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Valve guide interference fit: Bronze vs cast iron guide?

General engine tech -- Drag Racing to Circle Track

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modok
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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by modok » Sat Jun 27, 2020 2:10 am

Probably if you got the reamer from a cylinder head supply place then it's probably going to be the right kind, straight or reverse flutes, piloted, and will work OK until it gets dull.
Which is actually not that long.

I prefer to use diamond hones, they last an incredibly long time, make a near perfectly straight bore, and leave virtually no abrasive grit lodged in the guide. Only real downsides is they are expensive, and if you try to take out too much they get can stuck.

it would be really nice to have a one pass hone in matching size to every live pilot. That would make perfect sense, a pilot for every hone, and a hone for every pilot.
Not worth it in the short term, but In the long haul it could be.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by MotionMachine » Sat Jun 27, 2020 1:58 pm

IMO the only reamers that work on bronze guides are the AV&V reamers. I bought one for 6mm and it works awesome. It was almost $200 but worth every penny for the job I used it on. I've bought the Goodson ones, Atlas, Kline, whoever else over the years, absolutely no comparison. You will regret trying to do this job yourself without proper equipment. Hell, most shops can't change and size bronze guides correctly. How straight and round the guide is has a direct affect on the valve job. If the i.d. is not straight or has taper or is barrel shaped, the pilot will locate in a different plane than the valve itself, so it'll never seat properly. There's a lot more to doing this job than you realize. Sorry for being direct, but the older I get, the directerer I get!

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by Nut124 » Sat Jun 27, 2020 2:10 pm

Thanks for the responses again. I appreciate all of them.

The reamers I ordered are K-Line finish reamers for bronze guides. They do have a square end. I have .315, 316 and 317 on the way.

.315 Bronze High Speed Guide Reamer
Manufacturer: K-Line
Manufacturer Part No.: KL1112NB

Should I ream to final size before taking it in for the seat cut or leave at .315? The shop mostly works on american iron and said they have pilots in 3 thou increments.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by Nut124 » Sat Jun 27, 2020 3:43 pm

dannobee wrote:
Fri Jun 26, 2020 11:44 pm
Well, you could, but the tools aren't cheap and you'll have more money into even buying the cheap tooling than just sending the head out.

But if you really want to, and time is of the essence (considering their turnaround time), call Neway manufacturing and tell them what you're working on and they'll set you up. There is a learning curve, but with the pilot, cutters and a concentricity gauge, it's doable. I always kept a cutter kit in the race trailer just in case something went south. Like I said, there's a learning curve, but with the proper gauges and going slowly while checking your work, it'll get you back on the track. It's no Serdi or Rottler SG, but it will give acceptable results.

https://www.newaymfg.com/
Thanks. I checked Neway website. Looks like I could buy two reversible cutters; 45/30 and 65/15 each good for both intake and ex, pilot and handle for under $400. I'm tempted to do it. I have two other heads I could practice with.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by dannobee » Sat Jun 27, 2020 6:48 pm

Let the size of the valve stem dictate which reamer you use. You'll want to check the factory spec for clearance and use that as your guide unless you're racing. If it's a track vehicle (as opposed to street or drag strip), it's likely that you'll want to add 0.001" clearance to the factory spec. As Darin Morgan said, "If your clearance is too loose, you'll know. If it's too tight, EVERYBODY will know." The risk is that the valve sticks in the guide and the piston hits the valve. Sneak up on the valve guide size, either with your reamer or a hone. And you'll need a concentricity gauge too, to verify that you're cutting the seats correctly with the Neway cutters. Any side motion will flex the pilot, so check concentricity early and often until you get your technique down. If you hone the guides, be sure to clean them really good before the next steps.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by AC sports » Tue Jun 30, 2020 10:15 am

Here's a head I just refreshed for a friend after a seasons work.
44mm inlet valves with 2l type chamber.
Slight valve seat and guide wear. Guides had been in maybe 5 years though.
Neway 30x45* +70* throat cutter. New guides reamed then flexhoned.
You do not have the required permissions to view the files attached to this post.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by Nut124 » Tue Jun 30, 2020 11:28 am

AC, thanks. That looks awesome!

My Neway cutters are arriving tomorrow. How did you fit the 44mm valves? New bigger seat inserts? My seat inserts measure just over 43mm OD.

How much stem to guide clearance are you running?

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by Krooser » Tue Jun 30, 2020 11:52 am

John Edwards made several Fiat videos before he passed. Look for "fiatnutz" on YouTube.
Luxemburg Speedway Hall of Fame Member Class of 2019

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by AC sports » Tue Jun 30, 2020 10:53 pm

Nut124 wrote:
Tue Jun 30, 2020 11:28 am
AC, thanks. That looks awesome!

My Neway cutters are arriving tomorrow. How did you fit the 44mm valves? New bigger seat inserts? My seat inserts measure just over 43mm OD.

How much stem to guide clearance are you running?
The head is from an australian delivered 131 mk2. They had bigger seats, throats and valves . Oe was 43.5mm . 44mm will fit with about 0.5mm seat left to prevent cracking. Guide to bore measured with micrometer and ball gauges is 0.04- 0.05mm in/ ex.
I run same on both cast and bronze guides. Maybe a little loose, but I know they wont seize at that. This engine runs 10.8:1 and it gets pretty hot, so better safe than sorry.

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Re: Valve guide interference fit: Bronze vs cast iron guide?

Post by AC sports » Wed Jul 01, 2020 3:08 am

I've also run them up to 0.07mm and still ok. Book says the new limit is 0.066mm. Problem with the Bronze guides sold by U.S. vendors is they wont specify and prob dont know exactly what they are made of. Better a bit more than not enough. I'm sure they source them from China, which is unfortunate cause u dont know exactly what your getting.

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