Compression test results 1966-- 425 C.I.

[Checkov]

Even after rebuilding the Quadra Jet and carefully looking for spark etc. etc. I am still getting rough running/ poor starting performance.

So I did what I now realize I should have done last year when I got it running after it supposedly sat since 1990 something.

So here goes:

1. 122
2. 130
3. 110
4. 119
5. 119
6. 112
7. 119
8. 130. ( I'm simply counting passenger to front 1,2,3,4 then driver to front 5,6,7,8)

This is a cold engine with spark plugs removed and the throttle left alone.

I am hoping someone will say the 130 PSI is lot typical but what research I have done points out about 150 PSI.

Thanks for any news good or bad. Checkov

[Checkov]

A little more info.

I went out and performed a wet test on the two cylinders that were considerably lower.

Number 3 went up from 110 to almost 150!
Number 6 went up from 112 to almost 120.

[bcroe]

Even after rebuilding the Quadra Jet and carefully looking for spark
etc. etc. I am still getting rough running/ poor starting performance.
1. 122
2. 130
3. 110
4. 119
5. 119
6. 112
7. 119
8. 130. ( I'm simply counting passenger to front 1,2,3,4 then driver to front 5,6,7,8)
This is a cold engine with spark plugs removed and the throttle left alone.
I am hoping someone will say the 130 PSI is lot typical but what research I have done points out about 150 PSI. Checkov

For a high compression engine, those numbers are pretty low. I also wonder if the original
timing chain has been replaced? Bruce Roe

[Eightballz]

compression tests are usually done with engine at operating temp and wide open throttle !!

[Checkov]

The car won't start .

[Eightballz]

at least do it with wide open throttle..

what about the timing? did you checked that? dwell angle at 30°?

procedure is:

1.-set dwell
2.-set timing
3.-set carb

you can tell by the movement of your 0° mark on the balancer that your timing chain /gear is junk...

[Checkov]

Ok, thanks. I have set the dwell, and I will re-check the compression tonight with the throttle open (just wire it open?).

I haven't checked timing in 20 years and I don't remember how to do that, I guess I could look it up.

Thanks again, checkov

[Eightballz]

...looks like you have some sort of compression so thats not your problem for now

you need a timing light..connect it to the battery and the #1 cylinder spark plug wire.

You should disconnect your fuel feed to check initial timing

If everything is set, crank the engine and point your timing light onto the balancer, watch your timing indicator and the TDC mark on your balancer..this one should tell you what your initial timing is. That should be a steady(!) reading…somewhere around 4-8°

If its not a steady reading then you need to replace your timing gear and chain.

You may also have a slipped balancer and your 0° mark is totally off…in that case you need to verify true top dead center. But first check your initial timing..

[Eightballz]

forgot to mention that you should disconnect vac adv during this procedure....sorry

[Checkov]

Eightballz, you mean when I check timing the vacumn advance vac tube should be off?

No problem, I'm having a surprisingly hard time finding a timing light...seems like just a few yrs ago they were in every car parts store. Might try ebay.

Thanks