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Username Post: 1987 Chevy Bus 366 Engine troubles        (Topic#244728)
jaredg 
Forum Newbie
Posts: 6

Reg: 02-09-09
06-30-10 04:42 PM - Post#1938659    

Hey all,
I need some help. I have a 1987 Chevy Medium Duty School Bus with a 366 big block. It has a holley 4 barrel carb and here are the issues:
-I have been experiencing slightly hard starts recently, but it usually does start eventually
-I had to let it idle for a while before driving or it would die quickly
-On shut down (after engine was real warmed up) I experienced long durations of "engine run-on or dieseling"
-I did the SeaFoam down the carb treatment, got tons of smoke out the back and it eventually cleared up and ran good. (this was the last time it ran good).
-Last weekend I couldnt even barely start it. when it finally did start one time I got some backfiring through the carb and the tail pipe and horribly rough idling. It never stabilized and quickly died.
-Today I advanced the timing slightly (not accurately but though it would help). It didnt.

What do you guys think is going on? I am really trying to learn how to work on this thing the hard way and not give in to taking her to a shop.

Here are a few pictures: The arrows are pointing at things I have no clue as to what are




Thanks for your time!

Jared

Edited by jaredg on 06-30-10 05:03 PM. Reason for edit: No reason given.

 
100 CHEVY 
Dedicated Enthusiast
Posts: 5632
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
06-30-10 04:53 PM - Post#1938664    
    In response to jaredg

Is yours that great big giant Holley with the governor incorporated in/on the bottom?
If it is,I have the same engine but 427,and ended up putting a quadrajet on it.Runs good now.
Still have the Holley-big as a lawn mower engine!
Sorry,all the help I got.
Mike.
"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 
jaredg 
Forum Newbie
Posts: 6

Reg: 02-09-09
06-30-10 05:23 PM - Post#1938674    
    In response to 100 CHEVY

Do you think a new Carb will fix these issues? I have been reading some good threads about success stories with quadrajet 750s

 
100 CHEVY 
Dedicated Enthusiast
Posts: 5632
100 CHEVY
Loc: Helena,Missippi,U.S.A.
Reg: 12-09-04
06-30-10 05:33 PM - Post#1938678    
    In response to jaredg

I can't say,since yours is in the bus.
Mine is now in a car and the conditions are different.I changed the carb because it was flooding the engine so much it would hardly run.
Can you borrow a carb to try?
You can post this problem down in the performance section and get some real experts on carbs to help.
Mike.
"You gonna leave it like that?
http://www.picturetrail.com/100chevy


 
Vaughn 
"13th Year" Gold Supporting Member
Posts: 15691

Loc: Colorado Springs, CO
Reg: 08-08-04
06-30-10 10:00 PM - Post#1938768    
    In response to 100 CHEVY

If it has been doing it just in hot weather, it may be either a bad fuel pump or (more likely) a choke out of adjustment.

Switching to Quadrajet may not solve your problems, unless you get a carb specific to the 366 bus (which will be tuned for it). Q-jets take a little knowledge to make them run well - plus, in order to get it to really run right with a Q-jet you will have to swap intake manifolds (from square bore to spread bore). The Holley is easy to rebuild and easy to get parts for, so you may want to stick with that as long as the casting is in good shape.

 
Impala65SS 
Valued Contributor
Posts: 3758
Impala65SS
Loc: Sweden
Reg: 08-23-07
07-01-10 11:45 AM - Post#1938996    
    In response to jaredg

  • jaredg Said:

-I have been experiencing slightly hard starts recently, but it usually does start eventually


check your choke function
  • Quote:

-I had to let it idle for a while before driving or it would die quickly

check your choke function
  • Quote:

-On shut down (after engine was real warmed up) I experienced long durations of "engine run-on or dieseling"

Too far advanced ignition...
  • Quote:

-Last weekend I couldnt even barely start it. when it finally did start one time I got some backfiring through the carb and the tail pipe and horribly rough idling. It never stabilized and quickly died.

Too far advanced ignition...

  • Quote:

-Today I advanced the timing slightly (not accurately but though it would help). It didnt.


I believe you, I think you are already too far on the ignition setting.

I'm guessing the distributor shaft bushings are worn or the distributor isn't fastened properly, or some thing is loose/broken regarding the timing.
Set up a strobe and test for the timing perhaps wandering at a steady rpm...

Check your cables are clean and free from cracks in the sheath (look under the hood in a dark garage for cross-arcs with the engine running).

Is the carb getting fuel properly?
Does the accelerator pump squirt fuel?
Does it make a difference if you pump the carb - prime the intake before starting?

I'm sorry, I can't say what the arrows point at...

http://www.youtube.com/watch?v=SXn2QVipK2o&a mp;fea...


 
jaredg 
Forum Newbie
Posts: 6

Reg: 02-09-09
07-02-10 06:54 AM - Post#1939379    
    In response to Impala65SS

Ok, so I first want to thank you guys for your replys. I think since the plan is to restore this old bus, I should begin to replace some of these old worn out components to at least if nothing else, start with fresh new parts.

- I already have a new Fuel Pump, just havent installed it yet. I will do that first.
- I would like to replace the distributor. The only one I found online that I can gaurantee is a match is the one on napa's site. If you search 87 Chevy B-60 366 gas it comes up.
- I would also like to replace the old worn out carb. I am 99.9% sure its a Holley 4150g with manual choke. So Jegs has this remanufactured unit that looks identical to a 4150g: http://www.jegs.com/i/Holley/510/0-1850CK /10002/-1...
Should I order it? Do you think it would be a direct replacement?


 
Impala65SS 
Valued Contributor
Posts: 3758
Impala65SS
Loc: Sweden
Reg: 08-23-07
07-02-10 10:22 AM - Post#1939477    
    In response to jaredg

Still, check what you have first - spend a small amount money on the strobe, a simple tach, a fuelpressure unit, oil pressure unit, compression tester, a good electronic multimeter - And get a shop manual ifat all possible - well invsted money too! Tune up tips and specs that are hard to find and if you get them from any joe - you have to trust his word... I've learned so much from BOTH asking joe and reading the books i get hold of... The way I see it, it's the only way to really learn - both aske the experienced AND read the theory as it was intended. Some stuff posted 40 years ago has been outdated by experience from the everyday mechanics, but so many misunderstandings are ruining engines and parts because the "mechanic" said he didn't need no damn books since he's got it all "up here"...

edit:
By the way that is not a 4150 carb - it's a 4160, vacuum secondaries and fixed secondary jets. Nothing wrong, just saying.
I'd still check out the current carb first.
http://www.youtube.com/watch?v=SXn2QVipK2o&a mp;fea...


Edited by Impala65SS on 07-02-10 10:36 AM. Reason for edit: No reason given.

 
jaredg 
Forum Newbie
Posts: 6

Reg: 02-09-09
07-02-10 11:36 AM - Post#1939493    
    In response to Impala65SS

Wow, thanks for correcting me on the carb model. I do have a 1987 Chevy Medium Truck Shop Manual which helps me a ton. I guess I'll start by swapping out that fuel pump and making sure the carb is even getting the proper amount of fuel. I sort of have a feeling that is part of it.

Yesterday I tried starting it again, notta. Just cranking, no turning over.

 
Impala65SS 
Valued Contributor
Posts: 3758
Impala65SS
Loc: Sweden
Reg: 08-23-07
07-02-10 01:29 PM - Post#1939532    
    In response to jaredg

Are you getting the #1 spark when the #1 is at "TDC-ish"?
If you're not sure, take out the #1 spark plug and have the engine cranked while sealing the plug hole with your finger - the wind push pushing you finger away is the compression from the piston going up when both valves are closed - i.e. TDC.

If the "wind push" is coinciding with the mark on the balancer and timing pointer "zero"-mark, you are in good shape too (the wind push is more reliable than watching the zero-mark, so you rely on the finger feel).

With the TDC established, make sure you have TDC (turn the engine by hand to TDC), untie the distributor clamp so you can carefully turn the distributor by hand if needed.

Connect the plug to the cable, ground the plug with a jumper cable and make sure you have a good view of the spark gap.

Turn on the ignition, turn the distributor slightly back and forth till you get a spark.

By that procedure you have reset the spark to ignite at 0°, and you should be able to start the engine in order to set the ignition properly.
http://www.youtube.com/watch?v=SXn2QVipK2o&a mp;fea...


 
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