Tight Valve Guides

[chrs1961815]

Many of you probably followed my previous thread with my rod issues. But they are now all fixed with pistons installed. I moved onto the valve train, but now I have another problem. The new valve guides in the modern kit are too tight. Is the solution to hone the holes until a proper fit can be achieved? I would have thought the shop would have done this.

[J Franklin]

What is the clearance?

[chrs1961815]

I should have explained it a little better: the valve guides are too big to even put in the hole. They would fit only by hitting them hard with a hammer which is way too tight. As I read, they are supposed to be snug, but not like mine.
Some information I gathered from previous threads:
"You will have to use an air hammer to drive them in with the correct driver pilot. Not too much.... but just enough to make them about flush in the valve port."
And this thread:
https://www.fordbarn.com/forum/showt...t=Valve+guides

The waters are a bit muddy now as it appears that it is supposed to be very tight, a press fit. Conflicting information. I assume it is supposed to be tight as that is what everybody is saying here. I will have to make a tool.

[Synchro909]

I wouldn't hone the holes unless you have a way of making them smaller again. One enlarged, the block is pretty much useless for another rebuild with properly sized guides.

[ursus]

The quality and sizing of Model A/B valve guides has been variable over the last 15 years or so. I have sourced mine from EBay when the NOS or NORS guides turn up.

[Jack Shaft]

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an air hammer has the power of a sledge hammer..

[chrs1961815]

So are the guides fine or should they be cut slightly on a lathe (if t hgv at is possible). I can mic them tomorrow.

[J Franklin]

You might have saved a lot of headaches by letting the machine shop do some of the assembly work. I had thought you were talking about the valve to guide fit.

[PC/SR]

If they are the guides I think they are they are a press fit with an air hammar. I do not have the deminsions of the modern guides I used, but, are the guides you have 1 piece, and straight, or are they the new "modern" guides that look like the stock guides but are one piece. The latter should slide fit from the bottom. I am just not sure of which guides you have. Are the guides for the straight stem modern valves? What are the deminsions of the valve stem, and the inside and outside diameter of the guide. Where did you get them and have you talked to the seller?

[McMimmcs]

Originally Posted by J Franklin

You might have saved a lot of headaches by letting the machine shop do some of the assembly work. I had thought you were talking about the valve to guide fit.

I agree totally. Sometimes money not spent is not money saved! Let the experts do their work and sit back and learn from them. With all these troubles it makes you wonder what the end result will be! My dad used to say not to hire a plumber to do heart surgery.

[Jack Shaft]

With the proper tooling this is an easy job,the guides are a press fit but can be done with an air hammer and mandrel.Mandrel shaft size is key to keep from breaking the guide while banging it in.

https://goodson.com/collections/valve-guide-drivers

[chrs1961815]

I am doing this with my son to help him learn and to save a little money. So it is worth it.

I am using the straight one piece modern guides with the stainless modern valves.
Following dimmensions estimated:
ID of guide: 0.345
OD of guide: 0.597 inches
Valve stem diameter: 0.34 inches

The valves move nicely in the guides, plenty of clearance.

[BRENT in 10-uh-C]

Originally Posted by chrs1961815

So are the guides fine or should they be cut slightly on a lathe (if that is possible). I can mic them tomorrow.

My instinct is that the guides are fine as-is. Additionally, I would say the bores of the block are within spec also. The guide bore diameter is supposed to be 0.5940"-0.5945 based on the factory print however you will need a decent quality inside micrometer (tri-mic) or a small hole gauge to be able to get an accurate measurement.

Yes, the guides can be machined as they are generally cast iron. I do this on other marque engines where guides are not available and they must be made. The issue is you really need to have a collet chuck for your lathe so that you can keep the TIR at a minimum. If your TIR is off when you cut them, the concentricity of the valve face to the seat will be off possibly requiring much more work to the seat.

.

[Big hammer]

If you cool the guides, like in a freezer for several hours, then they should slide in the bores. If you bang them in, you will make the valves tight in the guides!

[PC/SR]

Try cooling them first, and then Jack Shaft's post shows the tool to use. Drive the guide in until flush with the top of the guide bore, or, leave a quarter inch or so above for a bit more stem support. You might also cut quarter to half inch off the bottom which will make installing the springs soooo much easier. This can be done by any machinist. Drivimg them in does not materially reduce the interior diameter. They work fine and are in my opinion a little loose but OK for regular driving. I have mine knurled on the speedster.

[Kurt in NJ]

I have adjusted guide outside diameters many times with a drill press, just a little using sandpaper and "shoeshine " ,if the whole length needs adjusted I use a close fitting bolt/ nut and chuck that up, if a lot has to come off I use a file then finishing with sandpaper
But you do need to be able to measure to determine the needed size, when lacking a good inside measuring tools I have made a multi diameter plug gauge out of xtra guide

[johnneilson]

The "modern" valve guides are single pc interference fit guides, typically.
If one piece guide does not have a retaining step or flange it is a press fit.
With retaining flange slip fit from spring side, no flange press fit from valve side.

Typically done with air hammer, the mandrel is key. It should have a pilot to help guide you and a relief step to not crush the guide edge.

Also be careful to not push the guide down too far, it will interfere with valve opening and is a bugger to push back up, without a really long mandrel.

J

last note, if in fact the guides crush and the valve does not fit properly, a hand reamer can be used to re-fit for valve. Do not use typical standard reamer, there are reamers made for this with proper pilot taper. do not use in cordless drill, or corded drill.

[Bob Bidonde]

0.003" interference fit of the guide into the block is excessive. Check this Federal Mogul Service Bulletin SB2188. Federal Mogul specifies the interference fit (AKA press-fit) should be 0.001" to 0.0015".
http://www.partinfo.co.uk/files/SB21...DER%20HEAD.pdf

[Jim Brierley]

Modern, straight guides are always a tight fit, they need to be. I installed a set for a friend a few years ago, one guide was not as tight as I liked it to be, I used Loktite to be sure. Fast forward several months and the engine had another, different, problem. When torn down, that guide had slipped downward at least 1/2"! Since that incident, I buy guides from Mac's. they are 1-piece but have a shoulder for the spring to seat on, so the spring holds the guide in place. Another advantage of them is that you don't loose the length of the stock guide/spring relationship, so no loss of spring pressure.

[chrs1961815]

I will try to cool them and install them again. How far do they need to go down? I believe it is in my book, but I am too lazy to get it right now.

[J Franklin]

Never get lazy when rebuilding stuff, it will bite you in the end (your rearend).

[chrs1961815]

Just don't be lazy in the shop!

[alexiskai]

Originally Posted by Jim Brierley

Modern, straight guides are always a tight fit, they need to be. I installed a set for a friend a few years ago, one guide was not as tight as I liked it to be, I used Loktite to be sure. Fast forward several months and the engine had another, different, problem. When torn down, that guide had slipped downward at least 1/2"! Since that incident, I buy guides from Mac's. they are 1-piece but have a shoulder for the spring to seat on, so the spring holds the guide in place. Another advantage of them is that you don't loose the length of the stock guide/spring relationship, so no loss of spring pressure.

These ones?
https://www.macsautoparts.com/ford_m...iece-type.html

Mike's also sells them
https://www.mikes-afordable.com/product/A6510MODA.html

Very interesting that none of the other vendors sell a one-piece with a shoulder. I assume the tight fit everyone is talking about eliminates the need.