I Am Dreaming Of Easy, Affordable Power

DorianL

solid fixture here in the forum
Staff member
What I don't get about these kits is that they all talk about piston head volume, +5.00 cc So, these are domed with valve reliefs then ?

Have you miked the cylinders to see what size ? It might already be .030 or .060 over.

Not yet... I really would be surprised if this has ever been machined. Then again, I was not expecting a spun rod bearing of that caliber. :rolleyes:
 

DorianL

solid fixture here in the forum
Staff member
Now this is a silly amount of sludge. And it’s all over the lifter valley. There’s nothing much metallic in it. Just neglect!

0223DE1B-EB98-4F02-BBD4-B10578F59A5E.jpeg
 

Indycars

Administrator
Staff member
What I don't get about these kits is that they all talk about piston head volume, +5.00 cc So, these are domed with valve reliefs then ?
I don't know if there is a standard for specifying valve reliefs verses dome volume. You have to
know how the calculator your using handles that volume to get a correct number.

No, I doubt they will give you two volumes, one for the valve reliefs and another for the dome
volume. There will be just one volume and it should be obvious which one when you look at the piston top.

Make sense ?
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
5cc-8cc is generally just the valve relief clearance cuts in a flat top piston
similar to this

upload_2020-5-2_16-57-34.jpeg
P3831F-2.jpg
 

DorianL

solid fixture here in the forum
Staff member
I’m just trying to figure out what +5cc or +18cc means. Why + ? Shouldn’t it be minus ?

every sickroom kit is plus 5 to plus 18cc. Piston dome with reliefs. ???? So they are still domed ? Not flat tops with reliefs... that would be minus xcc?
 

Indycars

Administrator
Staff member
I’m just trying to figure out what +5cc or +18cc means. Why + ? Shouldn’t it be minus ?
Flat top with +5 adds to the combustion chamber volume, +18 for a dome subtracts from the
combustion chamber volume.

Technically it should be minus for a dome piston when do your calculations, but
when you look at it from the piston's perspective it's a Plus volume.
You still need to
pay attention to what your calculator uses.

Don't fret, if you keep posting then no one on this forum is going to let you go wrong !
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Last edited:

DorianL

solid fixture here in the forum
Staff member
I apologise gents, I am still struggling.

From what I could measure, my block is at 9.025. L31 Vortec heads are 64cc.

Let's say I zero deck and use a FelPro head gasket that compresses at 0.041 with a bore of 4.166
https://www.summitracing.com/int/parts/fel-1003/make/chevrolet

Let's say I use this rotating assembly

https://www.summitracing.com/parts/sca-1-91200
Piston Style:Flat top, with two valve reliefs
Piston Head Volume (cc):+7.00cc
Wrist Pin Style:Floating


Using this calculator:
https://www.summitracing.com/popup/calcsandtools/compression-calculator

I enter PLUS 7.00cc for the reliefs in the flat top.
(I guess what is confusing me is the +/- convention... I would think a relief should be a minus and a dome would be a plus.)

I get the following as result:

Snag.jpeg

I notice the calculator doesn't take into account ring lands and bore of gasket...

Incidentally, this looks silly high.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
yes its a bit too high for pump octane gas , so
the most obvious option
,if your using iron vortec heads , and wanting to build a 383 from a later single piece rear seal block,
is a dished piston,you want closer to 9.5:1 :D -9.8:1 :rolleyes: for pump octane gas
(I don,t know your high test or regular octane availability)
and Id use a .021 copper head gasket and only minimally decked the block,
(lets say 9.020")
lets say '002-.004 off to straighten the deck,
leaving more material for future work if thats required in the far future. max
be darn sure to order the pistons to match the bore diam,
as the pistons can be ordered in many over size options,
usually at little or no extra cost,
but if you fail to specify, exactly what you need..your screwed

https://www.summitracing.com/parts/sce-p110621

https://www.summitracing.com/parts/sca-1-92303bie
Id call SCAT 1-310-370-5501

and ask if something rather similar,
in a balanced assembly
in a single rear seal,
3.75" stroke
18cc dish piston,
ideally with 7/16" ARP rod bolts,
in a 9000 cast steel or forged steel crank,
assembly with full float pistons
was available or could be put together,
I know Ive done so,
and got what I requested,
and for not much more cash in the past

https://uempistons.com/series-1416-icon-premium-chevrolet-383-6-3-ic734.html

https://view.publitas.com/the-midni...nkshafts-catalog-volume-37-edition-1/page/6-7



yes theres an option for the larger port vortec heads that flow considerably more air
https://paceperformance.com/i-62556...haust-runner-65cc-chamber-up-to-530-lift.html
REMEMBER A DAY OR SO SPENT READING AND UNDERSTANDING ,
RELATED INFO
CAN SAVE YOU A GREAT DEAL OF WASTED TIME AND MONEY


http://garage.grumpysperformance.com/index.php?threads/sellecting-cylinder-heads.796/

http://garage.grumpysperformance.co...alves-and-polishing-combustion-chambers.2630/

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/

http://garage.grumpysperformance.com/index.php?threads/valve-seat-angles-and-air-flow.8460/

http://garage.grumpysperformance.co...xperienced-and-skilled-help.16177/#post-97651


http://garage.grumpysperformance.com/index.php?threads/more-port-flow-related-info.322/

http://garage.grumpysperformance.com/index.php?threads/port-and-runner-math.148/#post-34936

http://garage.grumpysperformance.co...this-info-on-world-products-235cc-heads.6972/

http://garage.grumpysperformance.co...n-chamber-or-piston-dome-or-port-volume.2077/

http://garage.grumpysperformance.co...uild-the-engine-to-match-the-cam-specs.11764/

http://garage.grumpysperformance.co...rt-a-non-issue-based-on-mis-information.6414/

http://garage.grumpysperformance.com/index.php?threads/vortec-related-info.731/

http://garage.grumpysperformance.co...ose-first-sbc-heads-you-buy.10910/#post-47875

http://garage.grumpysperformance.com/index.php?threads/the-new-215cc-vortec-heads.266/#post-35948

http://garage.grumpysperformance.co...-vortec-heads-and-other-heads.401/#post-34996

http://garage.grumpysperformance.com/index.php?threads/porting-can-help.462/
 
Last edited:

DorianL

solid fixture here in the forum
Staff member
Thanks Grumpy...

Those “thin” gaskets scare me. But then again... that’s not a shim, it’s a copper gasket. I hadn’t thought of that. With copper spray o_O

Ha ! Now that’s a good idea: call Scat and have something put together specifically for my application rather than rummaging through what Summit has off the shelf. The tangerine tornado had a balanced rotating assembly from Ohio Crankshaft.

If the block and heads check out we will have a 383 project.

The heads... I want to port them myself. A buddy of mine here spent a week with David Vizard and our plan is to carefully work on these... o_O
 

DorianL

solid fixture here in the forum
Staff member
Since this is a manual, it would be good for them to include the flywheel.
 

Indycars

Administrator
Staff member
I enter PLUS 7.00cc for the reliefs in the flat top.
(I guess what is confusing me is the +/- convention... I would think a relief should be a minus and a dome would be a plus.)
It's all about how the calculator handles the volume for a valve relief or dome that determines the correct answer.

I notice the calculator doesn't take into account ring lands and bore of gasket...
It's a small part of the CR, but it is technically part of the calculation.

That's a large bore for the head gasket, something like 4.060 would be more appropriate.

You still need to know the DCR to know for sure if pump gas is going to work. That means the you
need to know when the intake valve closes on the seat.

At some point I can do a simulation with my Dynomation 6 software. My Excel calculator takes into
account every space in the combustion chamber and also gives you a DCR if you know the IVC degrees.

Since you will be working on the heads it sounds like, then taking 2cc from the chamber would not be
out of the question (Engine #3).

http://garage.grumpysperformance.co...comp-ratio-cranking-pressure-calculator.4458/

upload_2020-5-3_12-3-16.png
.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
be sure that FLYWHEEL,and damper you select matches the intended application
and it is SFI certified, IDEALLY billet, your feet will thank you,
and ideally, you use a blow proof bell housing, thats a good idea

and I would select a 28 lb-36 lb flywheel,for street use.
if its the newer sbc single rear seal block.
be sure its for a single rear seal crank,
and they make 153 and 168 tooth gear designs,
you need to match your application, and your bell housing and starter
also be aware there are internal and externally balanced 383 SBC kits and 5.7" and 6" rod kits,
and some that require a neutrally balanced damper and an externally balanced flywheel

https://www.summitracing.com/parts/...MIyrK1kZaY6QIVFP_jBx05Vw71EAQYAyABEgL4HfD_BwE


as usual, there's a ton of related info in the links and sub links

http://garage.grumpysperformance.co...ectly-installing-bellhousings.584/#post-21691

http://garage.grumpysperformance.com/index.php?threads/a-brief-look-at-clutches.447/

http://garage.grumpysperformance.com/index.php?threads/engine-balancing.3900/#post-10338

http://garage.grumpysperformance.com/index.php?threads/selecting-a-flywheel.1042/#post-1945

http://garage.grumpysperformance.com/index.php?threads/harmonic-balancer.3554/#post-9433

http://garage.grumpysperformance.com/index.php?threads/sfi-tested-parts-sources.3011/#post-7917
 
Last edited:

DorianL

solid fixture here in the forum
Staff member
I am tempted to start working on the block already. Like cleaning up the edges, oil drain holes, etc. It would be good practice anyway. And once this goes to a machine shop for a hot tank and it checks out, I probably will leave it there until the rotating assembly gets here. I want them to have the pistons when they over bore it. No sense cleaning machine chips out twice. I plan to get medieval on it when cleaning.
 

Loves302Chevy

"One test is worth a thousand expert opinions."
Dorian, you worked the calculator correctly. The compression comes up so high (compared to a 350) because of the extra stroke. And you got the specs for the usual Felpro HG correct also (4.166, .041).
As far as cleaning the deck surfaces, do what Grumpy suggested: and Id use a .021 copper head gasket and only minimally decked the block,
(lets say 9.020") lets say '002-.004 off to straighten the deck,
leaving more material for future work if that's required in the far future

Why machine metal (and strength) away, only to try to replace it back with a gasket?
If at all possible, try to get a 383 balanced rotating assembly ALL INTERNAL. That way, the chance of you starting a new thread years down the road that goes something like My engine has a vibration after I replaced the flywheel or harmonic damper shouldn't happen, because you will use NEUTRAL balanced dampers and flywheels.
Here is another place to educate yourself with 383 combos:
https://www.competitionproducts.com...v-Dome/productinfo/SCA1-91255BI/#.Xq9ELMuovcs
1-90155Bi.jpg

Scat Internal Balanced Street & Strip AssembliesComplete rotating assemblies from the performance professionals of Scat crankshafts. These kits come complete and internally balanced, ready for assembly, All Scat rotating assemblies are available.

Part Type: Rotating Assembly
Application: Chevrolet Small Block (1-Piece Rear Seal) Street/Strip
Deck Height: 9.025"
Main Bearing Type: 350
Bore: 4.030"
Stroke: 3.750"
Actual Cubic Inch: 383
Crankshaft: Scat 9000 cast steel
Pistons: Mahle Forged Aluminum
Piston Dome Type/Volume: -19.6cc Inverted Dome, 6.000" Length
Compression: 9.5 w/64cc
Piston Pins: Included
Connecting Rods: Scat Bushed 4340 I-Beam
Rings: Matching Moly Ring Set
Rod Bearings: King
Main Bearings: King
Balanced: Yes (Internal)
Flexplate Included: Yes (Street Flexplate)
Harmonic Balancer Included: No
Manufacturer: Scat Crankshafts
Manufacturer's Part Number: 1-91255Bi
Quantity: Sold as Kit


BTW, SCAT is better than EAGLE.
 
Last edited by a moderator:
Top