Head Swap Options For 5.7L 350 TBI Engine

[99xcss4]

where are you getting your info for the tbi injector rates I have a 94 454 tbi and it came stock with 90lbpr injectors and use a fuel pump that operates between 28-32 psi I do not know what fuel pressure regulator spring is in it I have also read that old 454 tbi engines came with 80lbpr injectors and used the 4.3 305 and 350 fuel pump I do not know what fuel pressure regulator spring was used in these

 

[L31MaxExpress]

where are you getting your info for the tbi injector rates I have a 94 454 tbi and it came stock with 90lbpr injectors and use a fuel pump that operates between 28-32 psi I do not know what fuel pressure regulator spring is in it I have also read that old 454 tbi engines came with 80lbpr injectors and used the 4.3 305 and 350 fuel pump I do not know what fuel pressure regulator spring was used in these

Your 94 came with the high pressure version of the 46# 4.3L injectors but running at ~30 psi for 74 lb/hr. The 80# injectors are the older 454 12 psi units.

 

[99xcss4]

this is what I have been going by is it correct see post #3 https://www.gmfullsize.com/threads/454-tbi-vs-454-vortec.59727/

 

[99xcss4]

are the numbers free flow or a percentage of duty cycle?

 

[L31MaxExpress]

this is what I have been going by is it correct see post #3 https://www.gmfullsize.com/threads/454-tbi-vs-454-vortec.59727/

Not sure where Pauly got that number, but it is wrong. The 454 high pressure applications us 17104288 with Pink/Purple markings.

GM TBI Injector size, color and part numbers

TBI Injectors If you have any other injectors numbers add them to the list. xxxxxxx - color / color - 33pph - 2.8l and 3.1l xxxxxxx - color / color - 45pph - 4.3l engine NOTE: Some came with 2 differant size injectors? 5235279 - White / Green - 54pph - 5.0L / 305 Cars/Trucks

www.gearhead-efi.com

 

[L31MaxExpress]

are the numbers free flow or a percentage of duty cycle?

Static or Wide Open flow, some want to claim 12 PSI, but 13 PSI is what has always lined up better with the ratings. Which is why I always say a stock "12 psi" TBI system needs 13-14 psi to run the way it should. On your 454 truck you want 30 psi.

 

[PlayingWithTBI]

I do not know what fuel pressure regulator spring was used in these

It's called a "28 LB" spring running from 26 - 32 PSI. You can get one on places like Flee Bay, Amazon, etc.

 

[Majoraslayer]

Getting back on topic, I think I've settled on TPI heads if I do go with a head swap. I'm just not having much luck actually tracking some down. Also, I keep running into two different casting numbers referred to as TPI heads, so I'm not sure if there were multiple options or if it's a matter of one being for the 305 and the other is for the 350. Should 350 TPI heads be 14101083, or 10125377? Are there any other numbers I should keep an eye out for?

 

[L31MaxExpress]

Getting back on topic, I think I've settled on TPI heads if I do go with a head swap. I'm just not having much luck actually tracking some down. Also, I keep running into two different casting numbers referred to as TPI heads, so I'm not sure if there were multiple options or if it's a matter of one being for the 305 and the other is for the 350. Should 350 TPI heads be 14101083, or 10125377? Are there any other numbers I should keep an eye out for?

Never seen or heard of the 377s. Only seen the 083s or 14096217s on them as well as marine engines and GM 285 Hp and 300 HP crate engines. The disclaimer I will say on the 217s, GM drilled them with either a 72* or 90* intake bolt pattern on the center 4 bolts. Need the 72* bolt angle to bolt to an un modified TBI intake. There is really not much at all gained HP wise with any of those heads and they will trade off some low to mid speed power and fuel mileage. The 083/217s do not flow as well as even a Mexican 062 Vortec and those were dogs compared to the real ones used on the 96-02 trucks and vans.

I once tested a Mexican 062 head Vortec swap and after dialing it all in, they gained 15 whp on a TBI that was otherwise mostly stock. It had headers (shorty IIRC) and a decent exhaust (2.5" to single 3" with a nice Y-pipe and high flow cat) but had the stock cam and stock TBI. Both the TBI heads and Vortecs were installed with the same 1.6 rockers. The Vortec heads even got the benifit of thinner rubber embosed steel shim head gaskets. Under 4500 rpm the vortec head lost power and it took until 4,500 rpm for the vortec heads to match the swirl ports. At 5,500 rpm the Vortec heads were finally up about 25-30 whp. I say about because I forget the exact gain at 5,500. It cost the guy $1000+ to lose torque in 99.5% of his normal driving range. He used the GMPP intake, added the external EGR tubing, etc to pass smog here in DFW. Its not that the Vortec head engine performed poorly either, the TBI engine was already running great. With breathing mods and tuning I often saw them outperforming stock Vortecs on the same dyno, especially in torque numbers.

 

[98 Nitro]

Mexican Vortecs with the redesign to be less crackprone maybe, but original Vortec stockers are better at 3000 rpms and up easily and only lose torque off idle.