The Stovebolt Site Forums The Shop Area Engine Shop Flames from Carburator

Boy O Boy, is this stuff fun or what?!?

I have a 58 Apache that has an early 1960s SB 283 engine. I couldn't keep it running & it was backfiring flames up thru the carb. The old 4 bbl carb was 1000 years old & beat to death so i decided to replace it with a new one. I changed the intake manifold while I was at it. I got everything bolted up. Turned the key, hit the starter & danged if it refused to start but is still willing to shoot flames up thru the carb!

I've tried rotating the distributor slightly but no joy. Any ideas from you real mechanics out there?

Thanks
Bodega

P.S. I'm just a weekend recreational wrench turner & ya'll have been real helpful with past questions and problems I've had. Thanks!

Sounds like you may have a stuck or burnt valve sending compression back up to the carb.
Scott

A flat cam can cause this, too. Might wanna do a compression check.

Yeah, I was afraid of that. I thought about the valve but didn't know the cam could caus that too. I guess it's just time to quit band-aiding the booger & yank the engine. I wasn't ready to do that yet but, there ya go!

Before I do though, is there anything I can do to try to free the stuck valve? If it's the cam, I don't guess there's anything I can do short of yankin the booger.

Thanks for your help. I think I'm begining to understand how a massochist feels. This stuf is fun but it dang sure is painful!

Bodega

Bodega: I really would check that dist. again before you get into the heavy duty stuff. I agree w/Chevy & 48 also poss. areas of problems. Usually a backfire on trying to start is dist, when it is running and backfires look at valves then cam for the problem. Ben

popcorn The Truth is Out There (And you will find the truth)

Well, I guess the price of a new distributor would be worth eliminating it from the possibilities before I yank the engine (or at least the heads).

I had the old distributor out when I changed the intake. It seemed OK - doesn't seem like there's that much that could go wrong (it's an HEI). I cleaned it up but didn't rebuild it, though.

What would be wrong with the distributor that could cause this? It doesn't seem to be that comples of a device.

Bodega

Bodega: The dist. might be fine but on installation you might not have got it set back in the right place. Thats why they are made to turn right or left, then set w/timing light.

popcorn The Truth is Out There (Ok guys I know what I want to say but problay not typing it right)

Your could remove the valve cover and look at the valves as you turn it over (take out rotor so it doesn't start). Also compression or leakdown test would be an idea. Last, check the static timing is right and chain hasn't skipped a tooth.
Dennis

Could be you crossed a plug wire with everything apart. Check simple stuff first, then work your way up to heavy duty.

Roger that. Already went thru the plug wire routing drill. They're right.

I'm going to run the compression test on the cylinders before I do anything else. Then based on that, I'll decide on what action (if any) to take with the distributor. Ultimtely I'll have to rebuild or replace the engine but I'd like to put it off until Spring if I can. I knew from day 1 that it would have to be done. Maybe this'll just speed up the process.

I'm just glad that I enjoy the wrenchin' & that I don't have to drive the booger to work!

THX to all for the help & suggestions.

Bodega

My first thought was improperly installed distributor. Most of the guys have pointed out the major reasons for backfiring: I would check the distributor and wiring again for proper firing first. You didn't mention when this started and if you had done any work on it before this happend.

Distributor installed wrong (see manual for proper installation) change points too.

Improper plug wiring (18436572)

Stuck valve (remove the valve covers and watch the action with the rotor out as stated) and compression -leak test

bad cam or timing chain (procedure same as stuck valve)

bad vacuum leak?

I wrote this out for input and corrections so I could file this in my archives.

Well, It's time to yank the booger! Here's the results of the compression test:

1 - 120
2 - 130
3 - 105
4 - 40
5 - 35
6 - 110
7 - 30
8 - 125

Five out of 8 in spec. Could be worse, I guess. <g> Makes me wonder how in the heck it ran before!

THX for all the input. Now I gotta go see if I can rent an engine lift for tomorrow!

Before you start yanking the engine, do a little more diagnosis. Try a "wet" compression check, with an ounce or so of oil in the low-pressure cylinders. If the pressure rises noticeably, you've got piston ring troubles and it's time for a rebuild. Little or no pressure rise, and the problem is stuck, or burned valves. You can do a valve regrind, and nurse some more life out of the engine, or you might be able to unstick a valve with a dose of penetrating oil like Kroil.

There's also a procedure called a "cylinder leak test" where air pressure is put into a cylinder with both valves closed, the transmission in gear, and the brake set, to keep the crankshaft from turning. Air coming from the carburetor indicates a stuck or burnt intake valve (backfire), air at the tailpipe indicates a stuck or burned exhaust valve, and air from the oil filler indicates leaky piston rings. Bubbles in the radiator indicate a cracked head or leaky head gasket. Now, you KNOW what's wrong, and can take appropriate repair action. Sun Electric Co. used to have a slogan on all their testers: "We Test, Not Guess!" It still works today!
Jerry