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Head Flow Improvement Project
https://slantsix.org/forum/viewtopic.php?t=33857		 Page 1 of 2
Author:  wjajr [ Thu Feb 19, 2009 12:08 pm ]
Post subject:  Head Flow Improvement Project
Well I got the head pulled this afternoon.

Here is what I got:
Image

Some cylinders were burning better than others


Image

Still hone marks showing, top of piston has 30 stamped into it, thin carbon deposit around top of bore, and no ridge.

Now a few questions.
Some coolant managed to get dumped into bores # 5 & 6 which I sucked out with a vacuum, than turned engine over several times alternating wiping with a cloth until no trace could be seen. Should I spray some WD 40 on the walls to dry it out better?

Dose the #30 on pistons indicate 30 over? The bore mesured 3.41" with the carbon deposit in place.

What is a good method of cleaning the carbon off of the pistons, and top of bore? Scotch pads & drill motor?

Where is a good source for new manifold studs & nuts. A few threaded out of the head, rather than the nut, and several are rather rusted. Who ever installed them used some kind of goop rather than Locktite.
Author:  emsvitil [ Thu Feb 19, 2009 3:54 pm ]
Post subject: 
At 3.41, 30 sounds more like 0.30 mm bigger......
Author:  Joshie225 [ Thu Feb 19, 2009 4:45 pm ]
Post subject: 
Yes "30" is +.030" for a total of 3.430".

Time to CC the head and measure the deck height so we can calculate the compression ratio.

I would spray WD40 on all the cylinders. You can remove carbon if it's not heavy with carb cleaner on a rag. With heavy buildup a razor scraper works well if you're careful.
Author:  wjajr [ Thu Feb 19, 2009 6:49 pm ]
Post subject: 
Josh:
Quote:
Time to CC the head and measure the deck height so we can calculate the compression ratio
.

Here is what I have using the Plexiglas & grease method with syringe filled with colored water:
1=55 cc
2=54 cc
3=56 cc
5=54 cc
6=56 cc
*********
330 cc


Top of piston to deck measured at # 5 & #2 with angled feeler gages: 0.153 inches. Or, 3.886 mm. This is +/- a few thousandths by feel.

I will be using a Feel-Pro head gasket.

There is one vertical scratch in #5 just deep enough to catch a finger nail, less than the thickness of copy paper say .001" deep.
Author:  Joshie225 [ Thu Feb 19, 2009 8:12 pm ]
Post subject: 
8.41:1 with a 55cc chamber, flat top piston, .039" thick gasket with 3.50" bore, 3.430" cylinders, piston .153" down the hole and 4.125" stroke.

http://kb-silvolite.com/calc.php?action=comp

A 48cc combustion chamber would get you 9.08:1 with everything else the same. At .0066" per cc of chamber volume that's .046" off the head or block. Since you said this engine has a performance cam I'd certainly raise the compression ratio. I'd be tempted to go 9.5:1 and a 44cc chamber would get you there. That would require .073" off the head or block.
Author:  wjajr [ Fri Feb 20, 2009 6:02 am ]
Post subject: 
Thanks for the calulation Josh.
Quote:
9.5:1 and a 44cc chamber would get you there. That would require .073" off the head or block
Would the octane requirement for 9.5:1 be 87 or 89?

Using a higher octane gas is not a problem, would 10:1 be too much for this old girl, or would that turn her into a pinging magpie?
Author:  sandy in BC [ Fri Feb 20, 2009 6:23 am ]
Post subject: 
You cant know your octane requirement till you drive it. If you want to guess now you need to know your Dynamic compression ratio.....that requires your CR and cam specs .

I run 87 with 9.5 CR....but I planned it that way. My DCR is 7.48
Author:  Joshie225 [ Fri Feb 20, 2009 7:47 am ]
Post subject: 
As Sandy posted, we need to know about your cam to make an educated guess as to the fuel you'll need to run with a given static compression ratio. We need the intake valve closing point.
Author:  wjajr [ Fri Feb 20, 2009 7:50 am ]
Post subject: 
I don't know the camshaft specs, so I'll wing it I guess, no big deal. This is a non useful mode of transportation in my livery, more of a play toy involving wrenches, not lots of miles. So out of the six tanks of gas a year I use, an extra few bucks for "Gas with Guts"* won't kill me...

* Those of you driving during the seventies on the east coast perhaps remember Getty Gasoline's motto.
Author:  Dart270 [ Fri Feb 20, 2009 7:59 am ]
Post subject: 
I say take 0.060" off the head. I usually do NOT remove carbon, since some can drop between piston and cyl and score the cyl.

Before I put my heads back on, I run the pistons up and down, vacuum each cylinder, wipe the cylinders clean with a clean rag, then repeat several times running the pistons up and down their stroke to leave more crap on the walls.

Lou
Author:  wjajr [ Tue Mar 03, 2009 11:09 am ]
Post subject: 
Josh,

I ran the compression calculator & got a different ratio than you did; 12.597. You got 8.41, did I miss something?

ENTER YOUR DATA CALCULATED DATA
Cylinder Head Volume; 55 cc
Piston Head Volume; 23.54 cc
Gasket Thickness; 0.039 in
Gasket Bore; 4.509 in
Cylinder Bore Diameter; 4.50 in
Deck Clearance; 0.153 in.
Stroke; 4.125in.

STATIC COMPRESSION RATIO 12.597

PI*rxr*depth = 3.14*1.75*1.75*0.153=1.47 cu in
1.47 cu in * 16 = 23.54cc
Author:  Aggressive Ted [ Tue Mar 03, 2009 11:24 am ]
Post subject: 
I have had no problems with 87 or 89 octane fuel @ 9.5 compression ratio.
Author:  Shaker223 [ Tue Mar 03, 2009 11:30 am ]
Post subject: 
Quote:
Josh,

Cylinder Bore Diameter; 4.50 in
Huge bore for a slant!! :D
Author:  Joshie225 [ Tue Mar 03, 2009 11:46 am ]
Post subject: 
The bore is 3.430", stroke is 4.125", piston head volume is 0cc for flat tops. The other values appear reasonable. Try again with the corrected values and see what you come up with.
Author:  wjajr [ Tue Mar 03, 2009 11:54 am ]
Post subject: 
Quote:
Huge bore for a slant!!
Yeah, new meaning to "bored-out"... This is an "Elasto casting" block, new technology.

With correct bore dimensions compression calculates to 6.977.

This has not been a good numbers day for me, too much sleep last night...
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