Compression test results

[74Runneer]

So i think that i did this wrong but heres what i did: Unpluged the positive wire going to the coil, took out the spark plug, cranked it over 5 times. My carb is being rebuilt to i had the fuel going to a bottle. Also i couldnt warm the engine up because i didnt have a carb, but here are my results:1: 125 2:120 3: 4: 5:125 6:120 7:125 8:118 I couldnt get the 3 and 4 spark plug out because of my stupid headers. there isnt enough room to fit a knuckle bit to my wrench and there is just no room. I tried to use a pliers and just go under and twist it but the steering column was in the way.**What do i do here?Anyways are the numbers i have alright? I have a mild cammed 318**

 

[HT413]

Regarding the spark plug access, this is what i use on my 69 Belvedere 413 motor w headers. Easy access to all the plugs with these.

 

[MoparMitch]

Regarding the spark plug access, this is what i use on my 69 Belvedere 413 motor w headers. Easy access to all the plugs with these.

View attachment 123997

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[74Runneer]

Oh yeah i never thought about that, ill try that tomorrow

 

[Meep-Meep]

Method seems OK. Your numbers are low but that might be because of the cam. Is it kind of a lazy dog getting going? I wouldn't expect the engine to be very snappy with those numbers.

 

[74Runneer]

Well I don't have very much to compare it to because that and my suburban arw the only cars I've driven. It seems to be pretty quick and responsive with enough timing. I was told that my numbers would be higher if I warmed the engine up first. The engine has been cold sitting for a week before I did my test. I already have heads that I'm putting on and those had a nice valve job done so I'm hoping that and a new head gasket may help, along with warming up the engine first.

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And the cam is fairly large, it responds best with about 12-14 inches of initial advance. But then again it is only a 318

 

[74Runneer]

Checked the last two plugs today and they were 125 psi each.

 

[Roadbird]

Could be a number of problems for cylinder #3 to give that low of a compression reading for example: Improperly seating valve, damaged or broken compression ring on piston 3, bent valves, cracked pistons. Could be anything including scorched cylinder walls and crooked piston or connecting rod.

 

[benno440]

i was told its okay as long as there is not more than 10 psi between cylinders and anything under is okay

 

[Ghosty]

Could be a number of problems for cylinder #3 to give that low of a compression reading.

Did you mean Cyl.#8? That's the one that showed 118. He said #3 was 125. #8 is only 7psi (~4%?) under the top readings.

Percentage-wise, actually looks consistant, nothing that stands out across the board. And on a stock compression 318 street motor, 120-125 isn't too low from what I've read, especially cold. 110's and lower (warmed up) might be of more concern.

 

[74Runneer]

Okay great, and with my new milled heads with a new valve job im sure it will be up even more.