Mild 350 TBI Build Advice/Suggestions

[5SPD350]

I've been lurking this site, and others for a while just gathering info. I have a 92 C1500 350 TBI 5 speed, and the engine is getting a little tired. I'm mulling over ideas for a replacement. As much as I'd love to do a 5.3 or 6.0 LS swap, I really don't think I can get it done as cheap as staying TBI with my stock computer. I'd also prefer to stay standard as that is what's currently in the truck, an HM290/5LM60/NV3500 getrag. I'm really only looking to do a mild build up, but wondering which would be the better idea. Source a Vortec 5.7 Long block, or just put Vortec Heads on my 350 TBI 2 bolt. I'm considering basically this set up: My block with Vortec heads, a mild cam, carb intake, bored & ported 350 throttle body good for about 620CFM, injector spacer, salad bowl/hypercharger, wide open spacer, 350 injectors with the pressure increased, TBI chip and TPI fuel pump, Long tube headers, 2.5" pipe with an x pipe high flow cats, and magnaflow mufflers, and a 3 wire 02 sensor. Or, the vortec long block, with same mods. From what I understand, the Vortec 5.7 is full roller factory. And a 350 TBI only has roller provisions. I'm also clueless about the whole EGR issue. I will be able to pass inspection without emmissions so that's not a concern. I'm really unsure as to what cam to use. I keep hearing use an LT4 cam, but not sure if that's the hot cam or the stock LT4. It would be nice to have something lopey just for sound, but it's not neccesary. Also keep hearing about using 1.6 R.R. but something about limited valve lift on the Vortec heads without modifications. Also wondering if changing to a 6" rod would be any benefit vs. the 5.7" stock. Also unsure about the pistons, as to stay stock or go flattop. I want to be able to stay at 87 octane fuel. I also have a 1990 454 SS 14 bolt 9.5 5 lug posi drum to drum waiting to be installed. It currently has 3.73's but I will be replacing them in favor of 3.42's to make 1st gear not so useless, and to be able to catch 60mph in second. My main goals are to obviously have more power at least that of a stock 5.3L, keep costs to a minimum, run on 87 octane, turn at leat 5,500 RPM without it falling on it's face so as to be able to catch 60 in second with the 3.42 rear end ratio without sacrifcing too much low end torque,keep it manual, and keep it TBI. I'm not looking for a high horsepower monster, I'd be happy with anything in the 14's to be honest. This would be a street/strip style build. With most of it's time seen on the street/highway use, with an occasional trip to the track to make some passes. It may also do some light towing from time to time. Anyone with experience on a similar build up preferably running a 5 speed I would appreciate some input. Any opinions or suggestions are welcome though. Just don't tell me go LS, I really would love to as that would be my first choice but I don't think it's a reality at this point. Thanks in advance!

 

[shownshine55]

Go to tbichips.com for some build ideas. Brian has ideas listed from bolt ons to complete builds. I do know that your stock tbi intake will not bolt up to the vortec heads. Dart makes a replacement head that is very comparable to the vortec heads. It is the S/S Torquer head I believe. With that you can use your stock intake or upgrade to an edelbrock intake. There is also a tbi induction to vortec head intake out there. The LT4 cam you speak of is different than the LT4 Hotcam. the stock LT4 is like 470ish" lift vs 520ish" lift for the Hot cam. I myself have talked to Brian and he said that the tbi throttle bodies do not get along well with large lumpy cams. For your throttle body, I believe 620cfm would be hard to come by from the stock/modified tbi. I was thinking 490cfm was about the max that people were getting out of the small block tbi. The big block tbi gives you more cfm, but I cannot remember any numbers on them. I have a tbi engine that was put together using ideas from Brian. It has the Dart heads, a LT4 camshaft, edelbrock intake, free tbi throttle body mods, and several other bolt ons. I have not run this engine and probable wont either. I bought a ls 6.0.

 

[SCOTTYINWV]

Vortec heads
Comp or edlebrock towing cam
Ultimate tbi mods
Adjustable fpr
Longtubes

Most explained here.
http://www.gmt400.com/forum/showthread.php?12428-The-Ultimate-88-98-Performance-Toolbox
http://tbichips.com/?page_id=73

 

[5SPD350]

Thank you for the responses! I've actually pulled most of my ideas from Brians site in particular his "LKN Speed Economouse", "Blue Whale", and "Black Magic" projects. This is who I would be getting the Chip/Fuel Pump/Spring from althought I would change the spring out for an A.F.P.R. I've also take a look into a member of a few forums who has a Van with a TBI 350 who has since changed to TPI but had impressive #'s from the TBI. A member of a 3rd gen forum also did a Vortec to TBI swap I looked at two.

First, should I rebuild my TBI block and add the vortec heads? or find a Vortec long block to use? I'm thinking the vortec long block is a better idea as it is full roller from what I understand, and my block only has provisions for a roller cam. So if I don't modify it, I'll have to use a flat tappet cam I think? It's also a 4 bolt main vs. my 2 bolt. I recently found a 90k mile Vortec Long block for $600.00, which I'd prob try to get him down to say $450. Would that be a wise move over rebuilding my TBI block $ for $?

The Throttle body I am looking at is from CFM tech and is advertised at 620CFM. Per their website: "These Ported throttle Bodies are designed for maximum airflow with ported throttle bores, larger butterflies, thinned throttle shafts, button head butterfly screws, and machined top air entrance", "Stock 4.3/5.0/5.7 GM Tbi flows 480cfm. Our's flows 620cfm. More than enough for even modified GM TBI small block engines." RV morse who Brian also recommends avertises their T.B. at around 600CFM.

I'm also dead set on using Vortec Heads with a Carb intake and adapter. I'm not looking to use a TBI Intake on this engine because with the carb intake, I have the option to go carb in the future if say this engine was ever to leave my truck and go into an already carb set up vehicle. As far as the Vortec heads go, am I correct in saying the stock max valve lift is .480" with the stock springs and 1.5 Rockers? If so, the stock LT4 cam from what I have read has a max valve lift with 1.6 rockers of .476" intake, .480" exhaust. This is the cam the guy who built the Van with 350 TBI used, as well as a set of LT4 valve springs. I've also read the pushrod holes must be bored with a 3/8" drill I believe to avoid rubbing? If ran with the 1.5 rockers, that lift would be decreased from .476/.480 though right? But as long as a 1.6 rocker or less is used with that LT4 stock cam, the pushrod holes are drilled, and valve springs upgraded, there would be no need to do further modifications to the heads that I've heard of in regards to cutting the guides down right?

As far as the 6" rod vs. 5.7" rod, I don't think it would be beneficial at only 5,500 max RPM would you agree? I mean I know it reduces side load, improves R/S ratio, and allows for lighter pistons, but is that going to matter at that low of an RPM? Also the question on pistons, stock dish on TBI and Vortec 350 is 12cc. With wanting to run 87 octane would a flattop piston be a good upgrade or should I stay with stock pistons? With that set up of a 620CFM T.B. with supporting items (pod spacer, TB spacer, "power bowl"), Vortec Heads, Stock LT4 cam and springs, 1.6 RR, high flow exhaust and intake, upgrade fuel pump and correct fuel pressure, forgot to add I want to change from clutch fan to dual electrics, and a custom burnt chip, would this engine package be able to breath to 5,500 RPM before falling flat on it's face?

I'm not looking for peak power at 5,500 RPM, realistically with this combo I imagine it will occur at 4,600 RPM. I would like the shift point to be at 5,500 RPM as with the calculations I did on a Gear ratio to mph calculator inputting tire size, gear ratios, final drive, rpms. I found if shifting at 5,500 RPM, that would put the theoretical peak power of 4,600 round about smack in the middle of each range of RPM per shift, keeping the engine in it's power band. Lastly, do you think that combo in a Reg. Cab short box pickup could net a 1/4 mile time in 14's with a curb weight of about 3,717 lbs (3,907 with driver roughly)?

Sorry for so many questions, and I appreciate the responses thus far. Just trying to get my ducks in a row as tax season is coming up and I want to do this right the first time around.

 

[superdave]

As long as the engine in your truck is still somewhat usable, I'm a big fan of finding another low mileage Vortec or rebuildable core as a starting point. Going to the Vortec long block is going to give you some advantages and it won't put you down as long since you can prep that one before yanking your current engine. A 90k motor for $450 sounds great. You might be able to get by with very little machine work on that.

I have 138k on my 97 and I would love to build a motor, but mine runs like a top and I just can't force myself to yank it. I'm going to look for another motor in the spring to build.

 

[5SPD350]

My 350 TBI just turned over 172,000 miles. I think it's still got some life left on it. It just feels down on compression and oil pressure is a little low compared to a lower mileage one which I hear is common (or could be my sending unit). No knocking or anything like that, just getting a little tired I do believe. The Vortec 350 long block is sounding like the way to go 100%, I like the fact of already having the heads on it and already being ready for the upgraded roller cam.

 

[Horns]

Take that fvcking TBI off and throw it in the damn garbage.

 

[5SPD350]

Your suggested replacement for the throttle body would be?

 

[Keepinitoldskool]

I will be following this as I am in the same boat. I would like to keep my current tbi setup for simplicity but am afraid of the headache trying to tune it.

Sent from my SAMSUNG-SGH-I537 using Tapatalk

 

[Horns]

Your suggested replacement for the throttle body would be?

Carb are MPFI with a 411 swap. TBI being the first of the EFI, it's at that point where they didn't quite get it yet. Also tuning is a pain and is becoming obsolete. It's just a nitch area when it comes to TBI.

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