Author Topic: Head thoughts - Epoxy - Bronze guide life time  (Read 496 times)

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Online PeWe

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Head thoughts - Epoxy - Bronze guide life time
« on: October 12, 2020, 11:43:59 am »
My prior first hand head is now a restore object.
(Other ported head used now)

1. I have read about reshaping intake ports with epoxy for higher gas flow velocity.

Anyone with good experience of that?

I have read that std fuel with ethanol is aggressive, risk the epoxy can let go.

Which epoxy can work for this without  desolve, cracking up?
Z-Spar Splash Zone A-788
Devcon F epoxy
JB- Weld
....... ?

2. Ex bronze guides are too worn to not be replaced. 
(In valves have no side wiggling)
5mm stem bronze guides.
- Runtime of ca: 23.000 km (14300 miles)  normal for bronze guides?

I thought C630 aka Ampco 45 was really hard and should live longer.
It has run rather rich part of the time which might be one factor.
 - But IN should be affected too if rich fuel mix affect the guides?

- Is it a known method to prolong the lifetime of these guides?
(Except not overheat them)

There are no steel guides available (yet) what I have seen. I'm sure CycleX should write about it.

I have read about bronze guides for racing, steel for street.
Street where a normal season can be 5000km or even more. This head over 1000km this year ;)

Offline johno

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #1 on: October 12, 2020, 10:01:01 pm »
Hi Pewe,
When your on the edge nothing lasts that long.
Im sure Mike will give you the good oil but in my opinion epoxy ports are suited to race only applications rather than road use as long term the temp cycling and fuel has a negative impact on epoxy bonding. Generally the exhaust guides wear quicker due to the heat from exhaust reduces the lubrication factor.
Give us something to do Per.  ;D
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Offline bear

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #2 on: October 12, 2020, 10:03:11 pm »
G'day Per,

I will offer my opinion re valve guides, but I suspect it will differ from others on this forum with better engineering credentials than myself.

Bronze guides are more efficient than cast guides no doubt about that. But it must be remembered that these motors run two relatively large heavy valves per cylinder and should not be compared to later four valve motors using smaller/lighter valves.

I used cast guides and 7mm valves on my motors because I believe it was better to avoid the risk of excessive wear and mechanical failure that I think is possible using bronze guides in HP motors.

I'm happy to concede slightly higher temps and a little less mechanical efficiency, but I believe it is the lesser of two evils. Or as Russell Crow would say " The lesser of two weavels".  ;D         
The older I get the faster I was.

Online PeWe

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #3 on: October 12, 2020, 11:29:26 pm »
Thanks for your input guys.
I think a not perfect carb jetting helped the wear. Both too rich and lean at the same time during a longer period of time.

I ask here about similar experiences or an answer as " my guides are still fine after 50.000 km".
Or "hard racing with bronze guides keeping up better than my old stock guides".

About oil, oil used most of the time has rather much zinc and phosphorous.
- Too high content can do bad things with bronze guides?

The head bike has now has 6.5mm stems.

If searching for epoxy porting, shaping or similar, lots of information to be found. Many cars and bikes too. Discussions about which epoxy.
It would be good to find an epoxy that will stay in place.
I think that head should work better with reshaped floors.

Riding a CB750 faster than allowed is racing ;D

Aha!
7mm stems one of the ingredients squeezing 120-134 whp out from a CB750 with other mods and continue doing so!!

That's why my 6.5mm stemmed engine just hardly pass the 100whp line. ;)
« Last Edit: October 12, 2020, 11:31:36 pm by PeWe »

Offline bear

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #4 on: October 12, 2020, 11:54:11 pm »
Aha!
7mm stems one of the ingredients squeezing 120-134 whp out from a CB750 with other mods and continue doing so!!

That's why my 6.5mm stemmed engine just hardly pass the 100whp line. ;)

No mate, if stock guides where 6.5mm that's what i was using.
Remember I'm an old bloke and I've been knocked about a bit.
My memory is not flash. ;)
100whp in a road bike is quite an achievement, well done.
The older I get the faster I was.

Offline RAF122S

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #5 on: October 13, 2020, 01:28:01 am »
Mike R would know a bit about redesigning heads with epoxy as I believe he has done a few. He also has experience with port casting to tune ports so they are matching.
David- back in the desert SW!

Online PeWe

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #6 on: October 13, 2020, 01:36:29 am »
1000cc (almost 1005) make that easier.
Mikes billet block seems to be very durable too.

I read Johno's thread where Mike made a head with epoxy ports for him.
Good inspiration!!! ;D

The head I use now is not specifically adapted to the pistons. Maybe pure luck or more to get with the small details.
I'm convinced that 105 would be the number to work for with these parts.

I know a guy that got 86.8 hp/68.6Nm (DIN) with JE 62mm pistons, 34/28, 5mm stemmed valves, CR31. Cam I do not recall.

I saw the head, ports not that wild opened as my old head. "Only 750cc" when I asked the porting guy.

250cc extra can give 20 hp more?

« Last Edit: October 13, 2020, 01:38:17 am by PeWe »

Offline MRieck

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #7 on: October 13, 2020, 12:50:37 pm »
 I have done epoxy heads and ...in general....they are race based bikes. The most recent was a CB650 head. Johno's head reacted very well to epoxy with approximately 36CFM at .100 lift. That is the best # I've ever seen or achieved on a heavily worked K head.
 Eventually the epoxy will be compromised though it is pretty durable which is surprising seeing that one side of the head runs cool and the other side hot as Hades. If you don't use the bike all time it will last quite a while. I have used JB Weld. You can really improve stability by sinking some pan head screws into the bottom of the port after milling those areas flat. This was done on Johno's head and GS/GSXR heads I have done.
 I figured out what shape I wanted by using clay in the port and putting it on the flowbench. You can eyeball it and go for a flat intake floor ("D" port" design).
 You can get good results. My best on a GS1150 head was 184 RWHP with custom pistons about 1250cc, GXSR valve train parts and moderate cams. The individual who built the engine is a professional builder so his abilities can't be discounted.....he is top notch.
 An honest 100 RWHP out of these engines (without resorted to radical parts and compression ratios) is a noteworthy accomplishment Per. I also agree there are some more ponies lurking in the engine.
Owner of the "Million Dollar CB"

Offline MRieck

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #8 on: October 13, 2020, 01:51:48 pm »
Bronze guides vs iron guides. For the street I like iron guides. As a rule of thumb chrome stemmed valves work better with bronze and valves with treatments like the "Black Diamond" Kibblewhite uses work well in iron guides.
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Online PeWe

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Re: Head thoughts - Epoxy - Bronze guide life time
« Reply #9 on: October 13, 2020, 07:04:13 pm »
Thank you very much for your input, Mike.
I'll see what I'll do with that head. Replace worn guides that most likely got help by not properly jetted carbs. 2,3 by cracked boots. The lifetime is most likely a little longer.
I'm sure there is a reason for the various OD sizes when order  those guides ;)

Overheating stock steel guides is not that difficult either ;)

Epoxy seems to be an interesting option for that head that has spacious inlet ports. Even more interesting now after reading more success stories.

A perfect add-on for those with flow bench that can test with model clay for best result. Then the 2k version.

I know one guy here that got 200hp dyno on the crank. Suzuki GSX1100  82-83. MTC block, probably 1400cc, ported with epoxy shaping D-ports etc. RS carbs, maybe 36.

Just wait for the magic extra durable epoxy version that can  withstand loooong street use on ethanol enriched fuel.

My bike felt a little bit extra happy yesterday after I had removed the additional washers under needle clips going from 3.5 to 3. Plus one step bigger pilots, less fuel screws.
Called the dyno shop direct
Maybe possible next week. Shop very busy.

Edit:
"An honest 100 RWHP out of these engines (without resorted to radical parts and compression ratios) is a noteworthy accomplishment"

Not that difficult, JMR billet block 1000cc,  ported head with a good cam, bigger carbs and you are there!! ;)

The compression can't be too low I guess. I measured around 200PSI with the cheap compression tester with long hose. More might be risky.

My earlier builds had around 180-190. I think lower than 170 PSI make it dull, fun started at 175-180PSI. I saw differences when comparing different cams. More overlap cams really need higher compression by pistons vs chambers.

But this need a good lower end with good rods, stronger primary chains.

Just to be clear:
The ex guides are not worn enough for a head removal.
They can be used more.
But not good enough when head already is off.
The clearance is just possible to feel and visible, more on 2-3 of 4.

If they should had a better childhood (not too lean- too rich as they have suffered) they can probaly be safe for longer use. I think 40-50.000km in street mode, often crusing around on lower rpms.
« Last Edit: October 14, 2020, 05:50:16 am by PeWe »