The valve reliefs in your pistons can be fly cut before you install them; you don't have to wait until they are installed to do the cutting. Most porters have a jig setup for this purpose.

Don't use the .055 head gasket. I am not sure why you can't use the .030" gasket but if you can't, at least tighten the squish up a bit with the .042" head gasket. From what I know about the 259E cam, which isn't a lot, it likes at least 10.5:1 compression and with the thicker head gasket, she might be prone to detonate.

Have you given any thought to squish grooves?

 

Scott
for the average non wrench that wants to his on build do you check on that when people send you their jugs and heads for your package deal so when they get it back they just bolt jugs and heads back on?

 

WTF are "squish grooves"?

 

I just pulled a set of 251's(almost identical to the 259e's) from my 08 FLHX that had 10.5 pistons(pop up's for the 95cc chambers in my heads) but had been put together with a .045 hg's and it only had 175 psi at 900 feet, lazy lazy lazy below 3000 rpm. Putting the .030 hg's in and also putting in 42 degree closing cams to help bump the pressure up closer to 195psi. It just got back together last night so I don't have any details on final psi or the net gains on performance as it has yet to be tuned. Heat cycled only to seat the new rings/hone and will check the psi after the tune is done.

 

Two examples, different approaches are attached.

 

Cool, what is the theory of there operation???

 

http://www.somender-singh.com/

 

how do squash gruves work?

gtracer.. these are 103 jugs if that maters? I read with the cast pistons its static 10.8 actual? been told id lose 0.25 with stock humm

prodrag... they used a grinding wheel with 2" wheel approx. and touched up the ridge on the piston..thats where the clearance i feel is going to be the biggist problem..

maybe i will go with cometics and adj pr...but still think i might be able to touch up valve ridge on my own? or would have to mail the pistons cause no one in this area can do it.Just spoke to another shop today and they think im fine and also have a jig but have never had to use it wtf I asked if i could borrow it lol and they said no. best place to mail them? cast flatop 21966-07 cut for stock ......need to be cut for intake 18045-98 and exhaust 18044-98 valves aproximitlly 1.9 and 1.6 inchs

 

interesting read, on one of the pages from 2007 one head had a combination of groves and dimples, Dimpling i have seen before, and has been around quite a while.

But i have seen nothing about grooving. interesting.

 

I've been using grooves like the ones in your left picture for 2 seasons now. 206 ccp and rarely a hint of hot start. No ping.
They work well for me. WFO Larry did them.