s&thansen

First thing first I’m not looking to pull engine and rebuild it or drop $2k + into it in upgrades. I have an 86 base model Z28, stock torque converter & tranny, 2.73 rear end. This had carbed 305. It was swapped to a new budget built 355 I picked up brand new for $1K. It has 441 heads with 76cc chambers on it currently and the cam that was installed was an Elgin E-274-S, lift is .390 int, .410 exh, adv dur 258 int, 269 exh, dur 194 int, 202 exh.
jegs right now has their vortec heads I can get for $740 for pair. They have 64cc chambers and will take up to .475 lift.
Looking for opinions on 2 possible scenarios.
1 - thoughts on just swap to vortec heads and put in 1.6 rockers to change cam to .416 int, .437 exh.
2 - swap to vortec heads, and upgrade cam but staying within the stock torque converter spec.
I know I have to change intakes but I do have center bolt valve covers and I want to reuse our carb which is a Holley 625 street demon.
At the time 7 years ago I was just kinda dabbling and getting into cars. So just doing the normal newbie thinking “ well it’s a 350 so let it rip”. Now after reading learning yes hind sight always 20/20. I wanna change up some stuff for more performance. However on a budget and not looking for a drag car. I drive this on the weekends to car shows and putting around in the summer. Just looking for some more umf. I think I’m around 8-8.5:1 compression now with 441 heads and probly 180hp.
I put summit short headers and flow master American thunder exhaust. There is NO smog stuff left on it. I’m not tested.
Looking for your options and thoughts.
Thanks

brian p

A well traveled path but you'll still get a lot of different opinions. Put the vortec heads on, that's a legitimate, proven increase in hp. The rockers are a couple of hp at best, better to spend your money elsewhere and change the rear gears to something in the 3.2 to 3.7 range. Those 2 things alone will get you the biggest bang for not a lot of bucks.

sofakingdom

iTrader: (1)

That's a replica of the stock 929 cam that was used in virtually all "ordinary" vehicles in the 60s and 70s. It's pitiful, one of the main reasons for the wimpy 160 HP 350s of tghe 70s. I'd STRONGLY recommend putting something better in there. Even yerbasic generic 204/214 "Stage 1" would be better. Get a kit such as Summit K1102 or Jegs 200102. You don't want to go nuts with it though, with the stock gears and converter; the engine can't ever build up enough RPMs to benefit from anything real large. A Comp XE262 would be about as large as it could possibly stand, possibly even too much.

Yes those heads would be a YYYYYYUUUUUUJJJJJJE improvement. Any rockers that are less floppy than the stock stamped-rubber garbage will improve everything about how the car runs. Use steel, NOT aluminum. I don't think there would be much difference from changing the ratio, but if the heads will support the lift that whatever cam you choose will give, might as well go with 1.6 if you're buying rockers anyway. Something simple like Comp 1416 would be adequate.

Also replace the timing set while you're there. Use a "true roller" type.

The carb you have should be just fine with that combo.

Fast355

iTrader: (2)

10 ft/lbs and 15 hp even on an otherwise stock TBI 350 is what I found swapping the junk stamped 1.5s for aluminum 1.6s. There was not a single place the 1.6s did not add ~10 ft/lbs of torque. The stock GM stamped rockers were literally eating themselves with less than 10K on a Goodwrench TBI. The aluminum rockers themself were worth it for not having particles of steel from the stock rockers getting into the oiling system. Stock stamped rockers are JUNK even on a stock engine, always have been and always will be. An aftermarket rocker with a roller trunion will improve valvetrain geometry when used with a correct length pushrod, which minimize valve stem wear as well, by creating less side load on the valves and is even better yet if you ditch the dumb self aligning design, using hardened pushrod guide plates under studs and hardened pushrods. I am not a fan of steel rockers because they are heavy and add weight that must be accounted for with more valve spring pressure. Never had even a budget aluminum rocker fail yet in 20 years and have had a couple sets on engines for more than 200K miles.

sofakingdom

iTrader: (1)

Many steel rockers have lower moment of inertia (rotational equivalent of weight) than aluminum ones.

But that's mostly a non-issue in a street cruiser. The more important factor is, aluminum suffers from METAL FATIGUE, whereas steel does NOT.

Fast355

iTrader: (2)

I could see aluminum fatigue being an issue on very high spring pressure, massive lift, high rpm stuff. That being said the OP has a 929' 350 cam and sounds like springs to match. A set of say Scorpion 1.6s or 1.7s would last pretty much indefinitely on a setup like that. The aluminum rockers I have on my Express have been running for 2 years at 375 open, 0.578 lift on the intake and 6,000 rpm for 2 years so far and those rockers already had 30K miles on them with 300 open, 0.554 lift and 6,200 rpm. Adjusted the valves a few months ago to put more pre-load on the LS7 lifters and they showed no signs of any damage. They could break tomorrow, but they are rated well above what I am using them at. Scorpion claims the rockers I have can handle 0.950 lift and 950 open spring pressure not that I would want to test those claims on a street driven vehicle. I am not even half of the open spring pressure they claim, should last indefinitely in my application as well.

sofakingdom

iTrader: (1)

Average life span of a set of aluminum rockers on the street seems to traditionally be about 25k miles to the first failure or thereabouts. They mostly tend to break near the tip, right behind the roller. Sure, sometimes people get more than that; some also get less. It's just a statistical mean. Not sure what the standard deviation is, but it's pretty large, maybe 20k miles or so. (i.e. 68% will experience the first failure somewhere between 5k and 45k miles, or some such)

Aluminum rocker failure isn't a question of "ratings", or hardly even, spring pressures. It's METAL FATIGUE. Stress-on / stress-off cycles. It's the same reason that certain aluminum aircraft parts must be REPLACED - not checked, not inspected, not tested, NOT NOT NOT NOT NOT NOT NOT - REPLACED - every however many take-off / landing or ground-level / altitude or other similar stress application cycles. The metal FATIGUES, and without any external sign such as cracking or other identifiable ("inspectable") signal of failure, just suddenly ... breaks. Steel doesn't do that.

Aluminum rockers are like the Richmond drag-race gears as far as applicability to highway usage. They are PURPOSE BUILT, for racing. For THAT PURPOSE, they may well be FAR more reliable than stock components, perhaps even the most reliable parts available. But racing isn't a tens of 1000s of miles kind of deal. An engine used for quarter-mile duty for example, might see the equivalent of less than 50 highway miles in a full season of points campaigning (every weekend spring thru fall); this number of stress cycles does not compare to street duty. 1000 miles at 60 mph and 2000 RPM is A MILLION operations of each rocker; a race car at 7000 RPM making a 10-second pass operates each rocker only about 600 times per pass, plus of course burnouts and shutdown and whatnot. There's NO comparison in teh sheer number of stress cycles.

He's likely to get rid of the 929 and put something more to the point in there. I certainly hope so, for his sake.

Fast355

iTrader: (2)

Metal even aluminum does not fatigue until it reaches its rated strength. Saying that replacement is required because of a certain number of cycles performed under the rated strength of the material is ludicrous. That would be like saying you need to change your transmission case out every 50K because it is aluminum.

I have a set of Crane made stock LT4 rockers on an engine that have been there for over 100K miles, they had 50K on them when they came off the LT4 during a performance build. So 150K street miles on them. GM would not have used aluminum rockers on a LT4 had they not provided some form of durability in those engines. The LT4 was the hottest 350 GM ever built in a production vehicle as well. The later model 4.3L engines also have a pedestal mount aluminum rocker arm as well. Never seen any of those fail even on 300K mile fleet run trucks and vans. I have seen some of the LS ones fail, but that was due to the cut-rate pressed fit trunion retention design GM used.

sofakingdom

iTrader: (1)

Perhaps you should learn more about what goes on in the rest of the world outside of your van before shooting off your mouth. Like, talk to an A&P technician.

I've seen altogether too many aluminum rockers fail on the street, from MANY brands, to ever use or recommend any of them for that use.

Fast355

iTrader: (2)

I have used them on everything I owned for close to 2 decades. My L31 boat, my 305 and my 8.1L in the Tahoe, yes my vans, a couple of F-cars, and my Vette. I do have a pretty good clue about what goes on real world. Once GM adressed the early Crane 1.6s they sabotaged by having them downgraded in material strength from the Crane version they put in the LT4 with a recall, the ones in the GM LT4 aluminum rockers were even perfectly reliable. In 20 years I have not had a single aluminum rocker fail and I have beat the snot out of some of those engines.

I have had loads of issues with the GM stamped steel rockers over the past 20 years. Any L31 built after 2002ish when GM shifted to Mexican production has had garbage rockers, probably under heat treated and wear very quickly. The 2008 Mercruiser in my Bennington 26R wore the rockers out in 1,500 hours. My 2003 Sonora had worn rockers at 100K miles. The Goodwrench L31 crate engine in my 97 van ate them in 20K miles to the point it had valvetrain noise from the loss of preload. I run L31s to 5K all the time though so maybe I am just exceeding their abilities and galling them up early. Then again I work on a Koehler generator that runs at 1,800 rpm and it too developed valvetrain tick from rocker arms that the pivot ***** had worn almost completely through. So either the rockers are soft or the ZDDP greatly reduced in modern oils is wearing them. The generator engines are also horrible at wearing out roller cams. The fix is a flat tappet cam with oiling grooves or holes in the lifters. The L35, L30 and L31 powered generators and forklifts all do the same thing and they eat the exhaust valve seats and valves in ~5,000 hours as well but that is a byproduct of running on LPG or CNG at high loads and low rpm for hours on end.

Tom 400 CFI

It's weird that we're talking about Koehler generators and fork lift valves in this thread.

Engine Masters got approximately squat, going from 1.5 stock rockers to 1.5 full roller's on a 5-600 hp engine. I agree with "Brian p" that the money is better spent elsewhere.

Fast355

iTrader: (2)

Yet Holdener made 10 ft/lbs across the whole RPM range even on a stock L99 4.3L going to a 1.6.

With such a small cam, I would also skip right over the 1.6s and run 1.7s myself.

Tom 400 CFI

What's that got to do with the price of bread? I said:
....which was more about "flexy stock rockers" vs. aftermarket roller rockers, the stiffness and "lower friction, thereof.
While it seems obvious that changing ratio will change power, I still
....and I still wonder how we got to talking about Koehler generators and fork lift valves in this thread. "Hey LOOK!......a SQUIRREL!!"

No need to reply to this, it's all rhetorical musings .

Aaron R.

I dont have much experience with aluminum rockers and I'm not picking sides in the rocker debate, but I can't help make some observations and I'm afraid the "aluminum rockers are superior in every way" side is losing badly.

#1. Using a Kohler generator and forklift valves as an example in a rant against GM rockers IS weird.

#2. Talking about how you have 20-30k miles on your aluminum rockers so they must be superior just doesn’t convince me. That isn’t much mileage. I realize there was later mention of some more miles in other vehicles, but the first impression has already been made....

#3. I have owned a lot of GM products with stock steel rockers and never had a failure. The fact that you are having SO MANY indicates to me you have some level of lubrication insufficiency. You might need better oil. I have a GM 305 with stock steel rockers that I rev over 5k every time I drive it. I haven't changed the synthetic oil in over 50,000 miles and it still runs the exact same as when I rebuilt it and broke it in. It hasnt "eaten" the steel rockers yet. If you are having widespread issues with various engines "eating" rockers it's a pretty sure sign you have a lubrication problem. I recommend Amsoil to help solve that.

I do have a question for Fast355 about those engines eating rockers. Where any of them among that batch of 305's you pole vaulted?

Fast355

iTrader: (2)

What is hard to understand about the fact I have been running rockers that already had 30K miles on them on an engine for 2 years with spring pressure that would have already blown the pivot ***** through the stamped rocker arms.

I also aluminum rockers with over 150K miles on them and still going.

So what that I used a Koehler generator and a forklift example. Those are still Vortec 4.3L V6 and Vortec 350 V8 engines.

It is not an oiling issue, it is a metal hardness issue. Lack of oil would have shown up as the pivot ***** and rockers showing overheating, which they do not. They are just missing metal. Things like flat tappet lifters, flat tappet cams and stamped rocker arms being made the past ~10-15 years are not as good as the older stuff. The material is too soft and wears.

Fast355

iTrader: (2)

Why a generator is relevant. No surprise, like this unit it has a small block under the cowling. My whole point was the GM L31 R used in that unit built in ~2018 still ate its rockers quickly and it runs 1,800 rpm. I find it odd this one has a Blueprint engine in it, but GM has priced themselves nearly completely out of the L31 350 market.

Aaron R.

I now understand why we are including generator and forklift engines. Thank you for the clarity. Unfortunately I have developed more questions:


Can you explain "always have been, always will be" above vs your more recent disclaimer below that you were only talking about the last 10-15 years?



And can you also explain why you yourself suspected it could be an oil issue (quote below), but upon me bringing that up again are now suddenly certain that it is "not an oiling issue" (quote above)?

Fast355

iTrader: (2)

I meant an oil issue as in lack of oil or lack of changes. The lack of ZDDP however is still a suspect to me. Those pivot ***** have a lot of load on them, even with a stock cam. That being said to me if the engineers know they have an issue with wear running oils without ZDDP, still makes it a metalurgy issue for an engine designed to run on whatever API spec oil they spec. Hence not an oil issue in my eyes running the specified oil, rather a rocker arm material issue.

The only engines I have messed with that stamped rockers still on them have been built in the past 10-15 years. Not many OE built small blocks from 40 years ago still being run in daily use, atleast here.

The reason I say they have always been trash, is pretty simple. They are sloppy, they wear, they deflect under load, and the ratio is not even 1.5:1 at any point. Most are like a 1.38:1 average ratio. There is a reason even GM moved away from them on the newer 4.3L and the LT4s as well as some of the crate engines. The roller trunion rockers maintain their ratios and give the designed lift and duration at the valves. The older Ramjets had 1.6s which have been discontinued by GM Performance at which point they moved to 1.5 rollers that are still made. The Ramjet 350s had a drop in power ratings going from the 1.6s to the 1.5s when they changed part numbers to the version with 1.5s and that was both still having full rollers. Just the ratio change cost them ~5 hp and tq in power ratings. If it truly does not make a difference, don't you feel GM would have just kept the higher HP and TQ ratings.

I will also add back to back testing rocker ratio, needs to be done insuring the same lifter pre-load. A 1/2 turn of preload on a 1.38 effective ratio stamped rocker is not the same preload as a 1.5 which is not the same as a 1.6 or 1.7. Richard Holdener has run pushrod length thus pre-load tests on LS engines and found substantial differences in power from lifter pre-load being the only change. If you swapped from a stock stamped steel rocker, to a 1.5 rocker to a 1.6 rocker and put the same 1/2 turn from zero lash, all 3 combinations would be running different preloads on the lifters thus skewing the testing.

Fast355

iTrader: (2)

I also find the generator rockers wearing out interesting to say the least. Generators only run when utility power fails. They start instantly, rev to 1,800 rpm instantly and run as long as the utility power is out. That could be 15-30 minutes or 4-5 days depending on how quickly power is restored. Thus they do not have nearly as many cold starts as a vehicle, once they are running the rockers are being oiled well and the engines typically run long enough to prevent any kind of moisture buildup in the oil. The second part of that is running on CNG or LPG, the fuel itself is completely vaporized prior to entering the combustion chamber. There is zero fuel dilution in used oil, unlike engines run on gasoline. The synthetic oils in use do not break down or lose viscosity from fuel contamination. A generator runs constant speed as well, once it starts and achieves 1,800 rpm the governor controls the throttle to maintain RPM from no load to full load the whole time it is running. As such the rockers should not see damage from galling during excessive high rpm runs like GM engineers found happening during the LT4 design and testing causing their swap to the 1.6 roller rockers. It all leads back to my belief, the soft stamped steel just being inadequate for the ZDDP deleted oil. Since the engine calls for and used a specified API oil which had lower ZDDP values, that means the rockers are to blame. That generator has scorpion self aligning 1.5 rollers on it now for durability reasons. That engine specifically belong to my aunt and uncle, powers their 30 unit RV park, the office and tornado shelter basement at their park right in tornado alley a couple hours north of where I live. The 8.1L irrigation engine I work on also has Scorpion 1.7s on it and has for for 20K hours. The heads, cam and lifters have been swapped about every 10K hours on it. Bottom end had over 30K hours on it last summer when I drove out to west to Floydada, TX and spent a day putting remanufactured heads with Incol seats, Incol faced sodium filled valves, and a new cam and lifters on it. My great uncle pays me well for that job to keep his irragation pump engine going. Thing has tractor puller style headers and even with mufflers you can hear it 2 miles away. What an 8.1L looks like pumping water at ~2,000 rpm, 3/4 load with the air/fuel properly dialed in on Propane. It has ~40 ft of copper tubing for each the engine coolant and oil coiled into the discharge pond sitting in the 50F water and both systems have thermostats. It gets run HARD and for long durations without getting shut down. I find the roller rockers more durable on both, real world durability. So say I am wrong if you want, they work great for me. That 8.1L is the reason I now own 2 vehicles with 8.1L swaps. The bottem end has the equivalent of a 3500 truck towing a medium sized trailer at 70 mph for 2,100,000 miles and it still carries 30 psi oil pressure at hot idle and 50 psi at ~2,000 and zero taps or knocks. Bores also looked and measured like new.

Aaron R.

A long, and entirely inadequate answer. But thanks for your time.

Meanwhile I will continue daily driving my 40 year old small block with stamped steel rockers. In fact, on the way home tonight I will give it a few good revs past 6k, just for good measure. Gotta give those steel rockers a good workout or they get lazy.

Tom 400 CFI

Same. I can't help but wonder how my SBC's have gone 200, 300,000 miles, with this rocker epidemic that we've got going on! Wow!

That's a cool picture of a corn field.

Tom 400 CFI

Amazing! That 8.1 is longer lasting than a CAT, Cummins, Mercedes, Mack/Volvo.....30,000 hours and it's run HARD, huh? Pretty incredible. The two OE's should start putting 8.1's in snow cats! They'd double the engine life!....if only it weren't for the stamped rocker epidemic that they're subject to.

I see your corn field, and I raise you one, equally irrelevant, Snow cat with a short-life, non-roller rocker'd, C9.3....