383 TBI buildup, lots of pics!

[ImpalaGuy]

Originally Posted by Fast305

Why are you worried about going below 17 psi? Assuming you stll have the stock 61 lb/hr 350 injectors, you should be worried about getting it up around 25 psi and tuning it from there.

The injectors are 80lb/hr so it idled bad at higher fuel pressure. So far it has enough fuel at WOT at 17psi so I'm hoping to keep it there just b/c the fuel tables looking good and I don't want to redo them.

Originally Posted by Fast305

The hesitation is lack of tuning in the AE department as well as the increased throttle body size and plenum volume in your intake. The requirements are drastically different from the stock sized TBI and the tiny heated plenum of the stock intake. I bet DE is just as bad with possible surging on deceleration.

Yes I think it's the 50mm throttle body and the bigger intake. I remember when I put a 58mm TB in my LT1 and it was a bear to get right. We're messing with the AE vs. TPS and MAP tables but so far the changes are hard to detect. I may come back and ask you for ideas on this if it doesn't start to converge soon.

Deceleration seems okay but since it's an automatic there's not much there.

Originally Posted by Fast305

Idling poorly in open loop is a sign that the VE tables or the timing is off.

The open loop problem is idling as well as lots of popping/missing/spitting under accel or cruise. The strange thing is that it goes away almost instantly when it goes into closed loop, much faster than the O2 could make changes to the long term fuel trim. The fuel tables look really good above 1200 rpm but under that the datamaster data isn't consistent, perhaps because of the overlap of the cam?

Thanks for the thoughts -- I always appreciate help. I just got another spin from Brian... need to make a quite trip around the backroads to see how it does.

[rob jones]

Best of luck with your 383 project. Hope Brian can get you lined out & you get this streetable friendly as I would like to copy or build a very similar setup for mine without all the headaches involved of trial & error. maybe soon you'll be rewarded for all the time,effort,& $$$$$ and have a fun new toy. Keep us informed as Iknow I have really enjoyed this thread up to date. Keep those wrenches turning.

[ImpalaGuy]

Originally Posted by rob jones

Best of luck with your 383 project. Hope Brian can get you lined out & you get this streetable friendly as I would like to copy or build a very similar setup for mine without all the headaches involved of trial & error. maybe soon you'll be rewarded for all the time,effort,& $$$$$ and have a fun new toy. Keep us informed as Iknow I have really enjoyed this thread up to date. Keep those wrenches turning.

Thanks. I know we'll get it. A new motor install always has "bugs" to work out, either hardware (coil, vacuum leaks, etc) or tune. It took a couple dozen tunes to get my 396 LT1 tuned pretty close, and then another couple dozen to get it right where I wanted it.

So once I get it right I think this a really good bang-for-the-buck build for our full size trucks. Even with paying Brian for his tunes I'm still under $4000 for the whole thing, plus I've got the complete stock 350 in my garage. I could sell it and get my total cost down near $3000, but I think I'll keep it to drop back in the truck for whenever I get rid of it, and keep the 383.

[billvill]

Any reason you didn't spring for a set of roller rockers ? They are under $150.00 on eBay. I got a set a few months ago and they look every bit as good as the name brand stuff.

any updates??

man, i hate to bear the news, but I would stop dealing with Brian, and find a local dyno tuner near by! Its almost like a guessing game, with little progress. You just droped all that cash on a good motor to be testing all the time??

when my stroker gets finished, Im gonna get it dynoed, and live tune right there! this will take care of idle, part throttles, and wots! all done locally!

if you cant get it to a dyno, keep messing with it, its good you do tune a little bit. But i think the mail order is drawing this thing out to far. Atleast there is progress tho!

[ImpalaGuy]

[QUOTE=Tbi-MAX]any updates??
QUOTE]

I suppose I'll bring this thread back from the dead and give you guys a few updates. The truck is running really well now, and has been for quite a while.

The tune needed some pretty big changes in the AE (accel enrichment) area for the hesitation, and the open loop problems were from too much choke. The reason it took so long to get right was that both areas were so far off that changing them a moderate amount didn't make much difference. So if anybody builds something similar, these things take a TON of fuel to get over hesitation problems but yet it had far too much fuel from the choke. Weird, but it's dialed in now.

The truck pulls strong with the 383, a 2600 stall convertor and 3.73 gears. It feels like it would outrun the the 496 engine in my friends 2002 Silverado. I haven't had it dyno'd but do hope to get the track sometime this spring.

[rob jones]

Hey,glad to hear its running good. I'm starting my 383 build now.

[gmc406]

Nice unit, have you had it at the track yet?

[ImpalaGuy]

Originally Posted by gmc406

Nice unit, have you had it at the track yet?

No, the track is still closed for the winter. I hope to get there in the spring though. Somewhere I have the timeslips from when I base-lined the truck with the old 350, so it should be a pretty before/after good comparison.

[bealskr]

Originally Posted by Fast305

The GMPP intake may seem like it has small runners, no suprise it does. What it helps does however is build torque while giving good fuel mileage. The GMPP Vortec intake also has EGR provisions. The GMPP intake is very similar in design and size to the Edelbrock Performer 3704 TBI intake. I have the 3704 on a TBI engine that is making 325+ RWHP and pull it to 6,100 rpm WOT shift points. Torque forever. It has been bored to 2" and has a BBC TBI unit on it. I am about to help a guy convert his 1994 C1500 to Vortec heads, using the GMPP conversion package. To no suprise his block has roller lifter provisions and we are using the LT4 cam in it. His dyno should look very similar to mine.

Fast 305; I have done a 5.7 vortec swap into my 89 FS C1500 and used the Lt4 cam, Edelbrock TES headers, 46mm bored TBI, 80# injectors, and the GMPP 4bbl intake with TBI adapater. I had it tuned by Brian Harris at TBIchips.com and you can see it's dyno sheet at "tbichips.com/my projects/blue whale. If you look at my torque curve, it is extremely flat and long but lacks the typical "hump" in the mid rpm ranges. I am wondering if using the GMPP TBI vortec manifold would have made a difference...the two manifolds look very similar but I couldn't find any flow data for either of them. I considered the edelbrock 7116 rpm manifold but didn't want to lose my low end torque. What's your thoughts?

Ken Beals bealsj@mmcs.army.mil

[fastestbbc]

Impalaguy any update on this???

[Guss]

So what is going on any updates???

[chevy_addicted]

updates?

[webcat]

Updates?