|02-02-2013 04:58 AM|
|amc49||I used same stunt on DOHC Honda bikes and worked fine, you just gotta watch the valvetip to retainer flat clearance. Thinking the tips there were nitrided too, but they sank so fast into seats that the extra wear from soft tip once nitride removed seemed to offset each other.|
|02-01-2013 11:21 PM|
|200two-zx3||so I measured my valves after reassembling the head and only a few were a issue so I took a little bit off the valve not much and im all set!|
|01-19-2013 09:46 PM|
|200two-zx3||Wow that sucks, and yeah I can't beleave how much valves cost its stupid!|
|01-19-2013 08:43 AM|
|joynanbaby||he thought it was missing, started it up for me and I could tell one cylinder was not working, why he never yanked plugs|
|01-19-2013 02:40 AM|
Hey, grind a point on it and use it as a marking centerline punch for piston/valve cutout locations LOL.
Used to have same trouble with a friends' '70 Boss 302 (true boss) that ran in the tens 1/4 mi. The sodium filled valves had a tendency to snap in two. One came loose and piston struck it to sever rod, piston stuck high and the rod bent sideways to lock into its' paired mate turning a V-8 into a V-7..........the damn thing still ran 10.90s like that. The friend came back after two weeks saying he thought it was missing, started it up for me and I could tell one cylinder was not working, why he never yanked plugs I could not say..........needless to say he felt pretty stupid when motor was disassembled.
|01-19-2013 12:44 AM|
Here is why you don't want to use cheap valves.
The 2.19" head went through four cylinder walls and chambers on both cast iron heads. The poor 396 in my Chevelle died idling in the garage, after 15 years of service and several rebuilds. I had the heads done when I was a teenager and not much cash, they lasted quite a few miles and a couple sets of valve springs.
|01-19-2013 12:20 AM|
Yep three angles fine, just a stocker. By cheap valves I meant Honda, you often couldn't reuse them, and the prices for exhausts were astronomical.
I actually didn't lap tips, they had to be ground in varying amounts up to .005"-.006"+. You won't be able to lap that much off tip. I fitted a plate to side of 6 inch bench grinder, it was drilled with varying threads to mount various press-in valve guides outside threaded to fit in the plate. Plate made adjustable to be able to put guide in parallel and square and I used a fine grinding wheel shimmed to be dead straight when spinning. In short, I cut my tips on a bench grinder by inserting valve in guide and lightly spinning it against the turning wheel. Worked like a top, that was 70K ago and motor still runs primo.
Whatever, you should hold toward the LOOSE side of exhaust clearance spec, the gradual recession of valve into seat will close up the clearance instead of it getting looser. The added looseness of the cam caps muddies up just how much clearance you have in there because the cams kinda wobble around in the cam caps.
|01-18-2013 08:06 AM|
Hadn't run into the "cheap crap" myself, official Honda parts worked quite well at the time...
Did have a valve grinder in the shop, but it wasn't used much anymore - original Triumphs & older BMW's were the ones that called for it's use.
Boring & honing cylinders was the majority of machine work and even in the 80's some were amazed that was actually done in the shop since automotive work was always "sent out" even then.
The mention of grinding valve tips really "rang a bell", since that was the ONLY way to adjust clearance on small flathead power equipment engines...
"high tech" for valve adjustment was shim under bucket, since those tiny shims & their buckets were a LOT lighter than the large shims on top that could be changed without removing the cams... Buckets without shims have to be even lighter, so with better materials & tighter tolerances making valve adjustment less of a regular maintenance issue I can see why they are used. (bet they are a lot cheaper for the factory as well!)
To get back to the O.P. - once the seats are cut & the valves ground or replaced (as needed) & lapped in, you can assemble the head & do your measuring of actual clearances. Then you take the cams & buckets off again, see which can be swapped to get proper clearance - and order what you need or try some additional machine work like amc's suggestion of lapping tips to gain clearance where needed.
P.S. - forgot to mention, "three angle" cut on the seats should be more than adequate, I've seen some 5 angle cuts advertised but IMHO it's more a sales pitch for a particular tool than a real performance advantage.... That could be a long discussion in itself!
|01-18-2013 01:04 AM|
Oh, brother, don't get me started on cheap crap thin stellite coated valves.........
Beginning to have a true problem with available shops around here too to do any kind of quality work. Already running into people who talk the talk----then give you junk back after machine work. I may have to start sending my stuff to China to get it done correctly. With rebuilt stuff centralizing more and more to fewer and fewer places, I gotta wonder where they get people trained well enough to do it right. Then I think of my prison sentence at the auto store and how even simple starters and alternators could get so screwed up and it becomes clear. We're in a world of hurt here.....
|01-17-2013 12:47 PM|
With "rebuilt" parts being the more typical repair work done these days, few get into the machine work themselves any more.
My experience with major engine work comes from motorcycles, where repair was always done since "rebuilt" parts (like heads) didn't exist.
On those, we only cut seats & lapped valves in B4 final assembly - any bad valves had to be replaced not reground since they originally were hard faced (stellite) from the factory, and re-ground valves would have a softer face & wear quickly.
Amazing how valve adjustment intervals have gone from regular to never isn't it? Even without automatic adjusters it's gotten to the point they seem to figure the engine will wear out B4 it's needed....
If regrinding is appropriate for the Focus valves, amc's suggestions on tip grinding if needed, combined with swapping buckets may be enough to do the job without buying a bunch of new buckets. More labor, less parts $. Depends who's doing all the labor as to what's the cheapest route!
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