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Posted here periodically before, but was on a bit of a hiatus from the third gen world for awhile. I now have a place to work on my firebird, and am finally getting ready to pull the 305 out and drop in a 350 (305 needs a rebuild/runs like crap and smokes/leaks oil. Don't feel like putting money into one )
My main plan was to just hunt down an L31 longblock from a scrapyard or craigslist, and use TBI with it (I'm aware of the intake, and other fuel/ECU mods that will be necessary). But part of me is wondering if vortec heads are my best sbc option on a budget, due to the cost of the intake manifold. I'm aware that you can also use an adapter plate and run TBI on a carb manifold, but I have to pass smog where I live (Haven't found a carb intake w/EGR provisions).
Basically, what I'm wondering is if hunting down another 350 short block of some kind, and finding some other good set of heads (or another longblock altogether), and using my existing intake manifold is another good option? Or can the factory TBI intake manifold only be used w/the crappy swirl port heads from TBI motors?
I'm not building anything too wild - Probably about a 300 flywheel HP or so setup (Give or take). Enough for the car to feel like a beast compared to an L03 on it's way out I guess . I figure it's doable on a scrapyard budget, I just want to know about other possible part options to consider before just going for the L31.
My main plan was to just hunt down an L31 longblock from a scrapyard or craigslist, and use TBI with it (I'm aware of the intake, and other fuel/ECU mods that will be necessary). But part of me is wondering if vortec heads are my best sbc option on a budget, due to the cost of the intake manifold. I'm aware that you can also use an adapter plate and run TBI on a carb manifold, but I have to pass smog where I live (Haven't found a carb intake w/EGR provisions).
Here's a carb intake manifold with EGR for Vortec heads.
Looks like after I add in a TBI adapter plate, there isn't much in the way of cost difference between the two options I have there, if buying new (And Jegs has the TBI one for a bit cheaper). But that's still cool that there is a carb intake w/EGR. But is there any reason it would be better to go w/a carb intake w/an adapter vs just getting a TBI version?
Also, bringing this thread back up with some more specific engine ideas in mind - more specifically, two things I've been debating over...
#1 - Vortec heads, vs L98 heads - It's my understanding that the Vortecs offer superior flow, but that the L98 heads are aluminum, saving weight, and can still put out decent numbers. That, and you can run a factory TBI intake manifold with them? Correct me if I'm wrong/feel free to mention any other heads worth considering on a budget build - Or just flat out tell me to suck it up and go vortec!
#2 - Is a 350 really needed for my relatively modest (300 flywheel HP) power goals? - I know, I might get the evil eye from some for even giving any thought into staying w/a 305, but the only reasons I ask, are because I've seen quite a few budget 305 builds w/surprisingly good (and perfectly streetable) results - All with basically just heads, exhaust, and tuning/fuel system stuff on stock shortblocks.
L31's seem like a hot-ticket craigslist/scrapyard item (cheap + good power = they get snatched up quick for projects), whereas people are damn near giving away perfectly healthy L03's (which at least already have roller cams, unlike the L05?), and there's often people selling vortec head pairs for cheap who decide to go even bigger too.
Just something I've given thought on, to try and make my part search easier with the whole "use what you got/boneyard special" route that I'm going here.
Truthfully if I had to do it all over again with TBI I wouldn't touch the 305 and just build a 350. Albeit my 305 was nothing to scoff at (ZZ4 heads/cam and an edelbrock RPM intake) It was easily capable of bottom 13's but I got bored with it pretty quick. The same setup on a 350 would've gotten me into the 12's with ease. Build the 350, you'll be happier in the end I promise you.
I'm putting a 305 TBI together right now for my mom's 89 Firebird. I have the 081 TPI heads and TPI exhaust manifolds/y-pipe combo to help it out. LT1 cam too. I'm doing it this way so that it stays in stealth mode and gets no attention when the hood is up.
I think its gonna be quite a bit better than the OEM TBI setup. We'll see soon enough. I'm gonna most likely use those TPI heads when the next short block goes in (later on down the road) because they get good reviews on our forum.
The main thing I'm still curious about is the whole TBI-specific intake, vs the carb intake w/an adapter plate. Based on an EGR-provisioned carb intake I've found for 87-95 centerbolt heads, and a TBI-specific one, both add up to about the same costs if buying new, after getting the adapter plate with the carb one.
Is there some other advantage to using the carb intake I'm not aware of? The only thing I can think of is that it looks like it might be easier/cheaper to bore out the holes on the adapter plate, than do do it with the entire manifold itself w/the TBI? (Or does the plate on the top of the intake come off too?).
Furthermore, is an aftermarket intake manifold a must if going the non-vortec route?
I went both ways - it all depends on you situation. For smog legal (no headache with smog referee ) swap route factory intake is the way to go. For performance oriented solution - carb intake with adapter plate is the way most people go.
Going carb intake route gives you more options - there are a lot more mfg's that make intakes with Q-jet or even Dual jet mounting flange. With right flange adapter just about any intake can be used with TB-220. The only issue that one will run into are vacuum leaks, especially with poorly made adapter plates. Also, if you have 700R4 TV cable bracket will have to be addressed.
Boring out GM TB intake from 46mm to 52mm requires access to a CNC milling machine (Bridgeport or HAAS CNC center makes a quick operation) with right end bits and a bit of ssetup. Most GM intakes can be bored to 52mm, but there are few with thinner castings (do not have casting numbers) .
Well, at this point, this is an old thread, but I figured as the OP, and back in this dilemma, I'd just bring this one back up instead of creating a new one.
Here's the latest - Not much has changed with this car, with the exception of many things being disassembled/removed from the car. The good news/result of this project taking forever to complete? It won't be a whole lot longer before the car is emissions exempt in my area . The way I see it, this will open up more options for me with what engine parts I can use.
"Use Vortecs!" has pretty much been drilled into my head at this point as the go-to budget performance option for a street engine, but I was wondering about these heads as well?
On paper, they seem like a good option for a mild-moderate street engine. Plus, they can accept a higher lift cam than a stock vortec without the need for machine work/don't need a vortec-specific intake.
I also see classified ads for sets of rebuilt heads in my area at times (From "camel hump" 461's, to 882's and some others) - another possible option?
Same power goal in mind as before, but can go with other options, due to not having to worry about getting smogged by the time the car is back on the road. Retaining EGR would be a bonus, though (The TBI stays!)
72 cc heads on a 350 leaves you with compression problems. Either you add dome pistons, or you suffer with lower-than-optimal compression ratio.
Here's a thought: I have a bare pair of new-in-the-box aftermarket cast-iron EngineQuest heads. Never been used, but several years old. Vortec ports, Vortec combustion chamber (they breathe, they compress, and they burn just like Vortec heads. Also like Vortec heads, they have no exhaust crossover.
These heads are equipped with the conventional intake manifold bolt pattern. You add a $100 used-on-eBay Bowtie intake manifold that has EGR provision, or, with some modification to the center bolt holes in the manifold, you could use the original TBI manifold. You will have to supply exhaust gas to the manifold since there's no exhaust gas crossover in the head.
$450 plus shipping and they're yours. Add valves, springs, etc. and some creative exhaust plumbing that you'd have to do with any other Vortec heads, and you're set.
03-30-2013, 02:34 AM
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. I figure it's doable on a scrapyard budget, I just want to know about other possible part options to consider before just going for the L31. 
