Question about cylnder head work...

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Dec 16, 2011 | 01:46 AM

hboat

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Cruiser

Joined: Nov 2011

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From: Berkeley, CA

Question about cylnder head work...

I've had the '07 StreetBob signed below for about 3 months. It's my 7th bike (5 Triumphs - in the 60's-80's and a super built Sportster 1200S in the 90's). I love this bike, I'm impressed w/ how great it runs, and I've made lots of changes already, but I want to do a bit more. I want to maintain some 'long haul' reliability, don't want to go all out and do the crank and main bearing, so I'm restraining my self from a big (107") bolt on kit w/ 10.5 CR and a big cam so as not to stress the bottom end. I'm thinking of going w/ an Andrews 37 cam and decking my heads to bump up the CR up to just about 9.5 or 9.7. I'm primarily a street and twisty rider who may not open it up all the time, but damn...I just love the feeling of knowing that it's all there. I spin the revs up to 5200 or so pretty often, but rarely above that. So here's my question... Will porting and polishing my stock heads and going w/ larger valves and springs be of benefit for this build, or does that work just come on at the higher RPM's and become more of a high-end HP improvement rather than a mid-range torque thing. Any info about head work would be appreciated. Thanks, ride safe, but ride, ride, ride.

Dec 16, 2011 | 02:42 AM

Spanners39

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Joined: Dec 2010

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From: Coromandel Peninsula New Zealand

Big valves won't hurt a bit but head work even on std valves is always a good thing :-)

Dec 16, 2011 | 11:20 AM

thedonthere

Outstanding HDF Member

Joined: Dec 2008

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From: Ashland Ore.

Probably the single best thing you can do to help your motor breath. All the magic happens in the heads.
http://deweysheads.com/

Dec 16, 2011 | 11:26 AM

sbaalman

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Joined: May 2010

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From: Las Vegas, NV

I ran the Andrews 37 gear drive cam in my '09 Fat Bob and loved it up until the accident. Insurance $$ is buying a Stage IV 103" kit and new Andrews 54 gear drive cam.

So, if you are looking for an Andrews 37 gear cam set for fairly cheap - I will have one available next week. Only put about 1000 miles on it.

Dec 16, 2011 | 12:07 PM

hboat

Thread Starter

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From: Berkeley, CA

Thanks for all replies and the offer of the 54's... I'll probably stay w/ the chains for my cams. This work is about a month off and I'll check pinion run-out when I open the camcase...I'm guessing my crank is OK cuz my bike runs smooth...but I'll probably stay w/ chains anyway. I'm sure you can find a buyer for your 54's. Sorry to hear you had an accident--hope you're OK. We all think it'll never happen until...

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Dec 16, 2011 | 12:23 PM

Jackie Paper

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Joined: Mar 2010

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From: Honah Lee

Just my opinion but if you are trying for ever last HP for competition drag racing and going thru it on a regular basics then polishing and stuff like that makes sense. To do it especially if you are paying someone to do it and then drive it on the street makes no sense to me. Few 1000 miles and there will be the same build up that even with unleaded gas which tends to only get so thick and break off as compared to back in the days of leaded gas. Oil fouling is a different thing and will build up even more. Sure someone is going to say slick as a baby's butt will keep it from sticking and I agree but only a short longer if you drive it. Just my opinion.

Dec 16, 2011 | 01:24 PM

Spanners39

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Joined: Dec 2010

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From: Coromandel Peninsula New Zealand

Quote:

Originally Posted by grf000

That is assuming only poilishing gets done....the real trick with H-D heads is altering the port shape....you actually make them smaller, not larger, and alter the angle at which the gases leave the head.....which works regardless of how filthy the heads are internally.