Valve Float at 5600 rpm

[Sebastian_98XJ]

I’m having valve float problems with my 4.0 build
Currently running clegg stage 3 cam (219/225@ .050, 0.480/0.480 valve lift) with Mopar valve springs P5249464, adjustable 1.6 roller rockers and stock length pushrods. Engine is a stock 4.0 with 80K miles.
I’ve read in the forum that mopar valve springs would hold up to 0.525” lift, so I don’t know whats the problem. It runs pretty good to 5.500 rpm but starts to float at 5.600 rpm.

Maybe springs are too soft? Bad lift pre load adjustment? If the valve springs arte too soft, what valve springs would work in the stock head and stock valves?

[Russ Pottenger]

I may be wrong, but I’m guessing you’re still running the stock Pushrods.
Double check the Lifter preload, but I would suggest upgrading to a 9.600 .080w 5/16 Chrome Moly Pushrod.

[Sebastian_98XJ]

I may be wrong, but I’m guessing you’re still running the stock Pushrods.
Double check the Lifter preload, but I would suggest upgrading to a 9.600 .080w 5/16 Chrome Moly Pushrod.

Sorry. Forgot to mention that the engine have chrome moly pushrods. The roller rockers kit came with pushrod and aluminum valve cover (TD motion)

[Sebastian_98XJ]

So I was checking my datalog in HPTuners and valve float was ocurring at 5450 rpm. I adjusted preload to 1/2 turn and now runs good up to 5600 rpm and sometimes hits 5700 rpm. Anyway I set the rev limiter to 5550 rpm.

On friday I went to the dyno and made 227whp @5300 rpm and 251 ft-lb @4500 rpm (+34hp and +8ft-lb from stock 4.0. Graph is off by 200 rpm).
Pretty good numbers for a 4.0. Not much gain of peak torque but the area under the curve is a lot after 4000 rpm . Next upragde i'm going to port a 7120 head and put LS1 valves to maybe pass 230whp.

227 whp.jpeg

[Cheromaniac]

Those are impressive numbers for a 4.0.

[Russ Pottenger]

If you’re interested and would like information and pricing on my ported LS valve 7120 head feel free to shoot me an email.


Russ Pottenger
Bishop-Buehl Racing Engines
531 N. Lyall Avenue
West Covina, California 91790
Cell (626) 673-2203
Email: [email protected]