Author Topic: Bill's JMR Billet Big Block 72mm JE 12.5 to 1 Engine Build (Read 31153 times)

Bill/BentON Racing · « **Reply #50 on:** March 18, 2017, 07:02:44 PM »

Well, I prolly cut down the cherry tree and lots more! But I think they measure 73...mines bigger Frank!

LMAO, hehe. Trying to make next Saturday......stars gotta line up! Bill

kmb69 · « **Reply #51 on:** March 18, 2017, 07:10:22 PM »

Quote from: Bill/BentON Racing on March 18, 2017, 06:58:55 PM

Captain, looks like there may be room on the upper case, depending on hole size. You drill just one hole or more? Size? PM me is fine, thanks, Bill

This is a picture of Brent's DOHC "Magic Windows" from Facebook.
They are pretty big! Not sure if this is the right way on a SOHC.
We're already getting case "flex" when the power comes up.
Those "donut" DOHC cases have a lot of ribbing cast under the base surface.

Bill/BentON Racing · « **Reply #52 on:** March 18, 2017, 07:35:27 PM »

Damn they are windows

Sent from my SM-G925V using Tapatalk

gschuld · « **Reply #53 on:** March 18, 2017, 07:52:04 PM »

Quote from: Captain on March 16, 2017, 11:43:03 PM

Bill, have you ever considered putting "magic windows" in ? I assume you know what I am talking about ? If not then you need to know that it helps greatly with reducing pumping losses between adjacent cylinders (1&2, 3&4) and calms down any crankcase breather issues. Breathers should be all taken back to the oil tank anyway.
I did this to my engine in the mid 70's and proved its effectiveness then. I still do it to this day in any 78-83 DOHC engine I build.
There are no down side to this mod if you are wondering, only positives.

Captain

I'm not sure I am following fully with the cranking losses with the magic windows, but I'll take your word for it. Wow, those are some serious cutouts....any structural concerns to be worried about with this? Not exactly a straight forward basic milling operation either...

George

Bill/BentON Racing · « **Reply #54 on:** March 18, 2017, 07:57:12 PM »

Oh hell yes. Like Keith said, gotta worry about weakening the cases especially around the main bearings, Worry about crank flex. But I like the idea, going look closer at a set of cases soon.

Bill/BentON Racing · « **Reply #55 on:** March 18, 2017, 11:22:48 PM »

.020 Cometic, when going big, the opened up one works better. Getting there.

Captain · « **Reply #56 on:** March 19, 2017, 12:48:53 AM »

There is no problem in doing the "Magic Windows" mod in the SOHC or DOHC. I first did all this on the SOHC, learnt the benefits, grew them bigger and have carried this through to the DOHC I do today. The windows have no effect on the mains as they are well above them as all engine load into the mains is directly downward. In the SOHC engine you actually have the benefit of 2 cylinder studs between 1 & 2 and the same between 3 & 4 unlike the DOHC which has 1 shared between the cylinders. The advantage for the SOHC is that these studs are smaller and further away from any window machined into the cases and so this makes them stronger in this area than the DOHC. Also the SOHC actually has ribbing on the underside of the cylinder penetrations but you may not recognise them as such....... These are the "curtains" at the front that direct the returning oil downward in front of the crank and it's rotation. These also form a version of a support truss at least on the front side.
Now that I have explained the practicality of this mod you also need to see how this window remains open once the cylinder block is installed (Refer picture)
Why is this done ? In a 180 crank 4 cylinder engine the cylinders are "paired" (1 & 4 up and 2 & 3 down). That means that adjacent cylinders are traveling in opposite directions (one is traveling up whilst the other is travelling down) When this is happening it is displacing air "below" the pistons and this air is trying to travel back and forth between these two cylinders. The reality is that it is inhibited by the main bearing bulkhead that only has small opening and none are anywhere near the cylinder and so you get pressure rises and pulses that rob energy and HP. There are no down sides to allowing direct access to each cylinder flow back and forth far more easily...........None.

Captain

gschuld · « **Reply #57 on:** March 19, 2017, 03:58:44 AM »

Captain,

Very interesting, thank you for the more detailed explanation.

George

PeWe · « **Reply #58 on:** March 19, 2017, 05:18:18 AM »

Ok, I had a feeling that it was not that bad

I had ideas about additional case breathing to alternator side, plus between 1-2, 3-4
Went thru rather early when grinding with hand held drilling machine with RCS base gasket as guide.

Bill/BentON Racing · « **Reply #59 on:** March 19, 2017, 05:31:29 AM »

Captain, thanks, I like your way, no drilling, just machining, K.

gschuld · « **Reply #60 on:** March 19, 2017, 06:52:43 AM »

I'd be interested to hear what equipment was used to mill that out and the process in general. That certainly wasn't done on a 60yr old J-head Bridgeport

George

bwaller · « **Reply #61 on:** March 19, 2017, 07:16:49 AM »

I've read about this before and certainly trying to eliminate losses by pumping air back n forth is logical. The next step is venting/eliminating any positive pressure in the cases. How do you manage this Captain?

As an aside the 500's are better vented between pairings (I enlarged the windows, rounded & polished) I use a "reed valve" crankcase vent with the intention of creating slight crankcase vacuum. I don't think it would be large enough for a 750 & up. (1/2"ID in & out)

MRieck · « **Reply #62 on:** March 19, 2017, 08:33:29 AM »

The 2nd generation Hayabusa has large cut outs on the spigots. Been some problems with them but generally under hard conditions and increased bore size. they are all aluminum too. https://www.google.com/search?q=2nd+generation+hayabusa+block&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjM0OHk8eLSAhVVzWMKHU2dBIEQsAQINA&biw=1920&bih=871#imgrc=As1taopquLBcfM:

Bill/BentON Racing · « **Reply #63 on:** March 19, 2017, 10:52:08 AM »

Well, I say next time, trying to race Saturday....

MRieck · « **Reply #64 on:** March 19, 2017, 11:05:54 AM »

What's the sleeve wall thickness on those Bill? .070 or so?

dragracer · « **Reply #65 on:** March 19, 2017, 12:55:41 PM »

I thought you would have gotten purple rain finished. Seemed like an easier fix to me.

Wishing you success in getting it done soon.

dragracer · « **Reply #66 on:** March 19, 2017, 02:40:33 PM »

Quote from: Bill/BentON Racing on March 18, 2017, 07:02:44 PM

Well, I prolly cut down the cherry tree and lots more! But I think they measure 73...mines bigger Frank! LMAO, hehe. Trying to make next Saturday......stars gotta line up! Bill

That funny Bill. But you know what they say, its not the size that matters as much as how you use it. Lol. I will will probably be forced to bore mine to 73mm this time. The bore has been worn for a while. Fresh rings regularly has prolonged the inevitable overbore. I've been saving those new 73mm Arias pistons for years now in anticipation of having to replace the heavier 72mm MTC pistons. Both sets are for a K model so I never had maximum compression with my F3 head. The ideal thing would be to have a custom set of 73mn F model pistons made to completely fill the combustion chamber and have at least 12.5-1 compression. Then I might be as fast as you are Bill 😁

Bill/BentON Racing · « **Reply #67 on:** March 19, 2017, 08:04:20 PM »

Now that's funny! I'm so far behind you...Purple Rain only a 915 or was...I'm addicted to 1000cc plus rt now! Lol.So busy with work, I don't know and BabyFace tore his rt rear ACL.... $3500.00 surgery, oh well he's my buddy but gotta pay for that....I'm still blessed and know it. Lot going on rt now!

dragracer · « **Reply #68 on:** March 19, 2017, 11:56:55 PM »

Wow, the value we put on our fury companions. And i thought the $600 I'm into with my 4 legged friend on heartworm treatment was stout. I don't feel so bad right now. Hopefully your canine buddy will recover fully.

Ahh, so you're now addicted to the feeling of real horsepower. I can appreciate where you're coming from to an extent. I guess I try to keep myself grounded in the reality that we're only running the Street ET class where having a low dial doesn't have a bearing on the win light- its dependent on low reaction times and dead on consistency.

I'll be watching your tail lights this year my friend. Enjoy the ride. Hopefully you'll be ready for Commerce. We've got our first 5.60 index points race at a local track Saturday so we probably won't make this one.

turboguzzi · « **Reply #69 on:** March 20, 2017, 10:11:22 AM »

Quote from: MRieck on March 19, 2017, 08:33:29 AM

The 2nd generation Hayabusa has large cut outs on the spigots. Been some problems with them but generally under hard conditions and increased bore size. they are all aluminum too. https://www.google.com/search?q=2nd+generation+hayabusa+block&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjM0OHk8eLSAhVVzWMKHU2dBIEQsAQINA&biw=1920&bih=871#imgrc=As1taopquLBcfM:

not only hayabusas mike, suzuki has implemented between cyls passages also in the smaller GSXR's for at least 10 years

PeWe · « **Reply #70 on:** March 20, 2017, 01:42:58 PM »

How much power is gained by the windows? When cyl 1,4 go down the overpressure under the pistons will transfer to the 2,3 and push them upwards instead of building up a counter pressure obstructing the downforce of piston 1,4, right?
Same when 2,3 go downwards....

Any difference measured on dyno?

turboguzzi · « **Reply #71 on:** March 20, 2017, 02:42:09 PM »

suzuki says:
"This system reduces the distance air must travel to equalize lower-cylinder pressure, and it’s especially effective in reducing internal crankcase pumping pressure, windage, and associated mechanical power losses. Its incorporation yields an increase of approximately 2% in torque at high engine rpm"

Captain · « **Reply #72 on:** March 20, 2017, 03:26:20 PM »

Just so you can have some confidence in this modification to the SOHC. I first did this back in the early 80's (long before any of the factories) and have never experienced "any" failures or breakages directly due to this mod.
It is solid, proven and as long as you stay away from any cylinder stud or main bolt at least 12 mm you will have no problems.

Captain

Bill/BentON Racing · « **Reply #73 on:** March 20, 2017, 06:26:02 PM »

Captain, thanks, appreciate it, Bill

Bill/BentON Racing · « **Reply #74 on:** March 23, 2017, 07:18:05 AM »

Frank, I feel your pain! This no good, needs to have a chamfer like this! Goodson was out of standard chamfering cone. But I found one, be here tomorrow. I did try, but gave up, thin rail rings ain't going in without a chamfer! Lol, Bill

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Author Topic: Bill's JMR Billet Big Block 72mm JE 12.5 to 1 Engine Build (Read 31153 times)