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Aviacs
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PostPosted: Thu Aug 18, 2022 8:29 am    Post subject: Valve guides? Reply with quote

My first ever VW app of any sort.

I'm trying to refresh a set of heads from a Great Plains 2276 Av conversion in a Sonerai 2. (no response from them, 2 weeks)

Max rpm would be 3600 (80HP), typical cruise under 3400 (65 - 70HP).

The exhaust guides are badly belled, stainless ex stems are heavily worn barrel shaped .0025" to .0035" smaller at the ends of travel than in the middle.

40mm intake, 35.5 exhaust

With new 8mm stainless valves, what is a "good" guide material?

Available choices are "silicon bronze" "manganese bronze" & "silicon aluminum bronze" I can also make them out of 90500, Ampco 45, or 64200.

requirement is for durability/reliability. No shortened "racing" guides, e.g.

What plays well in this app?
What should the stem-to-guide clearance be for intake, and for exhaust, in this app?

Thanks!

smt
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RCP Phx
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PostPosted: Thu Aug 18, 2022 9:49 am    Post subject: Re: Valve guides??? Reply with quote

A little off topic but I've wanted a "Monerai" for over 40yrs!!! As far as guides go, they are all good choices with nothing special needed in this application.
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PostPosted: Thu Aug 18, 2022 9:57 am    Post subject: Re: Valve guides??? Reply with quote

witch ever material you choose, be sure to make sure the stems are straight, round and smooth with no nicks or ridges. I usualy go over them with 600 then 800 or 1000. depending on what they are. you can also DFL coat the inside of the guides. be sure the guides are honed straight. and use the good rocker arms with the adjuster on the pushrod end to help make the guides last.
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oprn
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PostPosted: Thu Aug 18, 2022 10:12 am    Post subject: Re: Valve guides??? Reply with quote

I wonder if additional lube on the top end would be helpful. Thinking of the Hoover mods for full time oiling and/or squirters to lube the stems. Just a thought...

I wonder if one head shows more stem wear than the other.
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Aviacs
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PostPosted: Thu Aug 18, 2022 11:12 am    Post subject: Re: Valve guides??? Reply with quote

Thanks so far.....

Per one question, all the exhaust valves & guides are pretty much the same amount of wear.

It looks like an angle plate can be used to work on a head, so that the mill head does not need to be nodded. http://vwparts.aircooled.net/Angle-Plate-for-Machi...x-head.htm

Since they don't sell it anymore,
Whether sine plate, nod, or angle fixture....what is the correct angle?

Thanks!
smt
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PostPosted: Thu Aug 18, 2022 1:20 pm    Post subject: Re: Valve guides??? Reply with quote

9.5 degrees
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PostPosted: Thu Aug 18, 2022 1:39 pm    Post subject: Re: Valve guides??? Reply with quote

Yes, 9.5deg. on the head angle.

There are lots of standard silicon-bronze valve guides available and even oversize stuff. No need to make your own.

If the stems were worn that bad, I would start from scratch on your rocker geometry. I pulled one of those engines apart, and it was terrible. Roller ball valve adjusters, big stack of shims under the rockers and the rocker geometry was WAY off. When guys set them up like that, they end up putting way more load on one side than the other. I prefer to set them up with equal angles at no lift and full lift. Then the wear is even and not focused on one end or the other.

.0025 on the exhaust
.0015 on the intake

Core drill the old guides, and tap them out.

Brian
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Aviacs
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PostPosted: Thu Aug 18, 2022 1:42 pm    Post subject: Re: Valve guides??? Reply with quote

Quote:
9.5 degrees


Great!
Thanks!

should be able to get to it tomorrow. Certainly over the weekend.

smt
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Aviacs
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PostPosted: Thu Aug 18, 2022 1:57 pm    Post subject: Re: Valve guides??? Reply with quote

Quote:
If the stems were worn that bad, I would start from scratch on your rocker geometry. I pulled one of those engines apart, and it was terrible. Roller ball valve adjusters, big stack of shims under the rockers and the rocker geometry was WAY off. When guys set them up like that, they end up putting way more load on one side than the other. I prefer to set them up with equal angles at no lift and full lift. Then the wear is even and not focused on one end or the other.


That makes sense. Now i have to read the books....Smile

Quote:
.0025 on the exhaust
.0015 on the intake


This is about what i imagined. Esp for heat transfer and good start on the geometry. Given the stem diameters on the intakes (.310" Maybe .3102" on one) and the center sizes of almost every guide (.315"-.316") I wonder if they were installed sloppy to begin with? OTOH, one mechanic on an airplane site said "don't make them too tight" if you will have to tank up with 100LL when not at home base" Waiting to hear what "not too tight" means in that case.

Quote:
Core drill the old guides, and tap them out.


I spun a step drill earlier today, but could not find what the ideal major dia is, esp with such sloppy guides? Started with a .405" (13/32" marked) drill. Now i wonder if that is big enough?

Also, notes say drive them in toward the combustion chamber to avoid pushing the crusty end up the bore. I assume that means mill or counterbore the heads off first. But is there a "standard practice"?

Thanks!
smt
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oprn
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PostPosted: Thu Aug 18, 2022 2:29 pm    Post subject: Re: Valve guides??? Reply with quote

It's my personal opinion that there should not be a crusty end. Bead blast the heads first, then do the machine work. Bead blasting them after the machine work risks damaging the new guides and seats. Also what happens when you do all the machine work, clean the heads and find that the head you just invested all that time into is cracked?
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PostPosted: Thu Aug 18, 2022 3:20 pm    Post subject: Re: Valve guides??? Reply with quote

On used heads I always sand blast them good and clean first. Inspect for cracks.

Then I use a countersink tool with a 3/8" pilot to knock the tops off the guides. Then core drill with a CDR-7194G from here. https://goodson.com/collections/core-drills-reamers/products/serdi-core-drills

Drive them out towards the chamber side.

Then I use an 8mm AV&V solid carbide reamer to size them.

Brian
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PostPosted: Thu Aug 18, 2022 3:29 pm    Post subject: Re: Valve guides??? Reply with quote

It may be worth a try to push the guides out the simplest way, but if they don't move easily then best to use use one trick or another. I think we will all agree just pushing harder is not going to work if they are stuck as usual.
But if they were lubed with anti-sieze when installed they may come out easy.
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PostPosted: Thu Aug 18, 2022 6:32 pm    Post subject: Re: Valve guides??? Reply with quote

Pushing them has a tendency to make them swell making them even harder to get out with the danger of marring the hole in the head. I like to tap them and use an all threaded rod to pull them out. Pulling tends to stretch them and make them thinner. Far less chance of wallowing out the hole.

Do whatever you like.
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PostPosted: Thu Aug 18, 2022 8:18 pm    Post subject: Re: Valve guides??? Reply with quote

Or just drill them really quick with a core drill, and you can just about push them out by hand.

Pretty sure I could have both heads drilled and guides out before you get two of them tapped. And WAY less pounding on the head.

Brian
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PostPosted: Thu Aug 18, 2022 8:19 pm    Post subject: Re: Valve guides??? Reply with quote

Aviacs wrote:

Available choices are "silicon bronze" "manganese bronze" & "silicon aluminum bronze" I can also make them out of 90500, Ampco 45, or 64200.

requirement is for durability/reliability. No shortened "racing" guides, e.g.


I personally gravitate towards Manganese Bronze over silicon bronze or aluminum bronze.

I know 90500 is a nice material to work with. I have not used it for valve guides, although I have used a lot of bushings made from it in industrial applications.

Not a huge fan of 64200 aluminum silicon bronze myself, but many fine products are made from it. It seems almost abrasive when cut. Shavings were very gritty and surprisingly hard. They got stuck in my fingers like iron filings. Could just be the way it was cast though. Who knows. On the bright side, it is probably the best of the bunch when it comes to corrosion resistance… good for exhaust valve guides maybe? Don’t know enough about it to make a good call.
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Aviacs
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PostPosted: Thu Aug 18, 2022 8:33 pm    Post subject: Re: Valve guides??? Reply with quote

Quote:

It's my personal opinion that there should not be a crusty end. Bead blast the heads first, then do the machine work. Bead blasting them after the machine work risks damaging the new guides and seats. Also what happens when you do all the machine work, clean the heads and find that the head you just invested all that time into is cracked?


Did that last night. But using melamine T2. These will get dusted flat black again, so no need to go further. Chambers will get minor hand work to clean up.

Quote:
Then I use a countersink tool with a 3/8" pilot to knock the tops off the guides.


My guides take a 5/16" (nominal) pilot, thanks for confirmation on the counterbore

Quote:
Then core drill with a CDR-7194G from here. https://goodson.com/collections/core-drills-reamers/products/serdi-core-drills


OK, looks like they go to .437" So i'll spin a larger one up tomorrow. The one i made is, as mentioned, aprox .405"-.406" It did seem small after i compared to the guide.

Quote:
It may be worth a try to push the guides out the simplest way, but if they don't move easily then best to use use one trick or another. I think we will all agree just pushing harder is not going to work if they are stuck as usual.


Quote:
Pushing them has a tendency to make them swell making them even harder to get out with the danger of marring the hole in the head. I like to tap them and use an all threaded rod to pull them out. Pulling tends to stretch them and make them thinner.


Maybe i misunderstood something.
My notion was to leave a step just past the head boss, inside, so when the on-size pin or drift contacts, it essentially pulls, rather than pushes, the guide out? You think you are pressing, but the guide experiences it as a pull?

But that threaded rod sounds good, too.
Which presumably means a bore (step drill) less than.4375 (7/16" being the nearest common thread size?) Or is there a metric size to use that is bigger than 7/16" but less than .477-ish OD of the guide? The pilot/step drill can be made any size, so maybe 27/64" ( .422") and use the 7/16 20 to pull?


Last edited by Aviacs on Thu Aug 18, 2022 8:58 pm; edited 2 times in total
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Aviacs
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PostPosted: Thu Aug 18, 2022 8:51 pm    Post subject: Re: Valve guides??? Reply with quote

Also, I made a steel reaction plate* last week, and took the hole positions from comparison between both heads and some fudging. EMPI heads, the holes actually vary a bit in size, and in position.

Averaging them, i went with 7.600" centers, outermost studs.

cross ways was difficult: 3.10" centers at one end, and 2.995" at the other of both heads. I took it to be 3"

Distance back from center of end studs to inner studs varied from 3.200" to 3.180". I went with 3.190"

Oddly, distance between innermost studs was close between them, 1.220" vs 1.225"

The reaction plate has clearance holes and the studs from the block are somewhat flexible, so my dimensions worked fine for that.

However...

Is there a print that shows the intended dimensions, so when making the angle plate i can put some dowels and threaded holes in the right places? Smile

Thanks for all the in-depth info.
This forum is like a breath of fresh air.

smt

* reaction plate: local input considered that since the jugs are glued in (PO appears to have owned stock in a high temp RTV company), "they might not come out without distortion or breaking" So i made an expansion puller. The plate was for a place to react the puller stud. I have not used it.
The plate serves other duties, such as a platform for stops or indicator to establish TDC, etc.
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PostPosted: Fri Aug 19, 2022 12:11 am    Post subject: Re: Valve guides??? Reply with quote

Coring the guides to .437 is a good idea, I think you understand the process, stop short and drive out with a rod, (a few thou clearance on the rod)

Threading the guide is also a viable way to do it with no special tools, I used 3/8 I think. Not saying that's the best way but if you just going to do one set in your whole life it might be the way to go.

Pulling a rope VS pushing a rope, same principle.

I have not ever tried both coring and threading, just one or the other.

If you have a VGS machine then coring them out should seem simple.
Depends what tools you have to work with. if you have a nice press then maybe you would use that, but if you don't then that's fine, I hope you have good aim with a hammer, and if not then maybe make a tool for an air-hammer.

One guy I saw would thread the spring side and then pull them using a hollow center hydraulic cylinder port-a-power thing....pushing against the spring boss, and that was kinda neat but I'd never buy one just for the purpose. That made sense since it's the same setup used to pull rocker studs out of chevy heads.
I like to collect tricks. Craziest one I heard lately is heat the head up to 350F, then drive the guide out with driver that was gun drilled and fed cold water to instantly shrink the guide.

I don't know what material PEP makes a valve guide out of, don't need to know, they figure it out.
Sometimes I "make" valve guides but I'm not "making" a valve guide I'm just modifying the size of a valve guide. I doubt you could save a single dollar making your own guides from raw material but come WW3 might be good to have the practice.
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PostPosted: Fri Aug 19, 2022 5:33 am    Post subject: Re: Valve guides??? Reply with quote

Tap the chamber side to 3/8 -16 then core drill guide all most all the way leave about 1/2" thread a 3/8 bolt in and drive out with punch driving on bolt end,
this stretches the guide reducing its dia. slightly.
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PostPosted: Fri Aug 19, 2022 6:19 am    Post subject: Re: Valve guides??? Reply with quote

Brian_e, you are correct that you are faster than me but not correct in that I have never beat them out. I use a piece of heavy wall pipe in place of the valve spring, some heavy washers and a nut and wrench. They break loose with a pop and then just slide out as I turn the nut. I have never cracked a head or galled a guide hole doing it this way.

Modoc hit the nail on the head, you use the tools you have on hand. I am not set up to do hundreds of heads, just my own from time to time.
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