Comp-R lifters, Comp Pro-Magnum rockers & 918 springs = 6600 rpm valve float BAD
09-09-2007, 02:41 PM
#1
Banned
Thread Starter
iTrader: (7)
Join Date: May 2007
Posts: 221
Likes: 0
Received 0 Likes
on
0 Posts
Comp-R lifters, Comp Pro-Magnum rockers & 918 springs = 6600 rpm valve float BAD Well I got called in to address a problem with a road race car that is headed to the SCCA mid-ohio runoffs and wont run worth a crap and wont rev over 6600 rpm without breaking up/cutting out really bad...
I got it on the dyno yesterday and you hit 65-6600 and the car starts cutting out/missing really bad and they pulled it to 6900 where it sounded like it was floating the valves so bad that im surprised they hadnt hurt something already.
The motor combo is a 292 cubic inch de-stroker that is supposed to go 8000rpm without going over the maximum HP/TQ for the class.
LS6 intake/TB
LG Speced 23x/23x .600'ish lift cam for this setup
Stock LS1 heads /w Comp 918 valve springs
7.5" moly pushrods
Comp-R lifters
Comp Pro-Magnum rocker arms
Everything in the world has been swapped on this car. They listed: plugs/plug gap, plug wires, msd coils/truck/car coils, checked pushrod length,changed to some random double valve spring they couldnt tell me the pressures or details on, geometry, grounds etc etc. They had the car at synergy motorsports for 2 weeks and they said it wasnt mechanical and that it was EFI/ fuel injection related.
I swapped out aftermarket EFI setup back to a factory harness /w factory PCM and got it tuned/running right before we put it on the dyno. It still has the problem at exactly the same RPM
Solution:
I am telling it is valve float. I have a complete new set of 5.3 PRC Stg 2.5 heads /w Patriot Gold double valve springs, LS7 lifters and factory low mileage rocker arms / rails that I think should be swapped on the car and i think itll spin at least 7500 rpm no problem. Pro Magnum rockers are VERY heavy over the rocker and they have been adjusting the rockers to "1/4 turn past zero lash" and not the .002-.004 that comp-r's ask for.
Anyone else agree that this should fix the problem and easily give the car the 7500rpm its looking for?
I got it on the dyno yesterday and you hit 65-6600 and the car starts cutting out/missing really bad and they pulled it to 6900 where it sounded like it was floating the valves so bad that im surprised they hadnt hurt something already.
The motor combo is a 292 cubic inch de-stroker that is supposed to go 8000rpm without going over the maximum HP/TQ for the class.
LS6 intake/TB
LG Speced 23x/23x .600'ish lift cam for this setup
Stock LS1 heads /w Comp 918 valve springs
7.5" moly pushrods
Comp-R lifters
Comp Pro-Magnum rocker arms
Everything in the world has been swapped on this car. They listed: plugs/plug gap, plug wires, msd coils/truck/car coils, checked pushrod length,changed to some random double valve spring they couldnt tell me the pressures or details on, geometry, grounds etc etc. They had the car at synergy motorsports for 2 weeks and they said it wasnt mechanical and that it was EFI/ fuel injection related.
I swapped out aftermarket EFI setup back to a factory harness /w factory PCM and got it tuned/running right before we put it on the dyno. It still has the problem at exactly the same RPM
Solution:
I am telling it is valve float. I have a complete new set of 5.3 PRC Stg 2.5 heads /w Patriot Gold double valve springs, LS7 lifters and factory low mileage rocker arms / rails that I think should be swapped on the car and i think itll spin at least 7500 rpm no problem. Pro Magnum rockers are VERY heavy over the rocker and they have been adjusting the rockers to "1/4 turn past zero lash" and not the .002-.004 that comp-r's ask for.
Anyone else agree that this should fix the problem and easily give the car the 7500rpm its looking for?
09-09-2007, 08:42 PM
#2
TECH Senior Member
iTrader: (18)
Join Date: Jun 2002
Location: NW Houston, TX
Posts: 10,036
Likes: 0
Received 0 Likes
on
0 Posts
Comp R's are verry sensitive to pre load. If its an option, have they tried changing the lifters to something else? Also what are they running for valves? Can they get a hold of LS6 valves before the run offs? What about injectors?
09-10-2007, 10:36 AM
#4
On The Tree
iTrader: (2)
Join Date: Jul 2006
Location: Moorpark,Ca
Posts: 146
Likes: 0
Received 0 Likes
on
0 Posts
It's the rockers. I had the same problem with the pro magnum rockers, comp "R", Patriot dual gold's. Shut down at about 6300- 6400 rpm's. I had tried several different pre- load adjustment first, then I replaced the lifters with some lunati's. No change until I threw the stock rockers back in. It was a very expensive lesson. On the dyno the float actually started to show up around 5600 rpm, and started "Barking" at about 6300.
09-10-2007, 11:36 AM
#5
TECH Junkie
iTrader: (2)
Join Date: Jan 2006
Location: Fort Wayne, IN
Posts: 3,776
Likes: 0
Received 0 Likes
on
0 Posts
if you really want to turn this thing to 8000rpms, i might reconsider your valvetrain options.
1. a dual spring for sure 145+lbs. on the seat, 410+lbs. over the nose
2. maybe rethink lifter options, or set perload correctly.
3. shaftmount rockers, if it fits in your budget.
4. lightweight valvetrain components, valves, retainers, etc..
but right now it does sound like a spring issue to me. i would put your dual prc's in it, set you preload corectly and geometry and run it, and see what you come up with. just my 2 cents guys.
1. a dual spring for sure 145+lbs. on the seat, 410+lbs. over the nose
2. maybe rethink lifter options, or set perload correctly.
3. shaftmount rockers, if it fits in your budget.
4. lightweight valvetrain components, valves, retainers, etc..
but right now it does sound like a spring issue to me. i would put your dual prc's in it, set you preload corectly and geometry and run it, and see what you come up with. just my 2 cents guys.
