**1970 318LA TIMING ISSUES**

[temsinc]

I have a 70 Barracuda w/318 LA, MSD 6A Ignition, MSD Blaster 2 Coil, Brand new MSD Distributor mechanical advance, Edelbrock 650cfm carb, Edelbrock RPM Air Gap intake, Edelbrock RPM aluminum heads 340 heads (6017). It does not have the stock cam, I have no idea what size, it was in the engine when I purchased the car.

I recently added an electric brake booster vacuum pump because the car was not making enough vacuum for the brake booster at idle etc. I plugged the vacuum intake and now I have a high pitched pinging backfire. I have tried to dial in the timing, I.e. advancing and retarding it to eliminate the pinging to no avail. The only way I can see the TIMING MARK on the harmonic balancer is when the timing is retarded (clockwise) and it is well below the 10*....well below, then the car runs like s**t and stumbles.

I have checked for intake vacuum leaks, there are none. The carb is a POS that I have never been able to dial in since new. I have had a local mechanic try to dial in the carb, he changed out the MSD distributor and set the timing. The car would still stumble. That was when he noticed the car was not making allot of vacuum for the power brakes, hence the electric brake booster pump.

Anyhow, that's where Im at. Engine pings and I cannot advance or retard the timing to eliminate the pinging. Any suggestions? Thank you in advance.

Darcy

 

[Adam]

Did this engine ever run well as assembled?

I would suspect the dist is one tooth off. Verify by bringing the engine to 10 degrees before TDC, then pop the dist cap and inspect the rotor leading edge is in proximity to the #1 terminal. If you find that it is not we can deal with that easily.

Btw, you can easily confirm the balancer timing mark.. with the engine coming up to TDC take the #1 plug out and stick the end of a 3/8 fuel hose into the combustion chamber; rotate the engine towards TDC until it stops. Mark the balancer where it lines up with zero. Then rotate the engine the other way until it stops again and mark it. TDC should be directly between the marks.

Also swap the carb with another temporarily. If you have the same problem put a fuel pressure gauge in the line, before the carb; it is possible the pump is overpowering the needle & seat.

 

[moparleo]

You sure have a lot of 340/360 performance equipment on your 318. Do you honestly know what is inside this engine ? C.R. piston type etc... , you already said you don't know what cam is in it. Like a Dr. trying to diagnose an internal problem with out X-rays or blood tests. Just a lot of guessing will happen and you will never really know what you have until you open her up. May sound drastic but in reality you can find out more in a couple of days for sure with it opened up than you can find out in weeks or months and never know for sure. The worst kind of engine to buy is one that someone else has had rebuilt or hopped up. You just don't know what you will find. I am sure several members can chime in with their horror stories of supposedly "built" engines that were just tossed together. Great old saying " Caveat emptor " in English, "buyer beware"

 

[Litchkar]

I agree with Mopar Leo, the 318 had smaller combustion chamber heads I think 58 cc. The Edelbrock 340 heads are either 65 or 67 cc heads. This means that if the pistons are stock, the compression ratio is in the toilet. If this is the case it will never be strong. With out seeing inside the cylinders, you will never know. The pistons will need to be at zero deck or above to achieve about a 10 to 1 compression ratio. I had the opposite, 318 heads on a 340, the compression was too high and could not eliminate the pinging. By the way, how much vacuum does it make at idle?

 

[challenger6pak]

I would guess a mechanical problem, such as cam out of time, bad valve, or even a bad piston. The advice given to open the engine up is the way you should go forward with the motor. Running it more may cause more damage.