Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Skip White Heads BBC
View Single Post
  #141 (permalink)  
Old 06-04-2019, 10:50 AM
ericnova72's Avatar
ericnova72 ericnova72 is online now
More for Less Racer
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 53
Posts: 17,987
Wiki Edits: 0

Thanks: 280
Thanked 3,330 Times in 2,789 Posts
Higher compression is used to offset the low end power lost to reverse pumping/late intake closing...but at the same time also helps top end due to the added squeeze also making up for less cylinder filling due to less time available to fill the cylinder the higher the rpm goes.

I just noticed you mentioned having lost 2 to 3 tenths in the 60 foot the last time at the track...if that is correct it equals 2.5 to 4 tenths in the 1/8 mile and 3.5 to as much as 5 tenths in the 1/4 mile. What is lost in the 60 really badly affects the overall time.

Have you done timing changes at the track?? Reason I ask is I've had a couple of friends do the "twist the distributor and time it by ear and how good it feels" out front of the house the day before a track outing.....then get to the track and find a major chunk of ET has been lost. Worst one was a mid 12 second 1/4 mile 351 Cleveland 4V head powered Mustang, Dude timed it by how powerful it felt out in front of the house only to have it run a 13.60 the next day, a more than 1 second loss.
What you lose from mid rpm and up more than offsets the great feel of how overadvanced timing feels in low gear.
I'm wondering if you aren't also being fooled by the "butt dyno" and have the timing overadvanced and killing what the car is capable of. The midrange and up loss is almost impossible to feel while the low end boost from a lot of timing is easily felt and that can really fool you.

Io just have the feeling there are a couple of not obvious things hiding in there holding you isn't the slight compression loss
Reply With Quote