8 cylinder front engine iconic vehicle
  • User avatar
  • User avatar
  • User avatar
User avatar
By Crumpler
#119601
Hey you guys, I’m chasing a rich condition and trying to check off all the boxes on the hardware side before I go nuts with software side of ecu tune.

I have the Ford Motorsports 24 pound four hole injectors. I’m thinking they are three years old.
Limited miles.

Car warmed up fully.
It readings on exhaust manifold all pretty consistent 450 ish, except for number eight which gave me readings of 530 ish Degrees F.
Number 3 was cooler like 370.

Significant? Or red herring.
I have the stock 24’s that I can put back on.
User avatar
By Crumpler
#119602
This is the second half:

I have widebands on each side of the xpipe.
Both read same rich condition which doesn’t support bad injector, but maybe multiple failures. Odds don’t support that.
User avatar
By worf
#119643
Longer post later. Hopefully.

Have you ever seen the tops of your pistons? (i.e. Carbon build up?)
User avatar
By Crumpler
#120331
worf wrote: Wed Dec 01, 2021 3:00 pm Longer post later. Hopefully.

Have you ever seen the tops of your pistons? (i.e. Carbon build up?)
I have now.
:barf:

Pulled injectors, they all clicked with voltage on the bench FWIW.
All plugs fouled from recent pig rich runs.
Boroscope pictures show carbon build up, some moderate. It looks like some recent sludge residue with a mild to rough cobblestone appearance, I assume from last 30 years.
I was going to do a solvent clean through spark plug holes, with some endoscope tools unless that is insane.
I was going to do a warm compression test after wards and see if normal. Bigger decision if not.
Image
Image
Image
Image
User avatar
By worf
#120337
Apparently a longer response was not forthcoming :banghead:

Uniform carbon buildup can cause problems on individual cylinders because with our 1970s/80s-technology engines the cylinders aren't balanced. On an S4/GT/GTS cylinder 3 is the first to provide serious misfires with uniform buildup across all cylinders.

I have no idea which S3 cylinders will be 'problems' with uniform buildup. If anyone knows the answer to that question it's Porken.

Now, very heavy buildup on any piston can cause knocking and/or misfires.

Both of the above become much more of an issue with forced-induction since what we're effectively doing is removing the knock safety margin by ratcheting up the cylinder pressure.

In any case, it's hard to tell how bad carbon is with the heads on unless you've a hi-res 'scope and an eye for it. (And I'm not sure I could be sure even with a medical-grade 'scope.) If you see one cylinder with what looks like a lot more than the others and it corresponds with your non-uniform temperature measurements...

Warm compression test is a very good idea. It may provide correlating data.

When I do that I'll run the engine for a minute or three after doing one bank to keep the temperature more-or-less the same during the whole process.

Have you done a leak down test on this motor?
Last edited by worf on Sat Dec 04, 2021 11:55 am, edited 1 time in total.
User avatar
By Crumpler
#120340
Hey Dave thanks for the insight. That helps.

I just edited post with some pics, quality of pics marginal but you get the idea.

Build up did not correlate with temp changes on given cylinders FWIW.

No leak down test yet.

My immediate concerns with build up was that it would immediately ruin rings and score the chambers, from reading some horror story article online.
User avatar
By worf
#120341
Crumpler wrote: Sat Dec 04, 2021 10:47 am Boroscope pictures show carbon build up, some moderate. It looks like some recent sludge residue with a mild to rough cobblestone appearance, I assume from last 30 years.
Those look "typical" and not too problematic I would think. You run into problems when the layer is 1/8" to 1/4" thick.

(And yes, I have seen ~1/4" layer. On a GTS.)

One telltale is if the valve relief on the piston is clearly visible. If you can't see it at all then there's a ton of buildup.

Crumpler wrote: Sat Dec 04, 2021 10:47 am I was going to do a solvent clean through spark plug holes, with some endoscope tools unless that is insane.
I was going to do a warm compression test after wards and see if normal. Bigger decision if not.
Do the same test before and after. That way you will have some objective data about the efficacy of the procedure.

'Approved' chemical means of removing carbon will work slowly. One thing you do not want to happen is for chunks of the carbon to get loose in the cylinder. That can result in wall scoring when it falls into the wall gap and a ring grabs it and drags it up and down the wall.

So, with the heads on, one must dissolve the carbon. No. I don't have a great recommendation.

Gather your data first.

Do a warm compression test. Ideally all the holes will be +/- 10 PSI.
Last edited by worf on Sat Dec 04, 2021 11:56 am, edited 1 time in total.
User avatar
By worf
#120342
Crumpler wrote: Sat Dec 04, 2021 11:45 am My immediate concerns with build up was that it would immediately ruin rings and score the chambers, from reading some horror story article online.
Meh. On 928s at least, CB is the result of many, many, many heat cycles. The buildup is, effectively, diamond constructed through chemical vapor deposition. GTSs are by far the worst because of their 5x oil ingestion issues.

The shit is *diamond* hard and doesn't just come loose. I guarantee it. With an engine on a stand, heads off, it takes me a solid day to clean a medium-to-heavy layer off of all pistons.

Now... I suppose it's possible for the carbon to 'grow' like a horizontal icicle in such a way that a chunk could break free and then bounce around. But, on a 928 I wouldn't worry about it. Even if it's a GTS.
User avatar
By Crumpler
#120403
Got it. Thank you for the affirmation man.
By MFranke
#120818
Fwiw, a can of Berryman 2616 B12 in a tank of fuel removed all carbon on my piston tops. I don't know how thick, or how hardened, the carbon was before. But when I scoped the tops it looked like your pictures. After one tank, all the carbon was gone, leaving grey tops.

Might be worth a try.
User avatar
By Crumpler
#120832
MFranke wrote: Mon Dec 06, 2021 6:09 pm Fwiw, a can of Berryman 2616 B12 in a tank of fuel removed all carbon on my piston tops. I don't know how thick, or how hardened, the carbon was before. But when I scoped the tops it looked like your pictures. After one tank, all the carbon was gone, leaving grey tops.

Might be worth a try.
Got it, I will give that a try.
FWIW, I tried some gumout all in one treatment with PEA to the piston crowns directly and let it sit overnight. Pulling the solution back off it was definitely helping but not much. Maybe 10% cleaner and not worth the hassle to “clean” that way.
User avatar
By worf
#120846
Crumpler wrote: Mon Dec 06, 2021 7:11 pm FWIW, I tried some gumout all in one treatment with PEA to the piston crowns directly and let it sit overnight. Pulling the solution back off it was definitely helping but not much. Maybe 10% cleaner and not worth the hassle to “clean” that way.
You’ve got a bunch of that in your sump now. Don’t run the engine too much before you change the oil.
Crumpler, MFranke liked this
User avatar
By milrad
#120864
This job was major suckage. 1 clean in this pic. Like Dave warned, all 8 cylinders were a full day's work.
Image
User avatar
By worf
#120926
Note that #3 has the most build up. Compare it with #1. Zoom in on it.

I had a 25k-mile GTS, a decade ago, with so much buildup that the top of the piston looked flat. About 1/8”-1/4” buildup.

So much that #3 was more-or-less not firing.
Widowmaker Project

A teaser https://i.imgur.com/JxgfLt0.jpg https:[…]

Just watched a recent Doug Demuro video re[…]

Vacume oil change???

From the videos it looks like the filter is simi[…]

The 928 Photo Thread

Very happy with Carbone too. https://i.imgur.com/[…]