gofastwannabe

Mr. Moore,
It's about time for a valve job and was wondering about my 200cc heads. I may not keep the boat much longer and was not intending on upgrading to the 269cc merlins. My question is this, can I install larger valves in these heads without pulling the motor and scribing the combustion chambers and what would the results be? I will install stainless marine exhaust. I have purchased your BB book and have read it cover to cover many times and will use it for a blueprint for my next project motor. Keep up the great articles.
Look forward to reading!

Thanks, Ted

Dennis Moore

The combustion chambers are the same size as a large valve head so there wouldn't be any problem installing the larger valves.

I must add that with the small intake ports bigger valves will not be much help in a performance increase. The stock valves are fine unless you start increasing valve lift and duration with a bigger camshaft.

If you run a camshaft with less than .500 lift (stock valvesprings) and less than 220 degrees duration the larger valves will be a big expense with very little performance gain (check out the price of new intake and exhaust valves, valve seat enlargement, bowl blending and valve job. It would be considerable.)

Using the stock valves and a good valve job with a 30 degree backcut on the intake valves and some light pocket porting would be ideal.

You would increase performance much more with a better intake manifold and replacing the carb adapter (if you have the Weber 4 barrel adapted to the spreadbore manifold).

Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

gofastwannabe

Thanks Mr. Moore,
I was planning on using the cam you suggested in your book and adding a spread bore edelbrock rpm manifold while keeping my rochester quad carb. Is there an electric choke set up for these carbs? Do I need a choke?

Thanks, Ted