Valve guide repair

[MadMax]

Hello,
I'm trying to restore my valve guides. I need iron ones, as I will be running on butane, which burns much hotter than normal fuel. I heard you can ream the old guides to size and then install valves with oversized stems. But I couldn't find any
Or is it a better idea to ream the guide out further and press in a new std size guide? What diameter would the hole for the guide need to be? Are there tool kits for this operation? I have a couple of heads of buddies to do, so I would like to own the tool. It costs about $ 300 just to have the 16 guides replaced here in Germany
THX,
Max

[pat mccarthy]

look at www.goodson .com you would core drill the old ones out the ream to 500 and then drive the guild in you can get them in iron or manganese bronze the tool needed to do this is a seat and guild machine or ship them to me i will do them

[firebird77clone]

an age old solution to sloppy valve guides is to knurl them, then ream them.

* oh, that is what Danny's link shows..*

[MadMax]

Thanks Denny, but knurling is actually not an option, I've heard numerous times it's only a short lived remedy. I will be using roller rockers, so the wear on the valve guide won't be all that strong, though, but it should turn out a high mileage motor, as this engine is going into a 1970s Impala, which is just undergoing a full "like new" restoration (the other engines I'm just doing are for every day use)...
What do the others think of knurling? I'll have to measure the worn guides to see if knurling is an option anyway, ALL of the valve guides were passing oil (had no positive valve stem seals).
At goodson I found a reamer that will drill out from .343 (that's 11/32") to .500 in one go. Piloted of course. It costs $ 130. Is that a good price? I think that's the way I will be going. But I someone says this tool is available from somewhere else for half the price I would be glad to look into that
THX so far,
Max

[pat mccarthy]

you need to guild the core drill when drilling when you go from 11/32 to 500 or you will have much seat run off so like i said you need a seat and guide machine or a upt that holds each guide to the seat square. then you run the core drill thru the fixture .any machine tools are very pricey you will have more in to this then you think. you need reams 342.343. small brm hone guide cutter . guide driver and you need a gear box that slows the reams it a slower speed and more tq you could try to do this on a mill like a bridgeport but you need away to hold the head to the mill table and guide needs to be dead on or you will have to much seat to guide runout .i do not knurl i run a soild guides i use mang bronze guides . and when your done you need to do a valve job to true up the seats so there is no run out . i buy from goodson all the time if you find any reams or tools that are made for auto machining for 1/2 price of goodson new let me know

[jerry clayton]

U can get valves with stems .003 and .015 oversize and reamers/hones in those sizes--what application exactly is it for--your thingy says you have a 5.7 what year??? I will find the part numbers for you---another way is to ream/hone to 3/8 and use some other valves

[pat mccarthy]

PEP sells the over size valves if he wants to go that way.it has alot to do with how bad the guides are .but if you have one past clean up then it another ream and bigger stem or a new guide. not a big fan of over size stems. but there is allways more then one way to do some thing .i do not like them at all. if you know all the heads you have can go over size then you may want to do this but if not then you have reams just for one job good reams are about 50.00 each and you still need a hand held gear box to drive the reamers yes he could go to 3/8 on the ex side if there not there now

[pat mccarthy]

some of the iron guides you can buy have the spiral cut in to the guides for added oil if you go this way. i would have to think about it if i had not one tool and was not around any shops then the way dennys said is the way i would go if guides are not to beat out .this would be the cheaper way to go with out so many tools .when i do guides most all the time i go to mang bronze i feel this is better then iron so i go this way .but i do have knurling tools i just try not to sell a job with a knurl job if every thing is new .but i would on a re ring job

[nitrowarrior]

Everybody has given great solutions as far as this question goes. I noticed in the initial post, the concern seemed to be more of a BTU question. Butane, Propane, Natural gas, etc are a concern of vaporization on entering the cylinder. It's a dry fuel therefore the worry would more in the line of guide lubrication. As far heat goes, I like to think about my seats for duration of the cycles this thing goes through. It's a bummer that guide replacement is a tad high in Germany. Better safe than sorry I suppose should be the response to that.

[MadMax]

Sure better safe than sorry
The heads are GM 492 casts (thick castings). Valves are 1.94 and 1.50, 3 of the valves of this set of heads have oversized stems already, and they aren't worn yet. The others are (it wasn't me ). This won't be a racer, just around 300hp. It is only going to be a rebuild, just bored to a 355 with flat tops and a street cam, engine is going in a 1970s Impala.
The reason I don't want to knurl is exactly the hourglass shape of the guides. I will have to measure them exactly (haven't done so yet, but some seem to be past knurling, especially as the top of the guides are pretty worn.)
I have two problems:
1: I live in Germany, where special parts are difficult to get (oversized valves etc.)
2: I don't build many engines, maybe one a year, at the moment I'm doing two, but that isn't very often.
Especially reason two means I want to buy as little tools as possible for one specific job. If I buy a knurling set now for 50 bucks because the heads will be OK knurled, and in a year I get some heads where knurling won't do anymore, I'll have to get the drill-pressfit solution anyway. So I'd rather go there now. Or the oversized valve-solution, I don't know what could be a problem there? The valves are certainly a bit heavier, but if I use oversized valves with undercut stems surely the weight difference will be minimal
That seems to be by far the easiest and cheapest solution to me...

PS: The way I usually go is only to buy heads which I know are OK. This time I bought a whole engine (for really small money) and found out it had good heads (except for the guides), a new block, forged pistons and an Edelbrock cam set in it (I had actually only bought it for the connecting rods, the price for them would have been OK even if the rest was junk ). Lucky on that one, but now of course I want to make the best of that bargain

I'll have a look at PEP's big stem valves in a minute...

[MadMax]

OK, then I'll check the guides exactly at the weekend and come back here again later. The engine ran OK, I didn't check the rocker geometry before tearing it apart, I never used this engine. I only know that it ran OK, just used some oil. But as it didn't have positive valve stem seals that would be sure to be the case.
You'll hear from me soon,
Max

[jerry clayton]

Most times that I have seen a really really bad guide, the seat and valve were pounded worn really wide---If they aren't worn out like that, try putting some positive seals on the stems to cut down on the oil consumption

[shawnlee28]

The reason most shy away from the oversized valve stems ,is because most of the time this work is being done to enhance performance ,filling the intake and exaust ports with huge valve stems cuts down on flow and performance.
In a mild street build ,oversize stems would not hurt that much in the performance department.

[shop tom]

Knurling, whether finished by reaming or swedging, involves displacing the parent guide material to reduce clearance. It is a short-lived repair.

tom

[shop tom]

There are 3 types of guide knurling methods:

The K-Line type, where the knurling tool is like a spiral tap which cut grooves into to guide, pushing metal out of the grooves to shrink the guide ID. The ID is then reamed to size.

The Lisle method, which uses a cutting-swedging tool to groove and displace the guide metal, which is then swedged to the desired size.

The UTP method. Similar to the K-Line method, a small roller is used on a tool that spirals it through the guide, again displacing the guide material by grooving and pushing the metal aside. This method can tighten guides that are worn up to .020"

There are other methods and tools, but they are all variations on the above.

These methods all involve displacing the guide material. This is the weak point of knurling. Regardless of and additional oil supplied by the groove, the displaced metal wears more rapidly than the original guide material. The same thing applies to piston knurling, which is rarely done by competent machinist except in cases where pistons can't be replaced.

Guide knurling lasts about a year in normal driving with a stock cam and valve train components. Performance cams will tear up knurled guides in no time.

Knurling should not be confused with spiralling, which is simply grooving a guide for oil retention. This is not done to decrease clearance.

tom