65tripleblack

I answered your original question in post #5.
Just what is it that you're trying to do?
If you have a stock GM camshaft, then the 142 spring is too much......more than what you need. Why are you looking at beehive springs? Plain old 068 marshmallow is all you need with the very lazy 30-30 and any other stock GM cam for that matter.

TCracingCA

The Cam grinds from back in the day had a particular metallurgy, and unless I am mistaken the materials from which a cam were cut were the limitations on longevity, strength etc. and limited the level of spring that could be ran. Therefore guys started to cut them out of superior materials and now the rollers cam are of superior materials. Therefore GM thought the 142/585 springs good to run on their-- "back in the day" performance cams to the 140 grind. They were throwing mushroom lifters because of trying to gain more lift and faster ramping primarily on the more aggressive cam offering. Therefore lifter rides on the cam lobes pushing up the rod to the lifter and the lifter down on the spring. Yes higher spring pressures require break-in and then would wear more rapidly. Excessive spring pressure can wipe a lobe etc.. Therefore since the material construction of the cam I believe is the same whether 30/30, LT-1 gen 1, or 140 back in the day and GM was Ok with the 142 springs on a few of those, I don't see a problem overspringin the lessor cam for a positive open/close action in a lesser cam profile and especially for no float! But a higher spring will wear components faster, so it is a trade off!

Toddalin is a performance minded guy and is just looking for opinions, and options. I feel he can easily make his choices with darn good reason and common sense! And in this thread is just bouncing it off of the other brains (not that I have any!)

As far as the top heavy springs, there are only a few things that I like Top Heavy (would have to switch to Off Topic). Something that is wider at the top and tapers smaller doesn't seem good to me. I have this imagine of a simple top spinning and if something gets out of alignment, it starts wobbling and falls over! I definitely won't build a skyscraper that way!

babbah

Just put the stock springs in and "forgedda bout it"
For aftermarket brand I use Crower -

toddalin

The closest Crower (68301) would be 105# on the seat and 274# open so is also close to the cam cards 277# open value and a bit less than the Trick Flow 281# value. And they offer a titanium retainer. But of course more $$$ for Crower.

KCS

Those conical springs you're looking at were designed to increase the OD at the top for more spring load. You're confusing the purpose of those conical springs, that have been produced for decades, with the new conical springs Comp just recently released.

Link

Donny Brass

I either run comical springs, or ones from the hardware store

toddalin

None of those have an acceptable installed height or spring rate for a 151 cam.

TCracingCA

Crane was manufacturing the replica factory grinds that GM Performance parts was selling. Crane still offers those and has a specific 151 offering! These actually have two springs recommended for that cam (99848-16 & 96802-16). A 151 is a 2000-5600 power band range unit.

Also I found where GM does say you can run the Factory race springs with either the solids or the hydraulics!

toddalin

An Update and question for those in the know.

The best match for spring rate and open seat height and pressure I can find (at reasonable cost) is the 15106 Trick Flow ovate wire springs.

Unfortunately, there is only one set of steel retainers available for these springs (and the similar Comp Cams offering) and no titanium or even lightweight retainers are available. But, I found a machining facility that will make me 16 titanium retainers and 32 locks (7 degree) for $120 parts and labor. (That's a steal!) These are re-machined from NASCAR pieces.

OK, so my question. The stock Chevy spring seats are ~1.28" diameter and the springs will fit here. But, stock Chevy springs have an ID of ~0.883+" and these springs have an ID of 0.836", so are a bit smaller. Will this slightly reduced diameter still clear the "perch" for the valve?

Thanks

JohnZ

Note that the 142 springs were never used in production - they were over-the-counter only, designed specifically for the 2nd design Z/28 off-road cam.

toddalin

I did more digging and the receipt for the rebuild back in 1988 specifies Crane springs, retainers, shims, etc. and I would assume that they selected the springs most applicable to the cam card.

http://www.streetperformance.com/par...-99849-16.html

That would then be the #99849 springs which call for 100# seat pressure at 1.625" installed height and 282# at 1.187". Max lift is 0.494" and max RPM is 6,500. This equates to a spring rate of 415.5# per inch.

The cam card for the Crane Vintage Muscle 151 replica, also installed at the time, calls for 0.447" lift, spring seat pressure of 90# at 1.625" installed height, and 265# at 1.203". This equates to a spring rate of 414.7# per inch. Cam card also calls for Min RPM of 2200, Max RPM at 5200 and valve float at 6500.

Obviously these are the springs designed to work with this cam and there is no reason to think these were not installed at the time.

But most installations specify an installed height of 1.7" and if these springs were installed at that height by mistake, the seat pressure would be reduced from 100# to 96# (still fine), but the open pressure at 0.45" valve lift (1.52:1 rockers) would be reduced from 283# to 270#.

Could something like this cause the values to float early? While I make max power at ~5500 RPM (vs 5200 on the cam card), I can't get anywhere near 6500 rpm out of the engine.

TCracingCA

I also live outside of the Corvette world, and i will post up when GM racing deemed that these higher end springs could run on the general high performance cams, serving as performance replacements.

TCracingCA

Everyone here knows the installed height is important to running them as designed etc. coil bind etc. Your question would be better put to the tech guys at the manufacturer! None of them in this modern put out good old spec sheets anymore, but some will provide on request!I just don't equate to a single keeping you running at higher rpms. I will dig out an old Crane catalog when I get a chance and see if they provide a max rpm.

But my guess without knowing your engine would be that the limitation is more in the hydraulic lifter!

Avispa

You should keep in mind that GM cams were and are designed a lot differently than anything Comp makes (other than their vintage reproduction cams). Comp makes their cams so that they will make peak HP for any given valve duration at a particular lobe lift. The valve acceleration rates they use on many of their high power grinds are just not suited for hydraulic lifters, even thought they supposedly make them for that purpose. Sometimes you can get lucky and a particular high speed rated Comp hydraulic cam will work ok on a small block, because the valves aren't all that big, but on big blocks, forget it. The valves will float in the mid 5000s not because of the springs but because of lifter pump up. Going to stiffer valve springs is not going to solve that problem. The lifters will just bleed down more at full lift. GM cams generally have longer acceleration ramps and will let hydraulic lifters run to speeds not attainable with a Comp cam having similar duration at 0.50" lobe lift (the accepted standard for figuring usable duration).

Another thing to think about - Comp and more than a few other cam makers grind their cams with small lobe separation angles (108-112 degrees). Again, this is for maximum power. What you wind up with is a horrible idle (with almost non-existent manifold vacuum) and poor street manners. GM goes the other way with factory HP cams for the most part. If you're driving a weekend dragster, ok. Otherwise, you are going to be a bit disappointed.

In terms of mechanical principles, the only reason to use conical springs with a small OD in the spring pocket instead of the other way around is to avoid spring bounce while possibly eliminating the need for a damper spring. You are going to hit lifter pump up long before you need to worry about spring bounce though. Again based on mechanical principles, keeping the spring weight to a minimum is your friend. Use the beehive springs with small retainers if you want to use an aftermarket spring.

toddalin

Car is over at Steve Luvisi's (Automotive Expertise) now to have the needle put back on the tach (that popped off on the way to the Wheeler Dealers TV shoot), and check steering slop and alignment.

I'll take my dyno sheets and specs on the parts over to him for his opinion. Maybe I'll have him check spring height and pressure on one cylinder just to see if anything seems unusual.

Can anything be done to easily check lifter pump up/bleed down when the valve spring is off? The build receipt specifies new Crane lifters.

TCracingCA

Bottom left, 142 recommendation on hydraulic/mechanical cams by GM guys! But the 585 is not recommended for hydraulics and only mechanical. Therefore I am glad i looked this up. I run all solid mechanical cams! I have cars with each! 140 in the 63/64, LT-1 in the 68, 30/30 with tricks in my Father's car.

I am sure i can dig out more from Super Chevy, Hot Rod, The GM Power Manuals or Smokey Yunick etc..

toddalin

A follow up.

I had taken the car over to Steve Luvisi at Automotive Expertise to have some other work done.

The tach needle had popped off and I asked Steve to replace it and to fix the oil leak at the oil pressure gauge, and to check out the steering and have the car aligned.

Steve pulled the dash, sent the speedo and tach out for repairs, replaced three of the shorter bulbs with the longer ones, replaced the turn indicator lenses, replaced the oil pressure gauge with a new repro, new "filters and seals" in the dash and lenses, fixed the odometer and tripmeter, neither of which have ever worked in the 29 years I've had the car, tapped the holes under the dash that I use to mount the aux switches (that previously used nuts), cleaned everything inside and out, and touched it up so everything looks the same and better than new. Came out beautiful.

He also took the car over for a four wheel alignment and it was way out of spec. He said that he started to drive it over, then immediately took it back to his shop to see if one of the tires had like 5# of pressure in it. Nope, all at 32# where I set them. He said that he had to "herd" the car over but was a pleasure to drive with one hand coming back.

The cost of all of this, including the alignment and gauges that he sent out? Just $617 for everything, with $95 for the alignment and $330 to RR the dash and send out the tach and speedo. And, he gave my wife and I each an Automotive Expertise T-shirt.

When I went to pick it up I showed Steve the dyno sheets and parts list and he agreed that the engine shouldn't nose over like that before 6,500 and we measured the installed height on a spring, which was a bit over 1.71". Both the cam card and matching springs (if matched to the cam) specify an installed height of 1.625", and he said, that it's possible that this is the problem, or related. But he said that they looked like the stock GM springs and not Crane springs, as specified in the build sheet.

I left the car and he will remove a spring(s) and check the installed height against the pressures and see what's going on. If he does any work on it, other than adjusting spring height, I'll also have the pressed in studs replaced with screw in studs at that time.

TCracingCA

If it was just the installed height, so we would be talking about coil bind! But I would put money against it being that simple to get it to rev overall to 6500 unless those unknown springs are better than you suspect, but I am hopeful and that would be simple to fix.

toddalin

The opposite. If the springs were meant to be set at 1.625" and they were set at a height of ~1.71" (1.7"-1.72" typically specified for a SBC), they lose 35# of seat pressure (i.e., 0.085" x 415#/" = 35# of pressure) at both ends (both open and closed).

TCracingCA

Thought you wrote that they were installed at less height which would coil bind, so naturally more height over the recommendation would weaken the install having less tension!

But I think I did read right that you were still unclear as to what springs these were? Or were you able to identify them? That is a major problem, for anyone if it is just a quess which would require testing.