Chadeux wrote:
So in the thought process of trying to decide how to get the GTA rolling again. The "it's certainly a 350" I have seems like the right option if I wanted to spend no money and just wanted to slam it together and then ignore. The basket case L98 I have seems like the right answer if I want to tear it down and send it to a machine shop. So now I'm looking at other options. Like a 90s Vortec 350. I have questions.
Question 1. What exactly has to be done to a Vortec head to make it work with a bigger cam that actually makes power? Everytime I google for that answer I find something different.
Question the other. Does anyone know of a decent and reasonably priced EFI intake manifold that would bolt to those heads and fit under a flat 3rd gen Firebird hood? I'd use the stock truck manifold but I don't want spider injectors. My other dumb idea was a marine manifold that apparently uses normal injectors but I haven't actually tried to find one yet.
The Marine idea is a great one, but they aren't very easy to find. Find some marine salvage yards near water and you might get lucky, but expect to pay some moolah for it.
The suggestion I always come back to with a budget/easy SBC is to TBI it. I personally detest TBI for the most part, but I have work-arounds. First, many of the TBI issues have to do with the rest of the engine; loose guides and cheap valve seals cause oil burning, many of the blocks were not roller-cam-ready, etc. But if you keep those things in mind, you'll be fine.
TBI swirl-port heads were awful. They were the lowest-flowing SBC head Chevy ever cast including for a 283 in the 50s. They were going for low end torque and fuel efficiency. They failed miserably. Actual road MPGs were down compared to the electronic Qjet it replaced, the first batch only made 180 hp and sub-300 torque, and they fall flat on their faces at 4200 rpms. Some guys have ground away the swirl humps in the runners with modest success, but then you're still stuck with a tiny, inefficient port. Don't use swirl port heads. Period. I know you're making a low-end torquey motor, but the TBI heads are so small that they don't shine at anything except wheezing like a fat kid with asthma. (I was a fat kid with asthma so I can say that). Something like Vortec heads support greater bulk flow without huge ports which keeps the intake charge speed high. That's a win-win. You'll actually get more torque at the same low-rpms as the TBI heads, plus have more power above 3000. Throw in the fact that Vortecs have very efficient chambers and you can go about one full point higher in compression on cheap fuel furthering the benefits. Count on 8.7:1 with old-school heads, but 9.6:1 is easy-breezy with Vortecs.
Vortec heads flow very nicely. They flow more than any other production Chevy head on the intake side, and any shortcomings on the exhaust side can be handled with about 10 more degrees duration. They do like to crack between the exhaust valve and spark plug hole, so I suggest getting some aftermarket Vortecs from Summit which are not that expensive, they're brand new, cast thicker, and already allow more lift than stockers. Until you add up machining costs and/or aftermarket retainers for stock Vortec heads, you're darn close to just buying the Summit heads and bolting them on. IIRC, they are also drilled to accept either intake type; port mismatch notwithstanding.
For the TBI, don't use the 350 TBI unit. Its a horrid thing. They advertised flow at about 500 cfm, but until you get the nozzles on it and wet flow it, its more like 390. Get a 454 TBI. It actually flows a decent amount. The nozzles are still junk (they squirt liquid fuel at 27 psi unlike injectors that atomize fuel with 40-60 psi) because they are designed for volume. 2 nozzles are made to flow the same fuel as 8 injectors. Having said that, they are reliable and they physically work.
But as far as parts-bin surfing for the best of all, it won't happen easily. If I were personally doing it, I would spend the money on aftermarket replacement Vortec heads to avoid cracking issues, then put a Marine intake on it and hack a factory truck computer. (marine ECUs don't have enough control since they don't really rely on vacuum for anything, don't have as much varying climate needs, and don't have as many ways of changing the maps for differing conditions). Then I would get into and realize how much headache and money its going to be and remember that I'm pretty good at building Qjets.
BTW... Marine is also a good source for Vortec carb intakes. When marine engines went to Vortec longblocks, they didn't necessarily go EFI. Most had Qjets. You could order a ZZ4 intake for $$$, or get an Edelbrock carb-vortec intake for $$$$$$, or just find a junkyard Mercruiser vortec carb intake for scrap money. The Marine carb-vortec intakes are licensed copies of the ZZ4, so they would work beautifully. I have built a few handfuls of carbed vortec engines using marine carb intakes and they work great. Its one of the cheapest ways to get Vortec performance with a carb and not pay $400 for the intake itself.
