Slant Six Forum
https://www.slantsix.org/forum/

small V-8 TBI on slant six
https://www.slantsix.org/forum/viewtopic.php?t=24376		 Page 1 of 1
Author:  rlklaus [ Tue Aug 07, 2007 5:33 pm ]
Post subject:  small V-8 TBI on slant six
Was in a wrecking yard the other day, and found a late 80s 1/2 ton Dodge van with a Holly 2BBL TBI unit. Just a thought at this point, but would this possibly work on my Valiant, with the 77 Aspen 2 BBL intake?
This would be on a 66 Valiant with an overdrive 4 spd, so kick down linkage is not a problem.
Author:  SlantSixDan [ Tue Aug 07, 2007 5:51 pm ]
Post subject: 
The '88-'91 Dodge truck TBI system is junk, through and through. It's half-baked hardware controlled by half-baked software. You definitely don't want to waste any time, money, or effort trying to use it; a carburetor works better.
Author:  cavisco [ Wed Aug 08, 2007 4:55 am ]
Post subject: 
The TBI in my brother's 88 Dakota (3.9 V6) has worked flawlessly for over 280000 miles and is still going strong. YMMV. Of course there are much more refined systems available today, but from our experience, we can't complain. The bore spacing and bolt pattern look the same as a BBD. Has anyone measured the bore spacing and bolt pattern on one of these? Might be a good source for a throttle body to use with megasquirt etc.
Author:  SlantSixDan [ Wed Aug 08, 2007 7:49 am ]
Post subject: 
Reliability isn't the issue; the trucks start and run perfectly reliably, but they are notorious for poor mileage, performance and driveability, all of which improve dramatically when this system is removed and a carburetor installed in its place. My '89 has this system, so I'm quite familiar with it. It was poorly and cheaply engineered, was the subject of many TSBs trying to keep the trucks running correctly, the external idle speed control motor is a real clunker, and fleet managers who had these vehicles needed to keep lots of injectors on the shelf, because both the Bosch and Holley injectors are leak-prone.

Remember, fuel injection isn't necessarily better than a carb, nor vice versa. A good carburetor is better than bad fuel injection, and good fuel injection is better than a bad carburetor. Only good fuel injection is better than a good carburetor.
Author:  cavisco [ Wed Aug 08, 2007 10:11 am ]
Post subject: 
Dan,

I don't disagree with anything you have said. I know these systems had MANY problems. I guess we somehow got lucky. This has sort of been the "family" truck that has been tossed around to whoever needed it at the time and it has seen plenty of hard miles. The injectors have never leaked, performance and driveability have been great, (much better than any carb), and the truck consistently returns 22-25 mpg. All in all we have been very satisfied. Too bad our experience has not been the norm and sorry to hear you had so much trouble with your's.

Good day,
Scott. (cavisco)
Author:  SlantSixDan [ Wed Aug 08, 2007 11:09 am ]
Post subject: 
If you're getting 22-25 miles per US or Imperial gallon, you're doing amazingly well and probably have the one (1) truck with this system that runs better than if it had a carb. Hang onto it until it won't stay together any more.
Author:  cavisco [ Wed Aug 08, 2007 11:33 am ]
Post subject: 
This is a first generation short bed Dakota, so it's probably one of the lightest Dakotas made. I suspect the later models just got heavier. Anybody know? This thing is driven almost exclusively on the interstate with my brother's business, so 22-25 is not out of the question. Obviously mpg at a steady 60 is much better than at 90 mph. With a heavy foot in town it can drop to 18 or less in no time at all. Our experience with drivability and good performance may also be climate related. It is almost always hot here with only about 6 weeks of winter. A really cold night is when the temps drop below 20f. I would imagine you see much greater temperature extremes in 1 year than we see in a lifetime. Right now we are on our fourth day straight with 100f or higher at 80% + humidity.

Scott.
Author:  65 dartman [ Wed Aug 08, 2007 1:53 pm ]
Post subject: 
Quote:
The TBI in my brother's 88 Dakota (3.9 V6) has worked flawlessly for over 280000 miles and is still going strong. YMMV. Of course there are much more refined systems available today, but from our experience, we can't complain.
Had a 91 Dakota 4x4 club cab with the TBI and it had over 220,000 miles on it when I finally traded it in for an Intrepid. Never had any problems with the fuel system on it. Must have got another one that was "right".
Author:  Shaker223 [ Wed Aug 08, 2007 1:55 pm ]
Post subject: 
My brother has a 88 long bed with 260k miles on it...just had to replace the fuel pump...thats it....still has the factory trans fill too. 3.9liter gets 18 city
Author:  SlantSixDan [ Wed Aug 08, 2007 2:08 pm ]
Post subject: 
Again:

Durability/reliability of this system: Fine, no systematic or notable problems.
Driveability/performance/mileage of this system: Notoriously poor.

Remember, some people manage, by luck or whatever, to get good service out of poorly-engineered vehicles or components. Some people had nothing but good experiences with the Ford Variable-Venturi carburetor, but it has a well-deserved reputation for being a badly-designed piece of junk. Some people loved their Hyundai Excels. Doesn't mean their bad reputation was undeserved.

Having lived for five years or so with the particular TBI system we're discussing, I would not put it on a slant-6. Mounting the throttle body on the intake manifold would be fairly easy, and it might not even be too hard to adapt parts from the 3.9 V6 distributor to make a slant-6 distributor with the necessary Hall Effect pickup, but any amount of adaptation work, IMO, would be better invested in a better system.
Author:  cavisco [ Wed Aug 08, 2007 5:52 pm ]
Post subject: 
I don't think I would try to adapt this system to a slant either. There are much more refined and tunable systems available today. I would not hesitate to grab one of these throttle bodies or better yet, one of the MPFI throttle bodies. They look like they would bolt right on to the 2bll slant manifold.
Scott.
Author:  Matt Cramer [ Thu Aug 09, 2007 5:16 pm ]
Post subject: 
The possibility that the TBI might bolt to a Super Six manifold does sound interesting. However, I'd only try running it with an aftermarket controller. There's a really deadly issue with trying to put the 3.9 computer on a slant six:

The 3.9 is an odd-fire engine.

You'd need a separate system for ignition control on it, as the 3.9's ignition system has a 16 degree timing difference between some of its cylinders. I can imagine a couple of ways to make that work, but not one that isn't completely absurd, like running two distributors or adding a timing computer and a crank trigger.
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/