1978 bus

Post Reply
User avatar
framingsilly
Posts: 508
Joined: Fri Dec 19, 2008 9:59 pm

1978 bus

Post by framingsilly »

I have a 78' bay with a single progressive Carb. All tuned etc. Etc.
I'm getting a back fire out of the Carb. Hydraulic lifters adjusted, timing, and dwell. There Is some cracks on the intake runner boots. Would that cause the sputtering out of the Carb? STARTS and idles good. Just goes poof every couple strokes. I have a fuel pressure regulator on it set at 4 pounds. Also the brake booster Is not tapped into anything .Shitty set up 009 with single progressive. Is this worth messing with, or find dual carbs? Don't want to spend as much on carbs as what I paid for the thing. Could exhaust leaks cause this? Can't find any.
1972 weekender
1988 Vanagon
1968 Single cab
1984 Vanagon
1978 Transporter
1987 Cabrio
User avatar
framingsilly
Posts: 508
Joined: Fri Dec 19, 2008 9:59 pm

Re: 1978 bus

Post by framingsilly »

Here Is a pic of the sweet set up. I know about the fuel filter and fuel pump need to be mounted by the trans. Not driving this, so that Is on the to do list. I've done the brakes, and suspension so far.
Attachments
20130704_183128.jpg
1972 weekender
1988 Vanagon
1968 Single cab
1984 Vanagon
1978 Transporter
1987 Cabrio
User avatar
blue71
Posts: 784
Joined: Fri Dec 19, 2008 2:11 pm

Re: 1978 bus

Post by blue71 »

Maybe the cracks are causing some sort of vacuum leak/mixture problem leading to the backfire events? I poked around on Ratwell and if my understanding is correct maybe a leakdown test would be good to see if the valves are closing right?

"A leakdown test is most useful in determining if you valves are closing 100%. This is more of a problem with hydraulic lifter engines than with solid lifter engines. The reason is that the required lifter preload with the ability of the lifter to pump up too much causes the valve to remain open. When this happens to intake valves you lose some power and get backfiring in the intake. When this happens to exhaust valves, they burn because they are subjected to extreme heat expelling the gases after combustion and use the valve seat to transfer heat to the head."

My knowledge of the eccentricities of T4 powerplants is minimal, other than looking at the box of parts I have in my apartment from one and the case I have from Glenn's estate. I have heard many many things about progressives being a PITA though.
Nick a.k.a. Parts-whore, Young Nick, Subwoofer Nick, Nebraska Nick, Doc, the Amish connection.

Now: 1967 bug, 68 westy, 70 bus, 70 westy, 70 bug (FS), 71 westy, 71 bug
Past: 58 bug, 66 bug, 68 bug, 68 westy, 71 super, 74 super
WideFive
Posts: 1270
Joined: Tue Dec 16, 2008 6:00 pm

Re: 1978 bus

Post by WideFive »

Single carbs are for lawn mowers!

All the Buggy Fuchs love those Progressives, that alone should be enough to tell you they suck :lol:

I agree with most everything Chuck didn't say though :lol:
"There is no restoration process that can give a car legitimacy equal to originality."
User avatar
Moderator
Moderator
Posts: 42
Joined: Wed Jan 28, 2009 9:43 pm

Re: 1978 bus

Post by Moderator »

The following is an edited version of a post pertaining to this carb set up.

Well let see if I can rile up all the progressive 2-barrel lovers out there... that carb set up on a type 4 motor never works quite right, throw it away, don't waste your time trying to make it work right, almost every junk bus I've ever acquired with that set up had holes in the pistons, thing runs too lean, 9 out of 10 owners I've seen with that carb over the last 25 years all have told me the same story "my bus runs great now that the motor's been rebuilt, one of the pistons had a hole in it for some reason, I get like 30 MPG now", and that's only a part of the problem with that carb, the intake runners are too long and unheated (no heat riser) fuel will condense on the intake tubes and make it a bitch to get it to idle when cold.
User avatar
wwebner
Posts: 3951
Joined: Mon Dec 15, 2008 7:34 am

Re: 1978 bus

Post by wwebner »

The above post is pretty spot on about this carb/manifold set up on a T4 engine. The carb itself is not the problem as this carb was used on thousands of Chryslers and some Fords. There is no way to correct the manifold (get the carb sitting higher) as there is no room in the engine compartment. Nick's suggestion of a leakdown test is a good idea. I have a set of leakdown gauges and you are welcome to stop over and we can do it. This will determine whether the engine is not already damaged from this carb set up (burnt valve) before you spend any money on dual carbs. If your timing is correct and you have no vacum leaks,backfiring thru the carb could mean a burnt intake valve.
Bill
obsoleteman
Posts: 80
Joined: Tue Nov 17, 2009 1:52 pm

Re: 1978 bus

Post by obsoleteman »

I agree with the valve leak theory from either bad valves or poor adjustment.
BUT
I would eliminate all vacume leaks;
Make certain that the;
-choke and squirters(i.o.w.t. acc. pump) work properly.
-Points and timing are correct
-the distribtor advance works at all(rev the engine with the timing light hooked up-does the advance wait or make haste? or a bit of both?).
A combination of improper points gap and/or faulty distributor advance; vaccume leak; faulty choke and/or accelerater ; damaged linkage to the acc. pump; can all cause a flat spot. If there is enough of a flat spot- it will pop when you step on the throttle.
I have no encouragement for using aluminum Brazilian 009's on anything; that could be a flat spot pop on it's own.
I have seen some of these carbs work really well(but few). Mars Motors had a drawer of "idle air bleed kits" that they claimed were needed on the long V.W. Manifolds(but not on the Pinto engine). The carbs they installed worked quite well.
Many manufacturers used the "patents" to build their version. I think that the European versions of this carb were more often functional.
The one I had(when they first came out) was a real waste of time. The poorly made linkage caused one flat spot by delaying 'the squirt" until the throttle was half opened. Unless I "reved it up like an inexperienced preschooler at creative play", it would not get out of it's own way(no fun in traffic). If I did reved it up and dumped the clutch...it would leave twin tracks on the road. In short it could not be driven normally.
Post Reply