over run problem mn47 head

[datsun 1/2 dozen SD]

thanks for the knowledge i think my best bet is to run higher octane or a different octane booster

[Zmanco]

its now timed at 0 degrees from preveouis 15 degrees advanced

As zcarnut said, running with less advance will cause the engine to run hotter which contributes to this. If this is the only reason you retarded the timing, try putting it back.

 

Also, I agree that dumping the clutch to kill the engine is not a good idea. But letting it out just as you would after a stop won't hurt anything. It's not a good long term solution, but until you get it sorted out, I'd prefer that to allowing the engine to run on by itself.

[woldson]

WOW!!

Odd how it happened, but nevertheless inpressive! Cheers:)

[datsun 1/2 dozen SD]

i did put it back too 15 degree advanced same problem but i think runing higher octane should do it

[chiquete]

I have almost the same setup, but with the P30 block, L28(N47) valves and have no problem with dieseling... and i'm using 91 octane gas.

zcarnut did you know the numbers in this block/head combo?

[zcarnut]

I have almost the same setup, but with the P30 block, L28(N47) valves and have no problem with dieseling... and i'm using 91 octane gas. zcarnut did you know the numbers in this block/head combo?

 

Just use the L-series engine utility at:

 

Engine Design Utility

 

You will have to add/modify the data appropriately. For example, they do not list the MN47 head which has a combustion chamber volume of around 39.5cc.

[D1CNAR]

did you build the motor

check your timing chain i tcould be stretched

sounds like a timing issue or carb issue

[datsun 1/2 dozen SD]

yeah i did. new timing chain set i rebuilt my carbs to the problem is already fixed 91 with octane booster works