Engine '88 GT Has No Power Above 3000 RPM After Trick Flow 11r Heads Install

jrichker

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Kind of at a stand still now. We just replaced the FPR and Fuel Filter to try and fix the fuel pressure issue as we did not find any of the lines to be kinked or torn. There is a tiny screw at the top of the FRP that we were able to screw in and out to adjust the fuel pressure, but that did not seem to help either. I'm going to order a 190 lph fuel pump as a last resort, but at this point we're out of ideas. I linked two videos to show what is happening with the fuel pressure and at WOT.

Pull at WOT - View: https://www.youtube.com/watch?v=1rVZGYcKATU

Fuel Pressure Test - View: https://www.youtube.com/watch?v=4btsm8hD6bo


Fuel pump pressure & regulator test

Check fuel pressure:
The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.
Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.
Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.
Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.
Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

Fuel pump pressure test
Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground.



Caution!!! You have blocked the return line for the fuel pump! Pressure will rise very quickly past safe levels with a good pump
If the pressure goes up past 55 PSI, the pump is good and the fuel pressure regulator is bad. If the fuel pressure does not hit 55 PSI or more in a few seconds, the pump is bad or you have electrical problems.
 
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a91what

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Please set base timing at 10*
The 11r heads dont like much advance, in fact 28* was the point the cars nose over on pump gas, it's a much better chamber.

I need to know what the fuel was at.
How much timing does the tuner have in it?
When possible check compression.
How old is the ignition system? Have you check the cap and rotor?

Do the above before driving the car again.
 

JRerecich

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Please set base timing at 10*
The 11r heads dont like much advance, in fact 28* was the point the cars nose over on pump gas, it's a much better chamber.

I need to know what the fuel was at.
How much timing does the tuner have in it?
When possible check compression.
How old is the ignition system? Have you check the cap and rotor?

Do the above before driving the car again.
The fuel pressure? After just replacing the fpr it sits around 40 psi with vacuum line off and plugged and around 35 psi with vac line on at idle. As shown in the video above, pressure would not increase past 40 psi while revving it up as the car immediately started backfiring at 4.5k rpm. We set base timing to 14* btdc. Tuner just verified that was accurate. It has a brand new msd billet distributor with auto lite spark plugs and new spark plug wires. Fuel tank is dropped ready for new fuel pump to come in before we drive it again.
 

General karthief

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I would do the compression test before driving it, also back that timing up like mentioned.
That pressure gauge jumping around when it starts acting up could mean something.
 

JRerecich

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I would do the compression test before driving it, also back that timing up like mentioned.
That pressure gauge jumping around when it starts acting up could mean something.
Any reason I can't do a compression test with the fuel tank off and lines unhooked? If not, ill try and do that tomorrow. Hopefully replacing the fuel pump will fix the pressure bouncing around like that.
 

General karthief

wonder how much it would cost to ship you a pair
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You can do it with the tank removed.
Should be done with the engine warm but I'm thinking you have a valve or timing issue.
I would be rev'n it up till you verify some stuff.
 

GalacticPonage

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Had a very similar issue recently. The timing wasn’t advancing under load and it was staying around the base timing. Mines an auto so it’s pretty easy to put it in drive and load it up with someone under the hood watching the timing marks. Never figured out what part exactly was causing this but I replaced the distributor, tfi and coil all together and it fixed it.
 

GalacticPonage

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I’d swap the distributor out for a known working stock one if you have one just to see. It’s pretty common for MSD parts to be faulty right out of the box. Also your fuel pressure is good if it’s staying in the 36-40 ish range all the time. Its supposed to move under changing engine demand that’s why it’s vacuum referenced. Have you checked the plugs after running it like this? They should be able to tell you right away if it’s a fuel or compression problem.
 

JRerecich

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I’d swap the distributor out for a known working stock one if you have one just to see. It’s pretty common for MSD parts to be faulty right out of the box. Also your fuel pressure is good if it’s staying in the 36-40 ish range all the time. Its supposed to move under changing engine demand that’s why it’s vacuum referenced. Have you checked the plugs after running it like this? They should be able to tell you right away if it’s a fuel or compression problem.
Unfortunately, we welded a socket on our stock distributor so we could prime the rockers with oil. Just because the fuel pressure is good, could I still be getting insufficient fuel volume? We pulled all the spark plugs Friday and probably 6/8 had white tips which was, I'm assuming, caused by a lean condition.
 

GalacticPonage

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Unfortunately, we welded a socket on our stock distributor so we could prime the rockers with oil. Just because the fuel pressure is good, could I still be getting insufficient fuel volume? We pulled all the spark plugs Friday and probably 6/8 had white tips which was, I'm assuming, caused by a lean condition.

Yeah it could definitely just be leaning out. Since fuel pressure at the rail is good it could be injectors or more likely the tune. The easy check would be to pull the chip from the ecu and have it run on the stock fuel map and see if it stops. As long as the MAF is “calibrated” for the injectors I’d imagine that it would run okay for testing purposes
 

a91what

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Set the base timing at 10* I will not repeat myself or keep helping if I am ignored. I tune these cars all the time, we can do this methodically or you can continue to randomly guess. Find the answers to my questions in my previous post so we can fix the problem.

The fuel is the AFR the tuner is commanding.
 

John Dirks Jr

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You said in a previous post that the fuel pressure won’t increase past 40psi under throttle load. That is normal. Its like this. You set the pressure with the regulator screw to 40psi as you did. This is a fine number. You do this with the vacuum line disconnected. The 40psi is the maximum pressure the system will ever see. When the vacuum line is connected, the pressure drops because at idle, there’s a high vacuum signal. When you hammer the throttle the vacuum drops really low, basically creating the same condition as a disconnected vacuum line.

So, if you set FP at 40 with vac line off, by design it correctly would never go above that.

Fuel pressure is not the major thing that controls how much gas gets in under various loads. Its injector pulse (how fast the injector nozzle opens and closes. That process is controlled by the ECU which decides the conditions by getting info from sensors like MAF , TPS, o2...etc...
 

GalacticPonage

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Set the base timing at 10* I will not repeat myself or keep helping if I am ignored. I tune these cars all the time, we can do this methodically or you can continue to randomly guess. Find the answers to my questions in my previous post so we can fix the problem.

The fuel is the AFR the tuner is commanding.

The op said it was a stock ecu with a chip and he’s not running a wideband. The fuel is not dependent on the narrowband reading at WOT in this setup. He said it was tuned and ran well with that cam before so he would know what to have base timing at for it to work. Also he posted here for everyone’s opinion not just yours so don’t get the panties in a bunch if he didn’t reply to your questions from 12 hours ago lol
 

a91what

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Ok, so I take it you know then that the base timing adds to the curve in the ECU then yes? The stock unchipped a9l at 10* base runs 28* timing in good conditions. That's the limit of the 11r heads on pump gas for most builds.
Now the chip has ?? Extra on that stock curve plus the 4 he added with base timing at 14*. Let's just assume the chip has not altered the timing at all, he is now running 32* total timing at wot. That's more than those heads will like.

But since I dont know how this stuff works I'll just go back to helping in the tuning portion of this forum, where I answer tuning questions every day.
If chip is not required to make the car run remove it.
 
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JRerecich

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Set the base timing at 10* I will not repeat myself or keep helping if I am ignored. I tune these cars all the time, we can do this methodically or you can continue to randomly guess. Find the answers to my questions in my previous post so we can fix the problem.

The fuel is the AFR the tuner is commanding.
like I said in response to your previous post, the gas tank is dropped waiting for the fuel pump. Just because I didn’t specifically reply to your demand of setting the base timing to 10*, doesn’t mean I didn’t read over and ignore it. I’m just testing in the order of people responding, so give me a minute.
 

JRerecich

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The op said it was a stock ecu with a chip and he’s not running a wideband. The fuel is not dependent on the narrowband reading at WOT in this setup. He said it was tuned and ran well with that cam before so he would know what to have base timing at for it to work. Also he posted here for everyone’s opinion not just yours so don’t get the panties in a bunch if he didn’t reply to your questions from 12 hours ago lol
I am running a wide band, but it’s not calibrated correctly, so it’s off about +/- 1 as confirmed by the tuner. Yeah everything ran fantastically before we started, which was only a couple months ago.
 

General karthief

wonder how much it would cost to ship you a pair
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The op said it was a stock ecu with a chip and he’s not running a wideband. The fuel is not dependent on the narrowband reading at WOT in this setup. He said it was tuned and ran well with that cam before so he would know what to have base timing at for it to work. Also he posted here for everyone’s opinion not just yours so don’t get the panties in a bunch if he didn’t reply to your questions from 12 hours ago lol
Back up a second.B
Same cam but swapped the heads and now has a chip.
My opinion is he should not need a chip for this combo to run just fine. A chip can optimize the combo but if the engine had the problem when the tuner was running it the problem should have been resolved before the chip was installed. If the problem occurred after the chip was installed then remove the chip and see what happens.
That said, one member here should not, how do I say, 'call out' another members opinion when
#1 neither member had hands on this build
#2 some procedures were not done, ie: piston to valve clearance
#3 some procedures may have been done incorrectly
All this to say that @JRerecich is going to take the advice given and do what he thinks will work to resolve his problem based on what he knows about the build and his ability to check things and the advice given.
I don't know if these heads are compatible with regular 5.0 pistons, some tfs heads are not.
BTW, I also agree with setting the base timing back to 10* btdc
 

JRerecich

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The purpose is this post was, after doing extensive research on this forum and others, to see if people with similar mods were having the same issues and, if problems like this occur very often, what some common solutions were to fix it. This is not a debate over the parts we’ve decided to put on the car, as theoretically, all the parts should make the car run and drive in all rpms if installed correctly. This is a father/son project after all, so I really appreciate all the feedback as doing heavy mods like this is new to both of us.
Here’s the bottom line. The car ran great 3 months ago with #24 injectors, maf, chip, and cam. It made 217whp on the dyno before we tore it apart. I am doing a compression test today and I will not be doing anything else to the car until the fuel pump is installed and the base timing is set to 10*.
 
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JRerecich

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Compression Test Results:

Cylinder #1 - 170 psi
Cylinder #2 - 170 psi
Cylinder #3 - 165 psi
Cylinder #4 - 170 psi
Cylinder #5 - 165 psi
Cylinder #6 - 160 psi
Cylinder #7 - 165 psi
Cylinder #8 - 165 psi

This was tested on a cold engine. This brings me to believe that the valve train is superb. All these numbers held for around 5-10 seconds, without any drop, before releasing the pressure.