Bonneville America Forums Forums Technical Forums Performance Mods 904, Porting, Polishing, Bigger Valves etc.

Member Hasse and I are doing the 904 job on our 790 - 02s this coming winter. Really looking forward to it. As a "joint venture" it will also be twice as fun. There are some questions though, and one of the most interesting I have before starting is what gains different mods will give?

A Just the Big Bore without any other mods?
B The Big Bore plus porting/polishing?
C The Big Bore plus bigger valves?
D The whole shebang?

Machining like head work is rather expensive here in Sweden (and no Ian, it's out of the question to ship stuff overseas), hence the questions above. It's about knowing how to get the "most bang for the buck" before deciding...

Looking forward to input from the knowledge base!

I too am quite interested in question B. My local dealer has done a number of 904 jobs and mentioned also polishing the ports. He didn't quote a price, but I wonder if this additional work is worth it. I'm neither drag racing down the street nor doing a cannonball run; just curious if the end result is worth the additional cost (whatever it may be...any examples from experience?).

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I'm neither drag racing down the street nor doing a cannonball run

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Me neither. My biggest goal is getting more torque. The top hp up around the rev limit maybe not as much...

this thread may be of some help
http://www.bonnevilleamerica.com/forums/...6&fpart=all
here is my most recent run after 904 with port/polished head and +1mm oversize valves. I know Frank has the same setup I do but with different carbs. Matt (ditch_dr) did my port and polish, he has a thread in the vendors listing, good work and a good price. If you contact Bill Gately at bonneville performance, he will answer all your questions. I dont know if you will find a performance increase for every step like you want, but the dyno table thread should give you an idea. There are a lot of variables on the graphs (pipes, jetting, elevation, machine, etc.). I am very happy with mine, the torque is great riding two up now, the lag is gone.

I know Piper, that's what I said it was cheaper where I am in that thread.

comes down to what you want to spend. your money is the only limitation

Frank

Checkout this forum...

http://forums.delphiforums.com/acecafe/start


Look for a guy that call's himself Jojje1963....he is from your area and is extremely knowledgeable.

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I know Piper, that's what I said it was cheaper where I am in that thread.

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Cool. I was just pulling your leg.

That's cool I wasn't urked just pointing out that I knew it wasn't local for you when I posted that.