Valve guide guidance

[Grumpa]

Okay, I need some wisdom here.

Went through this '69 top end; new Rowe Ampco-45 bronze guides, three way cut on the seats just barely in spec with oversized valves, parallel honed the cylinders with fresh pistons and rings. I've put 68 miles on it and it's been running great.

It starts fine but after about a minute I would get some smoke for like 3-4 minutes then it would clear out. At first I was hoping it was just that the rings hadn't seated but suspected that it was oil from the head, so yesterday I tore it back down. Found oil in both intakes: IMG_0050.jpg

Also noted some galling at the bottom of both exhaust valves.

Here's the thing, with the exception of the top of the rear intake guide which was out by maybe .0005 or so, all of them were within spec. I'm tempted to pull these guides and put in some cast iron ones but being on the last cut on the seats I'm hesitant. Should I put some seals on the intake guides and put it back together?

Any ideas?

[T. Cotten]

Since nobody else wants to answer, Grumpa,

Please note that the most common way for oil to enter the ports on an aluminum head is when the bore for the guide has been damaged by removal of previous guides. Oil is sucked around the outside of the guide.

Did you use the little gaskets beneath the guides' flanges?

Galling of exhaust valves is usually a heat signature. Ampco is also known to constrict when over-heated.
You bubble-test every manifold assembly, right?
(When it goes back together, I suggest viton O-rings.)

....Cotten

[billpedalino]

I stopped using the bronze guides years ago for the reason stated above by Cotton. Cast Iron, particularly those by Rowe have worked very well for me, but I'm not sure if Rowe is back in business. Years ago we also used an imported cast iron guide that worked very well; I believe it was a British company. Unfortunately I don't remember their name; it was a LONG time in the past...

[Grumpa]

Thank you gentlemen.

Tom, I saw your link for the manifold leak test the other day but when I hit the link it went to a dead end. I just now copied it into another browser and it went just fine. I have to admit I have not tested the manifold like that but I will be from now on.

And it looks like you're right on the oil getting by the outside of the guides as well. I had heated the heads, froze the guides in liquid nitrogen and installed them with fresh gaskets but it looks like that didn't cut it.

Soooo for future reference what interference do you recommend for guide to head fit? How about valve seat to head? I've never replaced valve seats before but it looks like I'm going to lose my virginity now.

[T. Cotten]

Grumpa!

If there are "ant tracks" up and down the bore in the head, usually from a dirty guide removal in the past, then you will have to hone it oversize.

I believe the factory spec'd .002" for later Shovels, but heads were cracking. A thou and a half should be fine. (I've been away from motorwork for a decade and half.)

Before you replace the seats, please consider oversized valves.
Modern hardened seats require a dangerous interference, and you would have to rely upon the manufacturer's specs.

....Cotten

[Grumpa]

Okay, I rigged up a pressure check to see if I could spot any leaks from the guides before pulling them. IMG_0058.jpg No sign of leakage and upon pulling the guides they looked fine in fact even though they had .001 o/s in there three out of the four were still nominal. Honed them up anyway to .002 and put in later cast iron guides and plan to use seals.

My latest theory is that the intakes previously had later no-lead valves in them with the bronze guides honed to the early specs (.002-.004). Since the specs tightened up considerably with advances in metallurgy, my guess is that the valve didn't swell up enough in the guide and let excess oil in.

[Grumpa]

Update: Installed 18143-79A .002 o/s guides and reamed/honed to the later specifications. New guides means checking the seats and these needed cutting IMG_0111.jpg

[Grumpa]

Update #2

Using Rowe o/s intakes and Kibblewhite o/s exhaust valves and here I have to move the intake up on the seat face:IMG_0113.jpg Almost maxed out, next teardown these seats gotta be changed. Ready to button up: IMG_0129.jpg

[BigLakeBob]

I would think more like a .04-.06 wide area of contact would work better.

[Grumpa]

I would think more like a .04-.06 wide area of contact would work better.

Absolutely! That line is just showing the beginning of the interference; the seat is cut at 46 degrees and the valve is 45. Here's a picture where I went ahead and lapped after adjustment and it gives you a little better idea of the contact area: IMG_0117.jpg at least .050"

[Grumpa]

Anyway, installed: IMG_0131.jpg and buttoned up: IMG_0132.jpg

Now to fabricate some torque plates for the cylinders. I'm using three pieces of 3/16" thick aluminum but if that isn't enough or if anyone can share what they did, I'd greatly appreciate it. Never used them before, just read about them here on another post.

[kg993]

I used 3/4" steel. To me 9/16" of aluminum seems questionable but am curious what others think.

[T. Cotten]

Grumpa!

I don't think stacked plates will distribute the fastener stress the same as a solid piece. Although my H-D plates were 5/8" steel, I used ~13/16" magnesium for my Chief plates, so that I could manage the weight. In the attachment, you can see my benchtop clamp to hold the bottom plate firmly while torquing.

....Cotten

[motorhead1]

I stopped using the bronze guides years ago for the reason stated above by Cotton. Cast Iron, particularly those by Rowe have worked very well for me, but I'm not sure if Rowe is back in business. Years ago we also used an imported cast iron guide that worked very well; I believe it was a British company. Unfortunately I don't remember their name; it was a LONG time in the past...

Bill, here is one for a Knuckle I replaced many years ago. I also don't remember the brand but I can't help thinking that Dixie sold them.

[billpedalino]

Dan,
We were a high-volume motor shop in the late 1960's and 1970's and bought a massive amount of Dixie stuff; my boss and Harry were close friends. So you're probably correct; they most likely were from Dixie. They were cheap and worked very well. We also used to buy Covmo pistons through Dixie (also British). Same deal - very inexpensive and very good quality. We used them by the hundreds!