I just got a 73 400 small block motor fom a buddy of mine for free. It has 461 camel hump heads with a stock bore. He said it has a 280 duration,.590 lift hyd. cam(don't know what brand) and a 750 Edelbrock carb with a gm hei . I'm going through it checking things over before I try to fire it up . It;s on a engine stand right now,and I did a compression test and found some variations in several cylinders. Here is what I have :
#1 143 lbs # 5 165 lbs
#2 155 lbs # 6 142 lbs
#3 150 lbs # 7 160 lbs
#4 155 lbs # 8 175 lbs
Does the high lift cam have an effect on the readings I'm getting?
This engine suppossedly has less than 1100 miles on it since it's rebuild,but I have no clue on the quality of the work done to it.I was thinking about tearing it down just to check out the internals. If it was your motor what would you do? Any comments /opinions welcome.I haven't tore apart an engine for years, so I,m taking my time with this one. Thanks, Don

How did you spin the motor over on the stand.....what speed and how many revolutions? I think you can determine how your cam timing will effect your pressure numbers but my advice is to obtain a leakdown tester and determine something more conclusive............

Your readings are within 20% of each other and this is a cold test.I have seen much worse, it's not bad at all. If the vehicle is something you depend or race a leak down test would be good. If this is a good friend I would think he would not knowingly give you a "bomb".
If this vehicle is a toy I would put it in and see how it runs. Hell it's for free !!!
If it did blow up, hopefully you had fun doing it.

The engine is on an engine stand. I bolted up the starter and cranked each cylinder 4 or 5 compression strokes. I sprayed a little licht oil into each cyl. because the motor had been sitting for awhile and didn't want to crank it dry.Describe to me the process of performing a leakdown test.Do you think It would be safe to try and fire the motor on the stand? Probably only run it for a few seconds to see if it will run at all.Do you think if I could get the motor warmed up a little and then run another compression test it would even out some or the variances in the numbers? thanks ,,Don

Putting it on a regular engine stand and firing it up sounds scary. If you had a cradle and a trans behind it OK. So if it has flat tops or small dish and 64cc heads that puts the compression a ways up there. You could have the heads checked out as drop the pan to see how the bearings looked. Also see if the timing chain is sloppy at all.

I had a 412 about 15 years ago ,flat top piston with 882 heads..480 lift and 230 deg.duration at .050 performer intake and 600 vac.sec.with 1 1/2 primary tube and 3 in.collectors with 2 1/4 exhaust.in a 86 silverado.It was way too fast and I had a blast.Had to run 92 octane though ,too much compression.I'd say it made about 300 hp and 500 ft.lb. of torque.Good luck.

with only 1100 miles it may not even be broke in, how hard has it been ran?