99 5.7 vortec build advice

[MPCutt]

im relatively new to the site, but have read a lot of posts to give me ideas for my rebuild process. I've got a 99 K2500 CCSB with a tired old vortec 350 with 260k miles. I'm in the process of building a stock 350 out of a 96 doner truck to replace the tired old dog. This is my daily and I'm not wanting anything crazy, just wake it up a little. Now I'm doing this on a budget and and kinda looking for guidance from those with more experience with vortec upgrades. From what I've read on here, first thing I intend to do is TBI long tube headers (modified for O2 sensors and EGR delete). It's already got the larger 3/4 ton stock pipes, but I'm going to replace the cats with flow master high flows. I haven't decided whether or not to go with dual or single chamber flow masters. Any suggestitions? Now I know that i want to get a tune and I'm pretty well decided on black bear, I have 2 PCMs, the one in my truck now and the one from the 96 doner, is there any reason they would not be interchangeable. Send one to get tuned and keep the other stock? The motor that I'm building is going to be almost stock, maybe thinking about a cam, nothing crazy. Any advice there? I'm not looking for ridiculous HP gains or unrealistic MPG gains. I'm the one that bought a big heavy truck and don't expect hybrid mpg's, but anything would beat the 9mpg I've got now. Any guidance would be greatly appreciated. Thanks for reading.

 

[99'Subourbon]

Use the 96 ECM, won't have to do a crankcase relearn that way. Black bear is tops - well recommended.

Long tubes, 2.5 dual or 3" single. Performance = straight through mufflers, although I don't think there will be that big a difference between chambered or straight through at these levels.

Stock intake is fine, although you can get rid of the resonator to make more sound - otherwise just run a good filter, napa golds are near the best you can get (way better than any oiled filter).

If you are looking into a mild usable cam, look no further than the HT383/RamJet/Marine cam, the '395' cam. It's a great upgrade for the 350, and useable on the stock tune. Grab the comp cams, or alex parts, spring & retainer kit to increase your max lift.

If you want, you can throw in some 1.6 SA Roller Rockers to increase lift by .030.

While the motor is out, a 3, or 5, angle valve job on the heads with some light P&P wouldn't hurt.

Replace the stock spider assy with the updated MPFI spider.

uhhhh what else...

 

[89 8lughd]

Quick question 99 subourbon.the truck I bought has jba headers on with duel cats but goes into one muffler and one tail pipe. Would that strict the powers increase? I dont know what muffler is on it its like the size of a gas tank and quiet

 

[99'Subourbon]

Quick question 99 subourbon.the truck I bought has jba headers on with duel cats but goes into one muffler and one tail pipe. Would that strict the powers increase? I dont know what muffler is on it its like the size of a gas tank and quiet

Sounds like they put on shorty JBA Headers, and tied it into the stock exhaust system. Although the 3/4 ton/HD exhaust systems were massively better than the 1/2 ton system, opening up to a 3" single exhaust would still be better than stock, or 2.5" duals. Ideally, you'd replace the shorties with Long Tubes. From bolt-on to mild, 1-1/2" or 1-5/8" primaries would be best.

And yes, the stock mufflers are garbage, and severely reduce output flow (performance).

 

[89 8lughd]

Cool thanks for the info. Thinking about running two super 10s or two super44s for now until I get a few other things done to it like beefing up the transmission with updated parts along with a shift kit and billet converter and maybe gearing

 

[slowburb]

All this is on the right track. I'm not sure I'd delete the egr but that's just me. Same with the Flowmaster cats. I'd run some thunderbolts instead and still have the rear 02's deactivated through the tune.

You must like Flowmasters for some reason, maybe the sound? Maybe the infamy the have? They're not great performancewise but I'll agree they sound great. I almost think I liked the sound of my 2 chambers better than the magnaflows I'm running now.

Talk to your tuner about which pcm to use. He may want the one native to your truck for the best and easiest results.

 

[MPCutt]

Thanks for the info. I've already upgraded to the MPFI spider last year, works a whole lot better than stock. As far as the cats go, I am partial to flow masters but that's just cause I found some on the cheap, but I did find some thunderbolts that fit my budget.

 

[scott in cincy]

I need new cats too, with a similar build, should I upgrade to the k2500 manifold back system on a fresh 350? I don't plan to put in headers because my luck with them has been bad and leaky.

 

[OutlawDrifter]

+1 on the RamJet/HT383E cam & +1 on the thunderbolt cats. i can't imagine you finding flowmaster cats cheaper than thunderbolts($47.50 shipped).

run 2.5" pipes to a flowmaster merge, followed by a 3" mandrel bent exhaust with your choice of muffler. that will make the best power for a heavy pickup. i prefer dynomax ultraflows, hooker maxflows, or hooker aerochambers. the aerochamber will give you a similar sound to the flowmasters, but have WAAAYYYY less drone in the cab. i don't like magnaflow because they make cars sound like boats or have a glasspack sound to them.

 

[slowburb]

There is a video on YouTube of a 9C1/LT1caprice with hooker aerochambers. That is one of the meanest sounding 350's, IDGAF what anyone says.

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It is tough to find a shop that mandrel bends 3" pipe. Shops that do it usually charge a lot as a result. Dual 2.50's would probably be cheaper even with the added material. Remember than single crush bent/crinkle bent 3" is not the same as mandrel bent 3". In sharp turns it may neck down to less than 2.50".

I can't see any Flowmaster catalytic converter selling for less than a thunderbolt spun cat.