hi guys
i have stock GM 2.02 angle plug heads.they have SINGLE 1.250 od and .885 id valve springs in them.
i "had" ALUMINUM [ya thats right,i didnt know any better]retainers on the valve springs.
it has a 223 dur/480 lift hyd cam.

someone else built the heads 2 years ago and i didnt get all the particulars from him,so i know very little about the heads.[ya i know ..stupid!]

i just changed the aluminum retainers to comp cams steel retainers.
i also put on comp cams roller tipped rockers.1.5 ratio.
we checked push rod length and put 100 thou longer pushrods in.
we checked for rocker arm clearance on the rocker studs [sort of] but with this lift cam i would not expect interferance there???

we left the springs that were in it.[dont know what they are]

before the retainer and rocker arm swap i had no problem reving the motor to 6500 rpm [even 6800 a couple times by accident]
it pulled hard and fast, did not skip a beat.

i use the car for summer driving and i race it about 4 times a summer.

NOW the engine goes into valve float at anything over 5500 to 5800 rpm.
my 1/4 mile times went from 13.6 to 14.0!!!!! arrgh...[i got beat by my buddys mopar!!!!the shame!!! LOL!]

DOES ANY ONE KNOW WHAT HAPPEND HERE??

i'm going to change the springs to possibly a comp cams 941 spring.normally the comp cams book recommends a 981 spring for all there 480 lift cams [for the most part]but i want to make sure i have a real good spring in there to eliminate valve float.
the comp cams book says that you should not go over a 350lb spring with most of there 480 lift cams. they do not say why.
i dont have the comp cams book now i borrowed it and cant remember what the spring pressure is for a 941 spring.will there be a problem if i go over a 350lb spring?

IF I USE A 941 SPRING WILL I HAVE A PROBLEM??will it fix my valve float and revving problem? what other spring do you guys recommend?

[This message has been edited by z/27 camaro (edited 07-08-2002).]

When you swapped retainers you probably did not check the installed ht. or seat pressure. You need to do that, end of story.

You probably have more than enough spring but the installed ht is too high and the seat pressure/nose pressure is too low IMHO. Get your hands on a Rimac valve spring testing machine or use a bathroom scale and a hydraulic press but verify the spring constant (#/inch deflection) for the springs you have and set the springs up to provide the correct seat pressure and you will be back "on cam" in no time.

-Mark.

not disagreeing with mark.........but a few more opinions would be nice??
[i know i was a little long winded...LOL!]

mark.......no i didnt check the installed hight....but the aluminum and the steel retainers looked about the same thickness. i would think the retainer thickness would be constant no matter what you have on there?? i could be wrong?
we used the same shims that were already there.

------------------
69 Camaro RS/SS 350.
GM 2.02 angle plug heads.
223 dur/480 lift hyd cam.
69 z/28 alum high rise.
69 z/28 780 vac sec holly carb.
4 bolt mains,steel crank,forged flat top pistons.
Turbo 350 2800 stall with shift kit.
3:73 12 bolt posi.
functional cowl induction & ZL2 hood

[This message has been edited by z/27 camaro (edited 07-08-2002).]

Not all retainers are created equal.

The only way to know for sure is to check the before and after installed height and make adjustments as necessary.

If the system was on the edge of valve float with the aluminum retainers then the heavier steel versions may be the culprit. In either case the open and seat spring pressures should also be checked against the camshaft manufacturers recommendations.

Valvetrains must be viewed as a system. Changing one thing can have an effect on the whole.

------------------
The Red Beast http://www.geocities.com/casanoc

[This message has been edited by CarlC (edited 07-08-2002).]

Actualy, different retainers and keepers will affect the installed ht. There are higher retainers and lower retainers, even lash caps for the realy high retainers. Different keepers to adjust installed ht as well. Thickness is not everything http://www.camaros.net/forum/wink.gif Typical installed ht for small blocks is like 1.875 - 1.8 is common but you realy need to know what seat pressure you have.

-Mark.

With different pushrods you should also check rocker tip wipe across the valve stem. This should be centered across the tip (of stem), if not buy an adjustable rod and get it centered, then check length and obtain correct length pushrods.

------------------
Steve

What cam is that...223/.480?...it breaks the 47.5% rule for flat tap hydraulic. Could be a source of some of your troubles. Just curious.

whats the 47.5% rule???

its actually a dual pattern cam 223 intake @50 471 lift and 321 exaust @50 480 lift at 108 lobe seperation.
it was specialy ground for my appliction i'm told.....so no a no name. i'm told a lot of circle track racers use this grind now???

the car performed REALLY well until i chAnged the retainers and rockers so i doubt its the cam specs.

------------------
69 Camaro RS/SS 350.
GM 2.02 angle plug heads.
223 dur/480 lift hyd cam.
69 z/28 alum high rise.
69 z/28 780 vac sec holly carb.
4 bolt mains,steel crank,forged flat top pistons.
Turbo 350 2800 stall with shift kit.
3:73 12 bolt posi.
functional cowl induction & ZL2 hood

I see... you were quoting the intake's duration and the exhuaust's lift.

The 47.5% rule was explained to me by a tech guy at Isky Cams. I had never heard of it either, but I assumed it was common knowledge.

The 47.5% rule applies to flat tappet cams for chevy sb's with 1.5 rockers. The duration at .50 must exceed 47.5% of the total valve lift or your asking valve train problems according to the boys at Isky. For instance, take a Comp Cams Magnum 280H, with 230 duration and, 480 lift...230/.480 = 47.9% which exceeds 47.5% and would not pose a threat to components. Some of the Comp Cams XE dual pattern lobes break this rule, on the intake side. Some complain these cams are 'loud'...even as loud as solid lift cams (do a search to uncover a few XE users who have experienced this). Perhaps the boys at Isky are right.

Fyi