c6 wont go over 4000 rpm

i just got a 66 f100 with a carbed 90's h.o.302 and a c6. the problem is that the trans wont over 4k, i already turned the vacuum mod in some and it shifts later than it did but it still wont go over 4k at w.o.t.
i am a retard when it comes to auto trans so any ideas would help alot. it does shift nice and solid both times its just at w.o.t. that has the issue.


thanks,
jeff

 

Make sure the detent linkage rod from the carb to the trans is pushed to the bottom when the carb is at WOT. If that is OK then pull the vac modulator & lengthen the rod about 1/8 in. Put it together, drive it & shorten the rod until it shifts at what you think is the right RPM.

 

I can't speak for a C6 but on a C4, try wiring the kick down lever back, and see if that helps. When I put a 4bbl on my 71 Maverick, with the kick down wired back (because there was no provision for the rod on the carb) It would shift out of first at 70 if I kept my foot in it. The was with 279 gears and D70 14 tires. I didn't have a tack, but I don't think it was winding to it's limits for a fairly stock 302.
Another thing is what sort of manafold you are using. If there is no crossover area under the carb on a 180 degree stock type intake, it will pull a higher vacuum. On the same engine and trans, I put the 2bbl back on with 2 carb spacers and opened them up some. It still shifted about the same, and power wise it was almost as strong as the 4bbl. When I added the original kick down rod, the shift points dropped some, to a more normal level.

 

thanks, i will mess with the kick down in the morning. the truck does have a new holley and a new eddlebrock performer intake, and i did see on carb that the kickdownd was kinda hokey.

 

did you figure it out jeff?

 

still nothin, going to try swapin the vac mod and see if that does anything