1991 RS 305 TBI Questions - Third Generation F-Body Message Boards

SBChevyCass · 09-29-2009, 06:12 PM

Hey Everyone! I'm new to the TGO community and am interested in the knowledge of California Members who have battled the CARB Nazi's. Im looking to build a powerplant that will pass the CA sniffer and fool the CARB Referee's. All the while making enough power to pinstripe the town...

So Im on the hunt for an L98 long block...

1. If I get my hands on one of these, legally, am I able to basically bolt this down in place of my 305? Using my TBI setup, factory smog, and some higher flowing injectors?

2. If so, can I replace heads? Is there CARB legal ones that flow better than the clunkers?

3. Can I stroke this 350 to a 383?

4. How big of a cam can I get away with in either the 350 or 383 setup?

5. What are my exhaust options? (I curently have a 2 1/2 catback magnaflow exhaust with factory cat) Header/Cat/Exhaust sizing suggestions...?!?

I have about $2500.00 to work with. Im patient. Have another car to drive while working on this one. And love to wrench... Anyone ever been on this similar path??? The cars been in my family for 10 years, so buying another car is not an option... this babys got some serious intrinsic value to me. I will post pics soon. Again first day as a member! Go easy on me if my post is rough

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Russ-So Cal · 09-29-2009, 08:44 PM

You don't need to fool the smog nazis with anything. Don is making 372 hp at the rear wheels & 411 # of torque with a smog legal L98 bored to 355 ci. Any engine that was available on a Chevy or Pontiac in 1991 is smog legal without needing to see a referee. I would not bother spending the money to build a 383. There is not a smog legal fuel system on the market that will flow enough air to feed a 383. So you need to switch over to tpi, and go from there.

SBChevyCass · 09-30-2009, 02:53 PM

So just to be a little more clear...

you are advising me to scratch the stroker idea...buy an l98 long block... bore over a little... ditch my tbi...buy an entire tpi setup...and i will be smog-free with power, while still spending < $2,500???

I'd really like to stay TBI if I can, to eliminate additional costs so I can hopefully build a healthy exhaust system. If I do stay TBI what modifications do I need... err rather what injectors should I use.... again, im trying to keep this build within budget especially considering most builds cost about 25% more than predicted.

Dyno Dan, please advise.... seems you got the right ideas.

Kevin91Z · 10-02-2009, 03:12 AM

383's dont work with TBI or TPI engines very well, so scratch that idea.

TBI engines tend to run out of fuel around 300-325 flywheel horsepower. There's only so much you can do with two injectors. Plus the computer is horribly ancient. I dont tune them anymore due to the lack of available blank chips. You can upgrade to a EBL computer (search the TBI forum) to address this issue.

A nice 350 engine that wont overtax the TBI engine would be something like stock F-body TPI iron heads, a smallish camshaft with less than .480 lift, a set of decent headers like Hooker 2055's or Dyno Don's, the Edelbrock TBI intake manifold, larger injectors such as 65lbs or 72lbs, and maybe a Holley 670cfm throttle body.

You could also get some Edelbrock Performer aluminum heads with the 170cc intake runners. They'll handle a bigger camshaft like a ZZ4.

But you're still limited by the stock computer.

You could do a TPI upgrade on your existing 305 for way less than $2500. Dyno Don did it on his previous car, a 92 Camaro RS, and gained 18 HP and 70 TQ at the rear wheels. Then he put an LT1 cam in it and gained another 7 RWHP. Then save up some more money while you build up your 350 block on the engine stand to swap it in later.

SBChevyCass · 10-04-2009, 10:57 AM

Kevin,

Thank you for the info. A few additional questions for you....

So a TPI swap alone would grant me 70-80 torque to my wheels???? If so, thats incredible! Im assuming it would use a dif ECM as well. Right? Whats a decent price for all this im looking on ebay and the prices are all over the place... what injectors would i use on the 305?

Also a stock 305 with TPI could handle the LT1 cam??

last, how much does Dyno Dons headers cost? Eventually i wanna go 3" from headers and on but again, I'm stalled by legality... dont those headers need to be CARB certified?

92purplehaze · 10-04-2009, 12:34 PM

Quote:

Originally Posted by Kevin91Z

383's dont work with TPI engines very well, so scratch that idea.

elaborate please....

Kevin91Z · 10-09-2009, 02:41 AM

Swapping to a TPI setup will grant you lots more torque, yes. How much is a factor of the condition of the rest of the engine. The example I gave is only one example, so your mileage may vary, etc etc.
Yes you will have to change the ECM, have me make you up a custom prom, and re-pin your existing TBI wire harness to work with the TPI computer and sensors.
Yes a 305 engine will handle an LT1 camshaft with no problems. However if your stock springs have more than 100,000 miles on them, I'd recommend replacing them, as well as your valve stem seals, so you dont get the "puff of smoke" on startup when they wear out.
You'll have to contact Dyno Don directly about his headers, as he doesnt like to discuss business in public.

383 engines require a lot of air and fuel, and a stock TPI or TBI setup is not capable of flowing that much air. There are several 383 TPI setups out there that make less horsepower and torque than our 350 TPI setups. A 383 makes it own torque, so it wants a short runner setup like a Stealth Ram or MiniRam to be most effective. However, neither of those intakes are California emissions-legal, so you cant use them.

SBChevyCass · 10-12-2009, 12:12 PM

Kevin,

So i Have an option to buy an entire tpi setup off of a 1992 z28 350 for about $500. Includes all sensors, fuel rails, injectors, he said he will also throw in the ecm and harness and distributor... my question is, is that a good deal?

It looks to be in good condition, but he has an automatic and i have a manual, does that change anything with the ecm? Im assuming ill have to swap in some smaller injectors as well if i plop this thing on top of my 305 right?

Russ-So Cal · 10-12-2009, 01:02 PM

That sounds like a pretty good deal to me. I would try the 350 injectors first before replacing them. You would need Kevin to burn a custom chip for you to let the ecm know you are running a 305 instead of a 350. The ecm will then compensate for the smaller engine. Kevin might also need to modify your fuel map, and he might need to change the settings for wot, but that is all a part of the custom chip. The other thing I'm not sure about is that when GM went over to speed density in 1990, they changed from running a separate harness for the engine and a second harness for the body and put everything into one harness. If your tbi harness is in good condition, it might be less hassle and expense to have Don repin it for the tpi ecm rather than rewire the entire car. You would need to discuss details with Don and Kevin.
See Dyno Don's info in the sticky "So Cal Third Gen Friendly Companies" at the top of this page.