Thread: upper rpm question

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hello i have a 402 freshly built with a lunati cam 578 int 582 ext stock hei 750 elderbrock carb and the problem is it runs very strong up to 4700 rpm then it acts like it has a rev limiter it misses from all cylinders when it goes below 4700 it runs great again i had the heads redone before i built it any ideas thanks

What valve springs are you running? Sounds like it could be getting into valve float.

Another thought is how good is the HEI, I've seen them give up around 5500, if it's not tip top that could be a place to look.

did you build the motor or have it done? What ignition box are you running?

i had a MSD box do me that way ..made me change a whole lot of unnessarary stuff

i built it not the first one but is for this problem im running a stock hei but ti ran fine on my small block. the machine said the springs were good but i wonder how well they checked them it just seems like its allfull low rpm for valve float but it is very possible thank you