I have a 69 GS400 with a fairly stock 400 that I rebuilt several years ago. Since I rebuilt it I have had problems with the car pinging under acceleration. Makes it no fun to drive! I have checked just about everything, compression, dynamic compression ratio, timing gears, multiple distributors, timing curve (total timing was around 26 to minimize pinging, but it still would ping). I was told that it could be that the pistons were too deep in the cylinders. Pulled the head today and here is what I found (see pictures). I have some carbon build up but it looks like the pistons are ok. Can someone help me!?! On the gauge it is the top measurement (bottom is metric?
Tell us as much as you can about the rebuild. What pistons, what cam, what distributor. The more info you provide the better. Was the cam degreed?
Stock 30 over pistons from TA (manufacturec by egge). Stage 1 cam. I checked the cam with a degree wheel, it was correct. I was using a stock distributor with pertronix, but also tried points and an hei.
What is the distributor part number? Did you measure everything and come up with an accurate static compression ratio?
I have a 68 distributor (1111330) with a bushing restricting mechanical advance. I was running 0 degrees initial timing. I will have to look at what the hei part number was. I run super unleaded (91 octane). Larry, at your suggestion several months ago I did a compression test. You previously didn't think it was high.
I did not measure the compression ratio but did calculate it knowing the dish if the pistons, the heads volume and the head gasket. Calculated a compression ratio of 9.3:1 and the dynamic cr is 7.52:1
That should be fine. Maybe do a compression check and see what the cylinder pressures are. What about the distributor. Is it possible the ignition timing isn't right?
From earlier this year, here were compression test results: 1- 140 2- 143 3-130 4-128 5-135 6-125 7-130 8-133
My first thought was not correct installed dist. Is 0 degress, actual 0 degrees? Just sound weird, that it runs hot summer and pings winter.. It's a too little, too much timing issues..
