unshrouding valves, and polishing combustion chambers

yea it would be nice to come up with the cash to do some amazing build but ultimately as is so often the case the finances arent there. gotta work with what we got i guess...
 
http://www.secondchancegarage.com/public/585.cfm

http://www.hotrod.com/how-to/engine/0209hpp-engine-combustion-chamber/

https://www.hotrod.com/articles/0606em-understanding-compression-ratio/

head gaskets are rarely completely round, nore are combustion chambers
you,ll want to place a head gasket you,ll use on the heads and mark the area inside the opening as the only areas you can change,
(notice the gasket fire ring is NOT a perfect circle like many people assume)
ideally you,ll want to un-shroud the valves while opening up the combustion chamber volume, but not extend the combustion chamber past the front edge of the gasket fire ring as that usually causes gasket failure
before you spend a good deal of money porting and un-shrouding any iron cylinder heads, keep in mind aluminum heads are easily repaired in a skilled and experienced automotive machine shop thats equipped to do those repairs but damaged iron cylinder heads are either much harder to repair or good door stops
http://garage.grumpysperformance.com/index.php?threads/iron-vs-aluminum-heads.389/#post-7266

http://garage.grumpysperformance.com/index.php?threads/ccing-my-heads.14187/

http://garage.grumpysperformance.com/index.php?threads/iron-vs-aluminum-heads.389/#post-31684


http://garage.grumpysperformance.com/index.php?threads/tumble-and-swirl-quench-squish.4081/

http://garage.grumpysperformance.co...r-piston-dome-or-port-volume.2077/#post-60554

recessj.jpg

recessk.jpg

borenotch6.png





borenotch6.jpg

borenotch6.jpg

borenotch2.jpg

borenotch3a.jpg

borenotch7.jpg

gasketsh.png

http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html

https://www.musclecardiy.com/cylind...-valve-shrouding-improved-performance-part-9/

http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html

BlackoutSteve posted these pictures
What cylinder head?
With my 4.280" bore and AFR head, I am forced to use a 4.540" bore gasket because the chambers are wide and would otherwise allow the gasket to "hang" in the chamber.

For example..
428gaga.jpg

454gaga.jpg


laying a head gasket on the head and use machinist blue dye to show the areas inside the gasket fire-ring
8c3cd11a-b277-4018-b98a-b5648e0314be_1.74e42cf0e55dcba325d8cd403b5783b9.jpeg

http://www.skygeek.com/dymon-8000-s...MI8vPS24jm1gIVBolpCh2pnAoWEAQYAiABEgL2ZPD_BwE

thus the first logical step would be to carefully place a identical head gasket to what you'll use on the engine , properly lined up on the cylinder head and accurately scribe its inside dimensional limits on the cylinder head, a metal scribe , a dremel tool and machinist blue would be helpful here
keep in mind its one of several factors working together, things like getting the quench correct, polishing and un-shrouding the combustion chamber, getting the ignition advance curve and fuel/air ratio correctly matched and taking the time to polish the piston, dome, removing sharp edges from valve clearance notches , and polishing and very slightly rounding sharp edges on the valves, use of the correct spark plug heat range, removing exposed threads in the combustion chamber after you test by inserting a correct spark plug, certainly helps reduce any potential hot spots.
macbl.jpg

0209hpp_firech05_zoom.jpg

(a) Wedge chamber
(b) Hemispherical combustion
(c) Bowl in piston
(d) Bath tub

quenchd1.png


curtain-area.jpg

as valves lift of the valve seats, in the wedge head design they become far less shrouded by combustion chamber walls
a carefully contoured and smoothed port, and bowl area under the valve tends to flow better
http://www.enginebuildermag.com/Article ... _jobs.aspx
vortec_chamber11.jpg

a carefully blended and unshrouded combustion chamber also helps increase flow

pontiac combustion chamber design changes

0209hpp_fire03_zoom
0209hpp_fire04_zoom.jpg
0209hpp_fire06_zoom.jpg
0209hpp_fire07_zoom.jpg
0209hpp_fire08_zoom.jpg
0209hpp_fire09_zoom.jpg
0209hpp_fire10_zoom.jpg
0209hpp_fire11_zoom.jpg
0209hpp_fire12_zoom.jpg
0209hpp_fire13_zoom.jpg
0209hpp_fire15_zoom.jpg
0209hpp_fire16_zoom.jpg


edpont.jpg

http://ronspontiacpage.com/reference-pages/stockflowcharts.htm

http://www.wallaceracing.com/ultimatehead.htm

http://www.wallaceracing.com/ultimateflow.htm

http://www.sdperformance.com/listProducts.php?categoryID=5

http://garage.grumpysperformance.com/index.php?threads/aluminum-heads-polishing-and-porosity.14689/

http://www.edelbrock.com/automotive/mc/cylinder-heads/pontiac/performer.shtml

I recently ran across a couple posted photos of a guys BBC engine that was having issues burning oil,
if you look closely the pictures are rather useful in diagnosing the issues source.
if you look at the intake ports youll notice the lower 2/3rds show visual indications,
of oil flow contamination while the upper 1/3rd shows far less staining,
if the oil flow was coming from leaking valve guides , and spread through the runners during the valve over lap,
where the air flow may momentarily reverse direction in the plenum and runners at lower rpms, the oil stains,
would tend to be more uniformly spread, but the darker stains in the lower runners points more strongly,\
at the lower edge of the intake gasket that prevents oil from the lifter gallery are not fully sealing, it is very common if the heads have been milled
(ESPECIALLY ANGLE MILLED) or the person using the intake gasket used extra thick intake gasket oil seals.
this is one reason many guys prefer to dimple the under side of the intake manifold and block china wall mating surfaces,
and simply apply a bead of silicone gasket sealant to both adjacent mated surfaces then install the intake manifold,
with a thick intake gasket and a thin 1/8" bead of sealant around the ports and coolant passages

bbcrt1.jpg


notice the upper intake runner walls have far less oil stains, and the oil flow flowing over the hot intake valve back surface,
this un-wanted oil flow leak, rapidly forms a burnt ash coating,
that can and does reduce air flow and cylinder fill efficiency.

bbcrt2.jpg


I also have to point out the intake runners in the heads are not port matched to the intake gasket,
this, and not matching the matched intake runner exits to the intake gaskets,
is generally going to cost you a measurable loss in potential extra air flow at peak rpms

bbcrt3.jpg
 
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http://pautomotivemechanics.blogspot.com/2011/05/combustion-chambers.html

Combustion chambers


Combustion chambers
The combustion chamber is the space between the top of the piston and Cylinder-Head when the piston is on the top dead-center (TDC). This is where the air-fuel mixture is compressed and burnt. In Petrol engines most of the combustion chamber is formed in the Cylinder-Head, but head (top) of the piston can also be shaped.

In diesel engines, the Cylinder-Head is usually flat and the combustion chamber is formed in the piston head, although some diesel engines have a pre-combustion chamber in the Cylinder-Head.



§TDC is when the piston is at the top of its stroke and BDC is when it is at the bottom of its stroke.



Turbulence


Fig 2.4
The Cylinder-Head, valve ports and the combustion chambers of petrol engines are designed so of that the air-fuel mixture will be subjected to swirl, or turbulence. This movement occurs while the mixture is being taken into the cylinder (Figure 2.4) and also when it is being compressedin the combustion chamber.

Turbulence mixes the air and fuel and prevents fuel droplets from settling on the surfaces of the combustion chamber and Cylinder walls. The turbulence also helps to prevent local high pressure and high temperature areas during combustion, which could cause detonation.



Combustion chamber designs

For Petrol engines, there are three basic designs of combustion chambers, although there are variations. The names generally given to these three designs relate to their shapes, as shown in figure 2.5. These are:

1. Hemispherical

2. Bathtub

3. Wedge

As well as the combustion chamber formed in the Cylinder-Head, the top of the piston can be crowned or hollowed. In some cases the pistons have the depressions for the valves.



§These designs of combustion chambers do not apply to diesel engines, which have different Cylinder-Heads and different pistons.



Hemispherical combustion chamber


Hemispherical
In this design combustion chamber is approximately the shape of hemisphere. An intake valve is on one side of the combustion chamber and an exhaust valve is on the other. This provides a cross flow the air-fuel mixture enters the chamber on one side and combustion gases on the other. Because of this Cylinder heads of this design are also referred to as cross flow Cylinder-Heads. The position of the valves and ports to be used. Two intake and two exhaust valves are used on some engines. These arrangements assist the enginesbreathing.

This design is also referred to as a pent roof combustion chamber and is used in many passenger car-engines.

As soon as cross flow, hemispherical combustion chambers have an advantage because the spark plug is able to be located at the center of the chamber. Also with the spark located and the center, the flame travel distance is reduced and this provides rapid and effective combustion.

Burning of the fuel starts and the spark plug and travel rapidly outwards in all directions. This is known as flamepropagation. With this designed of combustion chamber of flame front of burning fuel has less distance, to travel than in some other designs.




Bathtub
Bathtub combustion chamber

This is the somewhat oval-shaped chamber in the cylinder head, with the valves side by side. The name has been derived from its shape, which has been likened to an inverted bathtub. The sparkplug is located on one side. This arrangement provides a short flame path from the spark-plug. The valves are usually vertical and the cylinder head and are in-line. A Relatively simple valve-operating mechanism is able to be used.

Turbulence in the combustion chamber is assisted by the shape of chamber and fact that it has a smaller cross section than the cylinder. This produces a squish effect when the air fuel mixture is compressed between the piston and the flat part of the cylinder head.



§Squish is the term used to describe the squeezing effect of the gases that increases their velocity and turbulence.




Wedge-shaped
The wedge shaped combustion chamber


In this design, the combustion chamber is shaped like a wedge, tapering away from the spark plug, which is located at the thick end of the wedge. The valves are inclined from the vertical, but all the valves are in-line.

Wedge shaped combustion chamber tend to have a smaller surface area than other designs and so have less area on which droplets of you can condense. This assists in reducing the amount of fuel that remains unburnt after combustion and so reduces the hydrocarbon emissions and the engine exhaust.
 
http://www.secondchancegarage.com/public/585.cfm

http://www.hotrod.com/how-to/engine/0209hpp-engine-combustion-chamber/

0209hpp_firech05_zoom.jpg

(a) Wedge chamber
(b) Hemispherical combustion
(c) Bowl in piston
(d) Bath tub



curtain-area.jpg

as valves lift of the valve seats, in the wedge head design they become far less shrouded by combustion chamber walls
a carefully contoured and smoothed port, and bowl area under the valve tends to flow better
http://www.enginebuildermag.com/Article ... _jobs.aspx
vortec_chamber11.jpg

a carefully blended and unshrouded combustion chamber also helps increase flow

pontiac combustion chamber design changes

0209hpp_fire03_zoom
0209hpp_fire04_zoom.jpg
0209hpp_fire06_zoom.jpg
0209hpp_fire07_zoom.jpg
0209hpp_fire08_zoom.jpg
0209hpp_fire09_zoom.jpg


The 1969-70 RAIV Head is known as A Spherical Wedge Combustion Chamber.
Its unique from all others Pontiac produced.
Just the 1969 RAV Had angled plug heads.






0209hpp_fire10_zoom.jpg
0209hpp_fire11_zoom.jpg
0209hpp_fire12_zoom.jpg
0209hpp_fire13_zoom.jpg
0209hpp_fire15_zoom.jpg
0209hpp_fire16_zoom.jpg

edpont.jpg


http://ronspontiacpage.com/reference-pages/stockflowcharts.htm

http://www.wallaceracing.com/ultimatehead.htm

http://www.wallaceracing.com/ultimateflow.htm

http://www.sdperformance.com/listProducts.php?categoryID=5

http://www.edelbrock.com/automotive/mc/cylinder-heads/pontiac/performer.shtml
 
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those arent detonation marks and thats not an "as cast" finish... that is intentional heavy texture experimented with by joe mondello and it was successful to the tune of 15 wheel horsepower on a 900 horsepower racecar everywhere else he tried it, it was good for 15-25 horsepower on the engine dyno... even in A-B-A testing where a good port was roughed out like this, it made more power, then smoothed with a 60 grit roll... the horsepower went down.

cfm and air speed were not measurably altered... the only observable difference to this textring of the intake runner and combustion chamber was on the dyno where the engine made more power... and the BSFC went down significantly.
 
There is Definitely Rocket Science in Combustion chambers Phil.
Much of it learned by trial and error.

I learned that on engine teardown to carefully examine the piston tops for Optimal carbon coverage outide of the Squish quench area.
Its really pronounced on a engine that has run on dedicated leaded race gasoline .

100% coverage desired with carbon leaded fuel.

Joe Mondello was a real smart guy.
 
Joe Mondello used a Needle Scaller Attachment in a common mechanics airhammer Phil.

We are looking at Vintage Oldsmobile V8 Technology used by Joe Mondello.
I recognize.

Pontiac V8 iron heads had fully machined smooth chambers.
 
I see a lot on valve unshrouding
On heads.
Is there and examples on blocks?
I'v seen time to time big blocks
With a notch cut into the cylinder
At about 3:00ish and 8:00ish
From a picture example on here
I'm under the impression the block can or should be notch?
 

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I see a lot on valve unshrouding
On heads.
Is there and examples on blocks?
I'v seen time to time big blocks
With a notch cut into the cylinder
At about 3:00ish and 8:00ish
From a picture example on here
I'm under the impression the block can or should be notch?
Its not usually done at all today.
Piston bore size is large on 489, 496, 502, 510, 540, 555, 572, 632.

Pontiac used to notch the cylinder bores.
Done on 389s. 421's 326, &350.
Ocassional find it was factory done on a few 400s.

I had it done on a Pontiac 455.
It was a waste of money.
Bore size 4.181 for 462 ci.
Next engine no valve relief notches put in.
It was way more powerful.
 
Thanks, AFR heads valves are 2.25 and 1.88 4.310 bore,didn't know if it was worth doing or not while I've got it apart,
Pistons are cut unshrouded already.
New crank will be here this Thursday
So I've been preparing block,heads20180527_120525.jpg 20180525_153425.jpg
 
putting shallow eyebrow relief recesses in the upper 1/4" of the bore wall has been done by hot rodders and even Ford, Chevy, and Olds, factory built engine blocks.
it provides a very minor increase in air flow and its easy to screw it up.
ideally you'll want to not go deeper than about .060 at the block deck , use the head gasket as a temp let and tapper the oval wedge shape eyebrow relief to no close than about .080 of where the rings reach up the bore wall.
as brian stated many shops no longer bother as the gains while there, are minimal at best.
recessj.jpg

borenotch7.jpg


recessk.jpg

gasketsh.png

domecheck.gif



http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html

http://garage.grumpysperformance.com/index.php?threads/piston-related-info.110/

https://www.musclecardiy.com/cylind...-valve-shrouding-improved-performance-part-9/

http://garage.grumpysperformance.com/index.php?threads/aluminum-heads-polishing-and-porosity.14689/

http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html
 
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putting shallow eyebrow relief recesses in the upper 1/4" of the bore wall has been done by hot rodders and even Ford, Chevy, and Olds, factory built engine blocks.
it provides a very minor increase in air flow and its easy to screw it up.
ideally youll want to not go deeper than about .060 at the block deck, use the head gasket as a temp let, and tapper the oval wedge shape eyebrow relief to no close than about .080 of where the rings reach up the bore wall.
as brian stated many shops no longer bother as the gains while there, are minimal at beast.

recessj.jpg

borenotch7.jpg


recessk.jpg

gasketsh.png

http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html

https://www.musclecardiy.com/cylind...-valve-shrouding-improved-performance-part-9/

http://www.chevelles.com/forums/155-2006/139134-grinding-bbc-bores-unshroud-valves.html
Thanks Grumpy!!
Sounds like if you're good with die grinder you can lay them in there.
 
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I have a some what unrelated issue ,
I got laughed at by total seal yesterday
When trying to buy new rings for pistons
I told him I needed .093 thick rings....
His comment was "are you building and tractor motor" in fact a minneapolis moline tractor motor. What's a better thickness .062 or .043 for a street motor
Looks like I'm starting from scratch
New pistons...

Have Skipwhite build a motor they said..
It will be great they said...
This thing is starting to sound like a bad Craigs list add...
 
Opinions are like a-holes. I'd go back and rethink what you have and reassess what it is you want and how much you can afford to spend. If money isn't a factor and self accomplishment isn't in the way, then just buy a Skip White and be done with it, otherwise keep plugging along.

Grumpy will never give bad advice on something as important as engine building. Use him!!!
 
I have a some what unrelated issue ,
I got laughed at by total seal yesterday
When trying to buy new rings for pistons
I told him I needed .093 thick rings....
His comment was "are you building and tractor motor" in fact a minneapolis moline tractor motor. What's a better thickness .062 or .043 for a street motor
Looks like I'm starting from scratch
New pistons...

Have Skipwhite build a motor they said..
It will be great they said...
This thing is starting to sound like a bad Craigs list add...
I would have told that guy to shut his Pie Hole.
Or I will find and do it in person with my fists.
 
Opinions are like a-holes. I'd go back and rethink what you have and reassess what it is you want and how much you can afford to spend. If money isn't a factor and self accomplishment isn't in the way, then just buy a Skip White and be done with it, otherwise keep plugging along.

Grumpy will never give bad advice on something as important as engine building. Use him!!!
I think you missed my point
It was a pun intended towards Skipwhite performance.....

Short of the long story
Skipwhite performance build a motor for me in 2015 fast forward 2018
They built junk from what I have ran into, Grumpy and the gang have gave me all kinds of advice and help so far.
Most of it was reading thru the posts.

That's why I've been asking al kinds of questions.

The whole Skipwhite performance jab
Is just in case someone is thinking about
Using Skipwhite performance to have a build done. If so plan on a bucket load of cash to do it again when it fails
 
I have a some what unrelated issue ,
I got laughed at by total seal yesterday
When trying to buy new rings for pistons
I told him I needed .093 thick rings....
His comment was "are you building and tractor motor" in fact a minneapolis moline tractor motor. What's a better thickness .062 or .043 for a street motor
Looks like I'm starting from scratch
New pistons...

Have Skipwhite build a motor they said..
It will be great they said...
This thing is starting to sound like a bad Craigs list add...
Down load the Total Seal Catalog.
Its a PDF file.
You can do it from your phone.
Its on mine.
Look by Bore size or engine application.

Thin Rings have a drawback in long stoke engines in A BBC OR Pontiac V8.
They see real high piston speeds not seen in LS.

Evacuation pumps required for Advanced Profile Rings.
Not a best match for a street engine driven thousands of miles.
 
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