Tuning a 1969 350, LOUD popping from carb?

[Richard/SIA]

At higher RPM I get LOUD popping from the carb.
Crackle or Pop, but no flame.
Acceleration response is still a little sluggish too.

Thought it might be from an exhaust leak, so fired it up at night so I could see where it's coming from.
No exhaust leak, it's the carb, appears to be mostly the primary side.
Very little visible fuel reverb, but the crackle-pop is LOUD and annoying!

Engine is a 1969 350 that appears to have been rebuilt, very good and even compression.
17.5" of steady vacuum at warm idle.
Idles nearly smooth at 650 RPM.
I do not know the cam specs, from the higher than expected compression I suspect the engine is not stock.

Carb is a new Edelbrock 1406 600 CFM, electric choke.
Manifold is an Edelbrock Performer RPM.

I sit at 4700 ft. elevation.
Leaned the carb two steps to compensate, primary and secondaries.
Advance set to 10º BTDC, no vacuum line connected.

All new ignition components, including wires.

The 1957 Chevy truck is nearly ready to drive, I just have to cure this fuel problem!

 

[58 Apache]

Power Valve

What size power valve and what total timing?

 

[Richard/SIA]

I do not think the Eddy uses a power valve?

Seems that they made a point of that, claiming that their design is superior as there is no power valve to "blow out"?

Unable to read total advance with my cheap timing light.

Poking around the web it seems I need to;

Check my advance weights.
Check my vacuum advance.
My timing light shows the timing mark to be very steady.
I do not get a jump in advance when I reconnect the vacuum line, so I'm looking into the vacuum advance in the morning.

Pull the valve covers to ensure the valves are all operating properly.
Seems unlikely, excellent compression and steady vacuum.

Sloppy timing chain, jumped cam timing.
Steady timing mark and vacuum seems to point to this not being the problem.

Worn cam lobe, sticking valve.
I sure hope not! :eek:
Again, this seems unlikely with the steady 17.5" of vacuum I pull at idle.

 

[MRHP]

Sounds like ignition problems to me. If you have hei ignition, make sure you do not have a resistor wire or ballast resistor wired in the circut. You need full battery voltage to the distridutor. If you have points ignition, make sure they are new and set properly. Also check the distributor for worn bushings. This will play hell with your point setting. What were your compression readings? A distributor that overadvances will also give your symptom. Try reving motor with vacuum hose off of advance can. Brian

 

[Richard/SIA]

Points are new, comp 135 PSI to 145 PSI

With this compression, and it being very even, a bad lobe or stuck valve seems unlikely to me.

I'm going to look at the distributor and vacuum advance some more.

I will post more clues as I find or eliminate them.

 

[62impala409]

Don't discount bad ignition wires or cap cross firing into another cyl. when the intake valve is open. Leo

 

[petepedlar]

I believe it was 1969........ there was a year or two of the 350's that had to have a stainless steel plate as well as the gasket between the carb and the intake. If I remember correctly I fought something like this for a week or more back in the day until a friend asked it I had the pate in there............

Dave

 

[58 Apache]

Valve Cover

I just replaced a cam that had 5 bad lobes that was 155 to 165 lbs each cylinder. 3 were exhuast 1 of which was completely gone. 2 were intake. I would have bet a weeks pay the cam was good when somebody told me to check it. When I put a dail indicator on them and proof positive. I chased a head gasket because after it warmed up it came back thru the carb and the power was good until warmed up.:takethat

 

[Ronnie Russell]

If we get to choose,, then I will go with Derry. Bad cam or valve related issue. Dial indicator on the valve retainers is a quick way to determine if lobes are good or bad. The results from this check will allow you to sleep well because of not having to change cam, not to mention, " where did all that metal go ?". OR saying many cuss words when indicator shows flat lobe. Gotta find out, one way or the other..

 

[Richard/SIA]

Vacuum advance = Trash!

No movement at all, so the weights are having to do all the work. no1:

$20.00 fix, so we will see what it does for me.
When some $$$ come in I will replace the entire distributor.

I will NOT be putting in an HEI, I've had too many failures from them.

 

[58 Apache]

Happy It Was The Easy Problem

What kind of HEI Problems have you had. I have seen millions of troble free highway miles on them and at one time the only racing dist legal for use

 

[Richard/SIA]

New vacuum advance, a GOOD thing!

Engine almost runs properly now!

Major improvement, now just a slight crackle at high RPM, throttle response is also MUCH better.

I may richen the secondaries one jet size, I think I'm getting close to a proper tune.

Of coarse it all goes away as soon as I leave the valley, I'm surrunded by mountains.
Going over the hill to Kalifornia may mean changing jets on the other side to avoid a too lean condition.

HEI = FAIL, as I have had to replace two coils and three electronics modules in three years. Yes, I did use the supplied dielectric grease under the module.
Two of the module failures were the same truck, five months apart.
I drive to avoid walking, HEI has made me a pedestrian too often!

 

[58 Apache]

The Ground

:? ANy chance you checked the ground of the Engine to chassis or alternator output voltage

 

[Don Jacks]

It's been my experiance that on any HEI that sees any kind of rpm,any thing other than a Delco module,is a screw-up waiting to happen.Just been my experiance

 

[Richard/SIA]

Well, FUDGE! Finally found time to look at ........

Well, FUDGE! Finally found time to look at the valve rockers with the engine running.

I cut up an old valve cover to make a fence, I despise oil dripping all over the headers.

Fired it up and let it idle, confirmed I need a new cam.
#5 exhaust has half the movement of any other valve.
Did not bother to disturb the other side, no point.

This is truck motor, so I'm thinking something cheap and near to stock for the new cam.
Is it the Edelbrock torquer that is basically an RV cam, or another?

With the granny gear and super low rear I could probably run almost anything, but this 57 runs out of RPM pretty quick even in fourth.
So far as I know the valve train and internals are stock 1969 bits.
: Damn the eco-nut's screwing around with our oil formulation! :takethat

 

[58 Apache]

E1065 Elgin Kit

:? Competition Products Elgin E1065 cam and lifter kit 99.95 can't beat them for the truck 214/214 @ .050 .465 lft 112 c/l good idle good mid and baord power band will raise the rpm in high gear.

 

[Richard/SIA]

I was about to get the Eddy 2102.

Edelbrock 2102 - Edelbrock Performer-Plus Cam and Lifter Kits, $124.95

Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 278/288, Lift .420/.442, Chevy, Small Block, Kit.

I will look at the Elgin E1065, have to check it's availability too.

Either way this is costing money I did not want to spend.

I even thought about putting in a roller cam, until I saw the difference in price! :eek:
Just cannot justify an extra $500 into a used truck engine. :