how well it breathes is a factor. The 4:11 rear will be an asset to a steeper cam. I run a Lunati Voodoo 276/268 in my 355, the LSA is 110* so it has good street manners, but it has a strong pull. MY rear is a 3.89 with a 2.52 1syt gear and the car weighs 3500 lbs. I was originally steered to the XE268H by Comp, but read the valve train noise complaints about it. The Voodoo is quiet under the hood. I've only had it up to around 5500 but it makes power all the way. If the car will see a lot of track time, Lunati has a great line of things like the Bracket Master, Bootlegger, Street Master and so on. http://www.lunatipower.com/Category.aspx?id=58
This is correct. I have an Engle roller tappet in the hemi in my race car (avatar). It was new when I got it, but somewhere along the line, the "cam card" had been lost. I called Engle and talked to an engineer. The first thing he asked me was how I was going to use it. When I told dirt oval racing, he said that anything .015 to .025 would work, but for my purposes, run on the "tight" side.
The reason the 30-30 has such a large lash is to cushion the impact at opening and closing the valves, it has to do with the intensity of the valve action. As said above you can tighten the lash at the track and it will help because it has the effect of increasing the duration and the lift, but in a daily driver it will be hard on the valves and seats.
the 097 is the solid lifter cam used in 57 270 and 283 HP motors clear up to 360HP 327-lash is 12 and 18-14" of vacuum -idle about 800 in a FI 283-ran damn good in my 57 Fuely
I always adjusted mine cold @.026"..... Didn't have to deal with the mess.. Once the engine warmed up, it was @.030" both on the intake and exhaust...
(Quote the earlier lash question.)And you may be right! Cold vs Warm lash setting. I had set a tighter clearance. The exhaust always needed more room when it expanded, and now realize (thanks guys) what the steep ramps were up to.
I guess physics has taken an odd turn. Carry on Edit: These guys may know better than me.. http://www.compcams.com/v002/pages/405/lifter-tech-faq.aspx#ValveLashSolidLifter
Update. I talked with isky and after a lengthy conversation I went with a 201525-a cam. 108 separation i will give another update when the cam is installed and its put on the dyno i will say it was a pleasure to talk with isky , very helpful and pleasant hopefully the cam will be what I'm looking for http://iskycams.com/shop/index.php?main_page=product_info&products_id=285
Solid lifters it depends. Iron heads are different than aluminum, there's a correction factor. Also as valves tend to recess into the seat over time the lash gets tighter, a lot of folks expect valve lash to get looser over time, not tighter. Excessive valve lash beats the hell out of the valve train, if too tight, valves will burn.
In my 355 SBC with Trick Flow alum. heads, the ones with CNC comb. chambers and termed as "street/strip", can't recall part # and my catalog isn't handy, I run a solid lifter version of that "268H", with the lifters that have an .012" hole EDM'd into the flat face of the lifter to bleed off oil between the cam lobe and lifter face, and because of the 16 additional oil bleeds from the lifters I run a high volume pump with a relief spring at normal pressure. Lately there have been several articles about using solid lifters, flat or roller, with alum. heads that say to tighten valve lash about .004-.006" when adjusting cold as the alum. heads expand more than the valve train and the lash increases when the engine heats up. I tightened my lash up .005" and really like the results, both on performance and valve train noise. Car is "A" Hiboy with no hood or top, and when you get up to road speeds on a smooth road @ around 3krpm & up and sorta feather the throttle to "level out" you can hear the valve train, and it is much quieter now with the tighter lash. I like it
Yup good enough for the Corvette and the original Z-28. ^^^^^ EWR have spun a different Chevy cam (hydraulic) to 7K plus but I have a hybrid valve train and I do not recommend it. The Duntov 30/30 will go 7K easy and do it everyday all day long. Other option if you are buying a new cam anyway and don't mind the price is the Z-28 Off Road cam. I don't think they are that pricey I am just a cheap bastard. Seb most of the guys that race 'em that seem to know their shit actually run 'em @ .024-.026. I think that it is like a lot of things GM there is design tolerances and real world tolerances. Look at Chevy hydraulic lifter preload for instance, the book says 1 turn after zero play, I normally run mine @ 1/4 turn and have run them as loose as 1/8 turn (which I do not recommend).
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