454 TBI Build

[Nasty-Z]

Have you done any work to the heads ? You will need to address guide height as well as a good spring package with rotator eliminator with those heads . They cannot be left stock with almost any aftermarket cam .

I have built quite a few 454 combos with the Vortec heads as well as a few 496's , excellent performer for the $$ spent , the heads will support more than most think .

I would loose the Holley TBI and find a good 454 Unit . Oh , and the Vortec F/P or a TPI pump will be fine.

TOM

[Sla90lx]

Tom, thanks. The heads are ready to go. I have the throttle body off of the ,sorry, 92 not 94 454. Picked up the holley real cheap and saw that the bores were larger than the gm. So stock would do better huh?

Chris.

[Nasty-Z]

Both the Holley and a BBC TBI unit share the same bore size @ 2" .

The factory unit is better by far .

TOM

[Sla90lx]

Okay. Did a search on comparisons with no luck. I'm sorry, I just like to know why something is different or better. It's been a few months now but I remember measuring both and seeing a touch difference in size, and I know holley claims it to be 670 cfm. Not saying I don't believe you just maybe myself.

[Nasty-Z]

The Holley 502-6 (or 502-9) TBI unit has 61 +/- PPH injectors and the regulator is good for around 20 psi +/- IIRC , with the regulator turned all the way up the Holley injectors will flow right around the 80#/hr the 454 OE injectors do @ 13 psi . There is a lot more room to grow with the OE unit. The Holley unit was never designed to replace a OE 454 TBI , it was sold for SBC engines as an upgrade over the OE SBC unit.

Holley used to offer an 85 pph injector but the replacement TBI unit that used these injectors was not a direct bolt on like the 502-6 (502-9) or the OE unit .

The MAP port that Holley wants you to use is at the rear of the unit , it intersects the IAC passage , if you are dead set on using the Holley unit , run the MAP sensor directly to manifold vaccum and not this port for the most accurate reading , this little detail has snagged more than one tuner.....

Stock 454 TBI uses a 2" bore , same as the Holleys , the only way you measured a difference in bore diameter is if you really don't have an OE 454 TBI and you have a small block version , the bore on those is 1-11/16" .

FWIW, the OE 454 TBI can be bored and sleeved to 2.244" max , whereas the Holley can not .

Be sure of which OE 454 TBI unit you have , 94-95 are different than the early units and run a smaller injector at a higher pressure (46pph @ 28-32psi) . The early units are 80 PPH @ 13 psi .

What intake are you planning to run with the Vortec heads ? Have you addressed the port mis match ?

TOM

[Sla90lx]

Thanks for the info. The only thing I'm dead set on, is getting this combination of parts right. If there's something that I can change now and avoid headache latter I'm all for it. I just measured both TBs again, stock 2.000 holley 2.025. I'm not trying to split hairs, just telling ya what I have. I see the map port and agree that's poor placement. I have started an album of this build I'll put a few pics of the TB and injector in there. I'm using the edelbrock rpm and did not see any port or alignment issues. I hope there's not something I've overlooked with that. Oh and it was a 92 which doesn't matter cause someone robbed the injectors before I got back to pull the engine.
Chris.

[Sla90lx]

Okay, time to move this one back to the front burner. I have run across an accel dfi setup and wanted to know if you thought this was better than tbi or overkill for my mild combination. I don't think I wouldn't use the gen 6 controls but rather a gm computer if doable. If I go tbi the gm tb needs injectors. The holley looks like a better unit and I like the pressure reg on it. If I can get the 85 pph injectors and run map to intake, are there any other problems with this tb? I know I'm overanalyzing this, I just want it right. If y'all tell me gm tb then that's the way I'll go.

Thanks, Chris.