"Luc - The Acadian Oppo" (luc5)
06/12/2015 at 09:50 • Filed to: PROJECT BIG STEEL
1
15|
"Luc - The Acadian Oppo" (luc5)
06/12/2015 at 09:50 • Filed to: PROJECT BIG STEEL | 1
| 15 |
I finally bought myself a timing light and a vacuum gauge. Last night I decided to tune the truck. The timing was set perfectly as per the factory spec of 6deg BTDC but the idle/fuel mixture was WAY out. The idle mixture screws were 3 1/2 turns out and I was getting a vacuum reading of around 14. So I put the screws all the way in then backed them off 1 1/2 turns and that gave me a reading of just above 15. After that I started to turn them back in and the vacuum was going down again so I went the other way. At 1 3/4 turns I got the highest reading of 17, at 2 turns it went back down to 16. So I left it at 1 3/4 turns out. This also smoothed out the idle big time. I took the truck for a quick spin around the neighborhood and there was no hesitation and the truck ran perfectly fine. The truck was running way too rich before so I’m hoping this solves that.
Would the idle mixture screws being 1 3/4 out greatly affect fuel mileage? Would it be dumping all sorts of extra fuel in the carb for no reason?
RamblinRover Luxury-Yacht
> Luc - The Acadian Oppo
06/12/2015 at 09:55 |
|
Would the idle mixture screws being 1 3/4 out greatly affect fuel mileage? Would it be dumping all sorts of extra fuel in the carb for no reason?
Yes, and yes.
|
Luc - The Acadian Oppo
> RamblinRover Luxury-Yacht
06/12/2015 at 09:59 |
|
Well in my case I couldn’t do it without the help of you guys. I’ve never had a carbed car until 6 months ago and now I have 2. Never learned to work on this stuff with my old man either. I’m learning as I go. Oppo has lent a great hand in my automotive education.
desertdog5051
> Luc - The Acadian Oppo
06/12/2015 at 10:21 |
|
Those settings are recommendations. Your actual settings will vary. You are on the right track.
BTW, You can also advance the timing up to 2 degrees and get better gas mileage. Just make sure that you are not getting any ping when you drive it. Check plugs after a
1000 miles
1609.3 kilometers to verify.
LongbowMkII
> desertdog5051
06/12/2015 at 10:28 |
|
also:
Highlander-Datsuns are Forever
> Luc - The Acadian Oppo
06/12/2015 at 10:29 |
|
Carbed cars like to run a little lean but it can lead to hard starting and overheating. It’s a trial and error for a while until you find that sweet spot, and yeah like desert dog said every car/carb is a little different so your car may not be quite the same as the manual. Just thank your lucky stars you don’t have 3-2 barrel side drafts or a double 4 bbl and are trying to tuning multiple carbs.
|
Luc - The Acadian Oppo
> Highlander-Datsuns are Forever
06/12/2015 at 10:32 |
|
From what I’ve read on the quadrajet the idle mixture should be in the neighbourhood of 1 1/2 turns out but mine was 2 turns more than that. I think I got it right. I’ll drive it for a bit on the weekend and see how it performs. From my quick test drive it seems to have helped a bit.
|
desertdog5051
> LongbowMkII
06/12/2015 at 10:38 |
|
Yep. That too. I figured he would want the gas mileage over the power on that thirsty thing.
|
Highlander-Datsuns are Forever
> Luc - The Acadian Oppo
06/12/2015 at 10:41 |
|
My experience is with a 430 C.I. (7 L) Buick with a 4 bbl, 2 primary and 2 secondary. The carb was set it an forget it. The timing, points, and plugs were the most important for a smooth running motor. When that car was tuned up you couldn’t even tell the engine was running it was so smooth and quiet.
aberson Bresident of the FullyAssed Committe
> Luc - The Acadian Oppo
06/12/2015 at 10:50 |
|
As long as you’re not fouling plugs or putting too much hurt on your wallet i’d use the settings where the truck runs best at. A popular saying amoung the weber community is that “you should get the carbs running at 95% and stop because finding the other 5% will drive you insane”
|
Luc - The Acadian Oppo
> Highlander-Datsuns are Forever
06/12/2015 at 10:50 |
|
Yeah I just got the truck a few weeks ago and have no clue what was done to it in the past so I thought I better check everything since it was puffing black smoke on startup(signs of being too rich). The timing was right which is surprising but the truck was not idling properly and guzzling fuel like there is no tomorrow.
If this doesn’t help I’ll do a full carb rebuild. I put new plugs in when I got it. I’ll replace the wires eventually and I’d like to put on an MSD distributor as the budget allows.
I knew this truck would be hard on gas but I wasn’t expecting single digit fuel economy on the highway.
|
Luc - The Acadian Oppo
> aberson Bresident of the FullyAssed Committe
06/12/2015 at 10:52 |
|
That’s good advice. I’ll run it like this for a bit and see how it goes.
crowmolly
> Luc - The Acadian Oppo
06/12/2015 at 11:03 |
|
Here’s something else to poke around with:
http://www.corvette-restoration.com/resources/how_…
Check out any of the articles written by Lars G. He’s known as a Qjet guru. Same with things written by Damon from Philly. Your stuff may not be *exactly* covered since it’s an ‘86 truck and probably has “computer controlled” stuff on it.
Can you post a pic of the engine bay just for reference?
|
Luc - The Acadian Oppo
> crowmolly
06/12/2015 at 11:07 |
|
The truck has an electric choke nothing else is electronic on the carb. I’ll give it a look thru.
Thanks!
brianbrannon
> Luc - The Acadian Oppo
06/12/2015 at 19:07 |
|
The idle screws shouldn’t effect your mixture much beyond idle so probably wont change your mileage unless you do a lot of idling
Jedidiah
> Luc - The Acadian Oppo
06/18/2015 at 00:46 |
|
This is your bible now. Use it well.
http://www.amazon.com/Rochester-Carb…