I have a XR288HR camshaft, which is 12-433-8 part number.

Comp cams spec sheet recommends 986-16 springs for my application.


Spring specs are:

Install height 1.750", 132lbs seat
Open height 1.250", 293lbs
Coil bind 1.150".


Ok.. So the XR288HR has .520/.540 lift..


So 1.750" - .540 = 1.210"

1.210" - 1.150" (coil bind) = .060" safety margin..

Seems a little close to me, and this is assuming 1.50" rockers are used. Since most aftermarket rockers are 1.52", that's .5472" lift which makes it even closer.

Considering a hydraulic roller lifter has about .050" of preload, and at higher rpms sometimes they "pump up" which leads me to believe there is serious risk of coil bind and broken springs.

I was thinking the '987 springs seem like the better choice as they have a 1.800" install height (even if the valve is short, you can use offset keepers) although at 1.800" they have a seat pressure of only 120lbs.

Looks like AFR195 part# 1040, comes with the 8017 springs by default, which are installed at 1.800" and have 135lbs seat, 1.230" open at 340lbs, binds at 1.050" and is 360/in.. Seems like the ideal spring.

However, I believe Tony had mentioned to upgrade to 8019, which is installed at 1.810" 155lbs, 1.210" open at 412lbs, and binds at 1.080" and is 428/in.

While Tony may be correct that the 8019 would control valve float better at 6000-6500rpm, I feel like those pressures will collapse the lifter at high .500s lift (in my case .576 with 1.6 rockers).

I'm starting to think that AFR 1040's as-optioned with the 8017s is a better option, and simply just get the hydrarev kit # 6150 since if I understand it correctly puts spring pressure on the lifter body rather than the plunger.


Any thoughts?

-- Joe

The only thing I can say is yes... the hyrdarev kit appears to put pressure on the parameter of the lifter, holding it in the block and against the cam better. It does not look to me like it effects the plunger.

Can't help you much as I don't know alot about this subject, but I can tell you I bolted a pair of out of the box AFR 195's, part number 1040, on my engine and I run it with a flat tappet cam and 1.6 rockers yielding .523 lift and have no problems whatsoever. I rev to 6200 and have seen 6500 before shifts with no sign of valve float or anything like that. Comp recommends '986 springs for that cam.

This might not help you at all since you are talking roller and a little more lift, but thought I'd post my experience in case it does help you a little.

The Hydra Rev absolutley does NOT affect the plunger. The spring acts on the outer edge of the lifter body.

.060 is accetable on the coil bind clearance... but you are almost using up all of the spring. What really bothers me about the Comp 986 spring is the lack of open pressure. Not even 300lbs... Granted you have a rev kit but still its a pretty weak spring for anything other than tooling around IMO.

The base AFR 8017 looks to me to be a better match. It gives you an additional .050 till coilbind and has more open pressure at your lift. It gives you room to grow on the cam or rocker ratio in the future if you want to. IMO 340lbs is about right for a fairly aggressive HR to the low 6000RPM range. It's mfgr'd by Amercian Wire (so is the 8019) and is a good quality spring as far as mass produced stuff goes.

I think the 8019 is too much spring for what your trying to do but not because of the pressure. The open pressure is not that big of a deal. Don't be afraid of the open pressure.

My probelm with the 8019 on your cam is that the 8019 will have too much free travel left, even at .576 lift. It's just desgined for higher lift cams. Because it has more pressure it keeps mild cam lobes under control better at higher rpm but I think all that free travel will become a libality with a real aggressive low lift lobe. It can be made to work if the lobe has a real soft closing ramp.

Spring surge is a difficult animal to tame and so far my best results have been by limiting how much free travel a spring has at max lift to around .100 or less. Incidently it only seems to be a problem on really huge mech rollers and really aggressive hyd rollers. I'm not sure how your XR288HR falls in on the "aggressive HR" side but if it's got any pop at all to it I'd err on the more conventional side of the way we've always sprung and ran hyd roller (ie 125-140lbs seat, 320-350lbs open and keep the RPM under 6500).

BTW I've used the 8019 in (2) motors now. (1) lower lift mild lobe and (1) high lift aggressive lobe. Both with good results. If you want to see the specific set up and combination info that I used on them let me know, I'd be happy to share.

Good luck with it.
Will

I would like to hear more about the hydra-rev kit.

Joe,
Have you run one in the past?

Quote:

Hi Pete,

I have not, however I've had nothing but valve float on a my supercharged combos.. While this motor will probably be naturally aspirated (still debating on 60cc or 75cc heads), I've heard a lot of guys on thirdgen.org run the rev kits and have had ZERO problems shifting at 6500 rpm.

I think I'll be putting one in my motor. Cheap insurance. i've broken too many valve springs over the years.

-- Joe

I know the turbo and blower stuff like big pressures to keep the valve from blowing off the seat from the boost. I saw some spec's on Andy Jensen's 5 second turbo'd small block. I think he runs near 1000 pounds of open pressure.

Defintely run a rev kit, imo reg use on a HR to 6500 is pushing reliabilty limits, almost at the crossover point for a solid. 150 on the seat on a HR is doable just leave plenty of p to v clearance in case.

Couple of things. In our club we have a member with the AFR 195 heads and the 8019 spring upgrade. No problems at all and with the standard GM hydraulic lifter. They come standard on the 195 Competition heads which I will be running. I will also be running the AFR rev-kit and as already correctly stated the springs only apply pressure to the body of the lifter and not the plunger. They keep the roller on the cam lobe.

I have the 8019 springs on my AFR heads as well. When I did the motor I replaced the original lifters with a cheap set from Summit. Nothing crazy, just a stock style replacement. I use an XFI cam with .57X lift on both valves. I've been to 6800 numerous times without encountering valve float.

I was/am concerned about crushing the stock style lifters, but thus far (3000-4000 miles) it hasn't been an issue.