engine rpm trouble

[lpd1]

we ran are engine over the weekend and we only turned 7200 with a 6:13 gear so we put a 6.21 still turned 7200 so we put a 6.30 still turned 7200 the only thing i could tell that it came to life quicker but quit pulling quickly, so i think the valve springs are to weak?? is that what you guys think? i know they are a weaker spring than we normaly run? dave

[Matt49]

Not completely out of the question if the track was slowing down and your driver was slowing down properly with it (by not wheel spinning).
Leave the 6.30 in it and see what it does next time out in hot laps when the track has hella' grip.
Or you could have a problem with your tach.

[lpd1]

thats matt49, i really thinks its the valve springs i was driving and it takes off like it means busines but it just quit pulling, the track was blowing dust and i was wide open off the corner and down the straights, i was watching the tach it was usally 6200 off the corner and down straight at 7 grand.?? how much more spring pressure do you need or how much rpms would you gain with about 30 lbs more spring pressure?? thanks

[Matt49]

I'm no motor expert...hell I'm no expert on anything...but valve float could certainly limit your top end. Sorry I can't tell you how much more seat pressure will help you.

[MasterSbilt_Racer]

Could be valve springs, could be cam issue, could be lots of things.

I had a similar problem once and the secondaries were not opening up on the carb. I couldn't figure out why the rpms were staying down. I went from a 6.21 to a 6.78.

[lovinlatemodels]

Check your valve lash see if has changed much. If not for the price of a few gaskets i would pull the heads and have the valve springs check. If they are brand new with a couple races on them i have seen them settle in and mite need reshimed to get back to pressure. It's cheaper then floating another week having the piston hit the valve it can get really expensive quickly.