Bad pinging issue?

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2manymopars

2manymopars

AKA mopar_daddy
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I have a 360 .40 over with unknown piston's and deck. I found the motor in the junkyard and it was just going to get me by while the 408 is getting freshened up. I got the motor in fired the valves adjusted and timed 30 deg overall It has an air gap and a 750 DP. On the first test drive I did not even make it off the block the thing detonated so bad, rechecked the timing added 5 gal of fresh 91 it got a little better, but still barely drivable. I tried a few other things the only thing that made a difference was adding 3 gal of 110 octane now it runs ok through first gear but as soon as 2nd hits it detonates crazy bad. Am i really going to need to run race fuel? Is this motor that built? What am I missing here? Ideas and help please.
 
Make sure 0 on the balancer matches TDC
 
you check compression yet? I'd say unless your compression is way up there it's just
a timing issue. Ping less with the vacuum advance off?
 
273 said:
Make sure 0 on the balancer matches TDC
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The timing mark is on true TDC. The vacuum advance is not hooked up and it is timed @ 30 degrees overall @ 3k rpm. I did not pull the heads to check the pistons or the T case cover to check the cam timing :eek:ops:. I did notice quite a bit of head work though ported,triple springs, machine on race valve stem seals.
 
I would check where the cam is timed at and just retard the timing until the issue goes away. With that much head work it may be pretty well built.
 
2manymopars said:
The timing mark is on true TDC. The vacuum advance is not hooked up and it is timed @ 30 degrees overall @ 3k rpm. I did not pull the heads to check the pistons or the T case cover to check the cam timing :eek:ops:. I did notice quite a bit of head work though ported,triple springs, machine on race valve stem seals.
Click to expand...

And you found this in a junkyard ??? Buy any lottery tickets lately....lol.
 
Do you have any idea of how long that motor was sitting? A build up of carbon deposits could cause detonation.
 
I,m guessing someone built the motor with high compression(12.5-13-1),can,t run on pump gas?Run the car with race fuel(C12)no pump gas and see how it does.Sounds like somebody already got frustrated with the car.Pull the heads and see what pistons you have in there.JMO
 
I think you will have to see how its built to find the root cause
 
Yes I found this in a pick a part under the hood of an 88' D350. paid 170 bucks for it. Don't worry guys #3 MC had just been pulled to check the bearings it was turned before re torque.
 

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Did it stop advancing at 3K rpm?

Might it have more timing above 3K?

Did you check it running it up above 3K to see if it kept going?
 
So I did a compression test and with the plugs pulled on 5 cranks this thing boasted 165 psi. I've seen 12.5 to 1 motors with less than that.
 
165 should run on 91.the 340 in my dart is 10:1 and cranks higher than that.ive got no problems running 91 with 34* total timing and 22*initial.there are 2 things that come to mind,timing is advancing further at higher rpm(like cracked said) or you have carbon build up.
 
Just a additional thought to add to the others.......Could you be using a plug with a excessive heat range?
 
guess you could always pull the heads and put on the thickness head gasket you can find to lower compression a little
 
I would try running a colder plug - Champion heat range 9. You will want to make sure the timing curve is right. At 165psi it should not ping but you will need to make sure the curve comes in slower. It may be too fast to be "all in" by 3K. Check the distributor for the slot length and springs. last - make sure the power valve is sized properly. If it's rated too low it make be going lean as soon as the gas is pushed.
nice score by the way....lol
 
Whatever you find, that was a score. Not sure about those forged steel rockers though.
 
$170 consider that free.
The cylinder bores look to have some wear, so this engine has been run.
I am with cracked, sounds like your ignition is causing you greif.
I think when you pull the heads it will have less than 9.5 compression.
 
sireland67 said:
$170 consider that free.
The cylinder bores look to have some wear, so this engine has been run.
I am with cracked, sounds like your ignition is causing you greif.
I think when you pull the heads it will have less than 9.5 compression.
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I am pretty sure it's got more than 9.5:1 The popup is pretty big and the block is just about zero deck, It should have been a clue when my air gap wouldn't fit. The big discovery was the pistons are in it wrong:banghead: oh well I did only pay 170.00 bucks for it.
 

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