Topic: APE Valve Guides

[danfr]

I got the new APE guides, which APE makes as direct replacements for these heads, pre-sized perfectly.

I know APE claims to have the guides pre-sized, but is this theory proven law? When I imagine guides being installed, I would think that the I.D. would slightly shrink through the middle, and therefore need to be honed to final size.

Also, does anyone have the pre-size specs?

[Retro Rocket]

Jay, the owner is a member here, try sending him a PM, look up "Big Jay"

http://forums.sohc4.net/index.php?action=profile;u=2267

[HondaMan]

Using Honda's OEM specs for the 750 as an example:
The ID of both Intake and Exhaust is 0.260" finished size.
The press-fit (interference fit) is in the range 0.0008" to 0.0012".

Press fit of either bronze or cast iron/Stellite within this press range will reduce the ID by 0 to 0.0004", typically, with Stellite being the 0 value every time. Bronze may occasionally shrink ID, but if it is properly lubed and steadily pressed, seldom shrinks much more than the .0004" with a -.0012" press.

In these heads, they are going into aluminum-zinc, which is pretty soft itself.

As an example: I just pressed 4 APE guides into a head at 250 degrees F and the guides were sprayed frosty with CRC freeze spray. In pre-testing, this yielded holes in the head that grew by .0004" pretty much all 8 holes. The guides shrank their OD about .0002" on average, once frosty, but you only get about 5 seconds to press them as they heat up quick! This changed the measured press-fit tolerance of the guides from 0.0012" on every APE guide I used to be only 0.0006" press, which amounted to tapping them in with a plastic hammer and the proper guide insert tool (with a .258" pilot in the guide). None of the guides bent, deformed, shrank, or distorted, and at least one of them slid in with the first tap. After the temps stabilized, the same hammer could not drive them out (a small plastic hammer) from the other side, so they are snugged well.

Had they distorted, as the CycleX guides are prone to do from their excessive OD, they would require a .259" reamer be run thru (one pass), followed by either honing with a suitable hone, or a sharp .260" reamer, one pass. The final clearnace valve-to-guide, as measured with the valve opened about 8mm from the seat, is .0005" to .0016" movement on the intakes, and .0012" to .0024" on the exhausts. Since the intake stems are .2590" and the exhaust typically .2585", these numbers fall easily together.

[danfr]

Hey Mark, Thanks so much for taking the time and sharing your thoughts and results! I really respect and appreciate your time. 0.0006 sounds really small for an interference fit. I can just imagine sitting at a stop light too long and my guides drop out 

The reason I am asking is because my coworker (as well as a sort of mentor), who has been doing primarily cylinders heads for many many years, finds it hard to believe that the guides do not need to be honed. That being said, his process is slightly different so perhaps he has different results. At the shop here, we heat up the heads by spinning them around in the jet wash. No I don't know the exact temperature but anything coming out of there is far to hot to handle without gloves. After the jet wash, the old guides are hammered out with a pilot and new guides are installed with hammer and pilot, NOT pressed in.  Guides are honed to size, then onto the Serdi for the seats. Maybe his approach puts more force on the guides causing their I.D. to shrink through the center.

[MCRider]

Hey Mark, Thanks so much for taking the time and sharing your thoughts and results! I really respect and appreciate your time. 0.0006 sounds really small for an interference fit. I can just imagine sitting at a stop light too long and my guides drop out 

The reason I am asking is because my coworker (as well as a sort of mentor), who has been doing primarily cylinders heads for many many years, finds it hard to believe that the guides do not need to be honed. That being said, his process is slightly different so perhaps he has different results. At the shop here, we heat up the heads by spinning them around in the jet wash. No I don't know the exact temperature but anything coming out of there is far to hot to handle without gloves. After the jet wash, the old guides are hammered out with a pilot and new guides are installed with hammer and pilot, NOT pressed in.  Guides are honed to size, then onto the Serdi for the seats. Maybe his approach puts more force on the guides causing their I.D. to shrink through the center.

I have little constructive to offer. My comment is that scalding for a human is around 125degF, so you may not be getting the heads very hot in the jet wash. Even with gloves they may be no hotter than 150degF, while Mark is talking about 250degF.

[HondaMan]

Hey Mark, Thanks so much for taking the time and sharing your thoughts and results! I really respect and appreciate your time. 0.0006 sounds really small for an interference fit. I can just imagine sitting at a stop light too long and my guides drop out 

The reason I am asking is because my coworker (as well as a sort of mentor), who has been doing primarily cylinders heads for many many years, finds it hard to believe that the guides do not need to be honed. That being said, his process is slightly different so perhaps he has different results. At the shop here, we heat up the heads by spinning them around in the jet wash. No I don't know the exact temperature but anything coming out of there is far to hot to handle without gloves. After the jet wash, the old guides are hammered out with a pilot and new guides are installed with hammer and pilot, NOT pressed in.  Guides are honed to size, then onto the Serdi for the seats. Maybe his approach puts more force on the guides causing their I.D. to shrink through the center.

I recently discovered that my 'destroyed' guides (both full sets of them) got that way when the machinist decided to take a shorter 'route' to installation than he has for the last 5 years. I had told him to do it as described above, and he seldom had to hone many of the guides. After a while, he started hammering them out 'cold' from the heads, which I guess he got away with for a couple of heads that had little use (like 20k miles). When he got to my head, with well over 100k miles and 40+ years of constant use (almost), he had lots of trouble getting the intake guides out. The Stellite exhausts just slip out with a hand pilot and small hammer, because they are so hard and slick. His "cold" extraction caused teh intake holes to become damaged to a degree. He then heated the head to 200 degrees (usually I told him 250-300) and hammered the bronze intakes in, which happened to be the oversized CycleX guides, and the Stellite guides. He never gave me back the OEM Stellite guides: I think he probably shattered them. I had a set of 4 cast iron guides in case he chipped one of my Stellite guides: he then used those instead.

Then while the guides were still hot, he reamed them with a .260" reamer, all of them. The bronze ones had been pressed in so hard that they rippled inside, and the CycleX ID is already smaller than stock "K" guides, to accommodate the later "F" valves with just one part number, so his reamer ground out large debris chunks and left big scars all up and down the bores. This debris, in a hot guide, then oversized the holes. The next day he happened to pick up the head to cut the new seats: then he discovered how loose they were (probably on the order of .010") and decided to re-replace the intakes with my spare 4 guides from the CycleX set of 8 I had delivered to him. I think he did it totally cold this time, because even the second set of guides showed stress lines (ripples) inside the bore. He again ran his .260" reamer through (and back and forth, judging from the marks I see in the guides) instead of a single pass, which is the proper technique.

Now...for almost 5 years he (or someone in his shop) had been doing my heads and given great results, with about .0010" clearance intakes and .0020" exhausts. Never has there been any damage or messed-up guides: now suddenly this? I am having a hard time believing his story line(s) about this incident. His delivery times in this year have tripled to about 3 months, though, so I had already started buying my own tools again, as I can't keep everyone's heads here for 6 months anymore, just to get new guides and seats in them. I may have him just cut seats for me, if he will do that part faster: he seems real reticent to replace guides, now. Somehow, this just doesn't add up?

The metals: the heads are zinc-aluminum casting alloys, the OEM guides are largely cast iron. The stock Honda fit-ups are .0008"-.0016" press fits. The iron does not expand as much as bronze: I can look up the precise numbers this weekend, but for a long time I've seen .0010" press fit for bronze into aluminum, or .0005" into steel, as the standard bearing practice in the shops where I've worked. It would then seem reasonable to use the .0010" press fit when the metals expand about the same, and the bronze doesn't get all stressed and deformed that way.

[lucky]

Hey Mark, Thanks so much for taking the time and sharing your thoughts and results! I really respect and appreciate your time. 0.0006 sounds really small for an interference fit. I can just imagine sitting at a stop light too long and my guides drop out 

The reason I am asking is because my coworker (as well as a sort of mentor), who has been doing primarily cylinders heads for many many years, finds it hard to believe that the guides do not need to be honed. That being said, his process is slightly different so perhaps he has different results. At the shop here, we heat up the heads by spinning them around in the jet wash. No I don't know the exact temperature but anything coming out of there is far to hot to handle without gloves. After the jet wash, the old guides are hammered out with a pilot and new guides are installed with hammer and pilot, NOT pressed in.  Guides are honed to size, then onto the Serdi for the seats. Maybe his approach puts more force on the guides causing their I.D. to shrink through the center.

Auto parts right? Not motorcycle heads.

[754]

In post #3 dan you mention guides fallng out...you better take a look at what are bikes have in them, it wont happen..
Most engine shops that are automotive are production..production ..production.. If there is a faster way they use it..

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 If you are picky, will take the time, and have the tools... Drill the tops off, drive them into the port.. Result..clean burnished hole that should stay on size...