tbi guestion

[tommym]

Hey guys has any one turned an old school 350 into a throttle body injection motor useing GM OE parts if so what wireing did you use the wireing from a donor car or get one from painless wireing

[Marv D]

The stock throttle body is VERY limiting (and not very pretty) so you mostly see later TPI injection if anything. That said,, I built a 383 for my 94 4x4 using RHS vortec heads, a GMPP throttle body intake made for the Vortecs, a Holley 680cfm TBI throttle body, a EFI friendly custom hydraulic roller cam, and I'm on the 4th chip for the OBDI factory computer. The project isn't for the 'plug and play' sort of guy. The computers available for the TBI are archiac, and chips are starting getting hard to find. If you want EFI,, I'd HIGHLY recomend looking to the aftermarket with a programmable controller, and MPFI. WAY more efficient, powerfull and your sanity will be more apt to survive.

[rfmaster]

Originally Posted by Marv D

The stock throttle body is VERY limiting (and not very pretty) so you mostly see later TPI injection if anything. That said,, I built a 383 for my 94 4x4 using RHS vortec heads, a GMPP throttle body intake made for the Vortecs, a Holley 680cfm TBI throttle body, a EFI friendly custom hydraulic roller cam, and I'm on the 4th chip for the OBDI factory computer. The project isn't for the 'plug and play' sort of guy. The computers available for the TBI are archiac, and chips are starting getting hard to find. If you want EFI,, I'd HIGHLY recomend looking to the aftermarket with a programmable controller, and MPFI. WAY more efficient, powerfull and your sanity will be more apt to survive.

Above is not entirely true

The old 1227747 ECM even though being back from the late eighties, early nineties is still an an ECM of choice when coupled with EBL (from dynamic EFI) board. It is cost effective and very capable when compared to after market EFI controllers. Factory TBI system is limited due to its use of two injectors - for example BBC TB and a pair of 80 lb-HR injectors at 13 PSI. However when stock fuel pressure regulator is removed and bypassed with VRFPR is used in its place solid 350 to 385 HP can be made - air flow is not a limiting factor for BBC TB when used on a 350 SBC. MPFI requires 8 injectors and higher fuel pressure but remove fuel delivery limitation from the EFI equation. In reality plug play EFI systems are for 30 min TV shows. EFI conversion will take time to complete - plain and simple.

All of the above involves DIY, plenty of plumbing. This is what a TBI + VRFPR system like that looks like from the front:



and top view:



Local JY's still have abundance of ECM's (plenty on evil bay)
//RF

[AusTx68]

rfmaster, you are an expert with EFI systems so this stuff comes easy to you. Knowing far less, I would certainly take plug and play over a stock EFI conversion. Take a look at the MSD Atomic EFI kit. Far less wiring and fuel line plumbing (no need for a return fuel line). This kit is definitely in my future!

[project 67 sub]

is that msd atomic efi boost friendly?
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[rfmaster]

Originally Posted by AusTx68

rfmaster, you are an expert with EFI systems so this stuff comes easy to you. Knowing far less, I would certainly take plug and play over a stock EFI conversion. Take a look at the MSD Atomic EFI kit. Far less wiring and fuel line plumbing (no need for a return fuel line). This kit is definitely in my future!

Thank you - and it was not initially easy! It took a year complete my first swap - there was a lot of trial and error and oh sh'*& moments!

I have not tried MSD Automic EFI, but from published specification it appears to be gear-head friendly system. Just be aware that some 'plumbing' will be required. Getting fuel safely to the engine is a key concern.

As for boosted applications - I would pose this question to MSD technical support. It is a speed density system so as long as 2 or 3 BAR MAP is used and SA, AE and PE tables are expanded to cover boost areas it should be able to handle boost applications.

//RF

[tommym]

thanks guys for all your info it was really helpful this web site has been really helpful I have found information that I did not know

[Marv D]

Respectfully.... I guess if were doing show and tell...

Big pictures so I'll just leave a link
My TBI 383 in the 4x4

and the Holley Commander MPFI in my El Camino

I know quality of pictures and the truck wasn't very clean when the picture was shot, but aesthetics wise,, sorry the TBI doesn't come close IMPO,, but,, is ONLY my opinion.

Both are Vortec style heads,, RHS 220c Iron heads on the 383 in the pickup, , and Edelbrock 170cc E-tec on the little MPFI 327 in my Camino. Both hydraulic roller motors, both with decent small tube headers and good exhaust, and even both are 8.9 to 9.1:1 compression motors.

The 383 is now on it's 4th chip trying to get thing right. (First two done my Howell Engine Management in MI,, best I got was 8.5mpg , the last 2 by a guy in San Deigo that does nothing but EFI off shore boat motors) FINALLY up to 14mpg but he's finishing the final chip (making chip #5 in 4 years now)

vs. the Holley 950commander, with a Holley supplied base map it ran OK, Bought TomZeeks $10 Fuel map program and in a week of running the motor around with the craptop connected the little MPFI 327, brought cruise timing up above the base map and it will run CIRCLES around the 383. Throttle response, tune-ability, drivability and ease of set up, efficiency and go drive it instead of years of messing with chips.


Sorry, I'll take a true programmable MPFI system myself 1000 times over a another TBI.

[rfmaster]

Marv

Both engine bays are prime example of excellence. I tend to get sloppy, due to lack of time.

My only comment is that 220 RHS heads (maybe) too big for street driving. What I mean by this statement is that 220cc heads really come alive above 2500 RPM. Below 2500 RPM cylinder inlet charge is relatively slow and may result in fuel drop out. This may be one of the reasons why when you first started you were getting lousy mpg. Fuel drop-out from intake charge also affects acceleration, WOT response - throttle response. Case and point - GM used tiny (peanut) ports on later 454 BBC equipped with TBI - these engines were meant to be used under 4500 RPM.

On the other hand in MPFI system, each inlet port has injector shooting directly into the back of the intake valve. With 170cc inlet ports air speed is very high and fuel sprayed by injector stays suspended, which results in a cylinder filled with air-fuel mixture efficiently. With 327 3.25 stroke, MPFI and 170cc heads results in a very good combination.

I have built 383 with Trick Flow 195 (currently on the stand - looking for a chassis to drop into) and another one is in the works with RHS220 iron heads - similar to yours. The 220RHS headed 383 is destined for high revving vette.

I do my own tuning - depending on the setup I run Wide Band O2 (WBO) (ZT2) in combination with ECM data logging to get my parameters in. I no longer use 'chips' - since I have moved to EBL ECM upgrade which allows me to flash EPROM updates without moving anything - just few keystrokes on the lappy. My EFI converted C20 was (and still ) a test bed and served me as a learning tool for DIY tuning. Generally, every time I drive it I run a lappy. At the end of drive I make fine adjustment in the areas that need it. Right now I have fresh 350 which needs more drive time, but with all the other projects I haven't had the time to focus on it as much as I want to. Still, the 6800 lb truck is getting 14 mpg cruising in a close loop (2250 RPM at 65 MPH). That's without lock up converter enabled and lean cruise mode. Also, need switch to electric fans. But I guess I digress.

//RF

[Marv D]

Very true on the 220 RHS Vortec heads.. We couldn't agree more. And they sure were not my first choice,, but I had such a deal on them I just couldn't resist,, then came the issue of having to use the $400 GMPP large runner TBI / Vortec intake to fit, and boring the intake to accept the larger diameter butterflies of the Holley TBI unit,, and and,, it and trying to make this all work in a stock configuration / stock looking, OBDI package. The truck is built for towing my trailer (NV4500 5spd, 3.43 gears she has no problem at 2600 in OD on the freeway, 3100 in 4th),, but as with everything,, the trailer grew more than the truck. And it's total STUPIDITY trying to pull a big 10,000 pound package around with a little 1/2 ton pickup. The proverbial tail wagging the dog!!!
I 'originally' thought I'd run this little 383 till I got things sorted out,, then build a 434 in another SHP block and move the heads, intake and all to the 434,, re-chip and be happy. LESSON LEARNED! But I'm DONE building gas tow motors. Gas is for RACING Diesel is for towing!!! LOL After pulling that 28' trailer with 40' motorhome with a little 325 Cummins,, and getting 11-12 MPG doing it... Just no comparison!!

Yeah.. sorry to carry the thread so far off topic. I think it's good for tommy to get both sides of the coin views. I tried to do like he said,, all GM parts and think it was going to be close to a plug and play with just a chip. But I ws sorely mistaken for the mess I put together. It runs great (now) , don't get me wrong,, but for the $ and effort invested,, I'll suggest aftermarket MPFI unless there is someone handy like rfmaster to help you through the tune , parts selection and setup.

Again nothing but my 2¢