underpowered 300 L6
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From: Lewistown, PA
underpowered 300 L6
I just bought a '77 F-150 3 weeks ago. The truck is in very good condition and is original. It has a 300 inline six w/ a np435 tranny/np205 Xcase. the man i bought it from owned it for 22 years and told me he rebuilt the engine 8-10 years ago and put about 23,000 miles on it. My promblem is it seems to be underpowered. It is suppose to have .030 overbore and an Rv cam. I put 31x10.5 on and it drives fine till i have to pull a mountain. 45mph is about all she'll do. does anyone have any ideas what may be wrong? i've always believed that this engine to have more power than this. any help would be greatly appreciated.
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From: spartanburg, SC
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From: Chicago
Well my first question is "till i have to pull a mountain" what exactly is that. If it's a really heavy trailer and with your 4x4 that might not be to bad going up a grade.
From what i have read on this site the 300 I6 has about 150 hp/260 ft lbs in stock form so if your pulling a mountain of a trailer 45 mph might be ok. I’m not sure what a “RV Cam” really does for power numbers, but I’m sure it’s not to far from the 150 mark.
If your trans or clutch is slipping that might explain the slow tow speed. Or if the truck is geared poorly that could explain the slow pulling speed.
One more thing that most people never think of when towing is the trailer brakes could be out of adjustment and be causing a slight drag it's a problem in 18 wheelers some times.
From what i have read on this site the 300 I6 has about 150 hp/260 ft lbs in stock form so if your pulling a mountain of a trailer 45 mph might be ok. I’m not sure what a “RV Cam” really does for power numbers, but I’m sure it’s not to far from the 150 mark.
If your trans or clutch is slipping that might explain the slow tow speed. Or if the truck is geared poorly that could explain the slow pulling speed.
One more thing that most people never think of when towing is the trailer brakes could be out of adjustment and be causing a slight drag it's a problem in 18 wheelers some times.
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Joined: Apr 2004
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From: Lewistown, PA
Thank you Phrogman 46 for those Hp & torque numbers. what i ment by "pulling a mountain" was simply driving up the mountain. here in Pa we have some steep grades. I will check on my gearing in the rear end. Although it does hold itself going down the other side of the same mountain.
