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I have a 1937 Dodge pickup with a 1990 350 SBC and 350 Turbo. The engine had a Holley intake with an Edelbrock carb when I got it. The current setup runs great year round but only gets about 14mpg, would a GM TBI improve MPG? What if I used GM TBI and a 700r4 would that improve the MPG?
I was going to mount a 2008 GM engine and trans but the engine accessory setup would not fit under the hood and the cost of an aftermarket setup was too expensive.
14 MPG is not bad with what you have. TBI is always better as long as it's set up and tuned right. The 700R4 add's another gear and TCC lockup so it's sole purpose of being used in newer vehicles was MPG.
There's a lot of other improvements with the use of fuel injection as well.
My old 83 G20 with the 305 HO, 700r4 and 3.08s pulled down the best highway mileage with a tweaked quadrajet and recurved hei on it. The TBI and later TPI pulled down similar mileage numbers with better all around driveability and cleaner emissions. A properly tuned q-jet getting 21-23 mpg running 70 mph down the interstate set a high bench mark. With an out of the box edelbrock 1406 on a performer rpm intake it would only get 15 mpg. I was able to get the edelbrock up to a solid 19-20 mpg with jet/metering rod changes.Quote:
Originally Posted by jayd
Jetting a carb and recurving spark is an art!
Its actually easier than chip tuning as far as only needing a wrench and a screwdriver but can take some math to get right.Quote:
Originally Posted by EagleMark
I dialed in two carb/distributer setups in older GM vehicles this week alone.
I am very methodical with it. I set the total timing to 32° @ 5,000 rpm, disable the secondaries and get the pimary jetting right. Then I dial in the metering rods to get the cruise mixture. Then dial in the idle mixture and speed. Onve that is done I tweak the step up springs amd accelerator pump circuit. Then I finally re-enable the secondaries and get the jetting to my liking. Finally I dial in the WOT timing, advance rate, and vacuum advance.
Last weekend I swapped a 1985 TPI 305 engine minus the TPI into a 1984 El Camino backed to a TH350 and 2.43 gears. The PO had butchered the CCC Q-Jet electronics so I went with a standard HEI and 80s fullsize G-van non CCC Quadrajet. I drove it all week and the car is getting 17 mpg average around Dallas Fort Worth.
The APT (Adjustable Part Throttle) circuit on the Quadrajets made them highly tunable for decent cruising fuel consumption. Most needed a boss / plug drilled out and then threaded for a removable plug. SMI is one of the best sources I know for quality Q-Jets.
I found an altitude/weather compensating aenoid carb that I played with on my G20. I wish GM had used the barometric pressure compensating aenoid in all of them.Quote:
Originally Posted by Buzz
A lot of people omit to factor in the cost of the accessory drive when embarking on a Gen III / IV conversion. The Corvette accessory drive generally (but not always) fits the best, and provides the most clearance at the front of the engine for E-Fans.Quote:
Originally Posted by jayd
Holley has offered a copy of the Gen III / IV engine Corvette accessory drive for a few years now. They have brackets available for some older style A/C compressors that make retrofits very easy. These are pretty much all I use anymore, if the under-hood space is tight.