Valve Seal to Keeper Clearance

dps650rider

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Have my top end apart to replace a broken valve spring and valve seals and see that I don't have enough clearance between the keeper and the seal when the valves are fully open. Measured this by assembling the seal, valve and keeper assembly with no springs and used a caliper between them and compared to the lift spec on the cam (0.415 intake and 0.400 exhaust). Even with the low profile seals I have there is almost no clearance on the intakes. I have another set of low profile seals coming from Hoos Racing but think it still may not be enough.

Any ideas? It looks like the keepers could be ground down 0.010 or so, anyone ever done that?
 
I cut about 0.030" from my guides, to get 0.010" clearance.
Lucked out, the guide seal grooves were wide enuff to let the seals set lower.

Other tricks to consider,
Pocket the valves,
Shave a bit off the valves' collet groove, making it appear longer...
 
I think I have 0.010 now. I didn't directly measure this, the cam lift at the intake is supposed to be 0.415. Assuming this is specified at zero lash, if I add the specified lash I now have a lift of 0.405. With a seal and keeper in place with no spring I measure about 0.415 between the keeper and the seal. I talked to Gary Hoos last night for a while and we compared measurements on various things including some seals. The seal I tested was a shorty I believe from Mikes. He had a set of seals that measured somewhat shorter and is sending them so I can try them. Really don't know exactly how they will sit on the guides but maybe I will gain a bit more.

BTW, last night I took a stock spring out of a spare head and the uninstalled length was the same as the "performance" springs I had in the engine. I don't have the specs but I know they used to be quite a bit longer than they are now. So here is a theory, the springs lost their tension and now have lost their ability to control the valves at high RPM causing seals to be damaged. I got some new KBW springs from Gary that are supposed to be good quality, maybe installing them will fix this once and for all.

Still, more clearance would be a good thing, that's what I am looking at. \
 
Ended up taking about 0.020" off the keepers since that much of them on my valves didn't make contact with the valve stems or the tops. Still going to try the seals from Gary Hoos to see if I can get some more...
 

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Well that is certainly as far as I will go with the keepers, as I mentioned the material removed had no impact on the contact area but if I went further it would. At this point I think I have enough clearance but if the seals from Hoos give a little more it wouldn't be bad.

I also have another motive on the seals. The ones that were in the engine have been there since 2014 and the rubber was shot. Pretty sure they were Mikes and I'm also pretty sure the ones I used to make the measurements were too. Gary thought the ones he has were not Mikes and maybe they are better quality. As of late I have not been impressed with some of the stuff I got from Mikes, the valve springs were and they were all sacked and one broke.
 
Hey Griz, one more question. Both you and Gary Hoos have said that a stock head gasket is OK on a 700 overbore. I got one from Gary and it measures about 77.7 mm and the bore is nominally 77.5. I set the gasket on the cylinders and the locator dowels don't hold it tight enough to prevent it from intruding on the bore a bit but if it is carefully centered it is OK. The last time I assembled it I used a 750 gasket. You still think it's OK to use a standard gasket?
 
Good question. Short answer: Yep, I do. I've used stock bore Vesrah head gaskets on several 700 cc. assemblies with success. The 750 gasket will cause a slight loss of compression, and I'd be concerned about leaving that big a gap below the squish band. It's probably a bit AR, but I currently use a custom made copper head gasket, .040" thick with a 78 mm. bore, with JE 77.5 mm. pistons. If you want to join in the craziness, Cometic or Lonnie Visconti at Copper Gaskets Unlimited can make whatever you want. The nice thing about a copper gasket is that if it overlaps the bore, you can trim it easily.
 
It's been awhile since purchase, so I don't recall the price more accurately than that it wasn't as high as I expected--a little south of $40 IIRC. The copper head gasket is in its 5th season with no trace of leaks or seeps. The key is careful prep. Copper doesn't behave like steel, quenching after heating softens it, so even a new head gasket stands a better chance of sealing well if you give it some TLC. I hang the gasket on a wire with a bucket of water close by. Using two propane bottle torches with flame spreaders, one in each hand, I heat the gasket cherry red and dunk it. Then it gets a couple or three coats of Permatex Copper Spray-a-Gasket.
 
All back together and it runs great. I ended up using the titanium retainers Gary Hoos sent and shaving 0.010 off the bottom of the ones on the intakes to get a bit more clearance. Once I checked these out there was no way the OEM ones were going back in. I liked the way they kept the springs centered, the installed height was just about perfect and they are light!

One more good thing about this, removing the carbon seems to have cured my detonation problems. No doubt the carbon was caused by the valve seals which were all shot. I ended up using seals I got from Gary, there were a bit lower profile and seemed to be better quality.

Thanks to Griz, Gary Hoos and TwoMany for the advise on this.
 
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