1.6 ratio roller rockers, yes/no?

[grumpyvette]

1.6 ratio rockers rarely gain much hp unless your severly under camed and the engine needs a big increase in lift and duration, and if thats the case a new cam will have far better results, now changing to roller rockers versus ball piviot rockers can easily free up 20hp because of less frictional losses but again the ration has little to do with it, 1.6 ratio rockers should really be looked on as a tuneing tool that allows you to add small amounts of lift/durration to match the engines needs rather like advanceing or retarding the cam timeing a few degrees. 1.6 ratio rockers frequently cause valve train geometry problemd and clearance problems with little gain to show for your trouble, in fact after testing several times on several engines Ive found that they tend to lower your valve float rpm level about 150rpm on many engines, now that being understood, 1.6 ratio ROLLER rockers when installed with the correct clearances and geometry on an engine running a stock cam that has been retarded a few degress to raise the torque peak due to the combination of slight changes in cam timeing at the valves that the TWO MATCHED CHANGES can and do produce can through the lower frictuion and slightly increased efficiency at the higher RPM range work almost as well as a mild cam upgrade but your not going to see major hp increases, 25 hp-30hp would be a very big and very unlikely gain due to the lower friction, higher lift and cam retard combined.

if your still set on doing it, comp cams and crower cams both make GOOD REBUILDABLE ROLLER ROCKERS that are much better than the cheap crap available in some of the cast aluminum roller rockers costing almost as much

this type lasts and works very well

this style (NOT THIS BRAND NECESSARILY)is far more likely to wear faster or fail under extreme loads

this style gains you little if any improvements on most engines in spite of what the advertizeing says from what Ive seen on dyno results

 

1985,1992,1996 vettes

keep the rubber side down and the fiberglass off the guard rails

[flibuoy]

I support the above opinion that 1.6 rockers are a tuning aid. They are not a particularly magical big HP increase aside from gains due to slightly reduced friction. Manufactureres are quite happy people are buying them like they are an easy cam swap. Tuners often use both 1.5 and 1.6 on same engine to max the particular application exhaust/intake needs. I have only limited experience myself..but after $ and time to change to 1.6 some years ago I could NOT tell difference on street. A little more effort and about same $ will get a cam that WILL make changes..better or worse john

[Mudge]

5-7 HP from stamped rockers to 1.6 rollers usually from what I've seen, mostly I like the friction reduction but the minute amount of life increase isn't going to do much, and the friction reduction of course shows its bennies at higher RPMs not at the lower.

[John Scott]

I went with the 1.5 intake/ 1.6 rockers (steel CompCam Pro Magnums, formerly known as Hitech) on my exhaust by recommendation from AFR claiming they liked a dual pattern cam, which mine was not. A band aid yes, but I wasn't in the position of buying another solid roller. Push rod lengths were checked and found .200+ longer than stock were neccessary for correct geometry. If you are playing with diferent ratios you really need to confirm the correct length with an adjustable pushrod length checking tool. CC has them for a nominal price that give measured lengths per revolution of the adjusting end. Also note that 1.6 rockers might cause guide and seal interference. Sigh, I learned that the hard way a couple of engine projects ago. Don't just bolt on a set of 1.6s and expect to go racing. I've noticed in some dyno tests that the 1.6s might work better on the intake side, others on just the exhaust, sometimes only on specific cylinders, and sometimes not at all. A really well researched cam head combo. shouldn't need a rocker ratio change.

John

[Mike C]

I ALWAYS preach against 1.6 rockers as I see them as a crutch. MOST people with mild street cars considering 1.6 rockers have GM cylinder heads without screw in studs. In order to safely use 1.6 rockers in non self-aligning rocker motors, the heads should be removed and the pushrod slot elongated OR drilled out and screw in studs and guideplates installed. All of a sudden your "cheap" swap is a PITA requireing a top end gasket set AND pulling the intake and almost all the other stuff trying to avoid with a cam swap. Or you bend all the push rods and wasted $200+ and have to do it all over. So I agree with Grumpy, tuning aid on a very high-performance engine, or a band-aid for lazy mechanics. Even cheap rockers are 50% more expensive than the Energizer cam kits. I still prefer single pattern cams over dual pattern cams in SBC with any sort of decent head, and dyno tests seem to bear me out. SBC have problems in the intake, not the reasonably short, well flowing exhaust. I do like the comp magnum roller tip rockers, not for lift/power, but for longevity. It is my experience that they reduce side-loading of the valve improving guide life, and max longevity is usually a priority to me.

[DavyZ]

Originally posted by grumpyvette:

...comp cams and crower cams both make GOOD REBUILDABLE ROLLER ROCKERS that are much better than the cheap crap available in some of the cast aluminum roller rockers costing almost as much

this ...

So Grumpy, what do you think of Harland Sharp roller rockers? Are there any good aluminum ones??? Curious minds want to know.

 

Davy

[grumpyvette]

yes there are very good aluminum roller rockers out there. the erson billet aluminum roller rockers are very good, the CRANE PRO roller rockers were standard equipment on the LT4 corvette and you can be very sure CHEVY tested them before letting themselfs get involved in what could be a warranty nightmare if they could not stand up for tens of thousands of trouble free miles. I have not used HARLAND SHARP ROCKERS FOR YEARS so I don,t know about thier pressant production roller rocker quality, they may be some of the better ones available, (I DON,T KNOW) but I can tell you that there are CHEAPLY MADE IMPORTED roller rockers that do not hold up well to heavy valve spring pressures that look similar to the harland sharp roller rockers,I have seen several fail within 30,000 miles of street useage. like most things you get what you pay for, and if you see full roller rockers new for less than about $150 Id be really careful, theres a reason they charge over $350 for the ERSON AND CRANE ROLLER ROCKERS quality parts cost more money

 

http://www.mrgasket.com/ersonmain.html

(look under valve train components about 1/2 way down the page)

 

http://www.cranecams.com/master/goldpro.htm

[John Scott]

Originally posted by Mike C:

or a band-aid for lazy mechanics.... I still prefer single pattern cams over dual pattern cams in SBC with any sort of decent head, and dyno tests seem to bear me out.

I wouldn't consider myself a lazy mechanic, but after a head that liked a single pattern cam, Ported Dart 215 Pro1s w/.8 exhaust/intake ratio, had what I considered lacking of intake low rpm velocity for a street application, I changed to AFRs also a REALLY good head that prefers a dual pattern. At this point in my budget, the cost of another roller cam wasn't an option. Financial ability, not laziness. Check out the quality drag boards where time slips, not dynos are the rule and cams are picked by the heads, not a preference for one pattern or another. I'm willing to bet the AFR 195s with they're .7-.75 ratio will make more power with the dual pattern. AFR has quite a sound reputation and their techs are not going to mislead someone into a cam that will make less power. BTW amazing how many engine designs are coming out with 1.6 rockers on both intake and exhaust. Cams can be custom ground for your preference of either ratio. Some builders prefer the faster valve events of a 1.6. If incorperated into the design, there's nothing wrong with using a higher ratio rocker.

John

[DavyZ]

Originally posted by grumpyvette:

... I have not used HARLAND SHARP ROCKERS FOR YEARS so I don't know about thier present production roller rocker quality...

I have some HS rollers that I bought second hand and they look like quality pieces to me. I was able to get them cheaply enough it made good sense to use them, plus they are rebuildable. HS has been around for years so I'm not too worried about getting parts or replacements. I do have some new Comp Cams roller rockers as well, but they are not true rollers. I figure one set will go in one motor and the other in another.

 

Thanks for the info

 

Davy

[Mike C]

Have you been following the Engine Builder Challenge in PHR magazine? Did you see the motor entered by Crower? They wound up keeping the 1.3 ratio "break-in" rockers on the exhaust side becasue it didn't need anything more. Their engine was running a flat-tappet mechanical cam. (This is a very interseting ongoing segment with some excellent ideas for high-powered street engines. If you want to make big power and drive it, throw out those hydraulic lifters!)

 

If a motor makes more power with a split duration cam, it is my opinion (and we all know about those...) that something else is out of whack relative to the cam. NA SBC do not need added exhaust flow relative to intake, unless there may be some sort of restricted exhaust PAST the cylinder head. Like everything else, in dyno-matched and tuned combinations, small to large gains can be had, so be wary of my blanket statement. But seat of the pants, or street-car level power, will not be affected significantly if the right size cam is chosen for the rest of the combination.

 

In reading up on LS1 rockers, you should use a cam specifically designed for whatever ratio rocker you plan on running. Using the 1.8 rockers on a cam designed for the 1.7s will result in broken valve springs because the effective ramp speed gets out of the designed range. This further illustrates to me that 1.6 rockers should be either planned for or not, but not used unless the package was specifically engineered for that ratio. Or it is a pretty small, mild camshaft. Cylinder head mods as noted above are the other reason.

 

I have a friend running a year old set of Harland Sharps. They switched vendors for pushrod cups, and a bunch had machining troubles. They replaced his no charge. No troubles since then. If you run them, and I think they are a good product, just carefully inspect the pushrod cup to make sure it is polished and no machining marks are evident, other than that they should be good for mild to wild motors.

 

I have had excellent luck with the Crane Gold Race rockers. I have the 11752's on my 355. They are 7/16" stud and designed to clear 1.630 springs. The cheaper Gold rockers hit the retainers even though my springs are only 1.44. Highly irritating.

[John Scott]

Mike, I found that different rockers sometimes require different pushrod lengths, even though the ratio is the same, of course as long as the roller tip is centered on the stem @ 1/2 total lift. I needed longer than standard to clear my 1.550 springs with the CC promags. No clearance issues with either ratio. Your information is interesting. I'd like to hear more. So, in theory, if a good head doesn't need more exhaust lift than intake, The 99.9% of the cams listed in my catalogs need to be changed from the dual pattern. I'm really curious if the Crower engine you mention has conventional 23 degree heads. If so, than perhaps its time to rethink cam designs again. My 27 years of shade tree hot rodding has seen single pattern cams evolve into what was referred to as hi tech dual pattern with asymmetirc lobes and what have you. Maybe I need to put my band-aid crutch 1.6s on the intake side. Thats what was making the most power on the Dart 215 heads. BTW the most effecient engine I've seen is running a 1.6 on both I/E. Nearly 3000 pounds NA 377. 6" rod, 11:1, Cam specs are 265 @ .050 .585, 106 lsa, single 4 barrel, small ancient unported Brodix track 1s. @ our 6000' this converts to a sea level low 10.30s @ low 130mph, 520 whp!! ..and is street driven on pump gas I guess my point is the blanket statements of don't use 1.6 rockers, don't run more than 10:1 compression (Mine has 11.2 and does fine) don't use a single plane manifold,blah blah, can have their exceptions with great results. I guess too often the average Joe will try to push More's law without upgrading or researching the rest of the components.

John

[Mike C]

Interesting. It would not surprise me if different manufactures, and even different modesl, designed their rockers for longer valve lengths. This would explain why different pushrods were required even within same ratio. Lots of roller cam springs are designed for .100 longer valves to accomodate the amount of lift, and race rockers you would think were designed for a similar setup. I have stock length valves in my motor with the 11752 but need +.100 pushrods to restore correct geometry. Believe it or not, the Crower motor was based on an old ZZ4 and used the GM L98 heads. It averaged 475.9 lb/ft and 409.7 hp (I forget the range, 2500-5500 or so?) with peak of 544.6 hp and 518.8 lb/ft using a 4.00" bore and 3.625 stroke.

One of the other mags did a rocker swap dyno tests last month and found the most power with 1.5 rockers on the exhaust and 1.6 on the intake. SB Ford's really respond well to split pattern cams that are heavy on the exhuast, but they have TINY restrictive exhaust ports and short well-flowing intakes.

Because of the averaging in low rpms used to determine qualifiers, lots of people went to longer strokes. I REALLY like the 377 for big peak power. Amazing how much going to the 4.125 or 4.155" bore helps to further unshroud the intake valve. Notice also that the serious small block race heads continue to increase intake valve size to 2.1" but seldom do you see more than 1.65 exhaust valves which also implies to me that these motors need further help on the intake side. Intake valves are often shifted off center to further improve flow and allow those big valves. I guess if you tuned the exhuast to take advantage of the added duration in order to maximize scavenging and therefore cylinder filling (which translates into better flowing intake?), the split duration cam might really pay off. I think on a vehicle that has to deal with a full length exhaust system that exits the rear and has to conform to the floor cannot take advantage of that. The more I think about it, the more there seems to be discrepancies in what the cylinder head designers and cam designers are doing. I wonder if the cam companies design there "street" performance cams around a set of stock cylinder head castings with only 65-70% i/e flow?

[John Scott]

Originally posted by Mike C:

the Crower motor was based on an old ZZ4 and used the GM L98 heads. It averaged 475.9 lb/ft and 409.7 hp (I forget the range, 2500-5500 or so?) with peak of 544.6 hp and 518.8 lb/ft using a 4.00" bore and 3.625 stroke.

One of the other mags did a rocker swap dyno tests last month and found the most power with 1.5 rockers on the exhaust and 1.6 on the intake. intakes.

The more I think about it, the more there seems to be discrepancies in what the cylinder head designers and cam designers are doing. I wonder if the cam companies design there "street" performance cams around a set of stock cylinder head castings with only 65-70% i/e flow?

L98 heads, Holy $#&+! Good points. I thought my builder was going wack-o on me when he said he usually, but not always, puts the higher ratio rocker on the intake. OH man! Sounds like I need to break out the G-tech and try some different combos...and to get up on current reading.

John

[Mike C]

I was just re-reading your post about that 377 again. I had a Comp "NOT FOR STREET USE" cam in my 355 back in '87. It was in a '68 Camaro SS that my brother bought from me. It was 300/300 advertised 265/265 @ .050 and .540 lift also 106 LSA. It was a monster. I had never ridden in a SERIOUSLY cammed car before, and man, was it a blast! I had the 4 speed I'm running now with 4.56 gears in the back. You'd let out the clutch about 1500 rpm and stand on it while it just cruised away, until about 3500 RPM when your neck snapped back, the front lifted up and the tires let loose! What a gas! From 3500 it flashed to 7500 almost before you could push the clutch in and yank the lever. It would flash 7800 or so on the shift, then blow the tires off again! I never ran the car, but I figured mid 11's would not have been a problem with the big gears and lightened chassis. I run the same motor with the baby roller cam now, and it's smooth and docile 425 hp or so, but I figure the monster cam made at least 475 hp. Big cam=big fun if you don't have to worry about driveability.

[Mudge]

One thing that is kinda interesting is that GM is using smaller lobes, but bigger rockers with the LS engines. I wasn't sure if this was a lifter float thing, or a way to reduce spring pressures since the lobe was less aggressive, or what.

 

Anyone?

[Guest Luigi]

Uh..I'm not sure that I agree. I see that at a certain level of desired hp, it is next to impossible to get enough intake lift into a sbc. This is where a diff ratio rocker comes in. the programs I have experience with will dictate a cam w .8 intake lift @ the valve. Tough to get with a 1.6 and a cam that will fit into a standard block. If I had the money I would run 1.8's on the intake side and 1.5's (or less) on the exhaust.

I never really thought that the exhaust was not lift limited (i asumed it followed along with the intake as far as flow requirements) till we bent all the exhaust valves in the ITS car at memphis....and finshed second place. The car wouldn't start but it sure didn't seem to care about the exhaust.

For my combo, the 1.6 allowed me pack a bit more lift on the intake side.

just my $.02

luigi

[Mudge]

Heads and cam go TOGETHER, but obviously a cam MFG can't suit every single set of heads out there with 100% success.

 

Why do you think that these LS1 people with OVERLY flowing exaust sides think that the reverse split cam is some kind of magic that nobody ever thought of? This is like going back to the 1910 era of "overlap is bad" kind of thinking.

[Mike C]

I agree with what you say Luigi, but endurance type racing engines with .800 lift are pretty unusual, more of a dedicated quarter-miler thing. Completely inappropriate for a street engine that may see 10k miles a year. I think for 99% of SBC, what we discussed is quite accurate. But in your case, you are using the 1.6 rockers to solve a dimensional problem, once you move to roller bearing big block size cam journals you can once again grind a cam that will work with the 1.5 rockers. Or if you have a relocated cam journals. Switching to 15deg, 18deg, or SB2 heads obviously changes everything as well.

[Mudge]

Nascar guys have to be in the .700-.850 range I believe(???), but 500 miles, going to be torn down after the race, may not be "endurance" and not probably a street car, those valve springs wont be happy for long. Not many heads (minus $14,000 SB2 stuff) have that kind of flow support either.

[Mike C]

Nascar uses big block chevy size cam journals so they can get more lift and run a larger base tappet. They run roller cam bearings and they use mushroom solid tappets.