|02-01-2013 05:18 PM|
Pluses on everything, except the intake and carb and to a lesser extent quench.
Negatives are the intake and carb. The Edlebrock Performer RPM and a 750 Holley would give more top end power with very little sacrifice on the bottom end. I know the calculators on CFM for a 355 lead one to about a 600 to 650 cfm carb but you'd find the bigger Holley or Edlebrock/Carter will better support a 400 plus horse top end, if indeed you want to crack that somewhat of a bragging right barrier.
The squish/quench could have been tighter which would be more effective if it was .040 inch. But the compression really isn't that off, my calculator produces 10.3 Static with a rounding to 60ccs in the head and assumes 6 cc's in the pistons. The dynamic assumes a 5.7 inch rod and I calculate the Howards 110235-12 really doesn't close the valve tight on the seat till 61 degrees After Bottom Center. This is a long ramped cam from the .050 inch lift point on the intake being 266 at zero (or there abouts) and 213 from .050 inch tells you there's 53 degrees of ramp between those two points. Assuming the cam is symmetrical that's 26.5 degrees on either end of the lobe from .050 to zip. Subtracting that from my 61 degrees you get 35 (then take out 4 for the advanced grind nets 31 which I didn't do) which is pretty close to someone’s calculation of closing at .050 which would not take into the dynamic effect of the rising piston shoving high pressure mixture past the almost, but not quite, closed intake valve. This effect is nothing like flow benching intake flow at .050 inch lift with a pressure depression of 28 inches of water. This is more like where compression goes with a burnt exhaust valve, that's a substantial pressure loss, 'cause the piston is pushing mixture out. So anyway running my personal DCR calculator it drives an effective stroke of 2.79 inches which reduces the 10.3 SCR to a Dynamic Compression Ratio of 8.46. Certainly 93 octane unleaded burning in an L31 Vortec chamber ought to be good with this. Perhaps not ideal but certainly acceptable within the context of a street performance engine which at least for a DD can't be taken to the same operation/configurational edge that a race engine can be pushed against.
So I'd say this is a darn good effort. Well thought out; you're to be congratulated.
I’ll sort of PS this; where some claim to run less than .040 inch squish/quench, this gets risky in that one can easily bang the pistons and valves and at high RPM the piston to head structure. For a street engine that will wear and that includes the softening of the valve springs with age, running under .040 can result in unpleasant and expensive experiences.
|01-30-2013 05:08 PM|
I have the speed pro H345NCP .030", flat top, 4 valve relief Pistons. They are about 6 cc volume.
Yes, 60.2 currently but will more than likely change to my 62cc heads once the pressed in studs are removed to make way for my screw in studs and guideplates.
Block has been milled some. I am sitting .016" in the hole. Hope this helps you help me. Thank you!
|01-30-2013 05:04 PM|
I have access to 93 fuel. Also, I'm going to work with my total timing more, maybe as low as 29 degrees and run the cooler AR103 spark plugs. If it doesn't fix the pre-det issue then I'm going to run the other higher CC heads along with the shim head gasket AND the 2 step higher cam with the IVC@.050" of 40.5 degrees which will quell the pre-detonation but raise my scr and my dcr. If I run the 62CC chamber heads with the same 1003 gasket (.041") then my squish will be even worse and counter productive to pre-det issues AS I'VE LEARNED THANKS TO YOUR ARTICLES RECOMMENDATIONS AND "TECHINSPECTOR1"! Unfortunately I am stuck with what I've got on hand except another cam option and I am trying to keep this car as much of a daily driver as possible and not have to run 2 degrees initial timing and lose the potential of the motor just because of pre-det and/or not enough money for fuel to run it. This is where I stand at this time but am open to plenty more information/opinions/expert advice on this matter. thanks again all.
|01-30-2013 04:51 PM|
I cc'd a chamber on my 2nd set of 062 vortec heads and got 62cc's. Also I am in the hole .016". The .025" is the piston slap or piston to wall distance. I know that has little effect on the overall compression of the motor but just wanted to input all the data when jeepstrokers.com/calculator asked me for it. Also my pistons are H345ncp .030" with 4 valve relief (about 6cc's).
|01-28-2013 12:20 AM|
355 SBC, would like Hp and TQ estimations.
Joel78Vette, What type pistons do you have in this engine? Flattop or dished pistons. Do you know the name brand or part number, or piston head volume? The cylinder head chambers are 60.2 ccs on the set of heads on the engine now correct! You also say you have another set with the chamber volume of 63ccs. These measurements need to be checked and correct! Has the deck of the block been milled, also did you measure from the top of the piston at TDC to the deck of the block. You said you have .016 deck clearance. Please post some answers.
|01-27-2013 11:07 PM|
|Joel78Vette||I stated 63cc because they were very mildly "cleaned" up. Originally I know they are 64cc. Just hoping is all.....|
|01-27-2013 11:04 PM|
And last but not least, another very good read
|01-27-2013 10:54 PM|
|bygddy||And i believe, with your current cam, and the 63cc heads and 0.015 gasket your still at 8.9dcr which is likely still to high for pump....the good quench will help, and depending on what fuel you have access to......maybe.....but not the safest choice.|
|01-27-2013 10:45 PM|
0.025 in the hole, flat tops 4vr we will say 7cc, 0.015 felpro head gasket, PN#1094, your 63cc heads (check and be sure, because they won't actually be 63) but assuming......this gives you 10.3:1 and 0.040 quench.....
You mentioned 0.016 in the hole at the top, then I believe said 0.025 further down? If the block hasn't been decked this is more likely...
|01-27-2013 10:42 PM|
Tech is truly a good guy here. Welcome to the forum,btw. he will likely do the math for you again,and he is one of the best here.The cam issue could be addressed at the same time. A small roller is always a good choice.
as they say in twilight zone
"please stand by"
|01-27-2013 10:30 PM|
First, the article and reply from both the "Inspector" and "BYGDDY" spoke volumes so far! Thank you!
I have been using Jeepstrokers.com/calculator instead of manually figuring out my compression ratio which is where I got 9.92 SC/9.25DC @1750 altitude. Correct me if it's off and I should stop relying on that please. My piston ring height is .282". I put my digital caliper micrometer on it to see what it was. Also, the best i could see I had .025 piston to wall clearance. Not 100% on that measurement!
Possible solution....I do have another set of 062 heads that may be about 63cc Chambers. Should I use those instead, Gentlemen? It seems to be the easiest and cheapest way to go to run this combo together and use this as a daily driver. I did have Howards 224/230 @.050", .501/.509 cam. Intake Valve closes at 38.5 degrees. That is two steps higher but I sent it back upon 2 out of 3 people recommending I run the smaller cam with this exact set-up.
I have a .015" shim head gasket but was warned about running only .031" quench. Another guy swore that he runs .020" ALL the time with these vortec heads and about slapped me through the phone multiple times explaining the quench preventing pre-detonation and that I would be fine running the .031" quench.
What do you think Gents about the head and/or gasket change as the easiest fix? I do have a set of one piece 7.3" push rods for the other heads instead of the 7.144" that I'm using now to make the transition go fast and easy.
Also, as of today I am brand new as a user vice a reader only on the forum. How do I simply "qoute" and "reply" instead of going to the bottom of the page to reply and having to re-log in every time? Thanks for any and all of your expert advice. MUCH APPRECIATED! You Gentlemen are Champions in my eyes. Especially you "Inspector"...I've read some threads w you in them and am impressed at your expertise. Again, Thanks. Joel
|01-27-2013 09:30 PM|
|vinniekq2||Maybe tech can match your engine to a better set of heads and gaskets for your application.Then see what HP you can get?|
|01-27-2013 07:26 PM|
"Proper" quench will help quell detonation, especially when your getting to the raged edge of pump gas....which it looks like you may be surpassing.
Piston Head Clearance Guide - Tech Article - Chevy High Performance Magazine
|01-27-2013 07:18 PM|
Don't confuse piston deck height (zero to maybe 0.045") with block deck height (9.025" to maybe 8.980").
With 10.6:1 static compression ratio and the intake valve closing at 37, the dynamic compression ratio is 9.27:1. If you have not heard the motor detonating, then it's because you either have not had the motor under load or your exhaust system isn't allowing you to hear it.
|01-27-2013 06:55 PM|
torque and horsepower estimation
I agree with techinspector1 that your compression is too high for pump gas... and that cam is a bit on the short side.
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