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Pinging [newly rebuilt engine]

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Lucky_B

Lucky_B

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Have tried all the usual things: i.e. adjust timing, degree timing, higher octane gas, Gas octane buster, adjust valves and I cannot stop pinging. I am assuming when the engine was rebuilt .030 over, I had the block skimmed and the head re-done (skimmed), I have increased the compression to a point that it now pings.

How do I lower the compression? Are there thicker head gaskets? should I use 2 head gaskets?

Help Please,

Weezer
 
Sandwiching two gaskets is just ASKING for trouble, IMO. Did you use the concave pistons or flat tops?

There's some "meat" in the combustion chambers you can safely remove, that may help. 93 octane without "boosters" is all you ~should~ need, timing retard should settle it out. Since you've tried all that without success, is the dizzy advance coming in too soon due to weak springs mebbe? How much did you deck the block/head?

OH! And welcome to the forum!
 
Distributor is a newly rebuilt from Advance Distributors The pistons are concave pistons. Unknown how much was taken off the head and block.

This is a 77 MGB

OH, thannks for the welcome been here awhile just never posted
 
Well, Jeff's rebuild shouldn't be at issue then... what carb setup? Roy has a point.
 
Has Stromberg carb, all pollution control devices California registered car requiringe smog certification

Weezer
 
eeep. I think we've found the issue. I don't have access to the needle charts but I recall seeing a good on-line reference posted a while back. Do ya know what needle is in it now? Have you tried a bit of an enrichment yet?
 
Do you still have the EGR valve on it, and if so, does it work? If it is inop, you might want to get it to work as that helps to quell detonation. How about a compression test? Check what the timing is at full advance (3000 to 3500 rpm) Does your car have the 4th gear switch for the spark advance? Finally, how warm is it running? Can you check with a non contact thermometer to verify that it is not too hot? Sometimes a new rebuilt can be tight and the excess friction can add to the problem. Keep us posted on your progress.
 
Yes, I do have the EGR in place. I also have the 4th gear vacuum switch. I have not looked at that possibility as of the EGR faulty.

I do not have the Compression readings. I will get that this weekend

It is not overheating as I have an aux fan to augment the original and i can keep the temp around 180 to 190 degrees. Checked with an infrared thermometer.

Thanks for help I think I may be close with the EGR not working. That will be my next check.

Weezer
 
Well, checked the egr valve - works as it should, Cleaned it anyway. I did a compression check and it reads: 1-155, 2-155, 3-125, 4-155. No 3 will go to 155 if I put oil in the cylinder.
checked advance at 3000 rpm and got 22 degrees of advance no vacuum connected.

Weezer
 
Have you tried a gunson colortune to see how the mixture is when she is running? Might help either focus in or move on to something besides mixture.

Where in SoCal are you?
 
With the quality of fuels available today as compared to what they were when that vehicle (and settings) were new, first thing I'd be doing is backing off the timing.

Pinging causes ring flutter, which causes oil burning.
Oil burning can cause pinging.
Lean mixture can cause pinging (but your color looks okay).
EGR opening too soon causes lean mixture (the only way to know is run it in "ping" mode for a bit, hit neutral and ignition at the same time, roll off the road, pull the plugs THEN).

Seen a lot of red cats with EGR dumping too soon.

Once pinging starts, you need to fully stop it prior to proceeding.

I don't have my books in front of me, but 22 degrees with no vacuum advance sounds a tad steep.

Back initial off 5 degrees and try it again.

Dave
 
The closest reference I can find is for a 1977 18V which is 26-30 at 4500 centrifugal.

The advance is a Lucas 5-13-10, starts at 5", ends at 13", with a total of 10 degrees advance.

The basic rule is advance the timing until it "pings", then back it off (usually with the knurled knob) until it doesn't.

Driving it in "ping" mode is going to take out the upper rings, if it hasn't already.
 
Thanks Dave

I will try what you have suggested. My next step is to remove the EGR and go from there I will also back down the timing

Weezer
 
Weezer - correct range through the whole RPM range or "just" at idle?
(wondering if the advance is a bit much for your car, Jeff can adjust, or you can back timing off as mentioned to compensate).
 
I am going to remove the EGR and see if that makes a difference. This only manifests itself when warm and accelerating. My distributor is a 45D (no Wheel) and it was recurved for my car by Jeff at Advanced Distributors, so I am confident that the distributor is good.

Weezer
 
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