- This topic has 25 replies, 5 voices, and was last updated 12 years, 8 months ago by
.
-
Topic
-
Now that I have my brakes worked out Im on to my next issue on the truck. The fuel milage is crazy low (3.5 mpg) I know theres several things going against me, first off its winter and it takes the truck awhile to warm up. I live in a mountain town with some hills and high elevation. Most of my driving is a mix of city and moderate highway (45 – 55 mph) . The truck is a 3/4 ton on a lift so I know that too goes against it. Even with all of that said to me its burning far too much fuel. So here’s what Im thinking of doing this weekend
– Adjusting the carb and choke. Until the truck is warmed up I have to keep the throttle open somewhat or it dies out
– Check transfer case. Ive noticed especially when the truck is cold I can change modes (4 high to 4 low, Lo and Unlock etc) The truck is full time 4×4.
– Change tranny filter and fluid. The truck doesnt always shift on time unless I let off the gas when accelerating. Excperince tells me this usually is the filter.
When the truck is cold I can select drive but the truck will not go into gear. I usually have to open up the throttle and it feels like its trying to go into gear but is hesitant. Im not sure if this is something to do with the transfer case or the tranny. When its warm tho it goes into gear just fine. .
The engine itself seems fine, surprisingly it doesnt smoke and I havnt noticed anything like a miss in it. The last owner changed the oil and plugs and wires before selling it. He said he had a friend rebuild the tranny not too long ago. Which I can somewhat belive but the truck has also sat in storage for 3 years
-
Replies
-
Your ’76 Chevy comes with a Q-jet. Later Q-jets are ‘hybrid” carbs or “E carbs” and pose additional problems when tuning or re-building. If your carb is original, it is likely to have the problems that make the Q-jet notorious. In the middle section of the carb (the middle of the sandwich) under the fuel bowls, you have two large and two small holes that are sealed at the factory. Eventually they leak and need to be sealed by a drill and tap method. (I’ll post a video that shows this). It is possible that your carb has already been rebuilt once or twice, but if the drill and tap method wasn’t used, the seals may be leaking again.
It is also likely that the throttle bores are worn and leaking. The video, I have in mind shows how to determine if they are leaking and how to drill and re-bush them.
There are several good remedies for an old Q-jet and the best depends on your preference and your budget. If you just go the all new route, you can buy a new Holley or AFB type carb. The Edelbrock AFB type carbs are very easy to rebuild and tune. A teenager can do it cross-eyed drunk.
If you switch to Holley or Edelbrock, you need a new intake manifold. The Edelbrock Performer is probably the least expensive and has a good rep.
If I was you, here’s what I would do. Buy a second Q-jet from a wrecking yard for 5 to 10 bucks. Buy one that looks good and use it temporarily while you take Eric up on his offer to rebuild your carb. Wrecking yards will sell them dirt cheap because they usually have a surplus. (You can find a Q-jet like yours on a mid 1970s Chevy 350. Stick with the Chevy Q-jet.) If the carb looks fair, and the throttle shaft/bores are not loosey goosey worn out, and the oil in the crankcase does not smell like gasoline, you’re probably looking at a serviceable carb to get you around for a while and improve your mpg. If you want to rebuild either carb yourself, you can do it in your spare time with the “second carburetor” method.
The fellow that first showed me how to rebuild a Q-jet told me something you might be interested to hear since you mention your transmission problem on the forum. He said if you can rebuild an AFB, you can rebuild a 350 automatic trans.Here’s the video. It’s the best one I could find on the net and it does show the Q-jet “secrets”. I’ve no doubt Eric could make a better video and who needs the ads?
http://www.spike.com/full-episodes/reh42f/powerblock-muscle-car-quadrajet-rebuild-season-4-ep-418
[url=http://www.ebay.com/itm/Holley-0-80555C-650CFM-Model-4175-Factory-Refurbished-/350517150199?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item519c7341f7#ht_2378wt_1163:1jmh12js]http://www.ebay.com/itm/Holley-0-80555C-650CFM-Model-4175-Factory-Refurbished-/350517150199?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item519c7341f7#ht_2378wt_1163
H[/url]ere’s the the Holley ‘Spreadbore” that bolts onto the stock Chevy intake manifold. I have no experience with these and have heard good stuff and bad stuff about them.[url=http://compare.ebay.com/like/390391563988?var=lv<yp=AllFixedPriceItemTypes&var=sbar:1oupfj0a]http://compare.ebay.com/like/390391563988?var=lv<yp=AllFixedPriceItemTypes&var=sbar
I[/url] think the “Thunder Series” Edelbrock is worth the extra few bucks.Thanks YardDog. Ill watch it so I can learn more but oddly enough I had a good buddy come by and offer me a good price for it as it sat so I sold it to him. I will tell you guys that I changed the oil on and it changed the tranny fluid. THe oil was black and needed changed nut the tranny fluid was perfectly clean so I refilled the tranny and added treatment. I also sprayed in some carb cleaner. The truck was still ahving stalling issues when cold but I noticed after it warmed up the base idle was lower and sometimes seemed to “wonder”. Good news is the tranny was much more responsive. It would sometimes hesitate very briefly going into gear but it felt a lot better going into gear and shifting in general. So theres that for ya. I do appreciate the vids tho YardDog Im sure the knowledge will help me
You know a transmission malfunction can also cause a fuel mileage issue. Thanks for keeping us up to date.
- You must be logged in to reply to this topic.