I got sent here from the main boards, hopefully some of you guys can give me some more localized help...
I'm trying to build up my 350 TBI to something a bit more than it is now. I've got all the supporting mods out of the way and I'm ready for a motor. Been considering lots of things, hopefully somebody can help me out. My goals are a daily driver that gets good MPG around city (high teens?) and passes smog with flying colots looking like a 305 TBI without having to pay somebody off. I have a 454 TBI unit and injectors to go with it standing by should I need it. Also installed a TPI fuel pump. If I could go mid or low 13s down the 1/4 I would be more than pleased. Its mainly a street car and I'll always give up a tenth here a tenth there for driveability and mileage.
First of all heads. First I considered iron L98 heads. My problem with these is some people say they don't flow too well, and I worry about the cost of any machine work I may need to get done to them making them not worth the cost.
The good thing about these is I understand they will support stock style EGR operation and look completely identical to L03 heads from the outside. They seem to be the best thing GM has to offer for a gen I though with the exception of vortecs.
Also considered Vortecs. Trouble here is there is no vortec intake manifold that is CARB legal. I don't want to take the risk of building this thing up and having them notice something THAT big and have my whole car be screwed. Also I dont know how vortec heads work with stock style EGR.
Also considered AFR 180cc heads. CARB legal, aluminum, so many advantages. Trouble here is finding an intake manifold that flows well enough to support them. My only options as far as I see it are stock, and the edelbrock one. Neither of which i'm sure flow enough to support the AFR heads making them a complete waste of money.
Edelbrock heads were also suggested. Seem to be almost the price of the AFR heads though.
Here are the two cams i've been looking at. Of course i'm open to any new ideas.
Don tried converting a g-body El Camino to tbi. Since the stock small block tbi unit won't flow enough air to make horse power, Don modified the stock tbi manifold to take a 454 tbi unit from a truck. No matter how much he "tinkered" with it, he could not get the maniofold to balance the charge between cylinders. It would either lean out the end cylinders or flood the center cylinders. He ended up changing it over to tpi.
I wish we could be more help but we're all about TPI here. You need to talk to Fast355 or BMonteSS for TBI help. They have managed to have decent TBI results where we have given up on it and made more power with TPI.
It matters what's sitting on top because if your heads and cam will handle more ariflow than what's on top will flow, you won't get any gains from the heads and cam. All engines are a system, with fuel system, cam, heads, and ecm working together. If they don't work together, you don't make the horse power you paid for, and you may not be able to pass smog in Cali.
Are you telling me a large TBI unit, which has what, about 50mm throttle blades, wont flow enough air for mid-low 13s in a car with all the mods listed in my sig running an EBL and a custom tune?
All I wanted to hear were some heads and cam combos passing smog. I'm well aware of what makes an engine tick. I'm sorry I even asked, thanks for the "help"
I'm sorry you didnt find what you wanted, but none of us here are running moddified TBI's. We're all TPI or stock TBI wanting to upgrade to TPI.
I would think a set of 180cc aluminum heads, headers, and a ZZ4 camshaft would be enough to get low 13's. It did on my TPI combo. I have never touched an EBL so I know nothing about it, but the stock TBI computer is horribly slow and limited in its ability to react to changes in the fuel and air. Plus we havent found two injectors big enough to get as much fuel as eight injectors.
Good luck in your quest. As I said, the guys on the TBI board would be more help in modifying TBI's than we would.
keep the overlap to a minimum. as for the heads make sure they have the heat riser so the egr works. to get performance parts to not be detected by the tech, keep the bling out. the more stock it looks the better. you most likely will be able to pass the sniffer with a properly tuned engine and the right parts, but the tech seeing somthing can fail it on visual alone. one trick i have used in getting an engine to pass the sniffer is changing rocker ratios around a bit.
one option on getting more flow out of an intake is to extrude hone it. also keep in mind it isnt how big the ports are, its how fast the mixture flows through it is what matters.
Another problem you may run into is getting the bigger tbi unit to evenly distribute the mixture. Don worked on an El Camino for a friend who was tired of getting bad fuel mileage on a carb. The engine was a 383 and the first attempt was to open up the stock tbi manifold to take the big block, truck tbi. No matter what he tried, he either had the center cylinders running rich or the end cylinders running lean. If the center cylinders were lean enough to pass smog, the end cylinders would be so lean that detonation was an issue. Richen up the end cylinders enough to avoid detonation, and the center ran so rich that it wouldn't pass smog. He did not try an Edelbrock tbi manifold, he gave up and installed a tpi unit on the engine.
another alternative to the manifold distribution isuuse would be to use a manifold for a quadrajet or holley and if one is availe use an adaptor or make one for the tbi unit.
I think you need to try the TBI board, you're going where none of us have gone successfully. Many of us have achieved your stated goals with TPI, none with TBI, so our ability to give you advice is pretty much limited to "if you had TPI..."
another alternative to the manifold distribution isuuse would be to use a manifold for a quadrajet or holley and if one is availe use an adaptor or make one for the tbi unit.
That technically wont pass the visual inspection but if you use a 50-state carb manifold I dont see why any reasonable tech would fail you. But for the cost of the carb manifold plus the adapter I would think the Edelbrock TBI intake would be cheaper.
Kind of off topic but I saw a 454 Z-28 pass smog a couple weeks ago. Guy had one of those 454 TBI engines in it, he actually did a real nice install passed visually and emmisions. I know it should have failed visual real quik but hey not all smog tech's can tell a bigblock from a small block, wish I had that luck. In the end it just comes down to how neat everything looks and nothing is out of place as to how you will do visually.
