head swap

I'm planning my winter project early and I wanted to do some research.
I wanted to switch my 906 heads to a set of 516's I've got. I planned on putting in new stainless valves, increasing the exhaust to 1.74, new springs and gasket matching the ports. Do I need to do anything else? Bronze guides? or just knurl the originals? what about hardened seats?
I also planned on surfacing the heads just to make them true.
I have trw low compression pistons and I thought I might see a nice gain in power by doing this.
Any reason why I should not do this?

thanks for the input
scott

every thing you listed is great ex that the 906 heads flow much better than the 516's & you may end up worse off even w the higher CR from the closed chambers. If you have not purchased those parts/services yet you might consider a set of stealths or another set of 906's(& people have milled them quite a bit) to prep & have em ready to throw on & on the local craigslist there was a set of bare 906's for $50 & no takers so they are out there cheap. I'm considering having my ace metal man weld up the open chambers closed in a set of 906's then milling them flat as the 906 is a fairly good flowing iron head & I have yet to see one that has cracked if it wasn't overheated but those stealths keep looking better all the time.

i think the aluminum head with lower compression would not work very well either. What about a set of 915's built up the same way?
I have several sets of 906's but i thought I would be better off getting the compression higher by switching to a closed chamber head.

thanks
scott

If you want to stick with the iron head,go with the 915.There hard to find a decent set,I know I'm still looking .A member here sent me an offer for some real nice 915 heads fully loaded,but a bit steep for my purpose.If you want his e-mail pm me and I'll give you his info,they may still be for sale.

with the work you mentioned, you would probably be money ahead in the long run to get some eddies.

the whole can't run aluminum with low compression is kind of a myth.

it also might be cheaper to keep your heads, pull the motor, and if it mics out good for cyl taper, do a hone job and get some higher compression pistons.

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with the work you mentioned, you would probably be money ahead in the long run to get some eddies.

the whole can't run aluminum with low compression is kind of a myth.

it also might be cheaper to keep your heads, pull the motor, and if it mics out good for cyl taper, do a hone job and get some higher compression pistons.

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also have guide inserts installed , knurling is old backyard hack quick fix , and hard seats would be a good idea if you plan to drive it alot . If this isn't an all out performance upgrade you'll hardly notice the difference .