Author Topic: Build thread for my 865  (Read 8744 times)

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Gremlinsteve

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Reply #30 on: September 09, 2020, 10:37:52 pm
Pics


Gremlinsteve

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Reply #31 on: September 11, 2020, 09:29:41 pm
Exhaust work


ace.cafe

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Reply #32 on: September 11, 2020, 11:15:26 pm
Exhaust work
They look like they should flow real well.
Do you have a target for intake vs exhaust flow percentage in mind?
The Bullet singles seem to like exhaust flow bench figures about 80-85% of intake flow in their crossflow hemi config.
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Gremlinsteve

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Reply #33 on: September 11, 2020, 11:36:52 pm
Exhaust flow


Gremlinsteve

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Reply #34 on: September 11, 2020, 11:45:28 pm
Some pics of an exhaust valve


Gremlinsteve

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Reply #35 on: September 11, 2020, 11:46:16 pm
Pics


ace.cafe

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Reply #36 on: September 11, 2020, 11:51:13 pm
Exhaust flow

Real good ! Picked up flow everywhere. Exhaust averages about 90% of intake.

Port looks nice.
I didn't know that they used a D port in this head.
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Gremlinsteve

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Reply #37 on: September 12, 2020, 12:11:05 am
Yes they d ported the head
The exhaust moves air

Flow work is still using the stock port exit diameter too. It wasn’t enlarged


ace.cafe

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Reply #38 on: September 12, 2020, 01:17:12 am
Yes they d ported the head
The exhaust moves air

Flow work is still using the stock port exit diameter too. It wasn’t enlarged
That's very good. Should bode well for high torque.
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Gremlinsteve

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Reply #39 on: September 12, 2020, 02:30:14 am
I can’t post video
But I have video of the whistle she’s making on the flow bench

Shows that the velocity is great


ace.cafe

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Reply #40 on: September 12, 2020, 05:25:54 am
I have been doing some rough calculations in my head.
I think you are just about right for flow at your 865cc displacement. Wouldn't hurt to get a few cfm more, but it should just about do.

Where I think this build will bottleneck is at the cam. I think that S&S cam is too short duration to get 7000 rpm out of 865cc. I would add 15 degrees to both ends of the intake duration to get a full rev range on this build. In other words, I think open@ 15°BTDC and close at least @45°ABDC(maybe even 50) at the .050" lift points will be needed to get the rev range up where the 7000 rpm redline is intended.

I think the S&S cam is a torquey type cam, not a real revvy cam, judging by the duration.

Our 500 flows more and has longer duration, and we peak at 6000 rpm, and hold to 6500 with 254° duration @.050".

Since not much other cam selection is available, I guess we'll see how it does with that cam.

You might also try raising the port roof a bit to get some more cross-sectional area because that small port is probably going to run into a high velocity issue early in the rev range with that ~30%displacement increase, and the cam has insufficient duration to add the flow back at the closing end.
« Last Edit: September 12, 2020, 05:44:10 am by ace.cafe »
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Gremlinsteve

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Reply #41 on: September 12, 2020, 05:37:48 am
I’d concur
I also don’t like the mild 353 lift

I think this head might touch 200 intake but it’s useless because I can’t swing the valve open that far using this cam

I’ve made roughly 25/30 hits on the bench

What I find interesting is unshrouding the chamber did not help at all on the intake flow


ace.cafe

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Reply #42 on: September 12, 2020, 05:47:19 am
I’d concur
I also don’t like the mild 353 lift

I think this head might touch 200 intake but it’s useless because I can’t swing the valve open that far using this cam

I’ve made roughly 25/30 hits on the bench

What I find interesting is unshrouding the chamber did not help at all on the intake flow
Then the short turn is tight, and flow is unsupported by the chamber wall. It is mostly going to flow out the long side for tumble anyway, so I wouldn't worry too much.

I would do a velocity test. I have a feeling cross-sectional area will need to go up a bit for 865cc.  I would do it on the roof for a slightly raised port.
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Gremlinsteve

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Reply #43 on: September 12, 2020, 06:15:47 am
Short turn is tight at .770


ace.cafe

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Reply #44 on: September 12, 2020, 07:05:18 am
I’d concur
I also don’t like the mild 353 lift

I think this head might touch 200 intake but it’s useless because I can’t swing the valve open that far using this cam

I’ve made roughly 25/30 hits on the bench

What I find interesting is unshrouding the chamber did not help at all on the intake flow
I notice flow flattens at .350" lift mostly anyways. I see this with most Enfields. The port flattens the flow at higher lifts. All the Bullets are also like that.

After your porting, the flow goes a little more up at .400" which is a benefit, but the cam can't use it.

Our experience shows these ports can benefit from raised roof. And with a port entry size 1.125" x 1.060" with a 432.5cc cylinder volume 33% larger than stock, the port is going to have to flow a lot more air thru that relatively small size which means velocity will be high. As rpms increase, it is probably going to start choking well before you get to redline and that will affect cylinder filling.. Normally, this can be somewhat made up by later intake valve closing, but we don't have that with this cam.
So, I recommend checking velocity, keep it under 400, and it will probably need more cross-sectional area in the port and intake tract. I think it will need to be equivalent to 1.125" round area, at least. When we did the 700(stroked to 750)Super Meteor twin heads, we used 32mm(1.25") ports and carbs.
I don't like to make it too big or it loses lower rpm torque, but it does need to be enough.
Our best results came from raising the roof.
Check it for yourself and see what you think it needs.
« Last Edit: September 12, 2020, 07:53:35 am by ace.cafe »
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