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Old 06-15-2005, 12:07 PM   #1 (permalink)
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American Rider Magazine 95 BB

Has anyone read the August issue featuring Joe Minton's 95" BB Conversion?

"Quote" "Our intention is to build a practical engine that does its best work under the conditions almost all of us consider normal riding."

Basically, Andrews TW21 cams, Wiseco flat top pistons, stock headwork with Cometic .030 head gaskets. They test it with Hard Chrome Sideburner, Bub Jug Huggers, Bassani Road Rage, and SuperTrapp 2-1 (best performer)exhaust.

They include the dyno sheets also.

You seldom see anyone recommend the TW21, even for low end torque, it is usually the TW26.

Opinions, please
Thanks
Dave
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Old 06-15-2005, 12:20 PM   #2 (permalink)
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Sounds like a very mild build. My personal opinion, you couldn't pay me enough to put wiseco pistons in a Harley. My
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Old 06-15-2005, 12:59 PM   #3 (permalink)
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Quote:
Originally Posted by springer-
Sounds like a very mild build. My personal opinion, you couldn't pay me enough to put wiseco pistons in a Harley. My
What are the problems with the Wisecos?

Thanks
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Old 06-15-2005, 02:47 PM   #4 (permalink)
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Again, this is just my opinion if anyone wants to argue the points go ahead but don't expect me to fight over it, it just isn’t worth it. If some can offer a viable alternative to my understanding I am open to learning.

Wiseco's are forged pistons and unless you are going to run some sort of boost in your motor or are racing, there is little need to run forged pistons. The main reason, as I understand it, to run a forged piston is for strength. A forged piston requires more initial setup clearance, usually .002-.005 more depending on application because it expands more when hot. Harley's by comparison have large bores and forged pistons require more clearance as the bore gets larger. This causes a noisier motor when cold (piston slap).

Forged pistons also require a more controlled break-in procedure, as the metal heat cycles it changes before taking its final shape. Motors with forged pistons should also be warmed up thoroughly before riding (most of us don't do this) or they can "cold seize", less likely if properly broken in.

Cast vs. Forged .... A cast piston will hold its tolerances better from the initial setup. It expands less when heated and maintains its original shape over the life of the piston.

Now with all that being said, I run forged pistons in my bike. But I originally was going to run Nitrous on it. I took great care in selecting my pistons and cylinders. I made sure that my forged piston measured at the tightest allowable tolerance for forged but fell within the maximum allowable tolerance for a cast piston. I then went through many heat cycles before I actually rode the bike. I used great care at the very beginning of the break procedure, which included riding it until hot and the cooling it off several times. I have had no problems with the pistons but if I had it to do over again, I would run cast pistons.

In the build, in the original post, they use a flat top and very little increased compression and suggest that it is a build for everyday riding. I see no need to run a forged piston in that situation. I would even go as far as to say that a good 95" build with 10.25:1 Cast pistons, a little hotter cam and ported heads would be in a similar cost range and yield much better results without compromising the durability and reliability of the motor. It would also be very useable in the normal day to day driving.

This leads me to the argument about “true” flat tops vs. popup pistons. It has been suggested that the flame front is compromised with a popup type piston. In the days of the shovelhead this was certainly the case. The popup type pistons in a shovelhead actually divided the combustion chamber into 2 parts and with only 1 spark plug the flame front had to climb over the piston and caused an irregular burn. It was very common to dual plug the heads when running higher compression on a shovel. This would actually fire a plug on each side of the piston popup and overcome the problem of splitting the combustion chamber. In the Twin Cam heads, they have a bathtub shaped combustion chamber and the “squish” pushes all the fuel towards the spark plug. When using SE 10.25:1 cast pistons, the popup doesn’t interfere with the combustion chamber like the shovelheads did. It essentially acts very much like a flat top does as far as the flame front is concerned.

Using the Cometic .030 gaskets can give you the "best" desired squish factor and can compensate for the commonly 1 - 2 cc oversized combustion chambers that the Twin Cams seem to have. But if you use the stock HD gaskets at .045 with the 10:25:1 pistons and the probable oversized combustion chambers you can achieve 9.9-10.1:1 CR and have a very fun to ride bike. If you want a little more, CC the heads and run the Cometic gaskets and you should be a little over the 10.25:1 CR, actually closer to 10.5:1. IMHO

Sorry about the rant, hopefully HDMD88, Grock or HDwrench will chime in and tell me why I am wrong.
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Last edited by springer-; 06-17-2005 at 01:23 PM. Reason: reran the numbers and wanted to correct CR
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Old 06-15-2005, 03:00 PM   #5 (permalink)
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Very GOOD reply! Thanks for taking the time to inform me of the pluses and minuses of Forged and cast pistons.

So, you're saying that the SE cast 95" pistons would be an excellent choice on this "Mild" build.

In the ARM article, they were building a 95" WITHOUT any HD parts. That way you could have the build done at any "Indie".

Thanks again for you input!
Dave
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Old 06-15-2005, 03:05 PM   #6 (permalink)
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Quote:
Originally Posted by foddlefadel
...In the ARM article, they were building a 95" WITHOUT any HD parts. That way you could have the build done at any "Indie"...
Translation: That way we can sell more ad space to aftermarket parts suppliers.

What's to keep an Indie from installin' HD parts?
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Old 06-15-2005, 03:14 PM   #7 (permalink)
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Quote:
Originally Posted by D_T
What's to keep an Indie from installin' HD parts?
That was going to be my next statement.

ANY indie shop can build a 95 with stock HD parts. A prefered build, in my opinion, would be to bore stock "seasoned" cylinders to 95", run 10.25:1 SE cast pistons, ported heads (Big Boyz of course ) and SE 257 cams. Total build cost for parts, boring and head work, less than $850. Then have your favorite indie shop do the work. I think this combo can yield somewhere in the 100/100 +/- range with a good exhaust and proper tuning.
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Old 06-15-2005, 03:37 PM   #8 (permalink)
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How do you think the above set up would work with the andrews 37 cams? Thanks.
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Old 06-15-2005, 04:49 PM   #9 (permalink)
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Haven't seen the article - prob won't land here for 2 months, but what power and tq did they get?
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Old 06-15-2005, 05:07 PM   #10 (permalink)
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Quote:
Originally Posted by uspatriot
How do you think the above set up would work with the andrews 37 cams? Thanks.
I am not up on all the cams. Someone that knows the cams timing and overall characteristics would be better suited to answer your specific question. But in general I can't imagine to much of a problem. It would probably depend more on what the overall compression ratio is. If you go for the highside of the build suggested (CC'in the heads and Cometic gaskets) then you would most likely want a cam that works good with higher compression. If you go with a lowside build you would most likely want one that works better with a little less compression. Then again there may not be too much of a difference in overall CR of the 2 builds that the cam choice is that much effected. I hope Grock or Doc or someone reads this and enlightens the both of us on this subject.

The build I suggested above is from what I have seen work. In fact that same basic build has yielded 110 Tq and 105 Hp (SAE), but that is very dependant on tuning, exhaust, carb, tempature, relative humidity, tire pressure etc.....

Here is the Dyno sheet but your results may vary based on all of the above mentioned.

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Old 06-15-2005, 05:16 PM   #11 (permalink)
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That looks a fairly mighty graph but that torque dip in the 'useful' area would bug my ass. I'm impressed they ran it to 7 in a 'why bother' kind've way but I notice it's in 5th......
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Old 06-15-2005, 05:28 PM   #12 (permalink)
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Quote:
Originally Posted by 58GT
That looks a fairly mighty graph but that torque dip in the 'useful' area would bug my ass. I'm impressed they ran it to 7 in a 'why bother' kind've way but I notice it's in 5th......
My guess would be that dip is from the carb. In an injected bike with a SERT, I would think that could be removed. Note that it has a SE ignition module, in this case based on the 7K RPM's it is the 7000 RPM Race module with the -10 degree retard. I wouldn't recommend exceeding 6200 with the cast pistons, as the manufacturer states.
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Old 06-15-2005, 06:39 PM   #13 (permalink)
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My understanding is that forged pistons need closer tolerances because they hold there size better. I like the Keith Black pistons my self. Hold there size and run much better than other materials used in making pistons. I would never use a cast piston if I have a choise. Machined forged piston is the way to go. The Springer is wrong on that part.

Last edited by doc ock; 06-15-2005 at 06:42 PM.
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Old 06-15-2005, 08:40 PM   #14 (permalink)
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Re post#1, depending on the year of the bike I think it would work well (not sure about a 05). It is typical Joe Minton think and there is nothing wrong with it, the TW21 is very similar to his old JM20. I would have used either KB or SE pistons, but that isn't going to make much difference to how the bike runs other then it might be quieter.
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Old 06-15-2005, 08:57 PM   #15 (permalink)
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Quote:
Originally Posted by doc ock
My understanding is that forged pistons need closer tolerances because they hold there size better. I like the Keith Black pistons my self. Hold there size and run much better than other materials used in making pistons. I would never use a cast piston if I have a choise. Machined forged piston is the way to go. The Springer is wrong on that part.
Keith Black pistons are not forged. And they do allow for very close tolerances. Much closer than forged. Still not convinced, I know the forged pistons I used, as decribed above, were a looser fit piston than a cast piston. This I am certain as I had to send the piston/cylinder set back because it was on the maximum allowable tolerance and I told them I wanted the minimum. Of course this is on a shovelhead and not a Twin cam but the theory is still the same.

Here is a good read about the Keith black pistons ......

Quote:
Hypereutectic pistons are used in some original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum.

With this in mind, we caution the reader about the use of non-T6 heat treated O.E. design hypereutectic pistons for high performance. Silvolite and others do make replacement-type hypereutectic pistons that are worthwhile for stock replacement applications. Original equipment design is almost never suitable for performance applications.

The KB line of hypereutectic pistons were designed around the 390 alloy. The result is a high performance part intended to give the performance engine builder access to the latest in piston technology.

Forgings have long been the mainstay of the performance business and did well in the big cubic inch engines of the 60?s. Now, with focus on peak cylinder pressure timing, ring sealing dynamics, cylinder air tumble and swirl, combustion chamber science, and extended RPM ranges, we need to consider some new piston options.

The KB T6 hypereutectics are considerably different than the forgings. The KB pistons have shown improvement in power, fuel economy, cylinder sealing, service life, and cost effectiveness. The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by.

The design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength.

The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal.

The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market.

Some current KB pistons are not super light for several reasons. If the piston is to be used as a stock replacement, more than a 10% weight reduction will mandate that the engine be re-balanced.

Common sense suggests that the introduction of a new product be extra strong at the initial release. As the product becomes accepted, weight reductions are scheduled as regular product upgrades, as justified with actual race testing.

There will always be a market for custom forged pistons. Small runs of forgings are more economical than small runs of permanent mold pistons because of the complexity of permanent mold tooling. Where quantities justify, expect to see future KB pistons developed that are lighter and stronger than anything else on the market. Machined head profiles are easily changed with our CNC equipment so we will stay current with new cylinder head developments. Volume production is expected to keep the price reasonable.

Our pricing policy has given the impression to some that we are building an economy, or in between, piston. The truth is, we are striving to build the "State of the Art" piston that is best, regardless of price. Reasonable pricing is just an added benefit.
Source


More interesting reading .......
I clipped the article because it directly addressed someones question that was unrelated ... all the pertinant info was retained and unedited.

Quote:
clearance suggestions from Wiseco

.....our recommended clearance is .003 clearance measured at the bottom of the skirt. Quite a few machine shops measure at 90 degrees from the wrist pin (common to several other manufacturers) and it can lead to problems. My personal observations are this. Seized Wiseco pistons at .003 are pretty rare due to most owners giving them a long (at least 500 miles) break in. For the guys going straight to the track or chassis dyno for an immediate beating, I'd recommend .004. The 500 miles gives the cylinder wall time to get familiar with the piston....... Forged pistons will almost always make more noise than cast, but to help compensate,-Wiseco offsets the wrist pins like the factory o.e. to allow the piston to "roll" up the cylinder wall instead of straight pinned pistons slapping the top land against the cylinder at rock-over at tdc.

Thanks, Brian Nutter-Wiseco Piston co.

I am not saying that you are not right, I just haven't seen anything to contradict what I stated earlier.
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