V-8 to I6 change

[65chevysub]

Has anyone ever changed their truck from a 283 or other small block back to a 6? My Suburban originally came with a 292 and PG. I now have a 283 with TH350 but my mileage is suffering big time(5-6mpg) and hard to get any speed up in a short distance(light to light). I don't remember having these issues with the old setup so was thinking of a newer 292 with the TH350. Any ideas on this?
This is my 283- I call it the "gutless wonder"

[padresag]

perhaps the eng has a problem
ron

[65chevysub]

I've been thinking that for years. I've had a pulsating vibration since it was rebuilt in 1996. Just doesn't want to get out of its own way. I know my truck is very heavy but right now I cant afford to rebuild it, or wonder if its even worth it. I may eventually switch to a 350.

[padresag]

Originally Posted by 65chevysub

I've been thinking that for years. I've had a pulsating vibration since it was rebuilt in 1996. Just doesn't want to get out of its own way. I know my truck is very heavy but right now I cant afford to rebuild it, or wonder if its even worth it. I may eventually switch to a 350.

just run a compression test to see where you are at. there are only so many things that can cause that type of mileage. mostly it is right in the carb or it is leaking somewhere. sometimes it is the nut behind the wheel. you should be getting a lot bettter mileage than that
ron

[65chevysub]

I'll start with a carb rebuild. I know its running rich. Then the fact that our highway dept has been messing with the stoplights doesnt help(lot of stop and go). As far as my driving habits, I dont race between lights etc. Just normal driving.

[Captainfab]

If that carb is any bigger than 500cfm it may be too big. Also Edelbrock carbs will not tolerate more than 5 -5.5psi of fuel pressure. If that is the sort of mpg you are getting, something is seriously wrong. I would swap it out for a 350 before I would go back to a 292. A 350 will get better mileage.

Originally Posted by 65chevysub

I'll start with a carb rebuild. I know its running rich. Then the fact that our highway dept has been messing with the stoplights doesnt help(lot of stop and go). As far as my driving habits, I dont race between lights etc. Just normal driving.

[64k10burb]

I changed a 70 Nova and a 69 Camaro from I6 to v8 many years ago. I could never imaging going the other way except for an OEM restoration.(if even that).


I say the others are right here, you have a problem with the engine or possibly the transmission. Also, a 350 will give better power than the 283 or a 292, therefore not have to work as hard=better mileage(under civilized driving conditions)

[65chevysub]

My carb is a 500cfm Carter. I used to have a pressure regulator on it but someone told me I didnt need it. It's an adjustable one. Should I put it v
back on? One other thing is I cant get it to idle at the 500rpm its supposed to. It may be timing but it keeps wanting to die on me so I have to keep the idle at 1000rpm. Im going to have a professional mechanic rebuild the carb and set the timing using the vacuum.

[Captainfab]

First the timing needs to be set correctly and then the carb. If you can find a mechanic that knows how to work on old school engines you will be fine. There is a ton of info in the 'Engine and Drivetrain' section of this forum that can help you get your engine dialed in.