I AM GUESSING THIS ENGINE IS OUT OF A 69 TEMPEST. THE BACK BLOCK CASTING IS 9793079? COULD BE 9790879? THE 4TH AND 5TH # IS A BLUR. THE NUMBER ON TOP OF MOTOR ABOVE FLYWHEEL IS K077. THE FRONT OF ENGINE IS 9790347? THE 3 COULD BE AN 8. ANOTHER NUMBER UP FRONT IS 237019 YN.
THE HP QUESTION. I HAVE A 4 BARREL INTAKE W/600 CFM HOLLEY. I HAVE #17 HEADS. ENGINE IS BORED 30 OVER. IF THE ENGINE IS A 69 TEMPEST MAKING 265 HP STOCK WITH 2BBL WITH 9.2:1 WHAT KIND OF HP COULD I EXPECT.

put a better cam in it. a ram air cam,a r/a 4 cam. run a 650 cfm and clutch fan. you could get 300 to 325. if you can afford roller rockers and or cam then you would get closer to 400 hp.

IT HAS A SLIGHT CAM IN IT. I HAVE A ELECTIC PUSHER FAN. AND I WILL BE RUNNING HEDMAN HEADERS. WILL THE 17'S LET IT BREATHE GOOD ENOUGH. OH YA, THE ENGINE CODE...WHAT DO YOU THINK IT IS.?

Try this site:
http://www.teufert.net/pontiac/page2.htm
The YN code and #17 heads lead me to believe you have a 68'tempest engine not a 69' which i think used #47, trivial,either way it was 265hp
What is your goal for this engine? Personally i think you need better flowing heads if you want any performance out of that engine.

David

I WOULD LIKE TO USE IT AS A DRIVER. I HAVE A 200R4 OD TRANS FOR IT. WOULD THE BIGGER VALVED HEADS LOSE MUCH MILEAGE? WHAT HEADS SHOULD I LOOK FOR? I HAVE A FRIEND WITH A FEW PONCHO HEADS LAYING AROUND THAT NEED REBUILT. HOW MUCH SHOULD I EXPECT TO PAY FOR REBUILD OF HEADS?