440 compresion ratio

[Rob344]

is there any way to find the compresion ratio on a motor thats already built? i bought my car and the guy said it had 10-1 compresion so i put 91 and a bottle of octane booster and it pinged real bad . So then backed the timing off and it still does it. The motor was brand new and was never drove before i got it. any ideas

 

[426HemiCharger]

http://www.csgnetwork.com/compcalc.html

OR

http://www.rbracing-rsr.com/compstaticcalc.html

 

[Rob344]

i dont have any specs on the motor exept it has cast heads.

 

[69 Runner]

I'm assuming you're saying it detonates under load. I'd check the advance in your distributor for the total advance, and WHERE it comes in. I'm guessing your advance is polling in way to fast (easily)

 

[Rob344]

thats exactly what is happening can you adjust the advance or do i have to buy a new distributor

 

[69 Runner]

It can be adjusted. The pod itself may be adjustable with an allen wrench through the vacuum fitting. But ultimately you will probably have to change the springs inside the distributor, and possibly limit the travel of the weights IF there is to much advance in it.

 

[Rob344]

where do i get springs at. i have the factory style distributor

 

[Meep-Meep]

I agree, get the timing light out and see what you got. Without vac advance you should have 36 deg total at something like 2300 RPM. This includes your initial timing.

Vacuum advance should go to the ported vacuum port on the carb. Ported means you will get a vacuum signal as you crack open the throttle but negligible signal at WOT. Timing with vac advance hooked up and the throttle open to expose the ported port can be as high as 50 deg BTC, but in a perfect world that's tuned to be at a light load cruise speed.

Checking the dizzy. You should be able to give the dist rotor a twist and it should snap back right away. No sluggish movement and not to much force to twist it. Recurve springs are available from the parts stores that sell hi perf stuff under the Mr. Gasket product line.