C10 Forum  

Go Back   C10 Forum > Engine & Drivetrain Forums > Inline 6 Talk

Notices



Reply
 
Thread Tools Display Modes
Old 05-03-2012, 09:42 PM   #1
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default 292 l6 back firing problems

So far my 72 chevy c20's 292 runs ok untill i get on a hill, like ill be going down the freeway and i'll start going up a grade and it will back fire here and there and only going up a grade, on a flat or down hill it runs good and its been doing for a wile. So a few months back i swaped the stock distributor (yes it was back firing then as well) for a H.E.I distributor and it still back fires on hills Well so check the spark plugs from time to time and there burning perfictly. well i finaly got a compression tester and cylinders 2-6 are all almost exactly at 130psi and cylinder number one is the only low one at 120psi could cylinder number 1 be the one thats causing the problem or is it something else? i know the timming should be alittle far advance from what the summit instruction. any advice? P.S i'm still have alot to learn about engines lol
dragun12 is offline   Reply With Quote
Old 05-04-2012, 01:13 PM   #2
Vin63
It's Better With Nitro
 
Vin63's Avatar
 
Join Date: Dec 2010
Location: Chino Hills, CA
Posts: 59
Default

How long does it take for you to be pulling a grade that it backfires? Is it immediate, or after a period of time? What type of carburetor are you running, and have you checked your float levels and/or floats?
__________________
1963 C-10: custom cab, shortbed, fleetside
Pontiac 462 ci, Kauffman D-Port alum. cyl. heads
4L80E, narrowed sheetmetal Ford 9-inch
Tubular front and rear suspension
Custom 6-piston front disc and 4-piston rear disc brakes
Vin63 is offline   Reply With Quote
Old 05-04-2012, 07:39 PM   #3
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

some times it both and i'm running the stock rodchester mono jet carb
dragun12 is offline   Reply With Quote
Old 05-05-2012, 12:14 PM   #4
chevywrench
Senior Member
 
Join Date: Jan 2010
Location: Tucson, Az
Posts: 150
Default

There is a little valve under the heat riser and carb. Its got a little thermo spring on it, and its weighted. If it stays closed, it will literaly boil the air/fuel mixture. I have never seen one work, and neither does mine...haha. I just got some saftey wire and wired it open. This should help out a lot.
__________________
Back in the Old Pueblo....yay....
chevywrench is offline   Reply With Quote
Old 05-06-2012, 07:41 PM   #5
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

ya i wired mine open along time ago. it did help but i think maybe my exhaust is might be getting the intake to hot still.
dragun12 is offline   Reply With Quote
Old 05-07-2012, 10:28 AM   #6
chevywrench
Senior Member
 
Join Date: Jan 2010
Location: Tucson, Az
Posts: 150
Default

That very well could be the issue. I know my carb gets very hot. However, I just sold the engine and trans. Going to do a v8 /automatic od swap. Im just tired of hunting down parts for the 292. The v8 will give me more options, and with a 4:11 posi rear end, the overdrive trans will allow me to drive it over 55mph!
__________________
Back in the Old Pueblo....yay....
chevywrench is offline   Reply With Quote
Old 05-07-2012, 10:30 AM   #7
chevywrench
Senior Member
 
Join Date: Jan 2010
Location: Tucson, Az
Posts: 150
Default

I just thought of something. When you did the hei swap, did you run a different power wire, or did you use the same wire from the old coil?
__________________
Back in the Old Pueblo....yay....
chevywrench is offline   Reply With Quote
Old 05-07-2012, 07:17 PM   #8
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

when i did the swap to the H.E.I i also got new wires and spark plugs
dragun12 is offline   Reply With Quote
Old 05-09-2012, 02:05 PM   #9
chevywrench
Senior Member
 
Join Date: Jan 2010
Location: Tucson, Az
Posts: 150
Default

Im talking about the power wire at the coil. The original wire has a resistor in it, that drops the voltage down to about 6 or 8 volts, to prevent burning up the coil. When switching to HEI, you have to run a new wire. I ran a 16ga wire from the fuse box that has power when key on, engine cranking, engine running. The original wire also connects to the starter, it should be yellow in color. Hope I didnt confuse you.
__________________
Back in the Old Pueblo....yay....
chevywrench is offline   Reply With Quote
Old 05-09-2012, 06:34 PM   #10
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

ya that also went bye bye long ago. ya i also retarded the timming and richend the fuel mix up to see if it would stop from back firing and nope
dragun12 is offline   Reply With Quote
Old 05-09-2012, 06:42 PM   #11
XXL__
Chief Factotum
 
XXL__'s Avatar
 
Join Date: Jan 2009
Location: Norcal
Posts: 4,159
Default

A true backfire is when unburned fuel gets ignited outside the combustion chamber-- either AFTER the exhaust valve opens, or before full compression stroke (although, it seems like that'd be called a "front-fire" or something.

Common causes for this are running fuel-air mixture too lean and/or timing too far advanced. As you mention above, you richened and retarded... but you didn't describe your method. I recommend using a timing light to set the timing. I believe you're looking for between 4-8 @ 600-800 rpm. Also, make sure the balancer is solid. When they get old and crusty, the outer ring can break loose of the rubber and cause both timing problems (because the marks have moved) and balance problems.
XXL__ is offline   Reply With Quote
Old 05-10-2012, 06:05 PM   #12
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

yes i used a timming light i retarded to 12 @ 1000rpm but summit says it should be about 13-14 @ 900-1000rpms and where its at right now my truck is so doggy and it isnt getting as good of gas mileage
dragun12 is offline   Reply With Quote
Old 05-11-2012, 09:00 AM   #13
chevywrench
Senior Member
 
Join Date: Jan 2010
Location: Tucson, Az
Posts: 150
Default

I set mine a 10 btdc and it runs great. I dont think I would follow Summits advice, it seems a little much. Seriously though, I pump the gas twice and just barely hit the key, and mine starts right up. I dont even think the starter makes a complete revolution. Maybe pull all of your plugs and do a compression test, or maybe a leak down. Just a thought, kind of hard to diagnose a problem over the internet.
__________________
Back in the Old Pueblo....yay....
chevywrench is offline   Reply With Quote
Old 05-11-2012, 05:50 PM   #14
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

ya thats the way mine is right now. i dont think i'm going to chang it after today i did a 78 mile round trip to work and only used maybe an 1/8 of a tank of gas, that engine is so weird .
dragun12 is offline   Reply With Quote
Old 05-12-2012, 11:31 AM   #15
gimmy 64
Junior Member
 
Join Date: Jul 2010
Location: menifee cali.
Posts: 2
Default

had a 68 panel truck with 250 six my truck did the same thing. turns out wasvalves sunk into head because of unleaded gas. valvles would get hot --backfire. put hard seats in and cured the problem.
gimmy 64 is offline   Reply With Quote
Old 05-12-2012, 08:47 PM   #16
dragun12
Junior Member
 
Join Date: May 2012
Posts: 25
Default

we did that when we rebuild the engine back in 09. so i dont think that should be a problem.
dragun12 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -8. The time now is 10:54 PM.


Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
2009 c10forum.com - your c10 information source