Considering stepping out of my comfort Zone. Opinions wanted

[zieg85]

I found a pretty good deal on a 1987 7.4L TBI in a running parts truck.  Considering purchasing it and converting my 85 C20.

My absolute #1 concern is can I expect the same or better MPG than what I can get now.

I know all the positive aspects of the TBI system and by theory should do slightly better than a q-jet.

I know I need to have my carb rebuilt as it is original and untouched except for the occasional new fuel filter but I have gotten as high as 15 mpg with this truck.

I know this is a considerable amount of work to convert my truck and don't want to get worse MPG for my efforts.

Please Vile and BD and any other experts out there let me know your thoughts. 

I also hope a side benefit to doing this swap would be that the truck would pass our emission test with flying colors and I could save about $50/year on my plates.

[dvdswan]

with a 454 your probably going to get anywhere from 10-14.  BB love fuel... and if that fuel has ethanol in it you will be less.

[Irish_Alley]

for a 350 your lucky to get 10-14 not real positive on tbi. dont thing its going to be a big increase.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=24315.msg203194#msg203194

[Captkaos]

Don't expect better mileage out of the bigger motor.  IF you get 15mpg and keep it stock be very happy.  IF you get close to 12 ( and by these numbers, generally highway and city hasn't mattered to my BBC's in the past) be happy.  What is the motivation for the change?

[zieg85]

Don't expect better mileage out of the bigger motor.  IF you get 15mpg and keep it stock be very happy.  IF you get close to 12 ( and by these numbers, generally highway and city hasn't mattered to my BBC's in the past) be happy.  What is the motivation for the change?

Thank you!!!, to all those who have commented on this thread and through PM.  Motivation was more an opportunity to buy and part out a 1987 with a 454 TBI and convert mine while I was at it.  My 1985 C20 has about 140K miles on it and is long overdue for a carb rebuild and I thought if an upgrade would yield me better emission numbers, and give me a mile or two better mpg I may pull the trigger.  I know a TBI system has better drive-ability but a properly set up q-jet works well for me.  I am happy with the performance and gas mileage the way it is right now and will opt to keep it carb'd.  As long as I keep the RPM's down that 454 does good mpg wise.  Get it up to 65-70 and she gets thirsty.  I wish I could find an affordable gear vendors OD unit for the back of my SM465.

[Captkaos]

Ok, I am looking at your sig, are we comparing 454 carb'd vs 454 TBI? If you are getting that mileage out of your current 454, you should be able to achieve the same with the TBI if the 15 your are getting is highway and not city...  Emissions will be better in my opinion as the ECM will be keeping the engine in constant tune.  Of course if you are happy with it overall...

[zieg85]

Ok, I am looking at your sig, are we comparing 454 carb'd vs 454 TBI? If you are getting that mileage out of your current 454, you should be able to achieve the same with the TBI if the 15 your are getting is highway and not city...  Emissions will be better in my opinion as the ECM will be keeping the engine in constant tune.  Of course if you are happy with it overall...

I don't have city, more like country/highway back roads with some highway (ish).  This truck hasn't been driven for over 2 years now undergoing a facelift just saw the TBI opportunity and thought I would get other folks opinions and experience...

[Captkaos]

I hate carbs (Q-jet is all I will run) Me personally, I would swap it...

Your mileage may vary (pun intended)