I have pulled apart my topend because i'm going to bore the jugs. I have andrews v8 cams and was wondering if it would be worth while if I have oversize valves installed. I plan on porting and polishing also. Another question - i noticed tha thte intake has an inner and outer spring and the exhaust has only an outer why is that?

Time to review the dozens of dyno charts to see what you need in order to get what you want. This will be a very subjective issue.

if you're gonna run the RPM high a lot then the bigger valves will help....if you're keeping the RPM low then the smaller valves will help

Ww

Depending on who is doing the port work, but larger valves can be installed and you can have the best of both worlds....meaning increase low end power as well as mid and upper rpm power. On a 1988 1200 ( I think that is what you have), and with the N8 cams I would go with larger valves and have them fitted, ported, flowed . I would also go with new springs and hardware. There is a lot of power in the heads when done properly. Up the compression to about 10.5:1 while you are at it and have a squish area set up.

Thanks for the replies. Shu I have 10.5:1 pistons on the way and i have read that the valves on stock head can only be opened up to 1.76 intake (from 1.715) and exhaust to 1.53 (from 1.47 or something like that) do I need to go bigger than that? If i have to go bigger than i need new seats right? Also the andrews site says stock springs are fine should i upgrade to a heavier spring? Squish area do i have to do this? I'm tring to keep the cost down if possible. Thanks agaiin for the info. Chris


Depending on who is doing the port work, but larger valves can be installed and you can have the best of both worlds....meaning increase low end power as well as mid and upper rpm power. On a 1988 1200 ( I think that is what you have), and with the N8 cams I would go with larger valves and have them fitted, ported, flowed . I would also go with new springs and hardware. There is a lot of power in the heads when done properly. Up the compression to about 10.5:1 while you are at it and have a squish area set up.

Please don't take this the wrong way, but if you want to do the heads on the cheap, don't bother putting in larger valves. Match the ports, blend the valve seats, lap the valves and put it together. Improving a cylinder head in just one area will not have much, if any effect. Larger valves without larger holes for them will do zero, zip, nada, nothing.

You stated your exhaust valves have only the outer spring? That's not right, All 4 valves should have the same spring setup. The V8 cams need a bit more spring travel over stock. Andrews sells titanium upper collars that give you .050" more travel. You really need that. With the V8 cams, you will want the heads flowing better than stock 883 heads will. I agree with Horse on budget headwork. A little flow can be gained by blending the seats to the ports. 883 seats usually hang out in the ports pretty far. Pretty easy to blend with a dremil and sanding drum. Intake work will mean more than exhaust. While you have the heads apart you can even do a bit of smoothing in the ports. The valve guide bosses could use a bit of aluminum removal. Porters give them a teardrop sort of shape. Flow can be gained there. Intake port diameter can be matched to intake. That will help flow too. See, it's not just the "big" things, the little things add up pretty good too.
Ted