I have a set of ported Vortec heads. I'm also using Comp Cams XR276HR-12

Specs: .503/.510 lift, 224/230 duration @.050, 112LSA

and using 1.5 crane gold series rollers.

When I set the valves (zero lash plus half turn) like comp recommends, it looks like the valve springs are experiencing coil bind at full valve lift. I know that the stock springs are supposed to be good only upto .450 lift, but I was able to stick a feeler guage between the coils.

My question is that how could I tell if I really need bigger springs or how much clearance between coils is acceptable with-out floating the valves?

THanks,
Mike (1bad91Z)

 

Your lifters are probably bleeding off while the coil is binding so that when you put the feeler gauge in there it has bleed off enough to allow that. Once you run the motor and the lifters pump up and don't bleed the binding will probably cause some major issues like broken studs or springs or various other valve train pieces.

Valve float would more likely happen do to the lack of spring pressure for such an aggressive cam profile I would think. I doubt those vortec springs have anywhere near the spring pressure requirements. I think comp cams reccomends a 1.45 inch dual spring that has like 130 lbs closed pressure and like 300 or so open pressure. I don't think vortec stock springs get over 100 closed. But since you will bind long before that it doesn't really matter.

Also are the valve guide posts on top machined down to allow that lift?

Your exhaust set up in your signature sounds awesome!

 

You'll probably need to install a couple of solid lifters to check for coil bind. The hydraulics will bleed down.

Minimum space between the coils is .060" at full lift.

That cam won't work with stock springs. You'll need the 986 springs. You'll also need to get the spring pockets enlarged for the bigger springs. Stock springs are only 1.25" wide and the recommended 986 springs are 1.437" wide. They won't fit in the stock spring pockets. Have the springs installed at 1.800 height.

 

Don't know!


Thanks, it sounds pretty damn mean, costs an arm and a leg though!!

To Stephen_87_IROC - at full valve lift, I was able to get a total of .060 - .070" on each spring (.040 in between the center coils, .015" above and below). I'm pretty damn sure that they are the stock springs but I could be wrong, but is the above clearance that I got, enough to handle the cam with-out trashing my valve train? A local shop told me it was fine, but Comp said as long as you can get .060" in the center that it would be fine. I couldn't get .060" in the center, but did get .060 total. Then, I guess I have to worry about hyd/roller lifter bleed-off and I dont have any solid roller lifters to swap in and check! Aahhh, this is starting to suck because I dont currently have the dough for springs, locks, retainers! What would you guys do? Do you think it will work or would you just pull the heads and have them machined for bigger springs?

Mike (1bad91Z)

 

If there is any one place in the motor (besides rod bolts) that can cost you lots of money in a hurry, it's valve springs. Have you ever seen how much damage they can do? Rolled cam lobes, pulled-out studs, broken rockers, bent push rods, etc.; and when they break .... well, let's just say that valve fragments in the cylinder are incompressible, and leave the rest to your imagination. I will however guarantee you that once you've seen the inside of a motor when it drops a valve at speed, you'll never ever question the importance of valve springs again.

Take a coat hanger and bend it back and forth a few times and see what happens. That's exactly what's happening to valve springs, hundreds of times a second. Remember, the way those heads come, they are NOT performance heads; they're REPLACEMENT TRUCK SERVICE PARTS, with heavy valves and weenie springs intended for a 929 (.390"/.410") cam, no matter how well the castings flow. They're not set up for high lift cams with super-aggressive valve action like those XEs. Those cheap replacement truck springs they put on those truck service part heads will absolutely not stand up to that cam; I'd bet you'll have major parts failure within the first 500 miles if you leave them in there. And Comp won't warranty the cam.

Bite the bullet and get the right springs now, instead of thinking you're going to save money and instead having to clean up a mess, and then get the right springs.

 

I've double checked clearance and I was able to get a total of .060 - .070" total clearance at full valve lift, but screw it! I'm just going to pull the heads and have them machined for the bigger retainers and springs (I'll end up getting the Comp springs, locks, and retainers). Even though Comp said that I have enough clearance, piece of mind is worth a $200 bill. I will how ever put the springs that I'm taking off on a coil compressor and get the actual seat pressure rating for the pull-offs. I'm curious to see how much lift if could have handled!

Mike (1bad91Z)

 

1bad91z:

You have made the right decision, the hassel of pulling the heads and the 200 or so bucks is time and money well spent.

Lonnie

 

Valve springs can make a huge differance in performance. Getting the proper ones installed will save a lot of broken parts.

While the heads are off get a couple of more things done. The spring pockets are going to be enlarged already for the new springs. Get the valve guides cut down for positive lock valve seals and have the guides cut down far enough so that the spring retainer doesn't hit the top of the guide.

 

To All - I watched the guys enlarge the spring pockets and install the new Comp dual springs, Comp retainers, and Comp locks. They also gave me new valve stem seals. Thats all they did, they did not cut the valve guides. Is that bad? All I know is that when I set the valves this evening, I had WAY more clearance between coils!! I can actually physically see space between coils at full spring compression unlike before when I only got .050" total with the feeler guage! Plus, now that I have the Springs,locks,retainers that Comp said to get on my Cam card, now my cam is covered under their warranty. I feel ALOT better about it ($166.27 later)!

Mike (1bad91Z)