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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
I need to keep this conversation specific to the EVO heads. I'm well aware the TC head has a lot more meat and can take the CR next to the spark plug. Hell, Jim's even makes a tool specific for this. My problem is putting CR's in the EVO head.
I recently got my heads back from some Stage 4 machining with the original request for CR's to be added somewhere around the spark plug. Low and behold, they didn't get machined per the claim that they would have to do a lot of build-up welding under the top fin because there isn't enough meat in the casting.
When I got them back I did some looking into it and yes, the meat is a bit thinner than on a TC head, but I personally see plenty of potential if the machinist is willing to bore a bit deeper into the top fin. Or, be really crafty and put them back where a 2nd spark plug would go in the rocker box opening. Of course, that route would be an automatic CR with wiring, but that's even better.
Does anybody know of a reputable shop that has proven they can install CR's on an EVO head?
I should specify that I have 2 sets of Evo heads and one set has them on the left and the other on the right. Done by different shops. Not sure if either is a better location than the other (no disrespect Kirby) but make sure they are good quality release. The one's on the left would always fill with carbon making them hard to apply... I would have to use penetrating oil every now and then to free then up... Maybe the guy who did them drilled the pilot hole to big? I don't now but it was an issue.... Never had that on the right side... Maybe cause it's closer to the intake Or Maybe it has something to do with burn pattern, who knows... Pilot hole is in the side of the D shelf Front cylinder, intake relief is on the right...
Last edited by 98hotrodfatboy; Feb 25, 2018 at 10:05 AM.
Thanks everybody for reaching out to me. I've decided to purchase my own mini mill and do it myself. I figure for about twice the price of a machine shop custom installing them exactly where I want them I can just buy the mill. Besides, I also have to widen the wrist pin width to fit the H-beam rods. I also bought a set of Evo heads for $50 at a swap meet in Long Beach to practice on before I attempt it on my $1100 heads.
I'll take pics. Long story short I'm putting ACR's in the rocker box opening using some special ACR adapters I got off ebay.
Last edited by Mattbastard; Feb 26, 2018 at 10:08 AM.
Okay I just realized those are the heads that are going on the bike man those are some big *** valves. What's the combustion chamber sizes of those heads?
Yea, I practiced on one head, which went really well so I didn't practice on the other. 91cc I believe. FYI, I put the head build sheet in my other topic in the Evo forum.
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EVO compression releases
