loose power on high end
 

This may not be the right forum to post this question, but this is where i always go. I have a 1970 4x4 with 71,000 miles original motor. I have had about a year and it looses power at about 65mph especially when I am going into the wind. the motor also starts to clatter a little. I replaced fuel filter, checked timing, and run medium otcane fuel and still the problem exist. Any ideas on what it might be.

Re: loose power on high end
 

Have you looked into your vacuum advance for your timing? Is it hooked up? If so, pull some vacuum on it to make sure it's holding vacuum... Just grasping at straws here...

Re: loose power on high end
 

yea..hook a timing light up..and rev it a bit in and you should see the timing advance to like almost 40....if not,check vacuum diaphram and also check weights in the dist itself. if those are working,id do a compression check of all cylinders...and lastly, with truck off,make sure carb is opening fully,by taking air cleaner off and looking down into carb.butterfly has to be straight up and down,then check the linkage to be sure its opening correctly...ok shot my wad..hope you fix it :)

Re: loose power on high end
 

it may also be a worn cam i had a 64 seemed to run great till i got in high gear then no power pulled valve covers and found valvs to be oppening very little

Re: loose power on high end
 

or weak valve springs too.

Re: loose power on high end
 

What size tires and what gears.There`s more to it,but this info would help get a baseline on the truck.In other words,could make your problem more pronounced.

Re: loose power on high end
 

I am running 33s with stock gears not sure what they are it is a 70 half ton with a 4spd. I put a quadrajet from a 1980 ranch truck that I have just to see if that maid a difference, and it seems to be running better. I think something might of been wrong w/ the old carb.

Re: loose power on high end
 

I had the same problem. It wound up being the distributor shaft bushing was worn so the timing was going out under load.