I'll tell you about my setup first--- The car is a 1993 Mazda RX7 with a LS2/T56 combo (MN12 trans) (LS2 from 2006Trailblazer SS with 15K)--- 2866 LBS with 6 gallons of fuel.. 4:10 rear gears with LSD.
As for the engine: stock lower end (may be running Katechs in future)-- GM stock solid valves.. Comp R series lifters--set @ .020 preload, Comp 921 springs with titanium retainers, Comp Shaftmount rockers 1.8 ratio (yes the geometry is correct--I did fit these under stock valve covers with serious machine work) The cam is a Comp cam --part # 54-000-11 232/238 .608/.621 with a 112 lobe separation.
Other parts are FAST 92mm (unported) Manifold 46# FAST injectors....ported 90mm TB by New era performance.. 4" intake...1.750" SS headers (Hinson supercars) into a 3" collector---merging to 3.5" ...no Cats.... Underdrive pulley..

So I went to dyno @ New Era Performance and put down 432.7 HP/410.9 Trq ...but got serious Valvefloat by 6550 RPM's... which seemed quite premature-- I then shimmed the valvesprings so they were @ .050 from coilbind (1.698 /1.711 installed height)---which added approx 26-30# of pressure---also set the preload at the recommended .002-.004 from Comp ....I gained a little---like 6800 or so till float (electronic limiter is set @ 7k)

So my question is this.... I have a set of intake and exhaust Xceldyne valves (free) with approx 20hrs on them---and copper beryillium seat for the exhaust---- should I run them---(or just TI intake and sodium filled Ex)---with heavier springs----or ditch it all together and replace shaft mounts with stock upgrade replacement trunnions?? I guess given the valve float----Im not sure where my peak power should be at... I think it may have started to float after 6k---but totally broken up @ 6550 (dyno run)

Ive searched a ton on this topic---any info would be greatly appreciated--- Ive been an import guy till now---this is my first V8---thanks guys.
Jared

 

Valvetrains work as a system and to be happy, every part has to get along with the others. Very often the parts are not compatible. I suggest that this is your case.

This is not something you can self-diagnose easily. You could change things one at a time, and sooner or later you might hit on a combination that works. It will be a slow, expensive job.

The biggest problem is that many people sell valvetrain parts, but very few folks are good valvetrain designers or "integrators" who know how to make things work together correctly. Almost always they use parts from various sources. That's why specialists like Manton or Smith sell pushrods, but not many other valvetrain parts.

The list of folks who do this successfully isn't very long.

FWIW, stock lifters and rocker arms and valves can easily be spun to the high 7000s with the correct springs, retainers, pushrods and cam lobes.

You may be "looking for love in al the wrong places."

Good luck.



Jon

 

More info needed here. What heads are you running?

1.8 rocker arms are less than ideal IMO. I've seen a lot of complaints come up with engines running them. I'm not saying this is your smoking gun to fix your float issues but I'd ditch them and run the stock 1.7 ratio. The more weight you can get off the valve tip the better and the closer you can keep that weight to the trunion the better. These things are out further and weigh more. This is why stock LS rockers are so small on the tip. Lots of guys run the stockers to 7K RPM without issues for years including me... Katech too I believe uses stock rockers.

Lastly and more importantly am I reading this correctly?

0.20 preload???? Thats way low. Not that this would cause valve float but why so low? Who set these specs out for you and why?

As I said more info needed here.

 

The preload isnt low. He already reset it to the correct amount. .002-.004". R series lifter have almost no preload on them.

My questions is.... Why are you trying to spin a motor more than you are cammed for? That cam is only good for about the 6400 range anyway

 

Well thats that it seems.

I still think those rockers are not worth the trouble though

 

overkill i agree

 

Thanks for the replies guys----yes, they are indeed stock 243 casting heads.....not ported. The reason I was trying to spin it higher is because I wasn't certain that it peaked @ 6400, It appeared that way, but wasn't sure if valvefloat was causing peak power to look like it was earlier. Thanks for clearing that up. even so, Id like a few hundred "overrev" (6700) past peak rpm. I dont want valvefloat near that range---as its hard on valvetrain. So Im getting the impression I should get the trunion upgrade for the stockers and call it a day. I hear lots of ppl running ls7 lifters, are my stock ls2 lifters the same? (I believe they are) They only have 15K on them. That should put me @ .575/.586 lift.... Should I expect to loose a little peak power with this change??
Are the yella terras worth the money...or is that going to induce the same problem?
Should I be looking at a different valvespring??

 

Would it be a bad idea to run the titanium intake valves?? I know its probably overkill, but I do have them in my possession. Thanks again for the replies.

 

Sounds like you are willing to pull the heads again. Given that, I would personally ditch the Comp R's and get Morel link bar lifters that are a little more forgiving on the preload and don't require an adjustable rocker arm like the Comp R's require. They are also a better lifter. Then either stock rockers or Yella Terra' in a 1.7 ratio. Finally, a stiff pushrod like an 11/32" or 3/8" OD if it will fit.

 

I didnt read everything here but there were issues with certain rocker arms eating ti-valves on ZO6 builds iirc. Just wanted to mention on a fly by. I'd still use them, but choose the rocker wisely

 

I am pulling the engine/trans out....have an issue with 1st gear syncro and reverse---due to a not fully disengaged spec 2 clutch (shimmed) ...SS clutch line 3" from header (no room)... possibaly boiling fluid. So pulling the heads isnt a big deal at this stage in the game.... I have enlarged the heads to accept 3/8" pushrods--- so I'll buy a set once I check for proper length. The Xceldyne titanium valves I own have a steel insert in the tip of the stem... I wonder if that is what the ones with problems lacked...prob should do some research on the subject.

Does anyone know if ill be ok running OEM lifters with shimmed comp 921 springs with titanium retainers (assuming I havent damaged them--gotta inspect them still) Should have 158# seat press, 411# open (If memory serves me correctly) ...seems like alot of pressure for a stock lifter to handle.... how much for the morels? who sells them? Thanks guys for all of the input---greatly appreciated.

 

The motor/trans will be coming out this weekend (1st and reverse syncro issue) spec 2 clutch not properly disengaging...was shimmed. So pulling the heads isnt a big deal at this point in the game. Being as peak power will be around 6400...ill prob leave the stock rod bolts alone and set limiter at 6900... The pushrod holes have already been enlarged to run 3/8" pushrods...so I will be sticking with the proper length 3/8".
The xceldyne valves I own have steel inserts in the end of the valve stem---I wonder if that will cure the problem that some have encountered? I should do some research on the subject. Will the stock lifters handle the pressure of the 921 springs? (158# seat / 411# open--the way they are currently shimmed) ...or are the morels def the way to go? Thanks for all the help guys...I greatly appreciate it .

 

Wow--I didnt think my first reply posted---so I typed it again---sorry bout that.

 

99blancoSS is a sponsor and he has the Morel lifters. That seems like a lot of spring load on the stock lifters. The offshore guys run the Morels because they can handle the higher spring forces and the constant high RPM use.

Here is a link to his web site, you may want to discuss further with him: Link

 

Theres guys that run them. Not saying its ideal but its been done. I ran Patriot Golds on stock LS1 gen 1 lifters that had 72K miles when I did the head/cam/spring swap. Ran great and held up fine for the three plus seasons I ran it. Lots of street and track use. Spun it to the 7K limiter almost daily. Stock rockers too I should note. Patriot Golds are 135/375