ANY HELP IS APPRECIATED 1988 mustang gt

Foxbody1988

Member
May 4, 2019
23
3
13
20
Fresno
Ok guys I have a lengthy question/issue. So I rebuilt my motor about 4K miles ago. Fresh bore, hone, pistons and rings.. the whole nine yards. I noticed it was lacking power so I did some compression checks. I only did 3 cylinders and they were all relatively low numbers between 65-100 to be exact. I knew at the point something was wrong. The only used thing I have on there is a cam which is in good shape, injectors, and the heads. They are turbo swirl gt40 x aluminum svo heads. I took them off and am getting a valve job done on them in the next couple of days. Upon taking the heads off I noticed there is excessive wear in the cylinder walls of most cylinders. No grooves thankfully. The motor was rebuilt by me about 4 months ago so it’s odd. That’s the back story for you guys, maybe you guys can help answer some questions now. The injectors are also used. From a junkyard but I purchased o rings, needles and baskets for them on summit. Every single one. I have the aero motive fuel pressure regulator and my bars read 55psi. I turners up the pressure pretty high because all Of my spark plugs are turning slightly white on the tips. They are gapped at 55. And the timing is it at 14 degrees. No tunes or anything. Questions
1. Could fuel be hurting my rings or flooding into my oil, diluting it and hurting my cylinders?
2. Does the computer try to adjust fuel and timing automatically? I took the spout connector out when timing*
3. What would cause multiple readings of low compression?
I had to take a plug off of another mustang for the maf sensor I got because I purchased a bbk 24ib injector tuned maf the unit and tube. so I’m hoping it was wired correctly. It ran perfectly just had a lot less power then I expected. No get up at high rpms. The cam is a stage three Crower cam 15513 .512 intake .531 exhaust. Stock pushrod length. Chromoly pushrods.Svo 1.6 roller rockers.
lots of things going on haha, I hope I didn’t lose anybody, this is all very frustrating. I thank you guys so much for any and all help. I basically need to figure out fuel, compression, timing, and if anybody knows the formula to adjust the valves please leave that below because I forgot haha. I believe I did when intake rises do exhaust and when exhaust is at top do intake. No pushrod movement, then 1/4 turn and on to the next. People are getting around 350 whp with my relatively similar setups. Mine doesn’t even feel close. I believe the leaning is happening at high rpms to because it smells somewhat rich at idle. It will sometime die when pushing the clutch in to stop from a roll, and sometimes when the power steering is putting a load on it. I have it idling at about 1000rpms I would like to be around 750 but it dies more frequently. TPS possibly? Sorry for being all over the place there is just a lot of things that are stumping me. Thank you all guys can express my appreciation.
 
Last edited:
  • Sponsors(?)


Mustang5L5

A little massaging and it went right in
Mod Dude
Feb 18, 2001
32,252
8,448
224
Massachusetts
I think your compression data is incomplete. What temperature did you test at? If stone cold, then numbers in the 100-120psi range can be expected. If hot, those numbers might shoot up to 150-170psi.

The big thing is to see all the number for all 8 cylinders are consistent. Less than 10% variation between them since the odds of all 8 badly wearing at the same time is low.

55 psi is high for fuel pressure. The ECU will compensate but slowing down the injector duty cycle to inject less fuel. Even heavily modified, the engine should still run well on 39psi of pressure.

Did you run codes at all? ‘88 don’t have a check engine light so no warning will be given that there are codes stored.

Did you degree your cam properly? To adjust the valves, you want to tighten lash up when that particular cylinder is on the base circle of the cam. Easy way to tell is when opposite paired cylinder begins to rise. Zero lash, 1/4 turn. Lock.
 

Foxbody1988

Member
May 4, 2019
23
3
13
20
Fresno
I think your compression data is incomplete. What temperature did you test at? If stone cold, then numbers in the 100-120psi range can be expected. If hot, those numbers might shoot up to 150-170psi.

The big thing is to see all the number for all 8 cylinders are consistent. Less than 10% variation between them since the odds of all 8 badly wearing at the same time is low.

55 psi is high for fuel pressure. The ECU will compensate but slowing down the injector duty cycle to inject less fuel. Even heavily modified, the engine should still run well on 39psi of pressure.

Did you run codes at all? ‘88 don’t have a check engine light so no warning will be given that there are codes stored.

Did you degree your cam properly? To adjust the valves, you want to tighten lash up when that particular cylinder is on the base circle of the cam. Easy way to tell is when opposite paired cylinder begins to rise. Zero lash, 1/4 turn. Lock.
I removed all smog equipment so I am throwing a check engine light. But haven’t checked codes. I don’t know how to other that counting light flashes with a clip of that’s what you mean. And the compression numbers were on a hot motor could barley get the plugs off the head without burning my fingers.
 

Foxbody1988

Member
May 4, 2019
23
3
13
20
Fresno
By the way here is the specs of everything in the motor
Machined 302 the original motor just bored .4030 and honed. Cleaned and balanced rotating assembly.
crank ground 10
Forged dss racing e series pistons
Svo turbo swirl gt40x alluminim heads
Svo 1.6 roller rockers
Hasting rings
Clevite bearings
Arp head bolts, connecting rod bolts, oil drive pump shaft, and chromoly pushrods stock length I believe it was 6.250
comp cam timing chain on the circle so it’s neutral
Trickflow track heat intake
24ib injectors
Crower cam 15513
Aeromotive fuel pressure regulator
New oil pump I forgot the brand
And everything else is pretty much stock with some other little goodies I can remember off the top of my head.
 

Mustang5L5

A little massaging and it went right in
Mod Dude
Feb 18, 2001
32,252
8,448
224
Massachusetts
I removed all smog equipment so I am throwing a check engine light. But haven’t checked codes. I don’t know how to other that counting light flashes with a clip of that’s what you mean. And the compression numbers were on a hot motor could barley get the plugs off the head without burning my fingers.
Here's the reader you want.

If your CEL is on, is this a CA mass air car? Those are the only '88's that came with a functional check engine light

View: https://www.amazon.com/INNOVA-3145-Ford-Digital-Reader/dp/B000EW0KHW/ref=asc_df_B000EW0KHW/?tag=bingshoppinga-20&linkCode=df0&hvadid=&hvpos=&hvnetw=o&hvrand=&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=&hvtargid=pla-4583795260709503&psc=1
 

bird_dog0347

I really enjoyed seeing your rear end up close
5 Year Member
Jun 7, 2012
1,002
854
154
39
Little Elm, TX
Tell us more about your MAF... You mention you have the 24# injectors with higher fuel pressure (overkill) and something about a plug off another mustang. Why is my first question? There are far better and easier ways to do that, that are proven reliable ways to go. Sorta sounds like you were either trying to reinvent the wheel or save money in all the wrong places?
 
Aug 11, 2019
33
8
18
48
Lafayette,IN
Sounds like you purchased the BBK maf used? A new one would've came with the correct adapter plug. And zero lash on the valves,you should still be able to spin the pushrod,you just don't want any up and down movement.
 

Blown88GT

Founding Member
Nov 13, 1999
1,815
371
124
Palm Beach Gardens, FL
...
Did you run codes at all? ‘88 don’t have a check engine light so no warning will be given that there are codes stored.
It's a California car; therefore more '89 than '88.
Pictures indicate poor oil flow. Since new oil pump, need to investigate why.
If the cylinders are that bad, what do the crank & piston rod bearings look like?
Code Reader pic. You will also want the extension cable.
1577233654291.jpeg

1577233725373.jpeg
 

Mustang5L5

A little massaging and it went right in
Mod Dude
Feb 18, 2001
32,252
8,448
224
Massachusetts
If it’s a CA car, then it has that weird one year only 5-prong MAF.

So it is critical to make sure the 4-prong aftermarket was wired in correctly
 

95BlueStallion

Drop into my dm’s gurrrrrl
10 Year Member
Feb 22, 2007
5,562
3,175
214
Cedar Rapids, Iowa
www.goodreads.com
That explains your poor pressure test results, but I’m not sure that fix is going to change your wear problem. I am thinking you are washing your cylinders with excessive fuel at idle. I would put the fuel pressure back down to 39-40 psi and get the car tuned. Or if nothing else, install a wideband meter and see what you have going on with your AFR as you drive.
 

Mustang5L5

A little massaging and it went right in
Mod Dude
Feb 18, 2001
32,252
8,448
224
Massachusetts
The wear seems to be concentrated on the lowest point of the cylinder wall.

When you rebuilt it last, did you use any abrasive materials to clean the deck or piston tops that may have fallen down into the bores and accumulated at the lowest part of the cylinder in the gap between the piston and wall?
 

Hoytster

I don't dare do that to my Knob
10 Year Member
Dec 30, 2002
874
548
134
37
Cornwall, PA
www.hoytspot.com
I'll second what 95Bluestallion said, that looks like fuel wash to me. I'm noticing the lack of carbon build up on the pistons that seems to correlate with the cylinder wear. Is that wear only on that one side of the pistons? How does the oil smell?
 
Last edited:

Foxbody1988

Member
May 4, 2019
23
3
13
20
Fresno
Oil smells like gas sometimes, but I just replaced the head and the machine guy said that since I had horrible compression, there Would have been almost no piston seating. Excessive wear. He said pistons need compression to seat them against the wall
 

Hoytster

I don't dare do that to my Knob
10 Year Member
Dec 30, 2002
874
548
134
37
Cornwall, PA
www.hoytspot.com
Compression is needed to seat and seal the rings, but I've never seen low compression cause excessive cylinder wall wear like that. Not saying it's possible, I've just never seen it. As stated above, I believe you have multiple issues. The compression issue was probably due to your cylinder head issues, but the cylinder wall wear is another.