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Old 11-06-2007, 05:03 PM
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is the chevy SCFI motor good?

is it good enough or should I look for a MPFI better?

how about TBI simplicity?

or just a conventional 4bbl sbc recipe?

I want to make a mild, potent, street driven powerplant, carbs are cheap and reliable but FI looks kind of high tech. (I don't want an expensive aftermarket EFI system though)

Augusto.

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Old 11-06-2007, 08:42 PM
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Scfi?

All things being equal carbs are a pretty good bet for the money. It's actually interesting that the more things change the more they stay the same, as fuel injection systems became more elaborate carb manufacturers had to keep up so the technology for carbs has undergone great refinement.

For 90% of the rodding world, a carb works very well. I would caution, though, that fuel injection is popular because it is easily tunable, and it can automatically change for drastic changes in air pressure and density.

If your heart is set of fuel injection, you can, for reasonable money, set up a pretty good system. Whether you choose TBI, SFI, or TPI - the heart is the brains, and for that I'd go with a Megasquirt controller (Spectra makes a controller as well, but I have no experience with them) for roughly $450. For ease, I'd pick up a cast away TPI off a camaro or such and simply bolt it on and go. Megasquirts have a good basic software package, and are infinitely tunable with a laptop. From the experience you gain there, really the sky is the limit. The greatest benefit, to me, about fuel injection is the ability to set the car to run either E85 or regular fuel..... also the ability to set a tune for nitrous/racing fuel and for daily driving.

You mention a fairly mild, potent driver - though - your definition of mild potent and mine could be quite different. (see my project Buick, I consider it mild because it's not full race).
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Old 11-06-2007, 09:11 PM
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there is a wrecked tahoe down the road and has a 350
CSFI motor, I wonder why I've never seen them on any mag as a hot rod motor.

Augusto.
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Old 11-06-2007, 09:22 PM
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Ahh, CPFI - meaning central port fuel injection. A friend who was a GM engineer told me this and my observations have found it true: Mechanically speaking GM makes changes for 2 reasons and 2 reasons only. Obsolesence, and Stupidity. Stupidity = first vega motors, the 2.8... you get the picture. Obsolesence = the change from TBI to CPFI. The TBI is a great system, and was around long enough so that the aftermarket - especially the 4x4 market really got into making improvements for them. The CPFI was a definite upgrade (lots more power, better fuel economy) but only was really used for a couple years until the LS motors became the mainstay. For that reason the CPFI was never embraced by the aftermarket. Another downside is the TBI and CPFI are not street performance oriented. That's not to say that the Tahoe motor isn't a great motor - the CPFI was also the induction for the venerable vortec motors; and even the aftermarket hasn't made much improvement to that head design.

I digress. The tahoe motor is a great motor - they never wear out because they have oil cooling, they are capable of having inexpensive roller cams, and the vortec head is a super head. That leaves the cam and intake. Buy a edelbrock carb, and a performer cam and you'll really like that motor. Simple, inexpensive, and a nice HP output.
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Old 11-07-2007, 08:07 PM
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the csfi injection system is only good for about 50 hp per cyl. and cannot be upgraded. UNLESS you replace the spider injection with real injectors. for pics, look in my photo album.
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Old 11-07-2007, 09:31 PM
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I have always been a chevy guy; didnt have much money as a kid. So chevy was the way to go, not to mention i love the trucks and cars much more than the other competitors. Universal interchanges, simplicity, reliabilty, affordability, and beautiful bodylines got me when i was young.
But i have never been a fan of the sequential central port fuel injection; especially now as an automotive performance specialist. I dont claim to be a genius, nor do i know close to everything. My confidence comes from knowledge, experience, and an unrelentless pusuit of exhausting my resources.
That being said I think this is the most problematic fuel injection system that GM has ever used. Sure it will run great for 100k give or take depending on the particulars; though the pressure regulators fail filling the cylinders with fuel; causing a hydrolock situation. The injectors are more failure prone than say TPI or TBI injectors because they are merely poppet nozzles. And once you try to replace a nozzle (injector) the plastic is so brittle that its almost impossible to not do more harm than good.
The heads are great and i will convince most people to either run an edelbrock intake and a good carb on older vehicles or an edelbrock intake and a tran dapt or holley adapter and TBI.
Keep in mind this is only my opinion and we all know the similarities.

Tom
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Old 11-07-2007, 09:38 PM
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Dont forget that wiring one of these SCFI_SCPFI engines is not an easy task specificaly to older vehicles and can be quite exspensive. I do not know of any aftermarket harness kits. There may be some though.
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Old 11-08-2007, 06:47 PM
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Quote:
Originally Posted by TRLBLAZR60

That being said I think this is the most problematic fuel injection system that GM has ever used. Sure it will run great for 100k give or take depending on the particulars; though the pressure regulators fail filling the cylinders with fuel; causing a hydrolock situation. The injectors are more failure prone than say TPI or TBI injectors because they are merely poppet nozzles. And once you try to replace a nozzle (injector) the plastic is so brittle that its almost impossible to not do more harm than good.

that is not an opinion. that is a fact. they are not that good, even if they do last 100,000 miles. GM went this route for 1 reason = profit.


when i was a kid, building model cars. cars came and went from my collection. one day i looked at my collection. and they were all chevys ! i was born a chevy guy
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Old 11-08-2007, 09:37 PM
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Most problematic? surely you must have forgotten about the cease oops I mean Cross-Fire.
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Old 11-09-2007, 08:33 PM
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Stoneshrink,
Sorry, I have had only 1 car that had crossfire injection, an early to mid 80s firebird with a 305; it didnt run! sorry I didnt include this engine or fuel delivery type. Im not that familiar with it, other than two small throttle body type injectors. set up in a cross flow design. What makes it so dreadful?
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Old 11-10-2007, 07:31 AM
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i had a 83 trans am with cross fire. it ran well. not tons of power, but it was fun to drive, back in 91.
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Old 11-10-2007, 06:15 PM
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Cease fires were notorious for cracking the intake manifold where the exhaust gas cross over was located (too thin of casting).
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Old 11-10-2007, 06:34 PM
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Augusto, what are you planning on putting this engine in? If youre trying not to spend a lot of money, then i would build a clean carb motor. The TPI is a good system if you can find a complete system with all the sensors and the ECM, However it would still need to wired correctly. If you can pick it up for a good price, Painless makes great wiring kits for a reasonable price.
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Old 11-10-2007, 08:11 PM
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I'm planning a chevy II buildup, it's a 4 door sedan but I think It'll look cool, it's already lowered a lot and looks fine, I have already discarded the tahoe's motor since there's a lot of esential parts missing, I have a 350 from a '80 blazer wich can be upgraded the regular way, I have a torker II manifold and a 600 cfm holley, will only need a cam and headers, wich must be custom made, I know I'll need a custom oil pan also, I think there was never a V8 chevy roaming this lands so I must fabricate my own pan.

finding a TPI here would be easier than finding a honest politician so I think the holley way is the most feasible alternative now.

this is my first chevy II project, I'll surelly appreciate all the advise I could gather, I think the first issue would be the 4 lug wheels and drum brakes, I will have to upgrade the whole drivetrain, how about the rear end is it any decent or should I discard it inmediatelly?

thanks

Augusto
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Old 11-10-2007, 09:17 PM
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Other then the 4 doors you're travelling known territory and Summit, Jegs both have conversion headers and 4 to 5 lug conversion kits for you car for cheap.....
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