76 L82 Corvette 355 engine build questions

[76GrayVette]

Hey,

I just did my introduction post as I'm new to the forums but I figured I'd go ahead and jump right in. Forgive me for the questions, I have been doing lots of reading and research but it's hard to get a clear, specific answer for what I'm looking for so I'm hoping some of you guys can give me some tips and advice.
Anyway, like I said in my introduction post, I have a 76 L82 Corvette 4-speed that I'm fixing up and I have the engine tore down for rebuilding.
My goal for this engine is to make it a nice reliable street engine that makes decent power(maybe 300-350hp/torque?) with more focus on lower end torque as I don't plan to spin more than 5500rpm very often, if at all.
So I had to have the engine bored 0.030'' over because of pitting in the cylinders and the block was decked 0.012'' to fix a nick in the surface.
Here are my specs so far:
355 cubic inch
4-bolt main (I know not necessary for my 5500rpm limit but cool to have, especially because it's the original block for the car)
Forged steel crank (turned 0.010'')
Stock 5.7 rods (supposed to be forged)
Forged Speed Pro flat top four valve relief pistons (part# KL2256F30)
Vehicle weight is about 3600lbs I think
It's a 4-speed car with the Borg-Warner T-10
Tire diameter is about 27in I think. They are BF's 255/60R15
I'm not sure about the rear end ratio (I haven't been able to find the stamp yet) but I was running about 3000rpm or a little over at 55-60mph in 4th gear
so probably 3.50 or 3.70
That's pretty much the basic specs.
I have a limited budget so I was thinking some mild heads, cam, and intake.
I had Edlebrocks E-street heads(5089/5073) in mind with their Performer Q-jet intake (2101) because they are in my price (and I think power) range and I've heard they are pretty good for the money. Again, I'm talking a mild build here. Not looking for wild HP numbers just some solid, very street-able power.

Okay, so the main questions/concerns are about matching my SCR and DCR with a cam that works with those heads and is in my rpm range (under about 5500rpm)
My first thoughts were to get the 64cc E-streets.
My SCR(according to RSR and other online calculators) would be about 9.98:1
Bore: 4.030''
Stroke: 3.48''
Head Gasket Thickness: Probably 0.039'' compressed as I'd probably be using Fel-pro recommended by Edelbrock for the heads.
Deck Height: 0.013'' (assuming a stock 0.025'' minus a shaving of 0.012'')
Piston top volume: ad for speed pro's say 6.1cc
Combustion Chamber: 64cc
Quench is 0.052'' with that gasket and deck height. I know it's not ideal but I don't want to go much tighter in fear of having problems. (Edelbrock recommends 0.050'' piston to head clearance with the E-streets) (Could I go tighter or no?)
When I plug that SCR into some DCR calculators I find that to get a DCR under 8.0:1 (I'd feel safer at 7.5-7.8) I have to use some fairly large, longer duration cams
such as 7.81:1 with the Lunati 10001(Adv. 280/290, 0.050. 214/224, 0.443/0.465, LSA. 112)
I tried the Edelbrock Performer Plus which has a bit less duration, and it was about 7.87:1. I don't really want a DCR that high and the lift is not as high as the stock cam.
So the concern here is if I try and bump SCR up too high for more power and then have to pick a bigger cam to avoid a high DCR and detonation, will I loose my bottom end power?
Or is it better to get the 70cc Edelbrock heads and have a SCR of about 9.3:1 and get a smaller cam with a DCR of about 7.7:1

Whew! I think that was the major stuff. Sorry about the overload. I don't expect you all to have all the answers for me and I know all these numbers are just estimates, that's why I'd like to err on the lower side to be safe and I'll measure what I can but I'm hoping you can tell me if I'm on the right track or if I'm way off.

Thanks again,
Hayden

Here's a picture to make up for all the words

 

[grumpyvette]

Hey,

I just did my introduction post as I'm new to the forums but I figured I'd go ahead and jump right in. Forgive me for the questions, I have been doing lots of reading and research but it's hard to get a clear, specific answer for what I'm looking for so I'm hoping some of you guys can give me some tips and advice.
Anyway, like I said in my introduction post, I have a 76 L82 Corvette 4-speed that I'm fixing up and I have the engine tore down for rebuilding.
My goal for this engine is to make it a nice reliable street engine that makes decent power(maybe 300-350hp/torque?) with more focus on lower end torque as I don't plan to spin more than 5500rpm very often, if at all.
So I had to have the engine bored 0.030'' over because of pitting in the cylinders and the block was decked 0.012'' to fix a nick in the surface.
Here are my specs so far:
355 cubic inch
4-bolt main (I know not necessary for my 5500rpm limit but cool to have, especially because it's the original block for the car)
Forged steel crank (turned 0.010'')
Stock 5.7 rods (supposed to be forged)
Forged Speed Pro flat top four valve relief pistons (part# KL2256F30)
Vehicle weight is about 3600lbs I think
It's a 4-speed car with the Borg-Warner T-10
Tire diameter is about 27in I think. They are BF's 255/60R15
I'm not sure about the rear end ratio (I haven't been able to find the stamp yet) but I was running about 3000rpm or a little over at 55-60mph in 4th gear
so probably 3.50 or 3.70
heres a calculator, you can use , but given the posted specs your running a 4.11:1-4.33:1 rear gear
http://www.wallaceracing.com/calc-rgr.php

That's pretty much the basic specs.
I have a limited budget so I was thinking some mild heads, cam, and intake.
I had Edlebrocks E-street heads(5089/5073) in mind with their Performer Q-jet intake (2101) because they are in my price (and I think power) range and I've heard they are pretty good for the money. Again, I'm talking a mild build here. Not looking for wild HP numbers just some solid, very street-able power.
THERES MUCH BETTER OPTIONS IN HEADS
Okay, so the main questions/concerns are about matching my SCR and DCR with a cam that works with those heads and is in my rpm range (under about 5500rpm)
My first thoughts were to get the 64cc E-streets.
My SCR(according to RSR and other online calculators) would be about 9.98:1
Bore: 4.030''
Stroke: 3.48''
Head Gasket Thickness: Probably 0.039'' compressed as I'd probably be using Fel-pro recommended by Edelbrock for the heads.
Deck Height: 0.013'' (assuming a stock 0.025'' minus a shaving of 0.012'')
Piston top volume: ad for speed pro's say 6.1cc
Combustion Chamber: 64cc
Quench is 0.052'' with that gasket and deck height. I know it's not ideal but I don't want to go much tighter in fear of having problems. (Edelbrock recommends 0.050'' piston to head clearance with the E-streets) (Could I go tighter or no?)
When I plug that SCR into some DCR calculators I find that to get a DCR under 8.0:1 (I'd feel safer at 7.5-7.8) I have to use some fairly large, longer duration cams
with aluminum heads and your 4.0 series rear gear ratio and that manual transmission you could easily run a bit more duration on a tighter lsa
such as 7.81:1 with the Lunati 10001(Adv. 280/290, 0.050. 214/224, 0.443/0.465, LSA. 112)
I tried the Edelbrock Performer Plus which has a bit less duration, and it was about 7.87:1. I don't really want a DCR that high and the lift is not as high as the stock cam.
So the concern here is if I try and bump SCR up too high for more power and then have to pick a bigger cam to avoid a high DCR and detonation, will I loose my bottom end power?
Or is it better to get the 70cc Edelbrock heads and have a SCR of about 9.3:1 and get a smaller cam with a DCR of about 7.7:1
Id try to keep the dynamic compression up in the 8.0-8.3:1 range with aluminum heads and select a larger combustion chamber like a 70cc if thats required, with the manual trans , the aluminum heads and a 106-108 lsa with a cam using rhodes lifters having that 216-220 duration your going to get a responsive mid rpm 350, do the math, but Id certainly try to keep the dynamic compression in that low 8:1 range , use the aluminum 180cc port heads, and the tight lsa to get a good power curve
Whew! I think that was the major stuff. Sorry about the overload. I don't expect you all to have all the answers for me and I know all these numbers are just estimates, that's why I'd like to err on the lower side to be safe and I'll measure what I can but I'm hoping you can tell me if I'm on the right track or if I'm way off.

Thanks again,
Hayden

Here's a picture to make up for all the words

I would certainly think the 180cc aluminum profiler heads and a crane 100172 hydraulic cam, rhodes lifters,plus a decent intake like a wieand street warrior would wake up the combo
theres also BRODIX 180cc
http://www.summitracing.com/parts/bro-1021004/overview/
trickflow
http://www.summitracing.com/parts/tfs-3 ... /chevrolet
DART COMPLETE TOP END SETS
http://www.summitracing.com/parts/drt-0 ... /overview/

http://www.profilerperformance.com/raci ... -23-degree

http://www.summitracing.com/parts/wnd-8126/overview/

http://www.summitracing.com/parts/rhl-8178/overview/
RELATED INFO

viewtopic.php?f=55&t=2857&p=7438&hilit=keith#p7438

viewtopic.php?f=52&t=82

viewtopic.php?f=52&t=5078

viewtopic.php?f=52&t=1552&p=6067&hilit=rhodes#p6067

 

[Indycars]

You can always retard the camshaft a 2-4 degree to adjust your DCR. Below
you see that with 4° retard, it drops the DCR from 7.8 to 7.55. Grumpy
usually recommends retarding the cam anyway.



What octane gas are you going to use?


You can download the SCR/DCR calculator here and compare 5 different
sets of engine parameters side-by-side.

viewtopic.php?f=99&t=4458

 

[76GrayVette]

Thanks for the fast reply guys.
Grumpy you've given me more to think about and read about.
Why are the Brodix, Dart, Trickflow heads better than E-streets? Better quality or flow? I'm just curios. The Darts are looking pretty good if you say they are better.

Also, I've read about cranking cylinder pressure being a factor in what octane gas you can run. I'm willing to use 93 octane or Florida's high test but I don't want to run race gas, I want to be able to fill up at the gas station. Some articles I've read say that a cranking cylinder pressure of about 200 is okay without getting detonation while others say around 165. I read part of your thread on DCR vs. SCR and saw an article that said it should be between 160-180. I calculated mine using http://www.not2fast.com/turbo/compressi ... sure.shtml and got about 185 with 9.95 SCR and the Lunati 10001 cam.
What are your thoughts on that?

I used the rear end gear calculator and put in 65mph at 3000 and got about 3.70. I know that's not what I said before, but everything on this car has been stock so far and I know my speedometer is a little off especially at faster speeds so it's probably 3.70 but you never know I guess.

Indy, thanks for the DCR calculator, it's great! I've been writing all my calculations down so far on scraps of paper and their hard to keep track of. This solves that.
Doesn't retarding the cam move the rpm band up?

Thanks guys.

 

[Indycars]

Indy, thanks for the DCR calculator, it's great! I've been writing all my calculations down so far on scraps of paper and their hard to keep track of. This solves that.
Doesn't retarding the cam move the rpm band up?

Thanks guys.

Great, glad you liked the DCR calculator. I got tired of doing like you did, so I created the Excel calculator for that reason.

Yes retarding the cam timing raises the power band, but retarding 4 degree only raises it about 200-300 rpm. It just another way to tweak the settings, but everything is a compromise.

Your rear end ratio can be measured by jacking up the rear of the car and turning a rear wheel one complete revolution while counting the drive shaft revolutions. If you are right then the drive shaft should turn 3.7 times for one turn of the wheel.

Note: If you have a positrac, then you need to have both wheels off the ground. If it's not a positrac, then raise one wheel. The drive shaft will turn 2x what it would normally, so you will need to divide that number by two.

 

[grumpyvette]

you might find reading thru these links very useful
look at the listed flow numbers of each cylinder head, if your max valve lift is .500 than the numbers reached over .500 lift are meaningless in your particular application, and add the flow numbers at .200 &.300.400 &.500, for both the intake and exhaust flow then divide each by 4 since your averaging 4 flow readings, once thats done you have a semi valid way to compare flow rates, the object is to find the heads with the smallest port size cross sectional area that have the highest flow rate for the lowest cost, naturally theres going to be some compromises made.

http://purplesagetradingpost.com/sumner ... eads1.html

http://users.erols.com/srweiss/tablehdc.htm

http://www.highperformancepontiac.com/t ... w_testing/
lets do a bit of math
just a bit of info on intake gaskets sizes to match port cross sectional areas

Calculating the valve curtain area
The following equation mathematically defines the available flow area for any given valve diameter and lift value:
Area = valve diameter x 0.98 x 3.14 x valve lift
Where 3.14 = pi (π)
For a typical 2.02-inch intake valve at .500-inch lift, it calculates as follows:
Area = 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches
SO lets do a bit of math
a cylinder head with a 2.02' intake valve and a cam with a .450 lift at the valve with a 1.5:1 rocker will in theory produce a valve curtain area of 2.79 sq inches, swapping to a 1.6:1 ratio increases the lift to .480 lift 2.98 sq inches, increasing the available port flow potential at least in theory by about 6%, but keep in mind the port can only flow at full valve lift for the limited time the valve remains at full lift and if the narrowest section of the port cross sectional areas less that the valve curtain area that not the valve restricts flow
THUS the most you can reasonably expect is a 6% flow increase , from the rocker ratio upgrade but reality and the fact that the valve is opening and closing perhaps 57 times a second at peak rpms, and the port may be more restrictive that the valve curtain area, on many small block combos suggests the results will be lower

RELATED INFO
viewtopic.php?f=52&t=148&p=34936&hilit=calculate+port+stall#p34936

viewtopic.php?f=52&t=5537&p=16750#p16750


USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php

COMMON SBC INTAKE PORTS
felpro # 1204=Port Size: 1.23" x 1.99"=2.448 sq inches

felpro # 1205=Port Size: 1.28" x 2.09"=2.67 sq inches

felpro # 1206=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1207=Port Size: 1.38" x 2.28"=3.146 sq inches

felpro # 1209=Port Size: 1.38" x 2.38"=3.28 sq inches

felpro # 1255 VORTEC=Port Size: 1.08" x 2.16"-2.33 sq inches

felpro # 1263=Port Size: 1.31" x 2.02"=2.65 sq inches

felpro # 1266=Port Size: 1.34" x 2.21"=2.96 sq inches

felpro # 1284 LT1=Port Size: 1.25 x 2.04''=2.55 sq inches

felpro # 1289 FASTBURN=Port Size: 1.30" x 2.31" 3.00 sq inches


the valve curtain area, cam duration and lift controlling that curtain area,or port cross sectional area will pose a restriction to air flow at some point,in the engines rpm band, but you can extend the effective air flow duration and efficiency with carefully timed exhaust scavenging, that helps draw in the intake runner inertia load of air/fuel,charge much more effectively if the peak negative pressure wave is correctly timed

 

[grumpyvette]

horsepower is simply a way to express the RATE that TORQUE can be APPLIED, the faster you can spin an engine and still produce useable torque the more useful it is to use GEARING to allow rapid use of the power produced.

the formula for horse power is torque x rpm/5252=hp

thus
if your engine makes 500ft lbs of peak torque at 3000rpm,you divide that to find your making 286 horsepower

if you make the same 500ft lbs at 5000rpm, your calculations show 476horse power

make the same 500 ft lbs at 6500rpm, you get 618hp

horse power always equals torque at 5252 rpm.

your component selection, displacement and compression, will determine the effective power band

viewtopic.php?f=50&t=422&p=518&hilit=horsepower+calculate+5252#p518

viewtopic.php?f=52&t=5078&p=18935&hilit=horsepower+calculate+5252#p18935

viewtopic.php?f=87&t=9731&p=37718&hilit=horsepower+torque#p37718

posting.php?mode=edit&f=69&t=9930&p=38054

viewtopic.php?f=55&t=8485&p=35535&hilit=volumetric#p35535

 

[76GrayVette]

Thanks Grumpy. The Brodix heads seem to have the best average flow. They are probably worth the extra money even for a mild build. I'll keep thinking and reading.
But I'm still wondering about the cranking cylinder pressure. Using the calculator I used in my previous post, I used 9.95 SCR with the crane 274 cam you suggested and I got a 197psi rating, even higher than the Lunati 10001 which makes sense as it makes a higher DCR as well. But is it too much? Do you have any links on cranking cylinder pressure?

Thanks for the method of measuring my rear end gears Indy. I'll definitively do that... when I put my driveshaft back in with its new U-joints!

 

[mathd]

I don't think that compression will be too high for 93 octane, if the timing and jetting are spot on.
Just dont run old gas.
To lower DCR you can retard the cam timing and also get a cam with wider lsa if needed or get bigger head.

 

[Indycars]

Thanks for the method of measuring my rear end gears Indy. I'll definitively do
that... when I put my driveshaft back in with its new U-joints!

You can use the yoke coming out of the rear end if you don't have the
drive shaft installed.

 

[87vette81big]

I think Gray's Corvette has a Richmond Gear 3.90:1 Gearset in the 1963-79 Corvette 10-bolt IRS 8.2" Ring gear diameter rear.

I used a 3.90. Richmond Gear in a GM 10- bolt 1971-81 Firebird Trans Am Camaro 8.5" ring gear pisi rear.
Used P225/70 R15 & P255/60 R15 tires.
27"- 27.5" tall.
3,000 RPM's exact @ 60 mph. Muncie 4-speed M21 & M20 Transmission.

 

[Indycars]

Keep in mind that until you measure things and know for sure, you are dealing
with some sizeable variations. It's not uncommon to see a 1 cc variation in
combustion chamber size from the stated value by the manufacture. Then
there is the variation in the rods, stroke(crank throws), piston pin height
and the block deck surface.

The variation you see has nothing to do with the camshaft used, the variation
shown in the table would apply to any camshaft.

 

[Altered76]

Our 76 Corvettes with the Manual trans came with 3.55 stock. Autos had 3.36 I think. But that was the only ones I knew they offered. Guess if you knew the right people you could have got something different. Then there is always the chance a previous owner changed them as well.

 

[76GrayVette]

Our 76 Corvettes with the Manual trans came with 3.55 stock. Autos had 3.36 I think. But that was the only ones I knew they offered. Guess if you knew the right people you could have got something different. Then there is always the chance a previous owner changed them as well.

I think you're right. I checked using the method Indy suggested and I got right at 3.5 turns for one tire turn so it must be the 3.55's. I guess my speedo is a bit more off than I thought.

So, I've been doing more research and I've got some new combos but I came to pretty much the same conclusions as before. I haven't had time to measure anything still so these are just more approximations to get me in the ballpark.

I'm not sure about the Weiand 8125 because I like the intake after looking at some flow numbers but several websites say the 8125 has the four center bolt holes canted for "Small Block Chevy 262-400 w/1987-Up Aluminum Heads" but then on other websites and sometimes the same website (summit has two different pictures) it shows it with normal angled center bolt holes. Anybody know if it will fit the Brodix heads?

The first combo is pretty much the same as the one I first posted just with some better parts.
Brodix IK180 heads with 64cc chambers
Speed Pro forged pistons 0.030 over
0.039'' head gasket
Weiand 8125 dual plane intake
Lunati 10001lk cam 280/290 Adv. duration 214/224 0.050'' duration 112LSA 107ICL
With this combo I'm at about 9.94:1 SCR and 7.8:1 DCR with 191psig cranking cylinder pressure.

The other combo is one that I think might work with the 70cc heads.
Brodix IK180 heads with 70cc chambers
Speed Pro forged pistons 0.030 over
0.039'' head gasket
Weiand 8125 dual plane intake
Crane Energizer 266 266/266 Adv. duration 210/210 0.050'' duration 110LSA 105ICL
With this combo I'm at about 9.32:1 SCR and 7.83:1 DCR with 191psig cranking cylinder pressure.

I know it's not the DCR of 8:1 Grumpy was talking about but my quench isn't ideal at 0.052 and I'd like to stay away from detonation and have no clearance issues.

So the question(pretty much the same as before) is which combo do you think is better for what I'm looking for which is a reliable, non-detonating, low end torque oriented street engine that will never see over 5500rpm most likely, keeping in mind I have the 4-speed and the 3.55 rear gears not the 4.0 we thought previously?
What do you guys think?

 

[grumpyvette]

with a compression reading of 191 psi cranking cylinder pressure.
your compressions a good deal higher than your calculations suggest, I,m thinking your either measuring something incorrectly or using the wrong value in the calculation, or your compression reading is in error??

read these links

http://victorylibrary.com/mopar/cam-tech-c.htm

viewtopic.php?f=52&t=727
with that much compression you can very easily select and use a cam with more effective duration

 

[76GrayVette]

I don't know Grumpy. I used the cranking cylinder pressure calculator here:
http://www.not2fast.com/turbo/compressi ... sure.shtml

And I've been using the compression ratio calculator Indy gave me plus several others such as the Wallace Racing calculator and the Pat Kelley calculator and they all seem to agree pretty well on SCR and DCR calculations.

I used the formulas and calculators on that Mopar page and I got an absolute cranking pressure of about 173psi using the 9.32:1 SCR combo and the 266 cam.

So that looks a lot different. I can't find any other cranking pressure calculators online so I'm not sure what to think.

 

[Indycars]

I'm not sure about the Weiand 8125 because I like the intake after looking at some flow numbers but several websites say the 8125 has the four center bolt holes canted for "Small Block Chevy 262-400 w/1987-Up Aluminum Heads" but then on other websites and sometimes the same website (summit has two different pictures) it shows it with normal angled center bolt holes. Anybody know if it will fit the Brodix heads?

I found this on the Holley website:
Weiand Instruction Manual : https://www.holley.com/data/Products/Te ... 89rev2.pdf
8125 – The P/N 8125 intake manifold is designed specifically for 1955-86 and 1987& later with aluminum heads (Corvette) Small Block Chevy Gen I engine applications

The 8125 looks like the one you need, but call Holley to make sure.

The other combo is one that I think might work with the 70cc heads.
Brodix IK180 heads with 70cc chambers
Speed Pro forged pistons 0.030 over
0.039'' head gasket
Weiand 8125 dual plane intake
Crane Energizer 266 266/266 Adv. duration 210/210 0.050'' duration 110LSA 105ICL
With this combo I'm at about 9.32:1 SCR and 7.83:1 DCR with 191psig
cranking cylinder pressure.

You seem to be stuck on a .039" head gasket, but
you can get something in the .028 - .032 inch range that will give a better
quench clearance and still be safe. It will help with detonation as you reduce
this distance. You just don't want to go below .038 inches, because you risk
actually having the piston touch the head at higher RPM.

You really need to measure the deck clearance in the 4 corners 1,7 & 2,8 cylinders.
It's not hard or expensive. All you need is a good straight edge and feeler gauges.
Use the same piston and rod assembly in each corner to eliminate any deviation by
using any different assemblies. If you have a dial indicator, which are not very
expensive anymore, maybe $50 for a cheap one. It's valuable in many other situations
when building an engine.

viewtopic.php?f=69&t=3814&p=15121&hilit=+used+the+%231+piston%2Frod+#p15121

Possible gaskets are :
http://www.summitracing.com/parts/mrg-1 ... /chevrolet
http://www.summitracing.com/parts/cgt-c ... /chevrolet

Notice that I used a .028 inch compressed gasket in the calculations below.

I don't know Grumpy. I used the cranking cylinder
pressure calculator here:
http://www.not2fast.com/turbo/compressi ... sure.shtml

And I've been using the compression ratio calculator Indy gave me plus several
others such as the Wallace Racing calculator and the Pat Kelley calculator and
they all seem to agree pretty well on SCR and DCR calculations.

I used the formulas and calculators on that Mopar page and I got an absolute
cranking pressure of about 173psi using the 9.32:1 SCR combo and the 266 cam.

The calculator at not2fast assumes an ideal engine ..... no heat loss and no
leakage, which you are never going to have in real life. It's got to be something
lower, but we don't know how low, we can only guess. Don't put too much importance
on that number, it's just one number out of many that you need to consider when
building an engine.

 

[grumpyvette]

JUST a bit of thought as to whats going on, look at it this way for a second, lets say your using this cam, the intake valve seats at a point of about 63 degrees AFTER BDC, that means the piston has already moved 63 of the 180 degrees past bottom dead center toward TDC, or TOP DEAD CENTER, or almost 1/3rd of the way towards the cylinder head compressing the trapped intake flow volume, so at low rpms on a 383 which in theory has roughly 48 cubic inches of cylinder volume , your effectively down to about 33 cubic inches your compressing.yet your still getting a 191 psi reading?

atmospheric pressure at sea level is about 14.7 psi... but the gauge reads ZERO
if the crank pressure reads 191 PSI and you divide that by 14.7, or one atmosphere you get 12.99 effective compression on that compression test. and that does not take into consideration the outside atmospheric pressure at sea level is about 14.7 psi, now your obviously not running 12.99:1 compression, but you can effectively use a bit more duration than the 210-215 degree range
now your calculations might suggest you have 10:1 compression, but remember the valve did NOT close at TDC so you already effectively lost some of the potential volume trapped above the piston as it moved to TDC.
now what I,m saying here without getting highly technical is that your dealing with an engine and compression level that will benefit from either a significantly higher octane fuel or a cam with a bit more duration to allow the valves to seal a bit later in relation to piston movement.
looking at that 191 PSI, ID call and talk to the tech guys at CROWER,CRANE and ERSON, but ID be looking for a cam that would breath well and bleed off some low rpm compression

 

[87vette81big]

I like Grumpy's Anology last spoken.

The closer you can get a True Deck Height to .000" at TDC the better.
Requires shortblock engine mockup work. Measure.
Dissasemble. Machine Deck Block.
Recheck.

Dished pistons tend to provide best flame front proegation. But not alwatys. Depends upon cylinder head combustion chamber design.d
.039 " headgasket thickness is the Fel Pro Race Headgasket. Compressed thickness. Its a Good headgasket.

There are Crevice volumes to measure also.

 

[87vette81big]

Sometimes a Positive Engine Deck Height works great.
Piston extends above the deck. Flattop piston used.
Some Pontiac engines respond tremendous .
.015" quench tight only.
Super Stock drag racing.

Premium Crower Rods used. Not china.