Need help with compression test results

[David]

I have a 318 with 600cfm carb,dual plane intake, and headers. The motor has just under 300,000 miles on it. I had a previous post describing some running issues and thinking it was the carb. It is not the carb, so I had a buddy do a compression test for me. All of the cylinders read a psi of 120 except for cylinder #2. The first time we did it, the psi read 95. So we tried it again and got 105. What does this mean/whats wrong? Also whats a normal reading for 318 on a compression test?

 

[Meep-Meep]

Did you have the throttle open? Engine warm, all plugs out and you should crank it at least 5 compression cycles. 120 might be a bit low - 95 is definitely low. I believe it should be around 150.

 

[65-440]

95 is definitely low, but not far from the rest of cylinders. could be burnt / worn valve, valve seat, weak spring ..... but looking at mileage ( >300,000 ) i would start questioning the rings. get the motor warm, squrit a little oil into the cylinder, re-do compression test and see what results are.... my moneys on a long over due rebuild ! good luck

 

[David]

Hey thanks for the help. My brother did the test and followed instructions that came with the kit. The engine was warm, disconnected the ignition coil, and went one plug at a time with 5 cycles each. I was thinking it should be around 150 but with that much mileage I figured 120 was alright. 65-440 those are the two problems I thought/feared it might be. The motor has never been pulled or rebuilt according to the previous owner. If I have to rebuild it I would like to get it machined and built to get more horsepower. SO is it worth rebuilding or should I look for a new motor? Thanks again for the help

 

[69HEMICORONETR/TCONV]

With 300,000 miles I definitely see some machine work in your future, ....the question is are you happy with a 318, I would think thing through to make sure I was satisfied with what I had before dropping cash into a rebuilt. Rebuild money could be spent on a larger engine if thats what you desire.

 

[David]

I thought it would be kind of cool to build one of those 400 horse 318s. I definately want a big block, but can't find one for a reasonable price. I also didn't want to have to do a transmission swap. But I guess I will look at all of my options and go from there. Thanks for the help and input

 

[detmatt1]

Your not all that far from Detroit, and we got some big bocks up here, not necessarily a dime a dozen but can be had very reasonably and you could do the round trip in a day. Let me know what you might be looking for and Ill see what I can find.

 

[David]

Hey thanks detmatt1. Ideally I would probably replace the 318 with a 440, but I would settle for a 383 possibly. I just want to get it back on the road lol

 

[69HEMICORONETR/TCONV]

Hey thanks detmatt1. Ideally I would probably replace the 318 with a 440, but I would settle for a 383 possibly. I just want to get it back on the road lol

I would throw the rebuild money at a good 440, These can still be had at reasonable prices.

 

[David]

Thats more than likely what I will do. I have a 904 trans right now. I know I will need to swap that for a 727 but can I still keep it an automatic?

 

[69HEMICORONETR/TCONV]

Thats more than likely what I will do. I have a 904 trans right now. I know I will need to swap that for a 727 but can I still keep it an automatic?

Sure,...I can't see any reason why you can't use a 727 Automatic,.... plus a 727 would be cheaper than a 4 speed, That A-833 stuff can get pricey.

 

[65-440]

cant go wrong with a 440 ! unless $$$ is a problem, and we all know times are tight, believe me, i've been finding excuses not to pull my trans and it needs a serious overhaul !! i really dont think the price difference is much b/t an insane 318 vs. a mild 440 build. 727's are easy to come by too .....

 

[David]

I also heard that if I switch to a 727 I will need to shorten the drive shaft is this right?

 

[David]

What all will I need to do if I were to replace the 318 with a 440?