'95 GMC Step-side, Needing Tips On Mild Performance Rebuild of Stock 350 TBI

[Ken Hunt]

Ignore my Avatar as it was from previous build of a square-body p/u, I plan to have pics of this '95 GMC project if I can first put together a reasonable plan to take its mild 350 2-bolt (with stock TBI and cast-iron exhaust manifolds ) and make it into something a bit more fun to drive and street legal. Am thinking something in the neighborhood of 280 to 350 hp, so will definitely need different heads and exhaust, plus, I am assuming, different cam and pistons.

I have the engine out on a stand, and want to do much of the work myself. I need to know where I can go to find out all the working combinations of engine hardware to do at least the following:

>provide proper air-flow in and out of the engine
>cam selection for nice engine lope and decent power
>proper heads and pistons specified for a compression ratio to maintain use of pump-gas if possible
>proper fuel delivery (TBI or Multipoint Fuel Injection?, fuel pressure?)
>computer selection to make it all work for a drive-able combination with decent power for fun (not a drag-strip monster necessarily)
>sources for brackets and hardware to make sure we can re-bolt on all accessories (alternator, power-steering, A/C, etc. )

>or... the wisdom to say the whole thing is more difficult than just dropping in an LS and doing a conversion.

Is there a cook-book to look up all the combinations that are common to this engine so I can see what will likely work to begin my parts search?

 

[Tim W]

Since the engine is on a stand, I'd make the engine a 383 stroker. You can't go wrong with vortec heads. Im running an LT4 hot cam. The cam has good power and has a choppy idle. I can get you my engine build sheet if youd like. I'm not sure what your budget is but i didn't cut any corners with cheap parts with the exception of my intake. The one I wanted was on back order so I just got what was in stock.

My fuel and ignition are Holley sniper

 

[LC2NLS6]

383 with vortec or good alum heads, cam 230+ at 50, headers, edelbrock performer rpm intake, holley sniper or terminator x efi (controls the trans unlike the sniper).

 

[Ken Hunt]

Thanks, good info guys. Being new to the site I looked for but missed the "The Ultimate 88-98 Performance Toolbox" thread, which appears to have been around for years. Not all the html links still work, but sure seems to be full of good stuff as well. How tough is it to get the accessories to bolt on after upgrades to block and heads?

 

[Schurkey]

How tough is it to get the accessories to bolt on after upgrades to block and heads?

As long as you use heads with the accessory bolt holes in the ends (everything built since...1969(?) you should be fine. Get the accessories and brackets from one application--mixing and matching could lead to problems.

Pay attention to quench/squish distance. If you don't use a thin head gasket, or cut the block, this distance will almost always be too huge.

Vortec heads look great...until you try to make the EGR functional. You'd also have to drill one hole in the right-side head deck surface, to make the coolant bypass functional. Consider the Summit TBI aluminum heads instead.

 

[Erik the Awful]

If you're only looking to make 280-350 hp, I'd stick with the stock TBI heads and port them. I'd only look at Vortec heads if I had them handy and had to stick to a budget. In my opinion, if you're wanting to replace the heads you'll want to replace the induction system as well and aim for 400-500 hp. Otherwise you're just burning cash.

The big question is whether or not you have the roller cam provisions in your block. If you do, go to the treasure yard and buy the factory roller setup - nab a couple extra lifters out of the next motor over. A roller cam is enough of an upgrade that there is absolutely no reason not to. If you're considering paying for a head swap, a roller cam is a no-brainer. Do it.

No matter which style cam you run you can ask here for a cam recommendation, but your best bet is to call the cam grinder you prefer and get their input. I called Lunati and got a great cam for my motor.

My TBI motor was garbage, but I got a four-bolt main TBI block with roller provisions from a friend. One of the pistons was chewed up from a broken valve seat, so I put a set of Speedway Motors claimer rods and a set of flat-top Speed-Pro pistons in it for 9.7:1 compression. I put Vortec heads on it (check carefully, most are cracked) and the Lunati cam with LS2 valvesprings. I'm running .515" lift with a 230° duration at .050". I had to switch induction and went with a Holley Sniper on a Summit intake and the factory ignition. I have Hedman headers and dual 2.5" exhaust with an x-pipe. It doesn't lope so much as thunder, and has torque for days. I'm hopeful that once it's tuned it will make over 400hp, but I'm currently driving it carefully with a junkyard 700R4 while I rebuild the original transmission.

With the original TBI motor, I took it apart and found water sitting in one of the bores. It needed overbore, so I put a set of flat-top .030" over Summit pistons in it. I ported the TBI heads. It didn't have roller cam provisions, so I put an "L79" flat-tappet cam in it. It has a vintage Edelbrock C3BX intake with a 650 Carter and a set of 2.5" outlet ram horn exhaust manifolds (won't fit in our trucks). I'm hopeful it makes around 300hp, but it's still on the engine stand.

 

[Tim W]

Im with Erik. With my truck being a 94 I wasn't sure if my block had the roller cam provision in it so I scored a vortec block for $100 and started from scratch with a completely bare block.

I had the block Magnafluxed and bored to a 383. I purchased My Vortec heads new so I knew they were not cracked. Looking back I wish I would have put edelbrock heads on my truck but I'm happy with how my truck drives. Its got power for days and sounds wicked.

This was the first engine I built from scratch so I didn't really know the heck I was doing as far as the internal parts. I talked to a ton of engine builders and got alot of input on part brands and their quality ect.

I learned don't settle for a HP/ torque number just to get it going. Get the most out of it while its apart.

 

[Tim W]

I did a little video of my truck at an
idle.

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[Don Loeser]

How much hp gains can a guy expect by just putting on vortec heads and intake on tbi setup. I have a edlebrock cam and longtube headers already. It's still pretty sluggish and want more power.

 

[Don Loeser]

Anybody out there? Just wondering if it's worth it. Anyone recommend?