valve guides

[azazzera]

I have a question if my exhaust valve guides need replacing. ill try and post a picture but I'm not so good with doing that so i will try and describe. when looking from the top of the block with the the valves removed the intake valve guides all have a raised piece to them that extends up past the block. None of my exhaust guides are like that. they all lay flush with the block, the orifice that they pass through. Thank you

[hanleyclifford]

Valve Guide Setting

Very interesting question which I have often considered. The key criterion for guide positioning of course has to be how it best carries the valve stem without binding at either end. In the case of the Atomic 4 there is plenty of leeway due to our relatively short valve "stroke", if you will. Maybe some machinists set the exhaust guides flush out of concern for build up of carbon, whereas the intake may be set closer to the valve head out of concern for carrying the greater weight. Just speculation, of course. I bet Dave has some thoughts on this.

[Dave Neptune]

I make valve guide tooling for 4 different companies as OEM work. The inserts or guides are manufactured for many applications. Probably these were to fit many different engines with this size valve stem. The two different inserts are probably the manufactures way of identifying the intake guides with a tighter fit and the exhaust guides which would be a bit looser. No worries.

The only one who really knows is the installer. These look like good iron or possibly even powdered metal which are really good. Most of the inserts used are sil-bronze in std engines. These guides are pressed in and then resized due to the sleve compressing in the hole. I also make the finishing reamers for sizing.

Take a good look at the guides as they are probably still in excellent shape once cleaned up. In these flatheads a bit of looseness in the guides is not really a big deal as oil encroachment into the combustion chamber is countered by gravity whereas in an overhead engine the gravity makes it worse when worn, the reason for the seals that are absent on flatheads. This leads to that puff of blue smoke when starting your overhead car or boat engine when cold or having set for a while, hours not days!

Dave Neptune

[hanleyclifford]

So my question to Dave is: when setting guides on the Atomic 4 would you personally set exhaust flush and intake a little proud?

[Dave Neptune]

Hanley. it doesn't really matter as long as the guide is working on a ground portion of the stem. A bit of extra length on the guide does give a bit more support but additional support on an engine such as the A-4 just is not needed at all.

Personally if I were doing the "guides" I would not mess with inserts. I would go to another method of rework. That method is for oversize valve-stems. These are getting more common in non hi-po engines. The stems are at +.015" so the existing guide is opened up to the new valves specs. Cheaper and faster once you have the tools or found a shop that does this. I supply Ford, Toyota, GM and many others with this type of tooling via an OEM account.

Dave Neptune

[azazzera]

Thanks so much for the reply and the information. I unfortunately did not think about the need to replace any of my guides befor I had the seats cut. The exaust guides/valves/seats are beat up more than the intake side. I'm assuming that that that's generally the rule. If I need new guides are the mmi ones all the same size. What are they made out of. How would they be removed and how would the new ones be put back in. I've seen on "the you tube". That an air hammer is common to install. With patients and the correct tools can it be a dyi job. I know it's a silly question because with enough patience and the right tools I could be a brain surgeon. Now for the next sill question based on what is seen from the pictures can a determination be made on if any of my guides need replacing.
Thanks again. Adam.

[lat 64]

I spent a few thousand hours using the very tooling that companies like Dave's made back in the eighties. I don't do it anymore except for hobby stuff like old sail boats, but I always like to read his advice.

If the seats were ground or cut properly, then the guides were most likely ok. They have to be in fairly good condition to hold the pilot for the tooling; so if they were bad, your machinist should have stopped the job until you authorized new guides.
The focal length in your photo is short and I can't quite make out the seats. But, from what I can make out, it looks like they only cut just enough material to get a proper seat. That's a good thing.This is another clue for me to think the guides are fairly good. The pilot did not wobble or flop around in the hole during the seat grinding. Call the machinist that did the work and ask. Costs nothing.
I don't recommend doing the guides yourself because they get so distorted when pressed in. Then it's easy to over ream them too and they are just as loose as the old ones. Seek professional help here. it's much cheaper.

Re: exhaust guide depth, Heat is probably the biggest factor in setting the guide low or near flush to the surface of the port runner. Like spark plugs, If it is long, it will get hotter. Just keep it the same length as the original and go dog go.

Russ

[thatch]

Bronze Guides

Since we're on the subject of valves and guides, I will add the question of why we are using steel rather than bronze for replacement guides. As we know, sticking valves is a common problem with A4's so, during the rebuild of a spare A4 I elected to use bronze instead of the factory style steel guides.
I realize that I am heading into uncharted waters here but bronze is a very normal choice when doing a head rebuild in the automotive world. I must admit that this (3rd) engine is a stanby that has not been run yet so I have no real world info about the alternate guide performance.
Tom

[hanleyclifford]

Since we're on the subject of valves and guides, I will add the question of why we are using steel rather than bronze for replacement guides. As we know, sticking valves is a common problem with A4's so, during the rebuild of a spare A4 I elected to use bronze instead of the factory style steel guides.
I realize that I am heading into uncharted waters here but bronze is a very normal choice when doing a head rebuild in the automotive world. I must admit that this (3rd) engine is a stanby that has not been run yet so I have no real world info about the alternate guide performance.
Tom

My guess is that the bronze guides will require more clearance than their steel counterparts since they will expand more. But they will probably take the wear and save the valves better. BTW, I drive my own valve guides using a Goodson tool suggested by Don. I also have reamers from Goodson which give me the fit I like.

[Dave Neptune]

Hanley, I make the reamers you are using, if they are the carbide ones.

Steel guides are OK but not nearly as good as cast iron or powdered metal. These materials are porous and do an excellent job of oiling the stem In a steel guide the oil is just in there for lubrication and not "absorbed" at all. Some of the bronze guides are also porous and hold oil like the CI & PM guides. The bronze requires a bit more work to install as they must be sized after installation and there are more than a few choices for the sizing process. There are 3 basic types of bronze guides until you get into the hi-end turbo screamers and their heat issues in the valvetrain.

For slow turning non hi-performance engines I still prefer the "over-size" valve. With these the existing cast iron bore is re-reamed to size in just one step, quick and easy. Enginetech has a good line of these too. The added weight is of no concern on these engines.

Dave Neptune

[hanleyclifford]

Hanley, I make the reamers you are using, if they are the carbide ones.

Steel guides are OK but not nearly as good as cast iron or powdered metal. These materials are porous and do an excellent job of oiling the stem In a steel guide the oil is just in there for lubrication and not "absorbed" at all. Some of the bronze guides are also porous and hold oil like the CI & PM guides. The bronze requires a bit more work to install as they must be sized after installation and there are more than a few choices for the sizing process. There are 3 basic types of bronze guides until you get into the hi-end turbo screamers and their heat issues in the valvetrain.

For slow turning non hi-performance engines I still prefer the "over-size" valve. With these the existing cast iron bore is re-reamed to size in just one step, quick and easy. Enginetech has a good line of these too. The added weight is of no concern on these engines.

Dave Neptune

Yeah, the oversize valve is a great idea - instead of replacing valve and guide just ream the guides right in the block for the oversize valves. Too bad Moyer Marine doesn't sell the oversize valves and a selection of reamers - could save our members some bucks on machine shop work. BTW, I always ream guides after installation; some distortion is bound to occur even if the guides are pressed rather than driven.

[lat 64]

Can they even be had?

@ Dave,
Are there oversized valves(stems) available for the A-4? If so, I'd agree. But if not, why consider them? Are they just a pipe dream?

Back in the day, I ran into lots of those oversized valve stems in heads previously remanned by large production rebuilders. Sometimes two or three different stem sizes in the same ol' chevy head. We only had OE-sized tooling so we couldn't use the oversized valves again,. We just drilled and pressed in standard sizes. New valves for many common engines were not costly so it was a better choice for us then.

One time I ran into undersized valve stems! I thought they were worn that way, but my boss said that way back in the dinosaur age, they had shops that would grind the stem smaller and use a thin bronze liner like the K-line style. Seems to me like a lot of trouble to avoid drilling out the guide boss and just pressing in new iron guides. My best time ever was a half hour to do all 16. Not including reaming or hone to fit though.

Bronze would be a good choice to help reduce sticking in an A-4 if the problem was rust. My own engine's valves were just stuck from oil goo and coked up carbon in combination with sacked out valve springs.

[thatch]

Hanley, Dave and Russ, Thank's for your input on my bronze guide suggestion. The guides I used were actually obtained from McMaster Carr (pt # 6381k606) which are a little shorter than the stock steel guides. My intention was to eliminate about half of the "rust area" which seems to be an almost chronic problem with our A4's. Obviously we would like to address the problem, up front, by keeping moisture out of the valve area, but this seems to be a challenge in some installations. When you add the relatively light valve spring pressure that we have and long periods of down time, we are incouraging, "steel on steel" stuck parts.
tom

[hanleyclifford]

The idea of using oil impregnated bronze guides is intriguing since a closer tolerance (at operating temperature) could be achieved but the cold tolerance selected might be tricky to figure out. http://www.engineeringtoolbox.com/th...als-d_859.html