got a question, for Jake Raby Options

[bd1308]

you said in a previous post that one should not go below 3500RPM in 5th gear, as the airflow is not sufficient enough for proper cooling.

i have some problems with this....

1) in my car, at 70mph, I am around 3200RPM in 5th...sometimes i am even running 3000RPM and occasionally run even 2800RPM for short periods of time. Are you suggesting that I should not shift into 5th gear at all?

2)I have also heard that the type 4 cooling fan efficiency goes down after around 4000RPM....it was mentioned by someone on this board, but the user name escapes me. Is this true?

I tried running 75 in 4th gear and I was running more than 4000RPM.....

I think i am missing something....

[grantsfo]

Is your speedo correct? If it is you have some damn tall tires on that car. I think the biggest thing you have to watch is engine load below 3500 rpm. If you were doing 60 on a slight grade in 5th I would shift up. If you were cruising on flat or downhill 5th at 3000 rpm + should be fine. If it was a real hot day with a lot of heat radiating off the pavement it might be a good idea to shift into 4th.

I have close to 400,000 miles on these engines and have never had to tear into one yet for overheating using the principles above.