Bad Fuel Head Or?

[356-930]

I run a '79 3.3 liter engine, SC cams, CIS - Euro Head, no intercooler.
Present problem is a fueling issue.
With stock WUR, 95psi system pressure, cold control 25-psi, warm 50-psi, AFR at idle set to 14.5 warm. AFR will not hold steady. It's 14.5 +/- .5 at best. Sometimes engine wakes up lean, sometimes rich. Drive it like I stole it and AFR settles on rich side between 12.5 and 13.5, engine seeks as though it's rich (which it is). The hotter the engine (never gets over 180) and the longer I drive it, the leaner it gets - until I flog it and it goes rich again.
Replaced stock WUR with UTCIS-PT digital WUR. Symptoms remains the same (using 930 starter MAP download from UT.) Only new twist with the DWUR is the engine sometimes seeks at idle like it's rich except AFR is 15.5 - 16.5 or lean.
Injectors cleaned with hi-press hydraulic cleaner, spray pattern of carb cleaner driven by air hose is good. Condition of fuel head unknown (plunger was frozen as engine in hibernation for 10-years - freed up with pliers, polished shaft with 3M abrasive - free operation after clean-up).
I've run this engine for 4,000 miles in this condition and would like to nail the fueling issue down so I can safely dyno and drag race without concern for the big bang.
If consensus is the fuel head, who best to rebuild?
TIA for your help.
Chris

[turbobrat930]

If you do need your fuel head rebuilt, there is a place in TX I believe, that does rebuild fuel heads. The guy specializes in Delorean CIS, but works on all CIS stuff. His website escapes my mind right now, as I am at work and dont have the bookmark saved on the work computer.
It is really early in the morning, I am tired, and henceforth might have missed it in the post, but what W/B O2 sensor are you using? Do you know if it is working good? Are you sure that you dont have a pinhole leak in you exhaust system anywhere? I have heard from some users that their A/F reading went haywire and found that a VERY small pinhole in the header was causing the erratic readings..... just a thought...or is my lack of sleep causing this?????

hope that helps....

[turbobrat930]

by the way... since you are not running an intercooler....I have a stock one I will give you if you pay for the shipping... I would think a stock I/C is better than none at all!!!!!!

[sand_man]

Originally Posted by turbobrat930

If you do need your fuel head rebuilt, there is a place in TX I believe, that does rebuild fuel heads. The guy specializes in Delorean CIS, but works on all CIS stuff. His website escapes my mind right now, as I am at work and dont have the bookmark saved on the work computer

It's Special T Auto:
http://specialtauto.com/porsche-parts/index.html

[sand_man]

Originally Posted by turbobrat930

by the way... since you are not running an intercooler....I have a stock one I will give you if you pay for the shipping... I would think a stock I/C is better than none at all!!!!!!

I agree, but he might have ditched it for space constraints: his turbo engine is in a 356

[turbobrat930]

Originally Posted by sand_man

I agree, but he might have ditched it for space constraints: his turbo engine is in a 356

AHHH, very nice!!!! I have been on vacation for the past month...so have not seen alot of the posts... that thing must FLY!!!!

[sand_man]

Originally Posted by turbobrat930

AHHH, very nice!!!! I have been on vacation for the past month...so have not seen alot of the posts... that thing must FLY!!!!

Yeah I agree, I think his car could very well be my favorite interpretation of a 356 "Outlaw"....EVAR!!!! For thoose of you who don't know, the 356 is one of my all time faves, having owned a '64 356 C myself...that I regretfully sold!!! I'm all about the "old skool"...don'cha know!

[356-930]

Originally Posted by turbobrat930

. . .but what W/B O2 sensor are you using? Do you know if it is working good? Are you sure that you dont have a pinhole leak in you exhaust system anywhere? I have heard from some users that their A/F reading went haywire and found that a VERY small pinhole in the header . . .

Wideband O2 is Bosch tied to Zeitronix data logger. AFR's double checked with on-board system and up-pipe system, both unstable. I have no exhaust leaks and question why a pin hole would contribute to AFR change/instability. A hole would not present fresh air, just let out some air/fuel that's passed through the engine.
And Sandman is right, no room for intercooler. In this little vehicle, there isn't even enough room for a water/air intercooler. I use water/methanol injection to make up for at least some of the cooler's benefit. It does let me run plenty advance which is a good thing when it comes to making power.
Chris

[mark houghton]

I would ask the same: Why would an exhaust leak cause AFR issues? Change in exhaust back pressure, or what? Just seeking to understand.

[Akila]

Dahhhhyaam!!! & ah, but, duh is that a chorme intake?

[turbobrat930]

Originally Posted by mark houghton

I would ask the same: Why would an exhaust leak cause AFR issues? Change in exhaust back pressure, or what? Just seeking to understand.

DonE, a little help here??? LOL

[JFairman]

looks like even the digital WUR is chromed.
did that do anything to it functionally or it's warranty?

have you had the CIS gauges hooked up while the idle AFR is fluctuating, and does the system or control pressure change at all as this is going on?

[sand_man]

I'm just curious, it's hard to make out in the pictures, but what BOV/re-circ valve are you using? Is it the the large 930 housing?

[930turbo]

I would check the mechanical pivot on the air meter to be sure it has smooth movement throughout the range.

[NathanUK]

A leak in the exhaust could cause air to be drawn in and give false AFR readings. This is the reason you do not mount the sensor near the tail pipe.

I agree with the above, check for a free, smooth movement of the air metering plate.

[356-930]

Originally Posted by Akila

Dahhhhyaam!!! & ah, but, duh is that a chorme intake?

Most of what you see, including fan and fan housing, is hand sanded/polished magnesium or aluminum. Feed pipe, turbo to boost relieve valve assembly, and CIS air intake horn are steel/chromed
The good news: It looks cool.
The bad news: Raw polished magnesium will oxidize before your eyes in a high moisture environment. Caught in a rainstorm once, all the magnesium instantly turned white. 4-polishing hours later . . . . (it really helps to be retired).
Chris

[356-930]

Originally Posted by JFairman

looks like even the digital WUR is chromed.
did that do anything to it functionally or it's warranty?

have you had the CIS gauges hooked up while the idle AFR is fluctuating, and does the system or control pressure change at all as this is going on?

Re: DWUR was sanded/polished (With fuel in/out ports sealed). Sanding/polishing what is basically a significant solid block of aluminum will have no effect on functionality. I am confidant the small print makes the warranty void upon Any modification to product, sanding included.
PS: Nothing on this vehicle is under warranty.
Chris

[JFairman]

lol...
then it's all good

incredible car you've put together!
something to be very proud of...

beautiful

[356-930]

Originally Posted by JFairman

. . .have you had the CIS gauges hooked up while the idle AFR is fluctuating, and does the system or control pressure change at all as this is going on?

No and that's a great test.
930Turbo and Nathanuk - excellent suggestion.
When engine built, I took the air plate/counter balance/pivot assembly out of the CIS assembly. Had to make tooling to permit re-assembly. Lubriplate on bronze bushings. Free then but now? Good question.
BTW, that assembly is a true piece of mechanical engineering genius.
Chris

[356-930]

Originally Posted by sand_man

I'm just curious, it's hard to make out in the pictures, but what BOV/re-circ valve are you using? Is it the the large 930 housing?

I believe it's the large 930 housing.
The donor re-circ assembly came from a 3.0 liter 930, non-intercooled. Circa 1977-1978?
Chris