Anybody know anything about valve springs?

alk

alk

Administrator
Staff member
Member
Joined
Jul 27, 2001
RO Number
5508
Messages
1,243
Getting some conflicting info online, and from the machine shop.

Short story is that I am already half way thru an off season rebuild of my ski boat motor, sbc, pre-vortec, hydraulic flat Tappets. I think on another thread I claimed boat motors don't wear out, they break? Well this one wore out. It ran ok, but a ton of what I assume was cylinder blowby was leading to excessive smoke back thru the block and to the air cleaner. So figured I would have some machine work done, and replace the bearings, pistons, cam, timing set - all the usual. I probably could have purchased a built long block for not much more than what I'm spending. But it's been too long since I built a motor, and was looking for something to keep me busy this fall.

I went a little bigger than the stock mercruiser cam, with the tamest marine cam that compcams sells.

The stock merc cam has , 200 / 212 duration, 400 / 410 lifts.
The cam I bought has 212/218 durations, 450 / 462 lifts.

The compcams website says I can NOT use stock springs, others have told me I can. I didn't get much help from compcams support. Anyone have any idea what specs are used to determine valve spring needs? There is card I got with the cam specs, but it did not include much about springs. It actually says “springs requited valvle spring specs fur with springs" . Not sure what that is supposed to mean!
 
IMO the engineers at the cam company know the answer so you need to find a way around customer support.
 
Thanks, I’ll give that a try. They were prompt on replying to my request, but did not give any real info.

I think my card is a misprint, because other forums claim the cam card will have the part number for the suggested springs.

I was hoping to find an online chart telling me how much spring pressure, height, etc, needed based on lift and/or duration of the cam. But not really seeing anything.
 
I'll Second asking the CAM company for the correct spring. Had an issue decades ago with a Ford 351M, new cam and was also told that I could use the factory springs, NOT. Randomly a spring would bind and snap. The other learned lesson is to use hardened shims under the springs. Rebuilt the motor and used the springs the CAM company recommended. No issues at all even at WOT, Truck is still running fine with new owner. It's a '78. Good luck.
 
A lifetime ago (mid 70’s) my first job out of the service was working in a shop that rebuilt cylinder heads. I spent several years there. Saw plenty of collapsed springs.
IMHO: Go for the springs the cam manufacturer recommends.
Can you use the stock ones? They probably don’t have the correct tension for the higher lift cam and since they are used they may have a bit of fatigue.
You could use them.. But is it worth it?
Way back then when I put together a set of heads for myself or friends to put on a motor we were rebuilding for ourselves the heads got new springs to go with the new cam and lifters.
 
For a higher then stock cam lift, the spring may bind. Not good. Some springs have larger then stock diameter and need a fly-cut of the head so the spring will seat. I decided to go another route. They have a spring design called a bee-hive. The center spring have a slightly larger diameter which allow the springs to compress a little more. They are a single spring set.

It's really stupid to do all the work to rebuild an engine and go back to a stock config so I'm glad you're going bigger. Generally, you won't feel any difference in performance until you get at least 100 HP...which is the cam (breathing). The higher the HP rating, the higher the torque/power RPM begins. Another part of engine power is the combustion chamber configuration. The cheapest power add on are the vortec heads. I get my first set when the cost was about $250 a set...valves and springs installed(circa 1999/2000). I think I have the price and time about right.

What engine do you have? I've been referring to SBC.
 
There was a long thread on iboats last year about this very issue, the need to cut the heads so that the springs don't bind, the problem the person was having was that the rocker studs were breaking after a period of time. He eventually figured it out, learned how to cut the heads himself and seemed to have solved the problem.
 
Yes, motor is a 350 mag, carb small block. Pre-vortec. Non roller cam.

My ski boat was already a bit scary fast, so I wasn't going to do much beyond a re-ring/bearing job. Then of course I pulled the motor out a few weeks ago, and started dreaming. At one point I was about ready to get a stroker kit, flat top pistons, roller cam, and vortec heads - with new intake manifold. But that would have gotten my rebuild towards 5,000 (and probably near 400 hp). So talked myself down from that one. Stayed with my crank, new bearings, new pistons and rings, boring, honing, etc. I have the new flat tappet cam in.

Just need to decide if I'm going to have my heads done, or go with vortec and new intake. Have changed my mind at least three times this week. If I stay with my heads and intake, should be able to finish this off for about $1,500. Another $300 if I go vortec - but then I'll have aluminum intake manifold, which I'm not thrilled about.

I think I finally found the chart I was looking for. https://www.onallcylinders.com/wp-content/uploads/2017/02/27/Valvetrain.jpg

Assuming it's correct, my springs are these - https://www.summitracing.com/parts/cca-981-16/ -- for the SBC with flat tappets, doesn't look like any of the cams use beehives.

Now I just need to figure out if springs with these dimensions fit in my heads ( or some vortecs) as-is, or if they need to be cut down. There are some good you-tube videos on cutting down the valve guides, and replacing the rocker studs with heavy duty screw in versions. This looks like machine shop work to me though. But a dill press in my garage? Sort of like that idea!
 
You can definitely get a cast iron intake for the vortec heads. Check Michigan Motorz. The Vortecs do add hp so if your old heads have to be redone it might be worth it. Find out if you have to do any other modifications to put Vortec heads on a pre vortec engine. I have a pre-Vortec 4.3 V6 but with a roller cam. The roller cam is definitely worth having because it is not as sensitive to lowered levels of zinc in motor oil. Flat tappets are and you have to be careful during break in.
 
My engine has a 1970 400ci small block bored .30 over for 406ci/6.6l. Vortec heads bolt straight up. Just need vortec style intake manifold. I'm using aluminum intake manifold in straight salt water...but I have a complete sealed cooling system. Welded water passages in aluminum exhaust manifold and cast iron risers. No place where raw water might get into engine.

I have cast iron intake for vortec you can have. just pay freight. Come to think of it, I have aluminum exhaust manifold for SBC. Slightly used square Edelbrock with snail end riser and unused but scratched up surface of round Glenwood with 30*(?) end riser $150 each.
 
I have a few bottles of zinc additive, guess I’ll be using that with every oil change.

Are marine heads any different? I thought I remembered that the valves, or maybe the seats, are not the same?

thanks Charlie, I think I will take you up the manifold - just need to be sure my machine shop still has the vortec heads he offered me last week. Any chance you can get me some pictures of the exhaust manifolds?

I have closed cooling setup, but never welded anything. Just one of those stainless plates between the riser and manifolds. Isn’t that enough?
 
cam and valve springs go together.springs depend on the cam used, and the relative sustained rpm the motor will be running at.
You or your machine shop must check for coil bind no matter what cam is installed
 
Alk. That's the cast iron intake manifold you can have. Probably weighs 25/30 lbs. Come to think of it, I have two slightly used set of cast iron center rise manifolds and risers that have welded water passages also. $100 a set.

Photobucket doesn't have my pix of the manifolds anymore. I'll try the cell phone, never done it before.

Well, I took a pix of one side manifold/riser, on my cell but need help sending pictures. I've posted the pics from photobucket a few years back. I'll look 'n see if they're someplace in my old posts.
 
Charlie - tried to send you an email but it was rejected. I want to get the intake manifold from you - but probably should have asked sooner, is it a square bore, or spread bore? I actually have carbs for either, but my holley is a real mess, so plan on using a quadrajet. Curious what made you decide not to use this manifold and go with aluminum - wieght, performance, or just because you can get an edlebrock with free shipping for under 200?

email or PM me please, and we can work out the details.

Not sure yet about the exhaust. I think these are the ones I have on there now, but need to measure my muffler diameter. https://www.michiganmotorz.com/indm...MI7dycsb6y5QIVjJ6fCh1PTwyPEAQYASABEgKsjfD_BwE
 
You must log in or register to reply here.
Back
Top