Learn Me - Valve Springs and Rotators...When to Upgrade?

I am lost in a sea of internet opinions, so I'm back to the group that always seems to come through with obscure information

The 8.1 in my Suburban 2500 wiped a few cam lobes and took out a few rockers, so I'm taking the opportunity to upgrade the bump stick. DD and towing duty, unlikely to ever see more than 4600-4700 rpm, but spends a lot of time at higher load. I bought the cam already, and just happened to see a comment about weak valve springs that sent me straight into the deep end.

Stock cam is about 0.47" lift at the valve, 204/209 duration. The new cam is about 0.51" valve lift, 228/236 duration. Nothing crazy, and very similar to the OEM HO marine cam (no idea on ramp rates). The cam supplier used to say any cam needs a valve spring upgrade. Their supplier went out of business, now they say just use the stock stuff. The internet is full of opinions, unfortunately all the way from "I used that cam and the valves float well before redline" to "I've got 40k miles with that cam on stock valvetrain, it's fine".

The only other cam manufacturer for these did not seem knowledgeable about this engine, or at least not the guy I talked to. He was definitely trying to sell me parts.

Stock seat pressure is around 90 lbs, 220 lbs on the nose with the stock cam, which is not a ton, and is in line with GM's tendency to use the lowest spring pressure they can get away with.

This engine has valve rotators on both the intake and exhaust valves, which I am inherently a fan of. The aftermarket says toss them, but it seems GM wouldn't have added such a thing to the engine if it didn't have a purpose, and I really like the idea of them. They are not known for failure, and I'm not building a race engine. They also sit under the valve spring so do not add valvetrain mass like some designs do.

Thoughts? Do I add several hundred bucks to the parts bill with some new springs, or does it seem like stock will be okay? Is there any way to tell if you're on the edge of valve float or does it just tend to pound things to pieces quietly until something finally fails?

It's probably wise to put fresh springs in, but if you're buying springs anyway, I'd get some that match the cam. You could look at comparable spec cams, and just buy their recommended spring.  There is likely something off-the-shelf that will be just fine. 

I'd be inclined to keep the rotators if you don't plan to rev to the moon.  They help prevent burned exhaust valves.

Having said that - I removed the rotators on my '77 Silverado's 350 (10.9:1, 231°@.050, 108°LSA), and had to get shims and offset keepers to maintain the correct spring installed height.  Nine years on that motor, and no burned valves yet, but not sure that the time/effort/cost was worth it.

The valves rotate around even without the rotators.  Some are of the opinion that rotators actually hurt since the springs can't act against to valve to precess it (or whatever the proper term is).

Lots of engines don't have them and have no problems.  If you are not running into valve float then you may not have problems using them.

IMO do what is most expedient for the spring combo you need/want to run, for your use case it probably makes no difference you could tell.

(but never use loose fitting keepers like Ford used to use!  I don't recall if Chevy ever infected their engines with them.  The keepers were a tight fit in the retainers and the valve could move around in the keepers.)

Im with you on GM using E36 M3ty springs. On LT1s with some miles people are picking up power just by swapping the springs, the OE springs are so borderline after some miles they arent cutting it. Id suspect these are probably similar. I would swap the springs,and go with whatever the manufacturer recommends with the rotators

Ive always been referred to Raylar engineering for the 8.1 stuff. Might give them a shout and see if they have a spring recommendation for that cam.

Ford pushrod 5.0s had the crappiest valve springs.  5k rpm float.....  valve springs are the most often overlooked part on pushrod engine combos.

Get good springs, good retainers and set the spring heights properly!  It's easy and Is definitely worth the effort.

Cams wipe lobes now because modern oils are designed for roller cams only,  

In reply to AnthonyGS (Forum Supporter) :

An 8.1 SHOULD have a roller.  GM's rollers are failing in service.  I have seen the cam lobe surface start to pit and spall, and I have seen the needles in the rollers fail causing either excessive slop in the roller or the roller locks up and skids.

I've done two cam swaps on 8.1s for this problem.  One of the times we did an "upgrade" because of course a 24' rollback tow truck needs a hot cam in it.  (Ever see a Topkick do a burnout?)  Kept the stock springs, it worked fine.

Thanks for the thoughts everyone. Yes, the 8.1 is roller hydraulic cam, and all of these early LS engines seem to be at some risk for this kind of failure. My parents' 2003 5.3 Tahoe had the same failure around 50k miles. My truck is at 225k.

@Opti - the cam I am using is from Raylar (BP202), and Larry's the one who said I should be okay with the stock springs. However, I've also found posts from Raylar on various forums saying that "any cam upgrade on the 8.1 requires upgraded valve springs", which is what started my spiral of indecision.

I could not find a case of people using aftermarket springs with the stock rotators.

I've not heard of loose keepers on the GM engines, but any aftermarket spring seems to also require unique retainers and locks.

I spent WAY too much time down the rabbit hole last night and found several people have used the BP202 and BP203 with stock valve springs. One actually posted dyno charts, and it doesn't show that valve float dropoff even rolling out to 5100 rpm which my truck will never see. As a result, I am leaning towards putting it together as-is and see what it does given my low RPM need - I should be able to feel or maybe even hear if it is floating with my stock exhaust, or I can find a shop with a dyno and see what happens.

Here's one of the dyno charts I found, same cam I've got with stock springs. Even with the new cam, I don't think I'm going to move my shift points up from the 4500-4600 rpm they are at now:

part of this is also that the camshaft geometry doesn't seem nearly as extreme as I was expecting, since this showed up last night:

Also, since everyone likes pictures of carnage:

I also did some math just for giggles since the 8.1 is a slightly different installed height than the Gen VI BBC - mine measures around 1.835". That installed height, plus the total valve lift of the cam, puts me right up on the coil bind limit for the recommended Comp 911 single spring, and dead on or slightly past it for the "upgrade" Comp 26120 beehive spring. The Comp cams are all about 0.03" less lift on the exhaust lobe, which puts the spring just on the safe side of staying .060 short of bind. I'll be checking the stock springs carefully when I get the cam in, but unfortunately this means if I do need springs, it will be some oddball collection of parts rather than an off the shelf solution. This may explain the reports of loud valvetrain I've seen from the people who did upgrade their valve springs to the Comp offerings with the Raylar cam.

I continued to be nervous as I went through putting everything back together, and eventually realized if I was nervous with the engine apart, I was going to be really really nervous any time the revs were up, so I broke out the credit card again. Also, those full roller rockers are HEAVY compared to the stamped steel stock bits.

Trick flow has a set of springs that are more reasonable (my opinion) than the Comp offering coming in at 125 lb seat pressure and 330 on the nose. Huge bump over stock 90/220 numbers, but should still work fine with the stock lifters. The TFS springs also offer slightly more coil bind margin and are 0.025" smaller diameter, not that this makes a huge difference. 

Lunati sells rotator eliminators that I suspect are the same as the Comp eliminators, but are half the price.

I'm using a set of Comp locks and retainers. The retainers I'm using are also slightly smaller to match the TFS springs, and the geometry is almost dead on TFS's retainers. The only reason I didn't go with TFS retainers is that they don't sell locks for 3/8" big block valve stems.

Bonus nachos, this setup saves around $100 over going with all the comp parts, and should be a bit more appropriate for my use case - fingers crossed no lifter noise like people report with the Comp springs.

So, we shall see. Finding information for this engine has been a somewhat remarkable challenge, it seems like there's a lot of bad information out there or information that is conflated with Mark IV and Gen VI 454 stuff. Some of the valve spring suggestions (200+ lb seat pressure!) for street/truck cam 454s is really wild.

In reply to gearheadE30 :

IIRC the 8100 uses the standard GM SBC/LS lifter. If so I wouldn't worry about the lifters. I've run more spring (over 400lbs open) for a lot of miles without lifter problems.

Opti said:

In reply to gearheadE30 :

 

IIRC the 8100 uses the standard GM SBC/LS lifter. If so I wouldn't worry about the lifters. I've run more spring (over 400lbs open) for a lot of miles without lifter problems.

I am not sure what is unique about them, but the lifters are unique to the Gen VI 454 and the 8.1 for the original part number. The replacement parts typically show interchange with the LS and the Duramax which somehow I never noticed during my research. Interesting, and definitely a good data point.

Can't believe I missed this thread until now. I go to sleep with images of uniquely canted big block valves happily cycling in my brain.

First, I wouldn't stress too much over the build in general. You're not asking a lot out of the design or parts.

That cam is a tad spicy (Cajun-spicy) for a tow vehicle, but not unreasonable. However, the term "reasonable" is coming from someone of questionable sanity who daily drives a habanero-spicy solid-roller 454 in an 83 Suburban, so I'm definitely fluent in this style of idiocy and my judgement in these matters is highly skewed. I would absolutely love to see videos of Pete's Topkick doing a dually burnout. You will run out of cylinder head long before the cam gives up.

The lifters are taller than the Mk IV because GM put a bunch more meat on the top of the lifter bosses for strength as well as material to run the dog-bone anti-rotation bits. They're otherwise compatible and share dimensions with the rest of the family.

I have learned many lessons in my years of engine building about BBCs and valvesprings. There's nothing short of a Pratt & Whitney Super Wasp that has heavier valvetrain parts, and carefully chosen spring pressures are the only thing standing between exuberant valve float and lifter annihilation. Remember that seat pressure is the more important number to consider for float margin, and nose pressure for lifter loading. Ramp rates have a lot to do with the amount of intake seat pressure needed--I would expect the Raylar lobes to be moderate. I tried beehives on a BBC, which resulted in a shattered tool-steel retainer. I also tried conical springs, which resulted in a shattered spring in 400 miles. Lessons learned: stick to the knuckle-dragging basics for the BBC with its heavy parts. They really do run better with plenty of spring. I would also do as you have and put springs on it. Those seem fine. .060 to coil bind is a good place to be and actually helps quell spring surge, mostly irrelevant for your RPM range.

Don't worry about the rotators. They'll be fine.

In reply to Nockenwelle :

Thanks for the feedback! It does seem like a spicier cam than Raylar led me to believe, but we will see once its in the truck. One of those things where the cam card comes with the cam...but not before you get it. I didn't really have solid lift or duration numbers until it showed up.

I did run an XR276HR in my Caprice with a vortec 5.7, and that cam is a bit hotter relatively speaking and still did just fine lugging around at lower revs. That was with a stick shift too, so my hope is with the 2200ish rpm stall stock converter it will be no problem.

I did not realize that seat pressure was key for float, that's good to know. We will see how it goes...I do have plenty of margin to coil bind and that was something that I had come across being maybe too much. Offhand I think my coil bind margin with no additional shimming of the springs is around 0.12" or a hair more. I figured surge was probably not a huge concern, but that does seem to mean that I could shim for a bump in spring force if I really needed to. 

Aside from looking at airflow or significant drops in power, is there any way to really tell if I'm getting mild float? I would guess that it might not be obvious if I'm dropping the valve on the seat rather than following the cam.

The thought of a shattered retainer definitely scares me...but hopefully as mild as my setup and rev range is, it won't be something I really need to worry about.

The relative spiciness of any given cam needs to be weighed against the engine's basic architecture and cubic inches. BBCs tend to want a bit more duration than most for a given size, and those 496 cubes will suck up a bunch more cam too. You should be fine with that converter. It will lope just enough to sound cool. Hope you already have or will be putting adequate exhaust on the truck--it will be really important to get power and fuel economy out of this combo.

Valve float is often misunderstood to be the lifter ski-jumping off the nose of the lobe at max lift, but that's actually referred to as lofting and isn't real common in mortal builds. The Pro-Stock guys do it intentionally at 10k+ RPM (and 800+ cubic inches, wow!) to cheat their way into even more than the 1-1/4" valve lift they make on the engine stand. The rest of us peons just have to contend with simple float, which is the valves bouncing off the seat as they close. The intake is far more critical in this regard. First, the valve is heavier and therefore more prone to it, needing higher spring force to resist. It's also more flexible due to the head size. Second, intake ramps are usually faster than exhaust, so closing velocity goes up (harder hit=more bounce). Third, among the four cam events, the effect of IVC point in the engine cycle is of much greater importance than the rest, as it directly influences volumetric efficiency and cylinder pressure. There's really no good way to know (mild) valve float is occurring without a dyno, or in a lab with instrumentation and/or high-speed video. Severe float is pretty obvious once the motor stops making RPM at full throttle. Once upon a time many years ago, I cam-swapped the 350 in my  old high school pickup with a basic flat-tappet kit. It came with 16 regular retainers and new springs and omitted the factory exhaust rotators. I didn't know enough to check installed heights, and the 624 heads on the motor had deeper exhaust seats to make up for the taller rotator-retainer, so the exhaust springs were all installed with about 40 pounds of seat pressure. I never did figure out why it wouldn't run past 4700 RPM until years later (still have the motor parts)...stopped pulling like it hit a wall. 

There are some pretty neat high-speed videos on YouTube of valve action during spintron testing. Good examples of surge and float to be found.

I just have a stock exhaust at this point. This was kind of an unexpected upgrade given the cam/lifter failure, otherwise I likely would have done some exhaust work first. I'll likely keep the manifolds and will definitely keep the cats, and make some kind of quiet cat back for it with an X pipe and some big Magnaflow RV mufflers or something of the sort. I've seen the cutaways of the stock muffler that convinced me I should probably do something with it, I just want to keep this thing as quiet as I can. May be a while before I get around to it.

The videos from Richard Holdener showed something like 10 hp increase at the top end going from manifolds to dyno queen long tubes, and that's not worth it considering the stainless works long tubes for the truck are something like $1300.

I had no idea the drag guys were using lofting intentionally, that is wild. I've seen the spintron videos and whatnot showing surge in particular, but I never quite understood how to take that theory and apply it to my own build. I guess I never noticed the float/seat bounce. I'll have to take another look at that.

All of my parts showed up, cam and lifters are in the engine and will do valve springs and seals tonight. The new timing chain and gears didn't really look any better than the original set but installed on the engine, there is SO much less slop in that chain. Definitely an improvement there. Cleaning and assembly always takes so much longer than tearing it apart.

Good stuff, thanks again for the pointers.

Just in case someone else finds this thread looking for rare 8.1 information on the internet, I've learned things in the last few days. Bad news, in a few cases.

• BP202 cam "works with stock valvetrain": no, in fact, it does not. Exhaust valve lift is 0.545". With the stock retainers, you get basically 0.530 out of it, or a bit less, before the retainers smack the seals. Depending on how I measured it, this number was anywhere from right at 0.510 to 0.530, which is not enough in any case.
• Comp retainers are an additional 0.035" deeper than stock, so if you run them, you are now limited to around 0.475" lift. I don't understand how this information hasn't been passed around 8.1 circles, but it hasn't been. I posted in a facebook group about it, and it appears that people have had the issue but it just never ended up on the internet. One guy actually split the valve guides because the retainer was interfering with the guide itself. I suspect this is the real source of the noisy valvetrain some people have after installing a cam.
• Comp locks are the same length as stock, it's just the retainer that is longer. So you can get that 0.035" back by doing the vortec ghetto grind.
• Comp sells +0.050" offset locks, part number 616-16, to work with their 10 degree retainers and a 3/8" valve stem. But you can't use them on an 8.1 or on a Gen VI 454 (and possibly others) because at best, the top of the lock sits flush with the top of the valve stem. Often, the locks are actually proud of the stem. Comp's tech line response: "well, it should be fine".
• I was pointed to a youtube video where someone ran into this on an L29 Gen VI. As it turns out, Crower also sells 10 degree +0.050 locks, though they cost twice what the Comp parts do. But they don't sit proud of the valve stem, and they do appear to work with the Comp retainers. Part number is 86111X1-16. I don't have them yet, but this is the route I am going to go to pick up some more clearance.

So, all said and done I will have to run +0.050 Crower locks, ghetto grind the comp retainers, and shim the springs 0.060". The maths tell me this will be good for 0.585" lift, and hopefully measurements back this up when all the parts get here.

The people who said their setups measured out fine when they spun the engine over did not account for the fact that the lifters collapse when you do this with a non-running engine with no oil pressure. Some people check with a fixed lifter, I just took one of my failed ones and marked the plunger, then installed everything with a small tester spring so I could manually actuate the rocker/depress the lifter plunger.

Other potentially useful info:

• I have the Lunati rotator eliminators. They fit great and don't have the clearance issues the Comp parts have.
• Stock rotators are 0.340" thick. Rotator eliminators are 0.300" thick, for all of the off the shelf brands. Factor this into your installed height.
• For shimming the springs, you can match the eliminator dimensions, which are 0.625" ID and 1.725" OD. The ID can't be smaller and the OD can't be larger, or they won't fit.