Rebuilt 403 Help!!
guyt
07-05-2002, 09:30 PM
I REBUILT A 78 403 HEADS REDONE BLOCK .030 CRANK .020-.020
8.5 TO 1 PISTONS 83CC HEADS EDELBROCK PEFORMER CAM AND INTAKE. MY PROBLEM IS THE MOTOR IS A DOG AND WILL NOT RUN RIGHT. I TOOK IT APART TO MAKE SURE THE CHAIN WAS ON RIGHT AND IT WAS. THEN I FOUND OUT I ONLY HAVE ABOUT 100 TO 115 PSI OF CYL. PRESSURE AND I DONT KNOW WHY. I SHIMMED UP THE ROCKERS AND I GOT 125PSI. BUT THIS IS STILL TO LOW. ANY HELP?
THANK YOU
8.5 TO 1 PISTONS 83CC HEADS EDELBROCK PEFORMER CAM AND INTAKE. MY PROBLEM IS THE MOTOR IS A DOG AND WILL NOT RUN RIGHT. I TOOK IT APART TO MAKE SURE THE CHAIN WAS ON RIGHT AND IT WAS. THEN I FOUND OUT I ONLY HAVE ABOUT 100 TO 115 PSI OF CYL. PRESSURE AND I DONT KNOW WHY. I SHIMMED UP THE ROCKERS AND I GOT 125PSI. BUT THIS IS STILL TO LOW. ANY HELP?
THANK YOU
Nick LaBorde
10-18-2002, 11:16 PM
Have you solved your low power problem with your olds? If so what did you find, if not maybe i can offer some ideas.
Nick LaBorde
10-20-2002, 05:53 PM
OLDS 403
I assume that when assembled the engine you chose a cam that was a little more agressive than stock. If the information I've been given is correct, the answer is as follows. 1. if your cam has .500" lift, a fully adjustable valvetrain is required. If it falls in somewhere below the .500" lift mark than you can get away with using adjustable rocker pivots or adjustable pushrods, which are available from Mondello performance products (Oldsmobiles are these guy's specialty).There web site is www.mondellotwister.com
If you didn't install a radical cam and are having this problem, it may not be valve train related. In your posting you mentioned a lack of compression, after getting readings did you give the low cylinders a few drops of engine oil and re-test? if adding oil to low cylinders icreases the results, this indicates a ring sealing issue. If results do not change then it is probably valvetrain or head gasket related. Another question I have is, when the cam was installed did you follow the insructions for proper degreeing? If the cam timing is wrong the engine will also be pretty gutless.
I assume that when assembled the engine you chose a cam that was a little more agressive than stock. If the information I've been given is correct, the answer is as follows. 1. if your cam has .500" lift, a fully adjustable valvetrain is required. If it falls in somewhere below the .500" lift mark than you can get away with using adjustable rocker pivots or adjustable pushrods, which are available from Mondello performance products (Oldsmobiles are these guy's specialty).There web site is www.mondellotwister.com
If you didn't install a radical cam and are having this problem, it may not be valve train related. In your posting you mentioned a lack of compression, after getting readings did you give the low cylinders a few drops of engine oil and re-test? if adding oil to low cylinders icreases the results, this indicates a ring sealing issue. If results do not change then it is probably valvetrain or head gasket related. Another question I have is, when the cam was installed did you follow the insructions for proper degreeing? If the cam timing is wrong the engine will also be pretty gutless.
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