Back Firing, Surging, and Bad Noises from Engine

[72rookie]

The old C-10 (Bessy) has started acting up. The engine has started back firing through the carburator, and surging, and sounds like hammer going off inside of the engine. This has all started happening in the last week and a half. Our initial thoughts were that the timing was jumping due to a possible cracked distributor cap. Last night we replaced the distributor cap, rotor, and plug wires and unfortunatly no change happened with the motor. I need your guys help to help diagnose the problem and put my worst fears to rest. Please help.

Thanks,
72rookie

[faribran]

need more info..... has any other changes recently been done?.... how many miles are on the engine.....

[72rookie]

Nothing has been changed to the engine. The engine has 164000 miles on it. The engine is facotry no aftermarket mods have ever been done.

[NoNeck]

The engine has started back firing through the carburator, and surging, and sounds like hammer going off inside of the engine.

Sounds more like the timing chain to me. Did it begin to back fire after winding the engine up to speed or at cruise? With 164K miles on the engine it would definately be due a new timing chain. They can stretch enough to literally jump a tooth on the cam/crank gears.

That could explain the back fire through the carb, the surging and that "hammering" sound (detonation) that you are hearing.

Just my thoughts.

NoNeck

[Kurt L]

just my .02 i agree with no neck. pull number one plug spin enginf over till you get number one up,pull dist cap see where rotor is pointing, if not at number one wire on cap the you have a broke timming gear or a broke tooth. if the engine is still stock then it probably still has the fiber gear on the cam thats most likely your problem.

[GASoline71]

Slacked out timing chain... or maybe losing a lifter lobe or 2. Pull the valve covers and see if any of the rockers are very very loose.

Gary

[Bears63]

Sounds like timing chain issues to me as well. Like Kurt_L noted, if that engine still is original and still has the fiber cam gear, then that is likely the problem. Those are known to disintegrate over time.

[CC69Rat]

No Neck is my pop .. We had an old Big Block once that had jumped time, it sheared off about 6 of the teeth off the cam gear. Nylon / Fiber whatever they were made from .. it had pieces all in the oil pan, bent push rods etc. It was a mess. I think yours might be from wear (?) but I completely agree. I'm thinking more jumped time though than a complete break. (It's still running, just not running good)

.. my .02.

Pull the cap and set to TDC, see where the rotor is. I think someone mentioned this already but I'd probably start there.

Later.

[geezer#99]

If it's a sbc then it could have nylon timing gears. If a six banger the teeth are steel. Did you pull the distributor out to change the cap and rotor. Distributor could have loosened enough to rotate. Normal rotation will retard the timing causing your symptoms. Check if the dizzy will move. Maybe it slipped a bit.

[RUSHNBOBO]

Originally Posted by geezer#99

If it's a sbc then it could have nylon timing gears. If a six banger the teeth are steel. Did you pull the distributor out to change the cap and rotor. Distributor could have loosened enough to rotate. Normal rotation will retard the timing causing your symptoms. Check if the dizzy will move. Maybe it slipped a bit.

Don't you mean 6 cylinder has nylon or fiber timing gears.

The straight 6 series 194-230-250-292 all came stock (except heavy duty) with a fiber camshaft gear (they were gear to gear, no chain)...the fiber kept down the noise.

[RUSHNBOBO]

Originally Posted by 72rookie

The old C-10 (Bessy) has started acting up. The engine has started back firing through the carburator, and surging, and sounds like hammer going off inside of the engine. This has all started happening in the last week and a half. Our initial thoughts were that the timing was jumping due to a possible cracked distributor cap. Last night we replaced the distributor cap, rotor, and plug wires and unfortunatly no change happened with the motor. I need your guys help to help diagnose the problem and put my worst fears to rest. Please help.

Thanks,
72rookie

The first thing to check with this symptom is retarded ignition timing,

The initial timing doesn't jump w/ a bad cap but it may crossfire if its really bad. You said you replaced the cap and all is the same, but did you check the initial timing? don't know how it could have got moved, but weirder things have been known to happen. Also be sure your wires are 1-8-4-3-6-5-7-2 (on sbc) one wire out of order will make lots of interesting noises.

If all this is ok, next check for timing gear chain for a jumped tooth, which has to be very worn to happen.

Also need to know what motor are we talking about ...I assume it's a sbc but if it's a six banger you could have a stripped fiber timing gear ...pretty common in these motors...this would be 230-250-292 series. They now make aluminum gears to replace.

[geezer#99]

I stand by my statement. SBC Nylon gears. 6 banger steel, no chain. Nylon wouldn't last long.
Even nylon in a 396 BBC.

[RUSHNBOBO]

Originally Posted by geezer#99

I stand by my statement. SBC Nylon gears. 6 banger steel, no chain. Nylon wouldn't last long.
Even nylon in a 396 BBC.

Maybe all these pros don't know what there talking about....url's and all..look em up ... w/fiber (not nylon or steel except "heavy duty") camshaft gear

Well here's one part# .....straight six 194-230-250-292 FIBER...I owned three of them!!!!

http://www.oreillyauto.com/site/c/de...3453&ppt=C0141


Cloyes - Engine Timing Camshaft Gear
$35.99 Each
Add To Cart
Add to Printable List
Online: Available
Call Store: Usually Avail. 2-3 Days
Find store with item
Limited Lifetime Warranty
Teeth: 54
Light Duty Engine
Fiber<<<<<<<<<<<<
Quantity Per Vehicle: 1

here's another, from "hot sixes" 194-230-250-292

http://hotsixes.com/index.php?option...&id=2&Itemid=3

this was copied from "hot sixes" ... there's about 10 more links I could post...that picture sure looks a lot like fiber ...hmmmm

"Fiber camshaft timing gears run a lot quieter than steel or aluminum cam sprockets. The down side is they can strip at any time & is more prone in older engines. It is advised if you are changing your camshaft or hotting up your chevy inliner that both cam & crank gears be repaced as they are designed to be run as a matched set."

I'll stand by my experience w/stripped fiber gears in L6 chevy's and apparently so does everyone else who is familiar with them.

You are partially correct on the sbc though....some sbc used a nylon camshaft gear through the late seventies. I'll give you that one.

[geezer#99]

I stand corrected.

[RUSHNBOBO]

Originally Posted by geezer#99

I stand corrected.

You sir are a gentleman, and I apologize for the tone and the overly long post ....
TTYL ...Rushnbobo........aka.......Dan

[72rookie]

Thanks guys! The engine is a 350 sbc! We have not yet pulled the distributor. Our plans for the weekend (actually my Dad's plans, I have wife plans) are to pull the valve covers to check the lifters as well as check the timing chain.

I really appreciate all the advice. I will keep you all updated. Keep the advise coming!

[dmack91]

I had a similar thing happen in a F**d 429. It was a bad/loose condenser. If you have HEI, ignore me.

[rcgroom]

A bit late on this post but this exact thing has happened with my 67 C10 with an in-line 250.

I have the cam and crank gear ordered from orielys and plan to begin on Monday with the work. Does anyone know of a step by step guide to doing this? I have looked all over and can’t find any help on this.

Thanks!
Chris
Posted via Mobile Device

[davepl]

Originally Posted by RUSHNBOBO

You are partially correct on the sbc though....some sbc used a nylon camshaft gear through the late seventies. I'll give you that one.

I can vouch for that - my 250hp 2bbl 350 (L48?) in a 1969 passenger car had a nylon upper gear from the factory, and I as the first person to open that motor.

It's only been seven years, I hope he sorts out the cause and we find the solution soon!