JesseRowe

To all. I bought this vehicle with a 383 stroker in a 80' C3. I recently had a cam failure due to use of wrong oils. The cam was replaced by a "qualified" mechanic. I ended up with a completely different vehicle. It seems they replaced the standard cam with a stage II cam. Since I just can not get this vehicle to perform as it was previously. The biggest issue or concern is the "popping " sound when going above 2000rpm. I guess it is a backfire through the edelbrock carb. I have tried the timing at 2, 4, 6 ,8 10 ,12 degrees, but as soon as the revs pic up the popping starts. Replaced the spark plugs, plug wires, aircleaner, carb fueling etc. Not understanding the timing light 100%, but with the timing set at 8deg BTDC the timing light shows 30 deg. Does this mean that they moved the distr. with a tooth to compensate for the lack of power at low end due to the Cam? Do I have a bigger issue? What can I test or try. Regards

bikerbilly18

i just solves very similar issue with popping. make sure spark plug wires 5 and 7 aren't crossed.

Buccaneer

This is only a guess, but...Since you are dealing with a carb, my first guess is that you are going too lean under acceleration which would more than likely be the accelerator pump in the carb. Also could be a plug wire issue, being off a tooth on dizzy or related. Valve train issue. I assume it only backfires through the carb and not the exhaust? Pop #1 to TDC and see if the dizzy is stabbed in correctly. Hope this helps you out a little.

'75

You need to go back to the qualified mechanic and have him get it right or find a real qualified mechanic.

BKbroiler

Try adjusting the intake rocker arms. Could be 1 or 2 set too tight.

cv67

Hes going to need to see it in person as you can see could be a number of things usually something simple

Could todays oils be to blame, maybe. The quality of cores out there isnt real good either

JesseRowe

To all thanks for the feedback. Will give this a go.

JesseRowe

Unfortunately I am a "once bitten twice shy" person when it comes to my c3. Especially out here in South Africa.

gerry72

Timing that is too far advanced will cause a popping (sounds and feels a bit like a misfire) but the sound is out of the exhaust. Too far advanced will also cause a significant loss of power.

I suggest you search youtube for tutorials on how to use a timing light. I think this will be of most benefit since what you write clashes on two points; Is the timing at idle at eight degrees or is it at 30-degrees? It can't be both.

If it is 30-degrees, then you are way too far advanced.

jnb5101

Afterfire-through exhaust, or backfire-through carb?

gkull

If you set the timing at 2 it will be 2. Not 30. Rotate the dizzy with the motor at idle till you get to about 10. Then post here

JesseRowe

I recently watched a clip on youtube where there was mention of your normal initial timing and an additional timing that could be caused by the cam being moved a tooth or so, and the dissy also having a few degrees in it. I agree I might not understand this, but is it not possible for the cam crank combination to be ligned up up as per timing marks and the still the dissy out with a tooth and then the timing light reading 30deg and the mark on the balanser/harmonic damper reading 8 or 10 deg?

JesseRowe

I thino the backfire is through the carb..

JesseRowe

The timing light connected to plug 1 will show a 8 deg reading BTDC, with advance blocked off. The dial on the timing light, at "low RPM", will show 30deg BTDC. As a novice I find this confusing.

gkull

The correct way to set your timing is to disconnect the vacuum advance and then run your car up to say 3500 RPM and see what the total advances and then you want to set it to 36 or 38 degrees

jersey68l36

"The correct way to set your timing is to disconnect the vacuum advance and then run your car up to say 3500 RPM and see what the total advances and then you want to set it to 36 or 38 degrees"

X2 on this method being the best way to observe total mechanical ign advance, but a degreed balancer is needed. Usually have the balancer degreed as part of things to do when rebuilding a mtr. But, a fall back is to get some balancer timing tape. The tape is supposed to be correct for the diameter of the balancer. After the tape is installed, spray some clear paint over the tape, so that it stays in-place, (for a while).

Does this motor idle okay??

gkull

I have dial type timing lights and all you need is a good stripe at the "ZERO" TDC . So you rev up the motor and turn the dial to where the stripe syncs on the pointer. the read your dial and adjust the dizzy to get the max advance. initial advance is immaterial and can only be changed correctly by changing the advance curve or limiting the added mechanical.

JesseRowe

Through carb!

JesseRowe

Idles OK