Diesel Power, Gas Engine
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Junior User
Joined: Nov 2010
Posts: 70
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From: Montana
Diesel Power, Gas Engine
I have an 86 F250 460 4x4 I recently installed a fresh engine. Built the truck for hauling quads, trailers, firewood etc. After a proper break in i loaded my quads on the trucks flatbed and hit the interstate for a 20 mile jaunt to my favorite trail. To my dismay I noticed a serious lack of power when climbing. RPMs just won't come up and I find myself losing top speed. The engine was bored .040 over, heads redone, installed an rv cam with edelbrock performer intake and 750 carb. Runs great otherwise, just was expecting to pull a hill with a load and still have some pedal to spare.
I'm a gas engine guy, don't care what anyone says I don't trust an engine without spark plugs.
I'm a gas engine guy, don't care what anyone says I don't trust an engine without spark plugs.
FTE Legend
Joined: Nov 2015
Posts: 30,912
Likes: 4,123
From: Angier, NC
A few things come to mind and in no order.
What gear ratios are you running and the size tire?
What RPM is the motor turning and at what speed going down the hi way?
What is the RPM range spec. of this RV cam?
What timing chain/gear set did you use and how was it setup?
What exh system are you running from heads out to the tail pipe?
Any 1 or combo or all can kill power but not knowing what you have we cant point you where to look to get more power.
Dave ----
What gear ratios are you running and the size tire?
What RPM is the motor turning and at what speed going down the hi way?
What is the RPM range spec. of this RV cam?
What timing chain/gear set did you use and how was it setup?
What exh system are you running from heads out to the tail pipe?
Any 1 or combo or all can kill power but not knowing what you have we cant point you where to look to get more power.
Dave ----
More Turbo
Joined: May 2008
Posts: 585
Likes: 11
That was the first thing that came to my mind. Stock replacement 460 timing sets have the cam timing retarded so you should use either a '72 or older or a '88 and later fuel injected timing set. Using the original type replacement set for a '86 will really kill your low end torque, especially with a performance cam. Also, where do you have your ignition timing set? Is the advance mechanism connected and working properly?
Thread Starter
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Junior User
Joined: Nov 2010
Posts: 70
Likes: 0
From: Montana
A few things come to mind and in no order.
What gear ratios are you running and the size tire?
What RPM is the motor turning and at what speed going down the hi way?
What is the RPM range spec. of this RV cam?
What timing chain/gear set did you use and how was it setup?
What exh system are you running from heads out to the tail pipe?
Any 1 or combo or all can kill power but not knowing what you have we cant point you where to look to get more power.
Dave ----
What gear ratios are you running and the size tire?
What RPM is the motor turning and at what speed going down the hi way?
What is the RPM range spec. of this RV cam?
What timing chain/gear set did you use and how was it setup?
What exh system are you running from heads out to the tail pipe?
Any 1 or combo or all can kill power but not knowing what you have we cant point you where to look to get more power.
Dave ----
Going 65-70 at 3000rpm on flat road is fine, slightest incline and top speed falls, a give it more throttle the engine starts to stumble.
Unable to get to my cam papers right now so no help there.
Got a cloyes double roller timing set that had 3 keyways in it, a guy I know told me about the retarded timing so I used the advanced timing key per the timing set instructions.
Stock exh manifolds and stock pipes to muffler. Previous owner had a large 2 into 1 muffler installed.
Thread Starter
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Junior User
Joined: Nov 2010
Posts: 70
Likes: 0
From: Montana
That was the first thing that came to my mind. Stock replacement 460 timing sets have the cam timing retarded so you should use either a '72 or older or a '88 and later fuel injected timing set. Using the original type replacement set for a '86 will really kill your low end torque, especially with a performance cam. Also, where do you have your ignition timing set? Is the advance mechanism connected and working properly?
The vacuum advance operates properly.
Posting Guru
Joined: Jul 2015
Posts: 2,239
Likes: 5
From: Northeast Ohio USA
Did you pay as much attention to the transmission and differential(s) as you did to the engine ?
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Joined: Jan 2001
Posts: 56,984
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From: Virginia
That carb should start moaning as you push it to the floor. I don't know how much weight you are pulling, and how steep the hills are, but you should hear something happening under the hood if you have it to the floor and the rpms are up.
The only driving experience I have had with a 460 is a stock 460 efi with a zf 5 speed. Pulling a 40hp tractor on a trailer up route 56 over the mountain to Vesuvius, it had to be shifted down to 3rd gear to make it. It's a pretty steep mountain and that tractor was decent sized.
The only driving experience I have had with a 460 is a stock 460 efi with a zf 5 speed. Pulling a 40hp tractor on a trailer up route 56 over the mountain to Vesuvius, it had to be shifted down to 3rd gear to make it. It's a pretty steep mountain and that tractor was decent sized.
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From: Denver Metro Area, CO
retarded
straight-up
advanced
Thread Starter
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Junior User
Joined: Nov 2010
Posts: 70
Likes: 0
From: Montana
Apologies that didn't come out right. The timing set had 3 key ways, one straight up (middle) one to retard timing (left) and one to advance timing (right). I used the key that advanced the timing to improve torque.
Thread Starter
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Junior User
Joined: Nov 2010
Posts: 70
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From: Montana
As I said earlier the drivetrain is all original, so to answer your question: no I didn't pay any attn to transmission and differentials. What would you suggest I look into?
Junior User
Joined: Nov 2013
Posts: 58
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From: Cle elum, Wa
For your gear ratio, look on the VIN sticker where it says "axle".
39=3.55
35=4.10
Have you checked fuel pressure and float levels?
What kind of oil are you using? It needs to have at least 1,500ppm ZDDP (zinc) to prevent the lifters from eating the cam.
39=3.55
35=4.10
Have you checked fuel pressure and float levels?
What kind of oil are you using? It needs to have at least 1,500ppm ZDDP (zinc) to prevent the lifters from eating the cam.
FTE Legend
Joined: Nov 2015
Posts: 30,912
Likes: 4,123
From: Angier, NC
Not sure on gear ratio other than its stock for an ext. cab xlt lariat, T19 4spd (no granny) with 235/85/16 tires on factory rims.
Going 65-70 at 3000rpm on flat road is fine, slightest incline and top speed falls, a give it more throttle the engine starts to stumble.
Unable to get to my cam papers right now so no help there.
Got a cloyes double roller timing set that had 3 keyways in it, a guy I know told me about the retarded timing so I used the advanced timing key per the timing set instructions.
Stock exh manifolds and stock pipes to muffler. Previous owner had a large 2 into 1 muffler installed.
Going 65-70 at 3000rpm on flat road is fine, slightest incline and top speed falls, a give it more throttle the engine starts to stumble.
Unable to get to my cam papers right now so no help there.
Got a cloyes double roller timing set that had 3 keyways in it, a guy I know told me about the retarded timing so I used the advanced timing key per the timing set instructions.
Stock exh manifolds and stock pipes to muffler. Previous owner had a large 2 into 1 muffler installed.
Now with the 3000 RPM at 65-70 speed it is hard for "me" to know if you have an over drive trany or the rear gear giving you that speed/RPM reading?
I also don't know why you have the issues you have?
Dave ----
Senior User
Joined: May 2009
Posts: 363
Likes: 0
I thought the T19 was an up graded T18 that has a granny low that is synchronized?
Now with the 3000 RPM at 65-70 speed it is hard for "me" to know if you have an over drive trany or the rear gear giving you that speed/RPM reading?
I also don't know why you have the issues you have?
Dave ----
Now with the 3000 RPM at 65-70 speed it is hard for "me" to know if you have an over drive trany or the rear gear giving you that speed/RPM reading?
I also don't know why you have the issues you have?
Dave ----