400 cid into '91 Gmc

[chuckander]

Hello,

I recently transplanted a 400 sbc with a set of preinjection 350 sbc heads (I already had them on in an older pickup) with an edlebrock airgap manifold. To get the stock TBI to mount I had to use an adapter for the bbc on top of an adapter to mount it to the manifold. I reused all the original TBI components. The problems I'm having is when it starts to warm up it starts to surge and under a load it surges bad enough to almost die. After warming up it won't idle and dies when in gear and not currently applying the throttle. Another problem it is having is it is causing serious blow-by into the crank case but when the spark plugs are pulled they are white like it is running too lean. I've checked and replaced all the vaccum lines and replaced the TPS, MAP, and IAS. The original manifold was an EGR manifold and the edlebrock isn't. I never heard the original engine run because it was blown. Do I have too much manifold for that system? Or is something else the issue. Thanks.
Sincerely,
Chuck

[Fast355]

Hello,

I recently transplanted a 400 sbc with a set of preinjection 350 sbc heads (I already had them on in an older pickup) with an edlebrock airgap manifold. To get the stock TBI to mount I had to use an adapter for the bbc on top of an adapter to mount it to the manifold. I reused all the original TBI components. The problems I'm having is when it starts to warm up it starts to surge and under a load it surges bad enough to almost die. After warming up it won't idle and dies when in gear and not currently applying the throttle. Another problem it is having is it is causing serious blow-by into the crank case but when the spark plugs are pulled they are white like it is running too lean. I've checked and replaced all the vaccum lines and replaced the TPS, MAP, and IAS. The original manifold was an EGR manifold and the edlebrock isn't. I never heard the original engine run because it was blown. Do I have too much manifold for that system? Or is something else the issue. Thanks.
Sincerely,
Chuck

Chuck,

An injection system is not going to cause crankcase blowby, but poor ring seal or a plugged PCV system will.

As far as your issue goes I see multiple problems.

You say it has a set of smog 350 heads on it. I take that to mean that it has a set of 882/993/624 equivalent slow burning 76cc chambers. The TBI factory spark map will be inadequate for these heads and the intake manifold will create the need for major fueling changes. The TBI heads were designed to require less spark advance and the intake swirl allowed the engineers to stay leaner.

Unless you have your EGR disabled in the PROM chip your fueling and timing will be even further off. The ECM will be advancing the timing and reducing the fuel in anticpiation of the EGR operation.

I helped build and install a 406 into a 1990 G30 based motorhome years back. It was a stock rebuild on the 400 with the exception of 5.7" rods, a 204/214 "RV" cam, and "810" casting 64cc TBI heads. We used a 3704 edelbrock TBI performer intake and a TBI setup from the vans stock 350. It ran very well on the stock chip with the fuel pressure bumped to around 15 psi.

Chris

[EagleMark]

Adding to Fasts post. All your symptoms are not surprising me for a transplanted TBI system and a stock chip. Then add an intake manifold that is rated from 1500 to 6500 RPM, so it does not help with any issue under 1500 RPM...

What is the fuel pressure?

What TBI? SBC, BBC and what injectors?

You did not mention the cam specs either?

Did you hook up the Park/Neutral wire to ECM so it knows if it is in gear?

VSS is another sensor that is often overlooked but can be a great help on idle. Some ECM can get by fairly well without VSS, while others can not.

What ECM and what chip BCC (four letter code) do you have?

All these things are important and can cause the issues your having... except the blow by. There's no way for TBI EFI to cause that.

Then the next step is your going to need to at least see data and read codes, for putting together a custom tune chip you'll need ability to save the data log. Without us being able to see what is happening is just educated and experianced, steps or guess to what is happening.

[chuckander]

The fuel pressure sits between 12 to 14 psi. I did no modifications in anyway to anything As far as the cam specs all i can say is it was an overhauled (not rebuilt) short block so the cam was new but is a factory spec cam for a '77 400. As far as the blow by could it be a bad manifold gasket? The motor had sat for almost a year before installing.

[buddrow]

The fuel pressure sits between 12 to 14 psi. I did no modifications in anyway to anything As far as the cam specs all i can say is it was an overhauled (not rebuilt) short block so the cam was new but is a factory spec cam for a '77 400. As far as the blow by could it be a bad manifold gasket? The motor had sat for almost a year before installing.
To reinforce Fast and Marks earlier statements, the blow-by is likely cause by work oil control rings which will 1. Contaminate your intakr charge, 2. Can cause a loss of compression, 3. It is a mechanical issue which you will never "tune out". The intake manifold will not cause blow-by it will only leak coolant or "vacuum". Now, be sure that blow-by is what you're experiencing. When u pull the pcv valve from the valve cover and place you hand over the hole do you feel air pressure blowing against your hand? That is the semi-compressed air blowing past the rings and out that hole. If you have smoke coming from the tailpipe that could be several different issues.

[chuckander]

I used a compression gauge and all cylinders sit between 148 to 150psi. I then checked the pcv and no pressure. As far as the blow by I was informed if it did get into the cylinder and down passed the rings it would have almost a propane smell. It does smell like raw gas. That's why I asked about a bad intake gasket. And there is no smoke from the tail pipe. Also forgot to answer from earlier it's a half ton pickup that had a sbc 350.

[buddrow]

Ok so why do you think you have a blow-by condition? If there is no air being pushed out the pcv hole then its not blow by. Is the pcv vavle wet with oil? Are your valve covers baffled? Rereading your original post, plugs are white? Its lean which will also cause the surging and other issues. You need a new tune. Maybe a large vacuum leak at the intake manifold? This situation falls into the the " call the doctor, hey doc i have a rash what do you think it is" catagory. Impossible to know for sure without some data or the vehicle in front of me.

[chuckander]

The blowby condition I was asking about was excess fuel blowing by the rings because the oil in the crank case smelled like raw gas and that the plugs were white like it was running lean. That is what was really confusing. That's why I asked if it could be a bad intake gasket. Would that cause a big enough vacuum leak to cause the surging, lean fueling, and raw unburnt fuel getting into the oil? No, the valve covers aren't baffled.

[buddrow]

An intake gasket leak can cause lean surging. Any fuel in the oil is excessive but will generally cause the plug to at least be wet and discolored if not covered in black soot. It may be leaking fuel when engine off and contaminating the crankcase. The surging is likely a lean condition, you just have to find the cause whether its the tune due to the engine combo or if its a mechanical issue. Take a sample of your oil and see if it ignites when exposed to flame or spark.

[chuckander]

I will check the oil when I get home.I Would I be better off reusing the tbi heads and manifold off the bad motor since I had them checked at a machine shop and they were still in good shape. I simply tried this one because it was already all together. The only thing I have to do with the tbi heads are drill the extra coolant hols for the 400.

[chuckander]

I drained the oil from the engine. There was no antifreeze or water in it and it was still very clean and clear, but it when I took a small amout and held a lighter to it, it caught on fire and burned steady for about a minute until I poured some baking soda on it. Yes I did it outside so catching anything on fire would be slim.

[buddrow]

Sounds like a fuel contamination issue. Now to find out where the excess fuel is coming from. Leaking injector and/or injector pod? I wouldn't change anything(heads, intake, etc...) just yet until you find how the fuel is getting into the crankcase. Obvious place of origin is the injector setup so focus on that initially and go from there. I assume you are not using a mechanical fuel pump so we can rule that out. Check for fuel dripping from the injectors after engine shutdown. Check for porosity in the tbi housing or possible modifications made to the throttle body has created a leak in the housing? All things to consider and inspect.

Buddrow

[chuckander]

I checked the tbi and gaskets before draining the oil and there was no signs of any leaks and I didn't start the engine but I truned the key on and pressured up the fuel system. There where no leaks there either

[buddrow]

Hmm. Fill it with new oil and see how it goes. The fuel has to be getting in there somehow so I'm still curious as to how.

[chuckander]

Put 6 quarts of new oil in( extra quart for the factory oil cooler) and replaced the filter. Run it for about 10 min. When it started to surge again. Shut it down and checked the oil. Can smell raw gas again. Checked oillevel before starting, immediately after shutting off, and then again 10 min. Later.

[chuckander]

Refilled with 6 quarts (extra quart for factory oil cooler). Ran it for 20 min until it started to surge again. Checked it right before running, right after running, then again 5 min. Later. Raw gas smell came back after running and as far as I could tell stayed the same when checked yhe second time. Also checked the tbi after running. No leaks from gaskets, body or drips from injectors. Checked spark plugs again and still white like lean running.

[chuckander]

Sorry thought first post didn't go through and forgot to mention plugs

[chuckander]

I went ahead and changed the intake gaskets and the gas getting into the oil has stopped and it runs nice and smooth.. when it's cold. Once it starts to warm up it'll surge slightly and then will refuse to idle at all. Ive checked all the other gaskets and vacuum lines for leaks and still can't find any. I'm at a loss at this point. .

[EagleMark]

Sounds like it's going into Closed Loop when surging and dieing? Still not surprised with a 400 on what injectors? What ECM? What chip? What fuel pressure? Where's timing set? What codes are set? Do you have a data log?

You could try disconnecting the O2 sensor and see how it does when warm.

What is Check Engine Light doing?

[chuckander]

It's still running the factory ECM, injectors, all under factory settings, fuel pressure is 12 to 14 psi. Check engine light only comes on when key is on and engine isn't. Like I said before the only after market part is the airgap intake manifold. It is running the preinjection 350 heads.

[EagleMark]

It's still running the factory ECM, injectors, all under factory settings, fuel pressure is 12 to 14 psi. Check engine light only comes on when key is on and engine isn't. Like I said before the only after market part is the airgap intake manifold. It is running the preinjection 350 heads.Yup, you've said that before! But I have no idea what factory ECM it is, or what factory injectors, or factory chip.

Even if I did the outcome would probably end up the same. Like a stock 400 engine needs more fuel then a 350, or less fuel then a 454, but I have no idea what injectors you used? The the air gap intake is designed for a modified engine and when tuning it needs more AE, but I'm not sure on a stock engine? It's power band also starts at 1500 RPM so it's not any help with a stock engine and actually a harm in idle and low RPM driving.

No matter what you do, the only way to get this engine to run right is with a modified chip, then some data logs to see what it is doing.

[chuckander]

Sorry, the pickup it's in is a '91 half ton GMC with the 350. I didn't know if they used different ECMs for the same pickup. I know they were different between engine sizes. Was there a letter or number indicator that I could look for? I know someone who has an aftermarket chip for a '95 chevy or Gmc. Would that work? Or do I have to look into a custom made chip? Was also told that if I replaced the airgap with a factory manifold that might work. I don't want to start throwing stuff at it if I don't have to.

[EagleMark]

There should be a four letter code (BCC) for the chip in the ECM on a sticker. Or it is also directly on the chip inside.

A 95 chip won't work in your ECM.

There's only one way to make the engine run right and that is to know what chip is in truck so you have a starting point of where to adjust from, then data log, adjust chip, burn and run it with another data log.

So you have 5.7L Injectors as well? These will require more pressure to supply enough fuel for the bigger engine. So adjustable regulator. What is your fuel pressure now?

Not sure what you mean by swapping back to stock intake might work? If the stock intake will install correctly on the heads it would be a better choice for a stock motor. But still not going to run right without a chip calibrated for the 400 engine. Chevy never made a 400 TBI engine so you can't find a correct chip for it!

Surging at idle can be from the chip alone, or vacuum leak, or throttle plates not set right or... we are just guessing here at possible situations and that's all it's ever going to be without a data log to look at!

[chuckander]

The 4 letter code that I can see is either ASDU or ASOU. Sticker is a little wrinkly. The fuel pressure actually fluctuates between 12 and 14 psi running. I tried plugging my diagnostic tool to the port and it can't make a connection. So getting a data log might be difficult. It looks like someone changed out the ECM because it has yellow marker on it. Would a set of big block injectors help? Or will I have to find a higher pressure fuel pump? The reason I asked about the manifold is because I figured less manifold volume would be better.

[chuckander]

Sorry misread you post I looked on the sticker on the outside of the ECM. I'll pull it out and look inside and get back to you.

[EagleMark]

1227747 and ADSU was used in that truck so probably correct.

With BB injectors you would not have to raise pressure or change pump.

I would not use that intake on a stock motor...

[chuckander]

What hardware, software, and specifications do I need to reprogram the chip for my pickup? Can I do it without removing the ECM? Or will I have to do it outside of the vehicle? Can I make any modifications to the factory manifold so it will fit? Or can I use an old carburetor manifold and simply use the factory adaptor I have for installing a tbi on the big blocks?

[EagleMark]

It's got a chip in the ECM, so no flash.

You'll need a Moates G2 adapter that requires soldering into the ECM, couple 27Fs512 chips, Burn 2 chip burner, ALDL cable, TunerPro RT software.
https://www.moates.net/gm-19851995-c-64.html

Not sure on the intake?

A four barrel intake and TBI adapter will work. Although the factory adapter works well, it's UGLY! :laugh:
Plus it adds a couple inches, make sure you have hood clearance.

[chuckander]

I looked up all the components you listed, but can't find the 27Fs512 chips. Where do I get those?

[EagleMark]

Push more buttons on the Moates website! :rockon:

https://www.moates.net/c2-sst-27sf512-chip-p-39.html?cPath=26

[chuckander]

I was told I might be able to use an ECM from a big block pickup without having to reprogram it. Is that true? Or just wishful thinking.

[EagleMark]

You could probably run one from a V6 to without reprogramming it!

Now if you want it to run right, cold, warm, hot, idle and WOT without melting it? You need a chip calibrated for the engine. Feel free to tell that to whomever gave you the wrong information! :rockon:

[chuckander]

Ok. Wanted to know before doing anything.

[chuckander]

You could probably run one from a V6 to without reprogramming it!

Now if you want it to run right, cold, warm, hot, idle and WOT without melting it? You need a chip calibrated for the engine. Feel free to tell that to whomever gave you the wrong information! :rockon: How do I find out what leg spacing I have for the G2 adaptor?

[EagleMark]

Earlier you said your chip was ASDU? That is from a 1227747 ECM and you would use the standard .060 leg spacing G2 adapter.
https://www.moates.net/g2-memory-adapter-060-leg-spacing-p-36.html?cPath=64

There's also a cheaper way but I've always just used the G2 from Moates soldered directly to board. Then with a chip the cover will clear. Before your done and changing chips all the time use a Zif socket plugged into the G2
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?172-7747-Flash-Chip-Conversion-(27SF512)

[chuckander]

I just ordered all the parts except the ALDL cable. I'm gonna get that directly from the gearheadefi forum that is advertised. What engine information do I need to program into the software?

[EagleMark]

Same files that are in the tutorial, $42.

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?466-TunerPro-starter-Tutorial!-New-users-this-is-a-must-read!-)

[chuckander]

Same files that are in the tutorial, $42.

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?466-TunerPro-starter-Tutorial!-New-users-this-is-a-must-read!-)
I got all the chips and the adapter, Burner 2 and ALDL cable, downloaded and registered my TunerProRT, and downloaded the Bin, xdf and adx for my particular ECM. Now I just need some help on what to do with it all.