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Old 02-13-2011, 10:15 AM   #61
supershaft
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Quote:
Originally Posted by pommie john View Post
Yeah. the dyno operator reckoned that mid to high 12s was OK for an airhead, but if it was a watercooled four, he'd be running it in the low 13s.
I don't know how to post my dyno charts but my airhead has been running fine for about 45,000 miles since I went from mid/upper 12's to low/mid 13's. I think that is long enough of a test. The bike will ping on regular when the ambient is hot and it won't with premium in it. A friend of mine that got me the free dyno runs where he works at jets all kinds of bikes but mostly big bore HD's. They jet THOSE in the 13's.

When you are jetting to the tits melting pistons almost always comes from pinging, pinging depends so much on combustion chamber shape. Theoretical peak power is too lean but the closer you can get to it in practice the more power you will make. How close you can actually get depends so much on not pinging and that depends so much on squish band/mixture swirl. It all depends!

supershaft screwed with this post 02-13-2011 at 10:20 AM
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Old 02-13-2011, 02:33 PM   #62
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Originally Posted by supershaft View Post
I don't know how to post my dyno charts but ...
You need to take digital photo of them and upload it to a site like photobucket so it's published on the net somewhere.
Then, on the photobucket site, each image will have a load of data next to it, one of which is "image code".
Copy and paste the image code into your post here.
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Old 02-13-2011, 04:25 PM   #63
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Originally Posted by pommie john View Post
You need to take digital photo of them and upload it to a site like photobucket so it's published on the net somewhere.
Then, on the photobucket site, each image will have a load of data next to it, one of which is "image code".
Copy and paste the image code into your post here.
Thanks PJ but I don't see myself spending all that time on it any time soon. I have spent too much time on this forum lately as it is! Half of it countering a bunch of BS. It's folks like you that make this forum fun for me! I will learn how to load a photo one of these days!

But still, your bike is pulling some serous ponies! I wish you would list the main mods. I am thinking you can get there without having your heads flowed by a real head specialist. If that is real wheel, IMO, much higher than that is going to take some serious and most often expensive head work. The last bike I worked on that had flowed heads was a Sportster. Branch Flowmetrics charged him $1500 for it. That sucker did HAUL! They only flow Harley heads now! They new what to do to an airhead too!
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Old 02-13-2011, 04:38 PM   #64
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Thanks PJ but I don't see myself spending all that time on it any time soon. I have spent too much time on this forum lately as it is! Half of it countering a bunch of BS. It's folks like you that make this forum fun for me! I will learn how to load a photo one of these days!

But still, your bike is pulling some serous ponies! I wish you would list the main mods. I am thinking you can get there without having your heads flowed by a real head specialist. If that is real wheel, IMO, much higher than that is going to take some serious and most often expensive head work. The last bike I worked on that had flowed heads was a Sportster. Branch Flowmetrics charged him $1500 for it. That sucker did HAUL! They only flow Harley heads now! They new what to do to an airhead too!
It is rear wheel horsepower...on a different dyno it measured 92! The engine was done by Jim Cray and it does include head work, dual plug heads, 336 cam, mahle pistons, 40mm Dellortos, err that's about it I think. It runs about 10.5:1 compression, not too high and I run it on 98 octane unleaded.

Jim Cray does a great job tuning airheads, I wouldn't go anywhere else.
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Old 02-13-2011, 04:51 PM   #65
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It is rear wheel horsepower...on a different dyno it measured 92! The engine was done by Jim Cray and it does include head work, dual plug heads, 336 cam, mahle pistons, 40mm Dellortos, err that's about it I think. It runs about 10.5:1 compression, not too high and I run it on 98 octane unleaded.

Jim Cray does a great job tuning airheads, I wouldn't go anywhere else.
Isn't that funny how different dynos vary so much! Was the other dyno an inertia (Dynojet)? Do you know if the ports were just smartly cleaned up or really flowed on the bench. You would definitely know if you remember the bill. I am still thinking you can get to your level with smartly cleaned up ports. 92hp on that same dyno is going to take some real flow bench time in my experience.

Simplex timing chain?

Late model clutch?
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Old 02-13-2011, 04:57 PM   #66
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Jim Cray does a great job tuning airheads, I wouldn't go anywhere else.
pj, Jim has previously said that the 170main jet is the only change needed when using the mufflers he designed. Do you know if any a/f ratio data exists for this?

Cheers


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Old 02-13-2011, 05:18 PM   #67
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Originally Posted by supershaft View Post
Isn't that funny how different dynos vary so much! Was the other dyno an inertia (Dynojet)? Do you know if the ports were just smartly cleaned up or really flowed on the bench. You would definitely know if you remember the bill. I am still thinking you can get to your level with smartly cleaned up ports. 92hp on that same dyno is going to take some real flow bench time in my experience.

Simplex timing chain?

Late model clutch?
Yep, simplex chain, late model clutch with K75 pressure plate ( you can't get free play with that set up, but it can take the power).

The ports had a full flow job.

And yes the higher horsepower reading was on a Dynojet inertial dyno. The operator of the DynoDynamics one ( that gave the lower reading) said his dyno reads 10-12% lower than a Dynojet one.
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Old 02-13-2011, 05:31 PM   #68
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pj, Jim has previously said that the 170main jet is the only change needed when using the mufflers he designed. Do you know if any a/f ratio data exists for this?

Cheers


..
Sorry. no idea.

John
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Old 02-13-2011, 05:46 PM   #69
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Yep, simplex chain, late model clutch with K75 pressure plate ( you can't get free play with that set up, but it can take the power).

The ports had a full flow job.

And yes the higher horsepower reading was on a Dynojet inertial dyno. The operator of the DynoDynamics one ( that gave the lower reading) said his dyno reads 10-12% lower than a Dynojet one.
That dyno doesn't read low, Dynogets read high. To start with, technically speaking inertia dyno's are not really even dyno's. Real dyno's don't HAVE to have a computer!

Man IF I ever have a real airhead rod, I am going to have some heads flowed and some long rods! I am out of the loop flow wise here in the states. Branch doesn't do them any more and Kenny Axtell has retired.

Do you know if Cray raised your port floors? Intake only? Intake and exhaust?
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Old 02-13-2011, 05:53 PM   #70
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Do you know if Cray raised your port floors? Intake only? Intake and exhaust?
No he didn't. At least, there's no liquid metal type stuff in there. I know he's done that on some heads, but he said he didn't need to with mine. I think there's a difference in port shape between some years and models. Some need it, some don't ( as far as I know).
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Old 02-13-2011, 06:07 PM   #71
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The exhaust takes welding. After you weld on them that much, both sides need to be trued. You've got to watch your rocker arm deck height and/or your push rod length or your rocker arm geometry will be screwed up.

What model head do you have?

The '88 on small ports have raised ports from the factory but they are not raised NEAR as much as I have seen Branch and Axtell raise them. So far, every airhead race engine that I have seen making more than just a little more power than yours had seriously raised port floors. Some just the intake with epoxy and some with welded up exhaust ports. Wrecking Ball has re-angled exhaust ports somewhat like a RS54. Early on Axtell straightened the intakes somewhat like a RS54 but later on he said that he figured it made virtually no difference if you got your focus right in the port bowl area which is really what raising the floor is ALL about.
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Old 02-14-2011, 12:43 PM   #72
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Jim Cray does a great job tuning airheads, I wouldn't go anywhere else.
I've ridden a couple of bikes with Jim Cray engines both felt really tight and just right.

Been talking to Richie Moore again tonight, I'll be investing in his +18% kit in the next couple of weeks along with a replacement camshaft.
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Old 02-14-2011, 01:18 PM   #73
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I've ridden a couple of bikes with Jim Cray engines both felt really tight and just right.

Been talking to Richie Moore again tonight, I'll be investing in his +18% kit in the next couple of weeks along with a replacement camshaft.
I'm biased of course. Jim's been a friend of mine for many years. I spoke to him last week and he was quite complimentary about Richie.
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Old 02-14-2011, 01:20 PM   #74
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What model head do you have?
I'm afraid I don't know. Jim used whatever he thought was best. Since they don't have any liquid metal in them, I'm guessing they must be quite late otherwise he wouldn't have been able to get a decent port shape.
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Old 02-14-2011, 02:24 PM   #75
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I'm afraid I don't know. Jim used whatever he thought was best. Since they don't have any liquid metal in them, I'm guessing they must be quite late otherwise he wouldn't have been able to get a decent port shape.
Don't get me wrong, you can get them flowing pretty well without them but raised floor heads can be magical. From comparing ports on Wrecking Ball, Junkyard Dog, and a few others that I have worked on to BMW raised ports, BMW didn't raise them NEAR enough. I bet it doesn't hurt but BMW's effort is half assed from what I can tell.

I think raised port floors have their roots in oval intake ports. Back in the early 30's Art Sparks and a Aerodynamicist professor from Stanford came up with oval ports for Spark's Offenhausers. I think Stanford had THE first flow bench and that guy made it. Offenhauser himself made them standard from then on. Then in the early 60's I think Smokey Yunick started raising them as we know it today with great results. MANY a production engine or even production aftermarket heads come stock with raised port floors now. It works! The problem with raising the floors in our heads is that it is a LOT of work!

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