383 Vortec/TBI Build Thread

[Daveo91Burb]

on trucks there is no heater core bypass. The control panel does not have the vacuum valve on hot/cold selector that cars tended to have.

here is the valve on my TA

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So water IS flowing through the core all the time, regardless of where the heat control is set? Oh well, all I know is the intake to WP bypass solved my problem. And I’m going to do it on my Vette just in case.

 

[Daveo91Burb]

New exhaust! Custom y-pipe with o2 bungs in both sides in case I ever decide to add wideband (he didn’t quite understand what I wanted - just wanted one second bung after the banks come together, not one on each bank, but that’s ok not sure I’m ever going to go the wide band route anyway.). I also had him install a like new cat that I had from my parts rig and a whole new tail pipe after the single magnaflow (which is also pretty new). I can get away without a cat in my parts but everything I’ve read is they don’t add much back pressure and I like driving with the rear window down but wasn’t liking the smell from the exhaust that came with it. And it had the added benefit of mellowing the sound just a touch. Overall pretty happy. I’m going to bring it back to him and ask him to add one more weld in front of the muffler, which I had installed previously and just clamped.

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[4WDKC]

Any updates?

 

[Daveo91Burb]

Any updates?

Not much. Been fighting two issues: 1) tranny leak, turns out it was just a bad seal at the dipstick tube. Finally got that resolved yesterday. I think. 2) engine oil cooler lines. Replaced both but with dorman not delco - junk. Aluminum flare fittings stripped right out of the bag. Finally resolved. Back to tuning....

Big issue to resolve next: sounds like an exhaust leak at medium to hard throttle under load. Exhaust guy that did the work insists it's not a leak. I even had him put on a different (brand new) cat thinking it might have been from the slightly used one I had him put on first. He thinks it's detonation, but it's running rich across the board, not lean - doesn't seem like rich would cause pinging? And it's very consistent, happens every time with medium acceleration. I haven't gotten a chance to hook up my laptop and see if that sound correlates with increased knock count - that's next. I'm still hoping it's something simple like the heat shield above the cat. I've also thought it might be the DS manifold (that's where the sound seems to be coming from) - I have another one that I could swap it with to check.

 

[4WDKC]

check the studs for the manifold to the block, I had one break on my truck and was told its really common on 4x4s. Exhaust leak sounds right, it will pull clean air in across the 02, make th eecm think its lean and then it will dump more fuel causing the rich condition you see/smell and to retarded timing timing could be causing knock.

 

[Derick C.]

I had issues with my oil cooler lines as well so I made my own.

 

[Daveo91Burb]

I had issues with my oil cooler lines as well so I made my own.

Cool. Do you have a crimper for hoses and flare tool? How much would a set up for that be? I went to a custom hose/tube shop and it would have been $150-$200 for the two hoses. Thanks but no thanks.

I might bite the bullet and buy the Delco set. I ended up cutting off the end section with the stripped threads and used the original fitting/flared tube end - spliced on to the dorman with a section of hose and four hose clamps. Chintzy as hell but I just wanted it back up and running.

 

[Derick C.]

Cool. Do you have a crimper for hoses and flare tool? How much would a set up for that be?

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I have this same setup on both my trucks.

 

[Daveo91Burb]

Awesome. Better coolers for both tranny and engine are on my list for the future.

 

[Derick C.]

I don't remember what I spent. The coolers are ebay coolers with A/N fittings, and the lines and fittings are from earls. It's not a kit its all self sourced parts and put together. You can get the A/N fittings for the trans on ebay, the fittings for the block I got at my local oriellys after I found out what the NPT thread size was.

 

[Daveo91Burb]

Finally found my exhaust leak. Started it up cold today and used my finger to feel around the welds before it got too hot. Found a steady stream of exhaust out the weld on the drivers side, just below the manifold collector. Heading back to the exhaust shop tomorrow - hopefully he can patch it up for me.

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[Daveo91Burb]

Finally got the exhaust patched up today. I showed him where it was and he agreed and touched up the weld on the spot. Sounds awesome now. Knocking off problems one by one. Although I think a new one popped up this week - seems like I'm getting a fluid leak from the steering box. Going to have to look a little deeper. But the biggest problem is a weird surging I'm getting at deceleration, between about 1700 rpm and 1000. You can see a 300-400 rpm oscillation in the tach and feel an engine braking effect that pulsates on and off in about 1 second cycles. Going to start playing with the tune now to see if I can get that out. It wouldn't be something going on with the 4L80e would it?

 

[Frankenchevy]

Does it ever hunt at idle as well? Either way...maybe idle air control valve?

...maybe Tps function?

 

[Daveo91Burb]

Does it ever hunt at idle as well? Either way...maybe idle air control valve?

...maybe Tps function?

It's rock solid at idle. 650 rpm steady once it's warm. But I've still been thinking IAC and/or TPS. I'm pretty sure I have both as extras in a box somewhere. Would be pretty easy to swap one at a time to see if there's any change. But I think it's something in the tune that's causing it. I don't have any EGR stuff installed and it's written out of the tune, but I'm still wondering if it's fully written out. That, or maybe there's a bogus parameter for the transmission that's causing engine braking to cycle on and off at those RPMs.

 

[Daveo91Burb]

But the biggest problem is a weird surging I'm getting at deceleration, between about 1700 rpm and 1000. You can see a 300-400 rpm oscillation in the tach and feel an engine braking effect that pulsates on and off in about 1 second cycles. Going to start playing with the tune now to see if I can get that out. It wouldn't be something going on with the 4L80e would it?

I think I finally got this problem ironed out today! Minimum idle air was misadjusted. Fortunately my re-man and bored throttle body already had the cap over the throttle stop screw removed, so I didn't have to worry about that. It made following the procedure here really easy. After getting the base idle adjusted I checked the TPS voltage at idle and had to adjust it slightly - ended up right at 0.51 volts which is pretty much optimal. Fortunately I have an ALDL to USB cable and a laptop with TunerPro RT so I could accurately see what the computer sees for TPS volts. Took it for a short test drive and the deceleration surge appears to be gone. Fingers crossed.