Thermo Quad Carburetor Backfiring. Will a Quadrajet replacement work?

[mycommander]

Okay, so three carbs later still having problems. Its back firing from the carb on a fast throttle response. The colors are pretty I guess. :)rotflmao But A very good source suggested the timing chain, the engine has 23k on, it ran fine when I bought it, then the carb gave me problems. No its suggested the timing chain? In my current state I can not afford to do that, so what I am wondering is, since the carb to use on it is no longer being made, and I do not have 300 plus bucks for one, does anyone have an idea what else it could be? I need to get this thing road worthy asap so I can move. I was told a Quadra Jet would work, if that's true, does it have to be off a Dodge? Etc.... Also my engine block has the serial numbers on it but also next to it it says 440-4. So what do I have? Until recently I have never heard of a 440-3 let alone a 440-4. Thanks. Scott

[Oz]

Lots of ideas of what the backfiring cause could be.

ENTER:  Backfir  in the search

And that is not a typo.  You get better results when you enter the root word without all the possible endings like... backfire or backfiring or backfired.

[RV Mech Tech]

Scott - before you spend any more money on parts spend some money on some tune up tools such as a timing light and especially a vacum gauge - these are the main diagnostic tools for a non-computerized engine - the vacum gauge comes with instructions and you connect it  direct to intake manifold vacum and it will indicate (depending where the needle fluctuates) the most probable cause and where to look at for the problem - this will also include ignition timing troubleshooting as per the instructions - learn to use a timing light and vacum gauge and you can out-perform even the most up-to-date auto shop on these older engines - many of the techs in the shops today  can run circles around anyone when it comes to hooking up  diagnostic fully-computerized equipment, but ask any of them how an engine works and how this affects a vacum gauge or timing light and most of them cannot give you an answer - moral of the story ? - back to basics - an engine is nothing more than a big vacum pump with ignition and fuel systems added on - always check for something that is not what it's supposed to be - is there a vacum leak somewhere ? - is the ignition timing where it's supposed to be for your engine ? - you can make this an endless money pit trying to replace parts and not solving the problem or you can invest in a few inexpensive tools to find out what exactly is the problem and save yourself a lot of money and you have an excellent library, resource center and many members that can help on CWVRV - let us know what you find !   Hm?

[mycommander]

RV Mech Tech,
Thank you for the advice. Actually the older engines is what I learned on. Also you are right, I do need to invest in the tools you mentioned. I had a timing light, but its no longer working. The vac gauge I will get for sure when I can gather the funds, and the timing light too. I have worked on so much computer garbage that all my tools are for just that. I will have to do it before May, because smog is do and the Reg too. Thank you for comment, and will do as soon as funds permit me too. I do enjoy the older engines, and the tools used. I wish it was like that on all the cars today.

[Froggy1936]

For the vacuume gauge you can purchase a dash mount gauge that after you diagnose your problem/s You can mount it inside to use as a fuel use gauge (keeping the needle higher wile driving = higher fuel mileage)  Also buying a timing light is becoming a problem as they are becoming obsolete (as are we and our rigs) Make shure you get one with bright light (white) You cannot see the cheap orange ligt in daylight conditions.  Advance Auto Parts still had them Last summer . Also a lot of older techs still have them tucked away somewhere  Frank 

[RV Mech Tech]

Scott - you are correct about the computer tools - I will  soon have to purchase a newer hand held scan tool for complete coverage for  diagnostics and I am looking at at least 4 - 6 thousand for a scan tool that is up to date and can be used  on the newer cars, trucks, and RV's - ( this of course is the Canadian price)  -  it's good that you got your base knowledge on the earlier non-computerized engines since you learned how an engine works and what affect problems will have that relate to the running and performance - the newer engines are still the same mechanically (some exceptions are electronically controlled camshaft timing, electronic control of the valvtrain such as the Cadillac 4 6 8 engine, etc.)  but the same mechanical diagnostic methods used on the older powertrains still apply on the newer ones- I have personally seen at least three so called top notch techs get stumped on simple mechanical engine defects  but the real professional will still use the simple tools such as the vacum gauge and timing light ( or magnetic timing pick up tool and on some cars there is no way of checking the timing other than going into the computer with a scan tool )- Frank has some good suggestions for the tools and the tool sales people such as Snap On, Mac Tools etc may have some timing lights or vacum gauges that they may sell you at a discount - keep an eye out for garage sales and flea markets and in the local want ads in the newspaper- you would be surprised what you can find,   

[4winds]

I bought my timing light at Advance Auto two years ago,  at that time they didn't have the cheap one so I paid almost 50 dollars.  Yes, it was worth it.  Ed i??

[JDxeper]

Harbor Freight has a couple of timing lights that are not to expensive

http://www.harborfreight.com/catalogsearch/result?category=&q=timing+light

They also have a fuel pump and vacuum tester

http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html

[mycommander]

We don't have Advanced Auto here, but Harbor Freight, yes. I will see what they run when all this dust settles, and can actually breathe and think about getting her fixed. I have seen the tools at H.F, they had a timing light for 12 bucks, but looked like 12 bucks! They had another I thing around 30 with the pick up, VAC gauge,I do not recall. I do like the idea of installing one in the dash.

[jkilbert]

harbor freight seels an indash vacuum guage for about $25. it'll do well to help diagnose problems. i have a vacuum/ "economy" guage stripped from a trashed winnie that i paid $5 for it works just fine, all you need to see is the engine vacuum, it's level and if it's steady. on my blazer i had the reading jumping all over instead of being steady. good sign of a bad cam.....and it was

[mycommander]

Jkilbert,
Thanks for the info for the vac gauge, what should the gauge read if all is in order for my 440-4?

[DaveVA78Chieftain]

It is a 440-3 industral engine.  There are general vacuum readings for  engines.  Here is a good overview:
http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm
My 440-3 runs around 16-18Hg at idle.  8 Deg advance @ 770RPM.
15-18 @ idle is typical.

Dave

[mycommander]

I am confused on the 440-3 and 440-4 thing. On the block after the serial numbers it says 440-4? So that's why I said 440-4. Oh well. Thank you for web site address I will look it up and record the info I have collected over these months. Thanks for the help.

[Elandan2]

The number on the right side of the block is the part number for the engine block itself.  In your case, your 440 block sand casting came from the "number 4" mold hence the -4.  The highest number I have personally ever seen is -6, but there may be numbers higher than that.  Your serial number of the engine is located on the top of the engine block immediately to the rear of the water pump housing.  The easiest way to identify a 440-3 engine is the spark plugs, they have the smaller tapered end spark plug that uses a 5/8 inch socket to remove or install.  The industrial engines (dash 3) have larger coolant passages in the heads and required the use of the smaller spark plugs.  Of course there were some other differences (i.e. forged crank), but the major one was the heads.  Hope that helps explain the difference.  Rick

[mycommander]

Yes Rick thanks! I do have the smaller plugs. Thanks so much for the info.