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I'm building a 5.7L engine for a 1990 full size chevy equipped with tbi and manual transmission. I would appreciate any opinions, facts and advice on my rebuild. The truck will be used a lot for pulling a boats, trailers and equipment. I need some torque. I'm not on an extremely tight budget. I need to know what I can have done in the machine shop that would help make some horses, such as milling the intake/exhaust ports? I've built engines before that turned out great but they were just stock nothing special. What would anybody suggest I do for fuel. Carb, or use the TBI? I can't make up my mind. This is my main hangup, because I need to make up my mind so I'll know what cam to use and whether or not I'll need a custom PROM. Any and all suggestions would greatly be appreciated. I need a strong motor without sacrificing to much gas mileage. No turbo or supercharger for now. I could live with 10-12 mpg but would prefer 15+.
 

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Posted by grandfisher:
"I need a strong motor without sacrificing to much gas mileage."

Then you don't want to go with a carb over EFI. And you don't want to go installing some stupid long duration camshaft. And you don't want to go milling anything.

Generally speaking, build the motor back pretty much stock like you said you have experience doing. If you want to increase power slightly, do it with a cam that is just one or two steps over stock. Call your favorite cam grinder, tell him what you want the motor to do and he will recommend a cam for you. This service is free to you and you'll get the correct cam every time. I'd also be thinking about freeing up some horsepower with the exhaust system, starting with headers.
 

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I'm doing the same deal I have to 89 chevy trucks. Super Chevy has a nice build from stock and horse power gains with each add on. Tbi is the best way to go for the money. Holley has two and four barrel tbi units. There a guy on ebay doing custom chips Read his page and the rv cam seem to be the best for tork, a good set of heads vortec and your there. Also do a tbi search there is a web site that tells you how to improve performance on the stock unit which will do just fine if you trying to save on mpg.

Craig
 

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Then you don't want to go with a carb over EFI..
Except he's talking about TBI. Anything's better than that. Typically you can pick up several MPG going from TBI to a Qjet. GM's TBIs don't really use high pressure injectors, they use medium pressure squirt nozzles. Watch them sometime as they squirt rivers of raw fuel on the throttle blades no more efficiently than a bottle of Mr.Clean.

Our 78 Qjetted crew cab with 4.10s and a TH400 gets better mileage than our 88 TBI'd regular cab with 3.73s and a 700r4. No Joke.
 

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curtis73 said:
Except he's talking about TBI. Anything's better than that. Typically you can pick up several MPG going from TBI to a Qjet. GM's TBIs don't really use high pressure injectors, they use medium pressure squirt nozzles. Watch them sometime as they squirt rivers of raw fuel on the throttle blades no more efficiently than a bottle of Mr.Clean.

Our 78 Qjetted crew cab with 4.10s and a TH400 gets better mileage than our 88 TBI'd regular cab with 3.73s and a 700r4. No Joke.
My sons truck which is one of the two 89's we have run's very well its got a GM crate motor 290hp with a 700r4 and get 12-15 mpg a ton of torque. I pull ed the other 89 back from California up hills never had to down shift, hit the pedal plenty of power left.
The thing is you can change the fuel pressure to 10-15 psi, you can all so use the injector from 454 Tbi. Lots of thing you can do. Its out there just do the leg work and you will see what I'm talking about.

Craig
 

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edelbrock makes a good tbi intake. I have one on my 1990 camaro with a 350. I also have a 454 tbi unit on top of it. I run it all off the stock prom for the 305.
 

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if you do have to have the block milled i would have the rotating assembly rebalanced. as far as carb over tbi go edelbrock 1406# thats my opinion and experience.
 

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I would install some small port after market aluminum heads, like edelbrock 170cc heads. Good heads can increase power by 30 hp in a mild engine plus the added compression that aluminum head can tolerate will generate even more power and torque. Power is all in the heads. If you are serious about making power, start with the heads.

Then I would used a better efi intake and a set of Thorley Tri-Y headers. Set the compression ratio at 9.25 to 9.50:1 and use the stock cam or maybe a cam one step up with around 6 degrees more duration than stock.
 

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If you have a TBI, chances are you have the "swirl port" heads which are terrible. If you pull the intake you'll see that the port entry is half cut off. You can barely fit your thumb in there. That plus the fact that the TBI itself only flows about 390 cfms is the reason those engines just plain suck.

Most of them were rated 180-200 hp, and that was optimistic. The cams are very small as well, so that truck will respond very well to the typical cam, intake, head swap. I would personally do vortec heads (cheap and have incredible flow properties), an Edelbrock performer intake, and a Qjet carb that has been properly tuned and rebuilt. If you want to get courageous, grab a set upper and lower manifolds for a later vortec engine and use the EFI from it, but depending on how you use it you won't see much mileage gain.
 

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Discussion Starter #10
Alright, as I'm getting more serious about this project I'm losing my concerns for gas mileage. I just found a place where I can get a 383 kit with balanced rotating assembly for a little under 700.00 I already have a set of vortec heads I would like to use, maybe I will consider a set of aluminum heads. I'm startin to lean towards a carb instead of the TBI. I will have headers and no catalytic. Just glass packs. Flowmasters too quiet. With the 383 kit, a Performer intake, a decent cam, vortec heads, and a good carb, I should be able to get around 400 horses and 440 ft lbs of torque according to some Dyno results I saw. Yeah, to heck with gas mileage.
 

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I think that is a good move...
I went down the road you're on except got talked into keeping the tbi and computer. fairly mild torque cam, vortecs, headers, even cop car injectors
Man did that suck, I had to send off the prom chip 4 times (with block learn numbers and all of that) It still was never right.
I was told i would have hard starts with a carb, but i had wicked drivability issues with my prom problems. Enough so that i pulled all of the tbi stuff and dropped in multi-port out of a late 90's vortec with computer and everything.
had to switch fuel pumps and more (lots of customising)

Anyway sorry for the rant...
If i had it to do over, i would drop a demon or a holley on it, unless yours will see mud - then go with a qjet style
 
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