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Twiggy - Long Rod Aluminum Block Engine Build-up
https://www.slantsix.org/forum/viewtopic.php?t=23948		 Page 5 of 25
Author:  dakight [ Tue Jul 24, 2007 5:27 pm ]
Post subject: 
I've thought about that issue some. As I understand it, the problem is with excessive back pressure in the oil pump putting too much stress on the gear drive. If the rear cam journal is grooved that will relieve some of the pressure. Also, you can calibrate the relief valve in the oil pump so that it doesn't get excessive. With all that you might be able to use the aftermarket pump with a slightly thicker impeller to deliver higher volume. With the head tilted you're less likely to flood the valve stems so that shouldn't be too much of a problem.
Author:  sick6 [ Thu Jul 26, 2007 2:22 pm ]
Post subject: 
this is a tangent, but:

if doc wants a real light engine, maybe he could try a head like heckshemi made, he said it only weighs 28 pounds:

http://slantsix.org/forum/viewtopic.php?t=24190

that would be incredibly cool on twiggy.
Author:  Doctor Dodge [ Thu Jul 26, 2007 9:34 pm ]
Post subject: 
I have a light weight head ready to go for Twiggy. 8) :wink:

So.... nobody "bit" when I said I could get this engine under 350 lbs. Do you think I can get it under 300 lbs?
DD
Author:  emsvitil [ Thu Jul 26, 2007 9:54 pm ]
Post subject: 
Quote:
I have a light weight head ready to go for Twiggy. 8) :wink:

So.... nobody "bit" when I said I could get this engine under 350 lbs. Do you think I can get it under 300 lbs?
DD

You drilled a bunch of holes in the head to lighten it................


:twisted:
Author:  Joshie225 [ Fri Jul 27, 2007 12:45 am ]
Post subject: 
I have a feeling Doug will have more 'factory' aluminum parts making up this engine than ever saw the production line. Most of the rest of us are stuck with anvils.
Author:  GTS225 [ Fri Jul 27, 2007 3:25 am ]
Post subject: 
C'mon, guys! Are your collective memories that short? Don't you rememeber that pic awhile back of Doug posing with one of the very few pre-production AL heads in his grubby mitts?

Oh, yeah....it'll be a lightweight.
Block, head, water pump, oil pump, mini starter, intake, tube headers to save weight.
Hmmmmm....Gun-drilled crank and cam? :lol:

Roger
Author:  sick6 [ Fri Jul 27, 2007 4:59 am ]
Post subject: 
Quote:
I have a light weight head ready to go for Twiggy. 8) :wink:
Quote:
C'mon, guys! Are your collective memories that short? Don't you rememeber that pic awhile back of Doug posing with one of the very few pre-production AL heads in his grubby mitts?
OOooooooooooooooooo! :D
Author:  DionR [ Fri Jul 27, 2007 11:36 am ]
Post subject: 
Rumor had it that someone has been working on a reproducible aluminum head for some time now.

My bet is that we are going to see one come into the light real soon.

Oh, and I missed the part where you said you were going to have it below 350 pounds. At the same time, I'm not even sure what the weight of an all iron one is.
Author:  440_Magnum [ Fri Jul 27, 2007 12:24 pm ]
Post subject: 
Quote:
Quote:
I have a light weight head ready to go for Twiggy. 8) :wink:

So.... nobody "bit" when I said I could get this engine under 350 lbs. Do you think I can get it under 300 lbs?
DD

You drilled a bunch of holes in the head to lighten it................


:twisted:

And he acid-dipped the block and is using plexiglass freeze-plugs :wink:
Author:  slantzilla [ Fri Jul 27, 2007 4:48 pm ]
Post subject: 
Quote:
Quote:
I have a light weight head ready to go for Twiggy. 8) :wink:
Quote:
C'mon, guys! Are your collective memories that short? Don't you rememeber that pic awhile back of Doug posing with one of the very few pre-production AL heads in his grubby mitts?
OOooooooooooooooooo! :D
Doug has already had more than one all aluminum motor together and running. :lol:
Author:  Doc [ Sat Jul 28, 2007 11:12 am ]
Post subject:  Piston Prep
I am using the "large dish" Silvolite 2.2 Turbo pistons in Twiggy. These pistons come with shorter / lighter pins that can be set-up as full floating.

With all SL6 pistons, pay close attention on how the wrist pin (piston pin) is oiled. I have seen a lot of galled-up piston pin surfaces in SL6 engines, I think the splash oil has a hard time getting all the way up into that area with the long stroke, small bore, tall block SL6.

Most pistons do have a small hole or a groove that splashed oil is suppost to get into. Some SL6 pistons don't have any means to get oil into the pin to piston running surfaces, I guess the manufacturer figures that hot oil will find it's way into the .001 to .002 worth of pin clearance. (not a good idea)

The best thing to do is put lot's of oil where you want it so I drill the pistons to take oil collected in the oil ring groove and force it into the pin journals. I drill a 'blind hole" from the ring groove, then drill a second hole from the pin journal area to intersect it.

Image

Image

I have seen some after-market pistons were a single angled hole is drilled between these two points but I have never had much luck doing that with a hand drill.

Be sure to deburr the holes carefully and check your work with the pin.
Also deburr the rest of the piston, blow-off the chips and you are now ready to check the weights on all the pistons.
DD
Author:  AndyZ [ Sat Jul 28, 2007 6:05 pm ]
Post subject: 
That oil ring land is scary small down there.
Author:  SlantSixDan [ Sat Jul 28, 2007 6:15 pm ]
Post subject: 
Doc, have you (or has anyone else) looked at moving the ring stack closer to the piston deck? Smokey Yunick did a great deal of destructive dyno testing with Chev small and big V8s, trying to find the upper limit above which the top ring land was too thin to support the ring load reliably; I'll have to look it up, but I believe in his high-power V8s he found the very beginning of top land softening at 0.10, so he backed off to 0.15, beat the snot out of the engines on the dyno, never got the top land to soften or fold up, and measured a 15% reduction in unburnt hydrocarbons in the exhaust -- which means fuel that was previously getting trapped and remaining unburnt between the side of the piston and the cylinder wall was instead doing useful work. It also allowed the piston to be shortened a little at the bottom, and (tying this back into the slant-6) would leave more room for pin oil holes and such. Of course, this would mean getting semi-custom pistons...
Author:  argentina-slantsixer [ Sun Jul 29, 2007 9:13 am ]
Post subject: 
Quote:
Doc, have you (or has anyone else) looked at moving the ring stack closer to the piston deck? Smokey Yunick did a great deal of destructive dyno testing with Chev small and big V8s, trying to find the upper limit above which the top ring land was too thin to support the ring load reliably; I'll have to look it up, but I believe in his high-power V8s he found the very beginning of top land softening at 0.10, so he backed off to 0.15, beat the snot out of the engines on the dyno, never got the top land to soften or fold up, and measured a 15% reduction in unburnt hydrocarbons in the exhaust -- which means fuel that was previously getting trapped and remaining unburnt between the side of the piston and the cylinder wall was instead doing useful work. It also allowed the piston to be shortened a little at the bottom, and (tying this back into the slant-6) would leave more room for pin oil holes and such. Of course, this would mean getting semi-custom pistons...
if you can move the uppermost comp ring .150 from the crown you can not only fashion some pretty neat pistons but you can also use longer, much longer than 198 con rods... I'm liking this...
Author:  Doctor Dodge [ Sun Jul 29, 2007 9:04 pm ]
Post subject:  Ring Groove Locations...
Remember, there is a large, deep dish in the Silvolite H1291 piston. (2.2 Turbo - hypereutectic piston)
Because of the dish, the rings need to be located further down the piston head (deck) so they can transfer heat and don't break the ring lands.

There are 2 KB (Keith Black) versions of this piston and those have the ring grooves up higher. One of those KB pistons is a flat top and the other has a dish. I have seen the ring lands break on these pistons so I get worried when the top ring groove gets to close to the piston deck.
DD

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