Box Stock

Limiting valve float? & Dumb q's

C

-Chip

Member
I built a predator for my yard kart that I play around with. It's not for racing or anything, mainly just for learning about engines. I've started getting valve float (no contact with piston though) and want to fix this problem. The easy and correct answer if PROBABLY change the gearing but I wanted to get some other opinions. Anyways, these is how it is built.

-predator 212 block non-hemi
-dyno cams CM .265 cam
-stamped 1.3 rockers (I know....)
-decent port and polish
-arc billet flywheel
-arc +.020" billet rod
-flat top hemi piston
-Chikuni "vm22" carb
-.009" head gasket (.035" piston to head)
-milled head to get .135" pv clearance
-22# valve springs
-lightly reground valves to verify uniform seating
-stock valve train
-no governor obviously
-homemade exhaust with ttr125 muffler (maybe too large?)
I top out right at 42mph with my current gearing. Its a 12tooth really crappy/cheap clutch from Amazon and the sprocket that came on the frame (I haven't counted the teeth)

I have a set of 26# springs that do not bind but understand that these will exceed the limitations of what the stock valve train should withstand. Is there anything else I can do to limit valve float besides springs, regearing or adding a governor?

If I do need to go to heavier springs, and therefore need new valves & pushrods (a good opportunity to correct some valve train geometry) is there a recommended weight to get the most out of my build?

Also where else can I find improvements in this motor, ie. e85, different cam, different carb, something I don't even know of???? This is my first build and it has been a fantastic learning process.

Thank you!!!
 
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A few things you could do .
Lighter valve train components . From the lifter through too the valve including rockers .
I believe ratio rockers require more spring pressure . If you go too 1/1 rockers it may rpm better .
Install the 26#springs and test the limits of the components .
 
I don't have a tach on this one. I'll get one installed tomorrow and see what it's saying. It's screaming when it starts to float though. I'm blown away with what kind of power you can wring out of these engines.

As far as lightening the valve train, I have some aluminum keepers that came with the 26# springs. What else is there besides that and lightweight rockers?
 
-Chip said:
I don't have a tach on this one. I'll get one installed tomorrow and see what it's saying. It's screaming when it starts to float though. I'm blown away with what kind of power you can wring out of these engines.

As far as lightening the valve train, I have some aluminum keepers that came with the 26# springs. What else is there besides that and lightweight rockers?
Click to expand...
i would not go anywhere near a aluminum retainer/keeper
 
@DynoDon got the tach on tonight. It's a really cheap one so I don't have a ton of faith in it's accuracy. I stopped and checked my max rpm's when I first heard a hint of valve float. It was 7440. When I was done riding it said my max was 7930 and I definitely floated them a little more. There are no signs of contact on my piston.
 
Pretty significant and sudden tone change. It gets louder, almost sharper sounding pops that are more distinct (not like backfires) and feels like the power falls off. Plus 2 other people that have ridden it said the valves were floating.
 
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According to Dyno cams the target is 7500 rpm. with 21 lb springs. Without ratio rockers!!!
If this is the cam you have

DJ-1110 Dyno "Super Box" CM Cam​

Is that the cam you have??

I have always liked either the F200 275 lift or the 308. But with the ratio rockers the 308 might be a little much. You might even try the 308 without the ratio rockers. It is a very good cam and will go up into the 8000s without any trouble. Also Might try a bigger carb or a WX 304 tilly. That will put a huge punch in the engine.
I saw meracer9 had one for sale the other day??
And 7,700 rpm at 42 mph. need larger front gear or smaller rear. gear. That engine should pull you faster. What dia tires are you running.
 
My cam is the "CL-CM-PRED" so basically the dj1110 but with 2* more timing which matches my flywheel.... Not that it matters for this discussion. I'm shopping for a new clutch right now and was thinking of getting a 15t which should help I imagine. My rear tires are 11". It might be too much but what about the P-open cam???
 
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You could try honing the valve guides for more oil clearance and reaming out the intake valve seal so it isn't sticky. That will allow the valves to respond a tad quicker.
 
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