Stock tune runability with modifications
Thread Starter
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5th Wheeling
Joined: Dec 2020
Posts: 43
Likes: 2
From: Cumming, Ga
Stock tune runability with modifications
Hey all,
so I’m having some runability issues with my motor rebuild hopefully someone has some insight for me. Here is the basic rundown I’ll keep it quick and to the point: (all emissions components have been thrown in the trash)
351w full rebuilt with gt40p heads milled down to a CR of 10.2:1 with a comp 35-512-8 cam, it’s a .480 lift cam if I don’t have that part number right+ scorpion full roller rockers. Stuck with the stock intake manifold for now. Before anyone recommends I get it chipped or aftermarket efi. I will install it just wasn’t in the initial budget. First couple days the truck ran ok, about as good as u can expect for the stock tune with so many modifications. After that at random it does not want to rev past 1500-2000 rpm or it is very difficult to get over that rpm. It only responds to very light throttle input anytime I give it more than a touch of throttle it just falls on its face (I have 93 octane in the tank right now)? Not sure what to investigate first. Is it related to the stock computer going into a limp mode or something of the sort trying to figure out what the engine is doing? Should I get an obd1 scanner and check the codes?
so I’m having some runability issues with my motor rebuild hopefully someone has some insight for me. Here is the basic rundown I’ll keep it quick and to the point: (all emissions components have been thrown in the trash)
351w full rebuilt with gt40p heads milled down to a CR of 10.2:1 with a comp 35-512-8 cam, it’s a .480 lift cam if I don’t have that part number right+ scorpion full roller rockers. Stuck with the stock intake manifold for now. Before anyone recommends I get it chipped or aftermarket efi. I will install it just wasn’t in the initial budget. First couple days the truck ran ok, about as good as u can expect for the stock tune with so many modifications. After that at random it does not want to rev past 1500-2000 rpm or it is very difficult to get over that rpm. It only responds to very light throttle input anytime I give it more than a touch of throttle it just falls on its face (I have 93 octane in the tank right now)? Not sure what to investigate first. Is it related to the stock computer going into a limp mode or something of the sort trying to figure out what the engine is doing? Should I get an obd1 scanner and check the codes?
Thread Starter
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5th Wheeling
Joined: Dec 2020
Posts: 43
Likes: 2
From: Cumming, Ga
Ok I got the codes read on the truck today. To answer your questions: I do not have a fuel pressure gauge installed sounds like I should consider installing one.
R&RFord wish I could tell you the base timing but all the numbers on the harmonic balancer are worn off which I didn’t discover til final assembly. I just set it where it was smoothest then retarded it a touch.
CODES (current): 327, 552, 565, 118
these are all emissions related codes so they don’t seem to help me much. Except code 118. I have a 160 thermostat for the initial run in but I’m about to pop in a 180. Does the temp of the engine affect how much fuel is injected per the computer?
R&RFord wish I could tell you the base timing but all the numbers on the harmonic balancer are worn off which I didn’t discover til final assembly. I just set it where it was smoothest then retarded it a touch.
CODES (current): 327, 552, 565, 118
these are all emissions related codes so they don’t seem to help me much. Except code 118. I have a 160 thermostat for the initial run in but I’m about to pop in a 180. Does the temp of the engine affect how much fuel is injected per the computer?
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Cargo Master
Joined: Nov 2009
Posts: 2,190
Likes: 620
Ok I got the codes read on the truck today. To answer your questions: I do not have a fuel pressure gauge installed sounds like I should consider installing one.
R&RFord wish I could tell you the base timing but all the numbers on the harmonic balancer are worn off which I didn’t discover til final assembly. I just set it where it was smoothest then retarded it a touch.
CODES (current): 327, 552, 565, 118
these are all emissions related codes so they don’t seem to help me much. Except code 118. I have a 160 thermostat for the initial run in but I’m about to pop in a 180. Does the temp of the engine affect how much fuel is injected per the computer?
R&RFord wish I could tell you the base timing but all the numbers on the harmonic balancer are worn off which I didn’t discover til final assembly. I just set it where it was smoothest then retarded it a touch.
CODES (current): 327, 552, 565, 118
these are all emissions related codes so they don’t seem to help me much. Except code 118. I have a 160 thermostat for the initial run in but I’m about to pop in a 180. Does the temp of the engine affect how much fuel is injected per the computer?
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Cargo Master
Joined: Mar 2010
Posts: 3,331
Likes: 292
From: Laramie, WY
You don't necessarily need to install a fuel pressure gauge. What you need to do if figure out if you have specified fuel pressure when the issues arise.
Replace that harmonic balancer and time it to 10 degrees BTDC. I would start here myself. My truck runs smoothly at idle at all kinds of interesting base timing settings, but then no good under load outside of a few degree window.
If the engine isn't at operating temp, the PCM may keep the engine in open loop mode, where it ignores the oxygen sensor data and goes off preprogrammed fueling (on the rich side). It should still run reasonably well though, just a little on the rich side & get crap fuel economy.
Replace that harmonic balancer and time it to 10 degrees BTDC. I would start here myself. My truck runs smoothly at idle at all kinds of interesting base timing settings, but then no good under load outside of a few degree window.
If the engine isn't at operating temp, the PCM may keep the engine in open loop mode, where it ignores the oxygen sensor data and goes off preprogrammed fueling (on the rich side). It should still run reasonably well though, just a little on the rich side & get crap fuel economy.
Laughing Gas
Joined: Dec 2005
Posts: 904
Likes: 115
From: Laurel, MS
As others have said, you really need to start by verifying your timing. You can either replace your harmonic balancer or find and mark TDC using this method. (He's showing how to do it on a Chevy V8, but the principal is the same.)
Logistics Pro
Joined: Aug 2014
Posts: 3,559
Likes: 852
My initial thought was cam timing being out, but then you never set the base timing?
You must set to 10 WITH SPOUT removed.
If you don't the stock EEC will think it is at 10.
With the lack of power you are saying, I'd say its retarded, advance it. If it pings, you've gone too far.
Once your base timing is set, should be good. If not, recheck your cam timing.
You must set to 10 WITH SPOUT removed.
If you don't the stock EEC will think it is at 10.
With the lack of power you are saying, I'd say its retarded, advance it. If it pings, you've gone too far.
Once your base timing is set, should be good. If not, recheck your cam timing.
Thread Starter
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5th Wheeling
Joined: Dec 2020
Posts: 43
Likes: 2
From: Cumming, Ga
Ok that’s a good copy on the all the timing related comments fellas. I’ll get a piston stop ordered to confirm the timing but I will tell y’all right now this is a computer/tune issue and I have already adjusted the timing time and time again incrementally to get it right. This is how it goes: first few minutes down the road runs fine (bout as good as can be for stock tune) after that power starts seriously lacking can’t get the motor over 2000 rpm. But if I stop and turn the truck off and fire it back up it goes back to running fine. Any Ford ecu experts on here maybe that have a good idea?
I appreciate any input yall I know I’m probably beatin a dead horse at this point
I appreciate any input yall I know I’m probably beatin a dead horse at this point
Logistics Pro
Joined: Aug 2014
Posts: 3,559
Likes: 852
What EEC are you running?
Where are your O2 sensor(s) located? Headers or stock manifolds?
What lbs injectors you running?
Is the throttle plate opening all the way when you put your foot down?
Hows your exhaust, catalytic converter, muffler, open pipe, full duel back to truck?
I doubt it is the EEC, could be, but I don't think so.
I run the 35-510-8 in a stock EEC, the only issue I have is a bit of a hunting idle.
Where are your O2 sensor(s) located? Headers or stock manifolds?
What lbs injectors you running?
Is the throttle plate opening all the way when you put your foot down?
Hows your exhaust, catalytic converter, muffler, open pipe, full duel back to truck?
I doubt it is the EEC, could be, but I don't think so.
I run the 35-510-8 in a stock EEC, the only issue I have is a bit of a hunting idle.