'93 454 TBI in California...

[thesameguy]

Hi guys -

I am wondering if anyone has any recommendations for California legal bolt-ons for a '93 454. This is not in a GMT400, it's in a P30, but this always seems like the best resource when it comes to TBI truck motors.

I'm looking for improvements in the mid-range ... Freeway RPMs hover around 2500, and I'm hoping to thicken that up for better hill climbing etc. Being in CA whatever it is needs to have a CARB EO# ... Being old engines, those parts are often hard to find and documentation is outdated etc.

I'm thinking along the lines of intakes and headers... Seems like that's the easy place for improvements. Any thoughts?

 

[thesameguy]

To reply to my own post, I just remembered that intake manifolds are exempt from CARB requirements so long as they preserve original function... So the question becomes any recommendations for a good intake that maintains EGR, etc.

 

[PlayingWithTBI]

Here's the counterpart to the one I have on my 5.7L

https://www.summitracing.com/parts/edl-3764/make/chevrolet

 

[thesameguy]

That's the one I keep looking at. It make a distinction of -1990 and 1990+, I guess on the basis of vacuum vs electronic EGR. I actually don't know which I have... being a P30-based motorhome, the chassis could be much older than 1993. Obviously I need to look, but I wonder if there's any way around this... I have a vacuum -> electric EGR adapter on my 60*V6 Fiero... maybe there's something similar for the 454?

 

[Schurkey]

First Guess: You'll gain nothing remarkable from a change to a Performer intake manifold except bragging rights.

If this were mine, I'd be looking at the overall condition of the engine: Cranking compression, ignition timing including making sure the electronic advance is working, all the normal tune-up items, air filter, fuel filter, EGR operation, VERIFY FUEL PRESSURE WHEN UNDER LOAD. Verify that the throttles FULLY open when you stand on the gas pedal.

THEN, AFTER the engine is provably operating up to design expectations, install bigger exhaust including fresh (legal) catalytic converter(s). The muffler used on the '97 Vortec 7.4L is VERY restrictive. I bet the TBI trucks have restrictive mufflers, too. Perhaps the OEM muffler is already gone given the advanced age of these vehicles.

You probably don't "need" headers, (good headers might help, so if you're inclined to spend that much money and effort, feel free) but all the pipes from the manifolds back are suspect. Stainless steel exhaust lasts MUCH longer than "Aluminized (mild) Steel".

 

[arrg]

I don't think you'll find many CARB legal upgrades for a P30. The intake you mentioned isn't listed as a replacement for your year, so that's out. There are no CARB legal headers for a P30, so that's out. I think Schurkey has the right idea here. Just make sure everything is working as designed and maybe replace the exhaust. That's about as good as you're going to make it if you need to stay CARB legal.

 

[arrg]

Over here near San Francisco they have Johnny Franklin Muffler that will do a true dual exhaust without catalytic converters and be street legal in CA for around $800 on my 93 C3500 Silverado 7.4, 454

That's not legal in any state.

 

[Schurkey]

The only non-catalyst legal systems I've ever seen involve an EPA exemption. A friend of mine has a Ford truck with no catalysts, and an exemption sticker on the radiator support--I think it's essentially a no-fire-in-tall-grass "farm truck" exemption.

Johnny Franklin is begging for a $10,000 fine; or series of fines.

 

[whiteboyslo]

Bump the timing up to 6-8 degrees BTDC. That was the most notable power upgrade to my 93 TBI 454. Not technically smog legal since CA will check your timing when you smog it, but it takes just a couple of minutes to readjust it back.

Mike

 

[Andrew7]

That's not legal in any state.

ok I had that wrong then it’s before 1975