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Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top End
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theastronaut
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PostPosted: Sat Jun 27, 2015 9:50 am    Post subject: Reply with quote

I made a graph of the cam lift so I could see exactly where the cam was lifting the valves the fastest. After reading a bunch on rocker geometry I like the idea of having the rocker 90* to the valve at the point where the valve is being accelerated the fastest.

I came up with .271" lift on the opening ramp and .320" lift on the closing ramp. Total lift was .543" so .271" would be at half lift, but I'm thinking it would be better to set up the rockers using .320" lift on the exhaust ramp since it's more important to have the valve under control while its closing?

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modok
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PostPosted: Sat Jun 27, 2015 12:36 pm    Post subject: Reply with quote

Mid lift the valve is not accelerating, it is moving at a nearly constant speed.
The acceleration is at the top and bottom of your graph.
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Stripped66
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PostPosted: Sat Jun 27, 2015 12:48 pm    Post subject: Reply with quote

modok wrote:
Mid lift the valve is not accelerating, it is moving at a nearly constant speed.
The acceleration is at the top and bottom of your graph.


PV, eh?
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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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FreeBug
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PostPosted: Sat Jun 27, 2015 1:42 pm    Post subject: Reply with quote

What Modok said. The middle of the curve is where the valve is moving fastest (highest speed), between the acceleration at the bottom and the deceleration at the top (left side of curve).
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theastronaut
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PostPosted: Sat Jun 27, 2015 2:59 pm    Post subject: Reply with quote

I made a note of the amount of lift at every 5 degrees of crank rotation, that is the line on the graph. Then made another note of the difference in valve lift between each of those. The area with the most difference in lift per five degrees of crank rotation would be where the valve is accelerating the fastest, right?
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Last edited by theastronaut on Sat Jun 27, 2015 3:02 pm; edited 1 time in total
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Stripped66
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PostPosted: Sat Jun 27, 2015 3:00 pm    Post subject: Reply with quote

theastronaut wrote:
I made a note of the amount of lift at every 5 degrees of crank rotation. Then made another note of the difference in valve lift between each of those. The area with the most difference per five degrees of crank rotation would be where the valve is accelerating the fastest, right?


Velocity.
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66brm wrote:
Bodacious wrote:
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor.

I don't think electrickery works that way
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modok
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PostPosted: Sat Jun 27, 2015 3:21 pm    Post subject: Reply with quote

"lift per degree" is lift rate, or speed

Acceleration is change in speed.

Imagine that was a graph of you driving to the 7-11 and doing a U turn and coming back. degrees is time, lift is distance from your house.
halfway there the distance is varying linearly with time, so you don't appear to be making any changes in speed, so you'd feel no g-forces.
But certainly would feel some g-forces at the U turn, and appears you accelerated quick and coming back slammed on the brakes. probably typical VW driving behavior LOL
Best to not make any sudden accelerations near your house so add some lash ramps, but once a block away then.......yee haw
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PostPosted: Sun Jun 28, 2015 8:50 am    Post subject: Reply with quote

As others have noted the point on your graph where there is the greatest vertical difference between adjacent data points indicates the highest velocity, not the highest acceleration. It is equivalent to going a steady 75mph on the highway, you are going pretty fast, but not accelerating. Basically, on your graph the places where the line is relatively straight there is little acceleration, and the points where it is curved are where there is acceleration. The point where the curve is "tightest" is where maximum acceleration is occurring. Finding this point graphically would involve drawing lines tangent to the curve at each data point. Where the difference in the angle of two adjacent lines is greatest is where maximum acceleration is happening.
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theastronaut
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PostPosted: Tue Jul 07, 2015 6:28 pm    Post subject: Reply with quote

You guys are right, I'm being stupid again. Embarassed I even originally said "fastest" (meaning speed/velocity) in my first post about RG. Not sure were I got hung up on acceleration as my intent was finding the point where the valve was moving the fastest.

Anywho, the point where the valve is moving the fastest is also the point of half lift, so it wasn't a hard decision of where to set up the rocker 90* to the valve stem. I had to shorten and re-tap my adjustable pushrod since the motor is so narrow, and eventually came up with 10.480" pushrods to get the rocker 90* to the valve stem at half lift (or max velocity). You can see in the pictures that show the pushrod tubes just how compressed the PR tube springs are, it was fairly difficult to get them in place. The cylinder tin needed a good bit of trimming to fit as well. I ordered a set of Aircooled.net's HD aluminum pushrods and had a friend shorten them. He was able to keep them all within .003".

The long block is assembled and I will be picking the flywheel up tomorrow from having it surfaced. The AN lines came in today for the oil filter hoses. I also trimmed the sled tins, and made new industrial tins to fit around the AA Sidewinder header tubes. The visible part of the block is painted with black wrinkle paint, but I shot a light/dry coat of cast iron engine enamel over the last coat of wrinkle while it was still wet to give it a flat grey color. I'm going to add a breather box vented from the fuel pump block off and oil filler, and drain it back to the sump.

I still need to match port one of the intakes and go through the 36's to freshen them up. I'm hoping to have it in the car this weekend, then start hooking everything back up. I'm planning on getting it running with the 36's for now and eventually finding larger carbs to go on it, preferably 45 DRLA's.

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modok
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PostPosted: Tue Jul 07, 2015 6:58 pm    Post subject: Reply with quote

WHOA! I thought sweep the floor would look a bit rougher than that.
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theastronaut
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PostPosted: Wed Jul 08, 2015 5:54 am    Post subject: Reply with quote

modok wrote:
WHOA! I thought sweep the floor would look a bit rougher than that.


Well, I had most of it already other than the exhaust, heads, PR tubes, and pushrods. Had to buy new bearings, rings, etc of course. The tin is leftover, it looks better in pics than in person. So it's still mostly leftovers.
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PostPosted: Wed Jul 08, 2015 8:24 am    Post subject: Reply with quote

Some have very nice stuff lying on the floor. Laughing
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theastronaut
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PostPosted: Sun Jul 12, 2015 6:13 pm    Post subject: Reply with quote

I bought a set of 32mm venturis from CB Performance and just now have started disassembling the carbs to clean and reseal them. I hadn't really looked over the new vents until now; just noticed they aren't made anything like the original Dellorto vents.

The original vents are flat top and bottom to match up with both the throttle bore and auxiliary venturi. The CB vents have one rounded end, and one end that ends in a point- the ID is opened up all the way to the OD. Also, the smallest section of the CB vents is only ~3/16" wide and located all the way at one end. The smallest section of the original vents are about 3/4" wide and only barely off center.

They can be installed with the thick end at the bottom so they match up better with the auxiliary vent and throttle bore but that puts the smallest section of the venturi all the way at the bottom. That doesn't seem correct as I've always thought that the smallest section should be at the top, closest to the auxiliary venturi. The diagrams of carbs always show the narrowest section towards the top.


So, use these or find another set of vents that are made better?

I do have one near-NOS 48 tri jet. Could find another and use those instead. There's a single NOS tri-jet in the classifieds but its $600 bucks. Think


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modok
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PostPosted: Mon Jul 13, 2015 1:26 am    Post subject: Reply with quote

Sorry, the CB vents are machined wrong and also don't fit right at the bottom.
They are only suitable as raw material for re-machining to fit the 40 and 45mm dells.

I'd be best to get OE 32mm ones from Europe. Or 30mm and bore out to 32 or 33
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PostPosted: Tue Dec 15, 2015 4:16 pm    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

Bought a set of 45's and rebuilt them, added 36 venturis while I was in there. Starting out with 55 idles, 145 mains, and 180 airs.

The machine shop screwed up the flywheel- said the friction surface was off by .035" so they "corrected" it. Which didn't correct it, they threw it off .035". Which also threw it out of balance... Mad Mad Mad Sent it to a real machine shop and they are correcting, lightening, and balancing it.

Hoping to have a full week off for Christmas break so I'll have a chance to get the engine in the car.

Will the engine go in with the sidewinder header mounted, or should I wait until the engine is in to install it? Also, does anyone know roughly how much header wrap is needed to wrap a 1.5" sidewinder?


Link


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Strive for perfection in everything. Take the best that exist and make it better. If it doesn't exist, create it. Accept nothing nearly right or good enough."
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PostPosted: Tue Dec 15, 2015 4:29 pm    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

It may seem like a small thing to point out but when your scratching your head when the engine won't fire just be sure to check the distributor clamp stud and case surface has a clean surface to ground through. Otherwise this "Floor Sweep" Engine is getting carried away as we usually do here. Looks nice.
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PostPosted: Tue Dec 15, 2015 10:39 pm    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

That flywheel machine job - twice - might reduce pressure plate clamp pressure... resulting in s a slipping clutch
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theastronaut
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PostPosted: Wed Dec 16, 2015 8:07 am    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

yamaducci wrote:
It may seem like a small thing to point out but when your scratching your head when the engine won't fire just be sure to check the distributor clamp stud and case surface has a clean surface to ground through. Otherwise this "Floor Sweep" Engine is getting carried away as we usually do here. Looks nice.


Good catch, I'll make sure it's cleaned to bare metal. Had that problem with another painted engine a few years ago. Me getting carried away with something... ? Laughing


VWCOOL wrote:
That flywheel machine job - twice - might reduce pressure plate clamp pressure... resulting in s a slipping clutch


The depth from the pressure plate mounting surface to the friction surface is machined to .830" to make sure the pressure plate clamps properly.
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PostPosted: Thu Dec 17, 2015 3:01 pm    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

...excellent
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PostPosted: Sun Jan 03, 2016 1:25 pm    Post subject: Re: Re-Sweep the Floor 1679cc- Heads/Cam/Exhaust? More Top Reply with quote

Any updates? I have something very similar coming together. I can't wait to see how yours runs.
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