Cam Failure Solution

[73383]

For all of you who followed my cam failure thread, I think, with the help of JohnZ and GerryLP I have found the problem.

I dug out all my parts reciepts and ran the numbers. The SportsmanII heads came supplied with springs and valves. They were for use with a rollar cam.
Springs were duals, the preasure was 125lb seat and 389lb open. Way to heavy for a flat tappet hydraulic cam.

From what I have learned the past few days I believe I need something like 100lb seat and 240lb open pressure. My cam is a Comp 280h flat tappet hydraulic with a .480 lift. Any help from valve spring gurus would be appreciated.

Oh yea, the builder has agreed to cover any parts needed.

Dennis

 

[vette-dude]

Buy a cam kit with the matching springs and new keepers from Comp or whoever you are getting the new cam from. Sounds like all you need is stock springs but Comp sells a set that is designed for the cam you get with the kit.


Randy

 

[73383]

vette-dude

I have spoken with comp already and I may end up buying new springs and retainers. First we plan to pull the springs, remove the inner spring,(they're duals) and test them. If the test out I may just use them without the center springs.

Also have to check pushrod length

Dennis

 

[vette-dude]

vette-dude

I have spoken with comp already and I may end up buying new springs and retainers. First we plan to pull the springs, remove the inner spring,(they're duals) and test them. If the test out I may just use them without the center springs.

Also have to check pushrod length

Dennis

sounds like a plan. Good luck.

Randy

 

[Jack]

A set of "Z-28" springs will be all you'll need for .480 lift hydraulic FT street cam. They can be had for as little as $15 a set ... about $45 full retail for Manley z28 springs. Manley P/N 22409-16 are single spring with damper (like OE) , OD about 1.25" (like OE) can use OE retainers. 110 # @1.7", 285# @ 1.21", CB about 1.16". JR motorsports (1-888-771-5574) has their house brand of z28 springs for $15 a set. 389# way too much for FT hydraulic. No need to get fancy ... the z28 springs are all you'll need for your .480" hydraulic FT street cam. Better inspect ends of your pushrods ... 389# could've easily fractured their ends if they aren't performance PRs ... look close for hairline fractures. I'm running the manley springs w/similar cam. G'luck.
JACK:gap

 

[JohnZ]

Find out from Comp what spring specs they recommend for your cam and either buy them there or match their specs to someone else's springs as closely as you can. The "Z-28" springs advertised aren't really Z-28 springs at all - they're higher-pressure springs designed for the 1st-design "-140" Z-28 Service cam, which was an over-the-counter replacement designed specifically for the Trans-Am cars, never used in any factory engine. The production Z-28 ("30-30" cam) used exactly the same springs as Grandma's 307 - 85# closed, 200# open; 6500-7000 rpm with those springs was a real tribute to Chevrolet cam designers, and that's why the factory "30-30" and LT-1 valvetrains are bulletproof.

 

[73383]

Update;
Springs should be here today from Comp today. Picked a 95# closed 220# open spring.
I also ordered adjustable pushrod. Found that my pushrods wear also to long. They were working on the exhaust side 1/3 of the valve stem.
Hope to get most of it back together this weekend and order correct pushrods.
Dennis