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I need to re-do the head on my 350. I understand the generic formula of cleaning and lapping but as I recall the stellite coating on honda's valves makes anything other than minor lapping a bad idea? So I have been looking into better DIY options for cutting seats/ valves and reaming valve guides. Will have to recycle valves as it seems the stock 350 valves are unobtainium. Not to worry I have enough heads and can choose the best of what is there. So, who has some input that will help me out?
 

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best valves

Fearra Top Fuel for Blown Applications

they will make any size you want

I have some one off tulips in my flatty and they were very affordable

best guides

Ampco Rowe 45 or NASCAR silicon bronze
 

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Is this for a racebike or a streetbike?

You can get stainless valves no problem - Kibblewhite valves are about 58 bucks each retail, guides are about 15 bucks each retail in ampco-45 according to my dealer price sheet. They've also got a 5mm stem diameter conversion. Valves the same price - guides about 23 bucks each. Both use modern valve guide seals, about 6 bucks each.

There's kind of not a lot between doing it as cheap as possible and doing it right -

If you've got a head with good seats and guides, and a set of stock valves that are in good shape you can probably clean everything very well, lap the valves with fine grinding compound (order from www.goodson.com) and be okay. But the seats are guaranteed to be too wide for best performance.

Once you're going for best performance you might as well do it right and replace the guides with ampco-45 guides, stainless valves like Kibblewhite or Ferea, springs, Ti caps, etc. Have the guides reamed and a good 3 angle valve job done, etc.

But that's pretty spendy.

Michael
 

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dont learn something new youll use once. send it to stanley. i can promise you wont be disappointed.

jc
 

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Rosko,
Changing valves and guides is an easy process. Heat up the cylinder head and knock out the old valves. A valve guide driver is a useful tool here because it is centered and doesn't peen over the end of the guide. Next take the new guide and drive it into the head. You may need to reheat the head and chill the guide. I usually do. Then you should run the proper sized reamer through the new valve guide to make sure that there is correct clearance for the stem. Valve guide drivers and reamers are available from Honda. They are not that expensive although the driver would be very easy to make on a lathe as it is just a driver with about a 2 inch long center post that matches the inside bore of the guide. The reamer may be an item that could be bought at McMaster Carr, too. I haven't checked there.
Honda valves are Stellite coated and can't be cut. They do need to be lapped. The seats will need to be cut. I have used the Neway cutters but they are expensive and I don't have good access now. I keep looking on e-bay but haven't scred yet. You may need to go to a good dealer for cutting the seats except most of them don't do a very good precision job of locating the seat and making it the right width. Good luck with that part.

Ken
 

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Neway cutters and valve guide reamers are available from www.goodson.com.

Most honda valves are stellite coated and won't stand up to much if any grinding. Especially once worn to the point where they need grinding...

Do you have to use OEM valve material too or just stock size valves in FCB? We're at the point in the 160/175s where stock valves when you can find them are about the same price as the good Kibblewhite valves.

If you have to replace the guides I'd use ampco-45 instead of cast iron if I could. Also - generally you can't get oversize guides from Honda and often the heads need them to be oversize. When you replace guides it's certain that the valve seat will no longer be centered over the guide bore center. Sometimes it's close, sometimes it's quite a ways off. Do your best when driving in new guides to get them in as straight as possible. I hand make tools to help with that.

For that matter they're almost never centered over the guide bore stock either, just closer than after the guides are replaced. Even in modern bikes I find the seats are generally not quite centered correctly over the guide bore.

Cutting new seats is fairly easy to do from a basic standpoint, but hard to master. It takes a fine touch to actually center the seat over the guide bore as the cutters are tapered and want to self-center in the existing seat. Juggling that with the various angles and widths takes a little while to figure out. With a little practice and care you can do a decent job (as nice or better than you'll get anywhere outside someone who really specializes in good work) yourself. You'll put 3-500 bucks into tooling to do it though. Use the best hardened carbide tapered pilots you can get.

For most racing valve jobs you'll want around a 1mm intake seat width and a 1.5mm exhaust seat width. There's a lot of debate among professionals about where on the valve face you should locate the seat. You don't want to be all the way out at the edge of the valve, though you can be a bit closer on the exhaust as it'll grow more with heat than the intake will.

You can use a black magic marker in place of machinist blue to show yourself where things are and make it a lot easier to see and measure.

You will want to keep the seat depths as even as possible between cylinders - if you have time cc both chambers to make sure you don't have one a whole lot larger than the other due to sinking valves deeper in one than the other.

It's a lot of work to do a high quality valve job, but well worth it.

Michael
 

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Michael is right. For a racing valve job you need to be extra careful about seat width and location on the valve. Stock specs usually call for a width of 2 - 2.5mm, centered on the seat and face. I like 1 - 1.25mm toward the outer edge, but about 1mm from the edge. You may need to redo the seats more often but on a race engine it is worth it. I miss not having ready access to valve tools. After you have done a bunch of 4 valve 4 cyl 600s, you can develop a pretty good touch. I did all of our CBR600 endurance heads and the 600 Katana heads for another team rcing ou of our shop. That is lots o little valves, in addition to my own FT500 and CB 350 heads.

Ken
 

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Nice stuff JB although I like shinier better

I stopped, a while back, hammering the guides in place and the wonderful results are guides that do not have to be reamed as long as they are properly clearance'd upon installation

another caveat seldom discussed is..........

guides do indeed have a very specific interference fit in their bores

if you want the cold hard truth....... you need a set of precision bar guages to actually determine the guide bore's actual size

I don't know many that can do it otherwise with conventional measuring tools...... even snap bore gauges are "iffy"

if your guides show evidence of aluminum galling once they poke into the port........

I am of the opinion the head has been hamred and unless it's rare and valuable enough to justify the extremely tedious and ultra precision work of boring new guide bores which must be closely indexed off the existing seats

and then you have to find an oversize or make a one off custom guide

IF, you remove your guides and find galling in the bores which will catch your fingernail

the bores are crap and can be with even shallower galling if it runs the entire length of the bores

you won't make it any better by stuffing in new guides

and if it's on the intake side...... it will always smoke and make you wonder why

on the exhaust...... well it will pressurize the crankcase more than it would if the guides truly sealed in their bores

oh what a ray of sunshine I am
 

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Hack,
So far the guides I've done in 175 heads have gone pretty smoothly. I heat the head to probably 250 degress and they TAP out pretty nice, hammer would be the wrong word in my case. Bores typically have a smooth, burnished finish on them. Going in is a bit iffier and I'm sure it takes some aluminum off the top 10% of the hole. I can usually tell by the "feel" if the fit is ok and the hole is staying clean. I'd have to check my notes but I think I was using .002" fit.

The stem bores seem to stay pretty round, I ream them to loosen them up a hair. I like the valve to drop down under it's own weight when held vertical, but not "flop" down...just kinda glide down. Hole and valve have to be ultra clean though.
I don't know if it's a good idea...but I'll scotch-brite the valve stem lightly to adjust for this gliding fit.
I don't have any experience with other engines, but the 175 is more likely to have problems with valves too tight than too loose. Long as they don't seize in the first race they tend to find their own happy spot pretty quick. (except when using iron guides...they'll seize over and over again).

I used a real nice outside mic for the guides....and yeah, a snap bore gauge...but I check the bore probably a dozen times, in different places and used an average of the readings to come up with the OD for the guides.

So far the process has gone well for me the several times I've done it...but it probably takes me three times longer than someone with some experience because I'm so careful of everything. I've only worked with alloy heads and Ampco guides so far.
JohnnyB
 

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JB........ what was the valve seat width the valve seated into?

an exhaust I presume?

I have one flathead, cast iron seats and decent grade ferrous metal valves

and they have been running literally WOT for over 8 years now

a local guy has it, I put a 30mm amal on it

geared it tall

and he has run it flat out at 65+ for all this time

I know he's blown it up a few times and I just always assumed he had to tend to the seats a time or two

he told me a few weeks ago he hasn't had to touch the 5 angle valve seats or valves since they were cut

and I have nimonic 80A in my flatty and it's had the crap beat out of it

they still look good

no they don't cycle as fast as those little ones but they are heavy and seat 65 thou on the intake sides and 85 thou on the exhausts


those of yours look like they must have seated on very narrow seats and ran very high rpm
 

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Hack,
Right on both counts. The seats were worn, rounded, crappy, seats that I ASSUMED had been cut when the new valves were installed but they had not been. The new SS valves basically conformed to the rounded cross-section of the old seats. Spring pressures are very high, and rpm runs up to 13,000. Yes, exhaust valves.

The guy that did the head...and did a great job on the other stuff...either neglected to do the seats, or thought that I was going to do them myself prior to racing (long list of other mods he was working on). I found the pictured condition after a season of racing and immediately knew the cause when I saw the seats with no decernable "flat" for the valve to seal against.

I recut the seats, installed new valves and it's been fine ever since. Subsequent inspections haven't shown the condition to be repeating...I left a decent size width which might have helped. I also wanted something wider to dump more heat out of the valve.

Tuned 175s are notoriously hard on exhaust valves and seats. Some design issues I think, once compression and displacement starts going up, heat in the exhaust valve area gets very high, very fast.

I don't know as much about valve seats/ valves as I should. I usually just cut the seats, check with blue, check for leaks, put it back together. Usually shoot for a seat width about .060-.070 centered on the valve...mostly cause I don't know any better :)
JohnnyB
 
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