Could someone look over the variables I have entered and answer the question that I have down below? I have a 350 that I am rebuilding for the Camaro (383 going to have to wait a little longer http://www.nastyz28.com/ubb/frown.gif ). I am reusing the orginal crank and rods but bought aftermarket pistons. The pistons are Federal-Mogul Sealed Power H345NP that are 30 over. I came across a set of S/R Torquer with 67cc chambers which is going to raise my SCR a lot from my 76cc 882s. So I need to figure out if I can run these 67cc heads with pump gas using this cam... http://www.cranecams.com/index.php?show=browseParts&action=partSpec&partNumber=100052&lvl=2&prt=5

The program that I am using to figure out DCR is Patrick Kelly's DCR program. It can be found here at the bottom of the page... http://members.uia.net/pkelley2/DynamicCR.html

When the program is started up I click the cam timing and overlap calculator tab...

Advertised Intake Duration = 272

Advertised Exhaust Duration = 272

Lobe Sepertion = 110

Intake Lobe Centerline = I couldnt
find this information on the spec page (given above) but the spec on the box (that the cam came in) says...
lobe ctrs int = 105
lobe ctrs exh = 115
Im assuming I put in the lobe ctrs int number 105??

I click the calculate button and get 61 for ABDC. I click the Dynamic Stroke Length Calculator tab...

Cranke Stroke = 3.48

Rod Length = 5.7 (I am assuming this is stock length)

ADV Intake Closing Angle = 61

I click the calculate button and get 2.79048142717871 for Dynamic Stroke Length. I click the Compression Ratio Calculator tab...

Number of Cylinders = 8

Bore Diameter = 4.03

Stroke = I check the box for dynamic stroke (2.79048142717871)

Combustion Chamber Volume = 67

Head Gasket Thickness = A pair was included in a gasket kit but there no info on it. Depending on the head gasket I have I am willing to go out and buy a thicker version. I entered .036 (assuming they make one that size).

Head Gasket Bore = 4.03

Piston To Deck Clearance = Alright this one is a problem for me. Is this the distance down the bore to the piston at TDC? All my stuff is at the machine shop and they are not able to get to my stuff for a while as they are busy. I think I can figure this out though. On Federal Mogul crappy site it says compression distance for my pistons is 1.56. That the distance from the center of the wrist pin to the top of the piston right?? Well if someone could tell me what the piston to deck clearance on a stock 350 (out of a z28 81 camaro), and what the compression distance on the stock pistons is, I could figure out what the Piston to Deck Clearance is with the new pistons. Or I may be way the F!!K off and dont know what im talking about http://www.nastyz28.com/ubb/smile.gif.

Next the program ask me "What type of pistons do I have?" I click flat. Then it wants me to enter how many positive cc the 4 valve relief create. This is another problem for me. As mentioned above my pistons are not in my possession now, and Federal-Mogul crappy site doesnt specify that information! I read somewhere on this board that a typical flat top piston with 4 valve reliefs adds about 6cc. Is this right? That seems a little high. At this point I would click the calculate button but I am unclear about the piston to deck clearance. Well if anyone can help me out I would much appreciate it. Thanks!

Piston will be about .025 down in the hole if you don't deck the block. That's what you want to put in the calculation.

<font face="Arial,Verdana" size="2">Originally posted by ULTRA_KILL:
Bore Diameter = 4.03

Head Gasket Bore = 4.03

[/B]</font>

see the boo-boo http://www.nastyz28.com/ubb/wink.gif Your head gasket bore is usually a number like 4.166 or so, its much wider than the actual cylinder bore. You can usually get all the info youll need of Summits part detail.


For the pistons, post the part number here & we'll get it.



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11.74/118mph, thats all..

I think your worrying the wrong way... I feel your SCR and DCR is gonna be too low, not too high.

I like to stay in the range of 9.25-10.0 SCR and 7.70-8.0 DCR for best power on 91-93 octane fuel with iron heads.

Those pistons are I think -9.77 CC, The stock deck height is .025" and gasket bore is always much bigger than bore like 4.100-4.166"

with the common rebuilder gaskets (4.166" x .041")

I get 9.073 SCR and 7.40 DCR

I would go to a steel shim gasket myself on that combo (4.100" x .015")

Then it comes out to 9.53 SCR and 7.84 DCR. That to me is great, right in the good range. Not only will you get the compression where it needs to be, but you tighten up the quench height.

A loose quench, lower compression engine will detonate more than a tight quench, higher compression engine on the same fuel and timing

I'm pushing the limits alittle with mine, but fine so far.. 10.18 SCR, 8.30 DCR.. Runs on 93 octane, but have to limit timing to 34* total. At 36* i get alittle ping, so I backed it down 2* to be safe

I really appreciate your help guys! I will have the machine shop (when they get around to it) check to see how much (if at any) it has been decked. As for the gasket thanks for catching that. The gasket I have is 4.125 x .041 I checked summit and jegs about the pistons (Federal-Mogul Sealed Power H345NP) like you suggested nick, summit had no info and jegs said 9.35:1 w/64cc. However they didnt mention with what gasket! Im still interested in figuring out the valve relief volume. If all else fails I can wait longer and get the info from the machine shop (dont know when that will be). Your right night rider, my compression is lower then I had exspected, im going to have to go out and buy a thinner gasket. I still not sure whether I have the right lobe centerline. As I mentioned above there is some info on the box that says lobe ctrs int. Is ctrs short for centerlines? Thank you for your replies, keep them coming http://www.nastyz28.com/ubb/smile.gif.

With a 0.041" headgasket, you'd really want to zero-deck the block to get good quench. It'll increase the compression a touch, but the added turbulence in combustion will end up keeping you further from detonation.
If your deck height is in the 0.02-0.025" range, you can either deck the block, or run one of the thin shim gaskets to keep the quench as close to 0.04" as possible.

I called the machineshop and they said my block has not been milled. I called Federal-Mogul to ask what size my valve relief were and they said negative 5cc. Im a little confused, do I put in -5cc into the calculation for valve relief? Also I have learned that my intake lobe centerline of 105 is correct. Using a .012 head gasket and putting in 5 for valve relief my DCR comes out to 8.304. My quench comes out to .037. Is this close enough to .04, BluEyes? Will I be fine on pump gas? Thank you all for your help!

It looks like you had it right with the 5cc for valve reliefs. They say -5 to compare them to domed pistons that have a positive value for the piston tops. Dished pistons have a negative value.
The recommended clearance between your pistons and head is between .035 and .040". More and you lose the effect, less and at high rpm the pistons could contact the head due to rod stretch.

The felpro 1094 .015 think is a good gasket for the price, comes rubber coated(painted) but some copper spray should help. The problem is that you need a RA of 55 on the block and heads - if the block has not been decked, then good chance its higher than RA 55 - same with the heads. Plus you'll need to run gasket seal around the water holes on the head and block(a light skim). I've heard its better to run studs with shim head gaskets as they have a much better clamping force, but have seen people use them without 'em.

GM has somewhat new composite gasket out thats .028, I would use that instead and have the block deck'd .012 off. Also make sure the pistons have a STOCK pin height, otherwise this will affect your over all piston to desk height and quench.

Flat tops have either 1, 2, or 4 valve reliefs - 2 and 4 being the most common. 4 valve relief pistons are usually between (-)5-7cc, dont use the negative sign when selecting "flat or dished".

With a dynamic over 8 I suspect your static is over 10. With iron torquers you'll detonate on pump 93. Thats a lot of compression with iron heads. With a 10.8 spec iron headed circle track motor head gaskets and pistons get taken out if run on pump 93. That's with camshaft that have 250 degrees of duration no less. What most folks that SAY they run 10.5, 11 or EVEN 12 to 1 compression on the street with pump gas and iron heads forget is they didn't take the time to measure, calculate and verify (verify is the real key to the equation) they REALLY had that amount of compression. On teardown they would be surprised when it was blueprinted. OR, they are running SOOOO much camshaft duration they don't have squat for low end or street manners.

So......take it for what it's worth. Keep the compression reasonable, 9.5:1 static. It's not worth the 1 or 2% difference in power to have to burn 100 octane, nor is it worth it if you have to detune the advance so it doesn't detonate under cruise conditions.

Talk it over with your machine shop and make sure what you are attempting to do is what you really want to get yourself into. Is it worth 5-10 HP to risk running race gas.

The other thing you need to consider is those are a production style head. Your chances of them have equal 67cc chambers from cylinder to cylinder is equal to your chaance of winning the lotto tomorrow. If you want to do it correctly you have the chambers cc'ed and equalized, if the heads are used they also should have a valve job and guides installed. The heads should be surfaced prior to installation, which will be part of the cc procedure most likely. Then you verify the deck height (which you have done already it sounds like) and then order the pistons to get the compression where you want it with the deck height you plan to run.

Just some food for thought.

I get the same number on the DCR, and get a SCR of 10.11:1 with that combo.

For the quench - how tight are the pistons going to be in the bores? It sounds like you're running hypereutectics, so the machine shop can fit them right on the tight edge of clearance.
With tighter quench one should pay closer attention to the piston-bore clearance to minimize piston rock at TDC.
How good is your machine shop? Personally, with a 0.025" deck height, I'd use a 0.015" or 0.018" headgasket unless I was sure it was being built up tight, and checking the deck on every bore.

You might be pushing it a little with the DCR, even with tight quench. For comparison, a ZZ4 crate has about 8:1 DCR with aluminum heads. A 10:1 350 with the LT4 HOT cam comes in at 7.8:1.
I can't say if it will run on pump gas for sure, you are probably looking at being borderline. I wouldn't use a thicker headgasket to bring the CR down though because of the loss of quench.
A cam with more LSA, or a greater ICL would bring down the DCR. Or polish the chambers - it will add a few CC's there as well as improving combustion effeciency.

Point taken Rick, 9.5 SCR it is. I told the machine shop to hold off on balancing the setup I have. Im going to take it off their hands to figure out all that is needed to be done to accomplish my goal of 9.5 SCR and .04 quench. Im doing this because the machine shop wont be able to get around to figuring it out for a while. Ill get everything back sometime next week. Thank you all for your replies, I will put them into consideration.