Ok, so I did a bunch of searching. I'm throwing a set of AFR 195's with an intake and cam in my L98. The AFR's are getting milled to 62cc to try and keep the compression up. Here is the calculator I used. You may have to scroll down a little bit: http://www.campbellenterprises.com/R...o%20calculator

Displacement: 349.85 ci's
Compression Ratio: 9.71:1

Does that sound right to you guys? I figure the .015 head gasket will help with compression. If the pistons sit .025 in the hole, and I run a .015 gasket, that should put my quench right around .040.

 

Your numbers add up.
I'm not sure why they would ask about deck height. As you guessed, the number needed is the piston to deck clearence.( It's a question of terminolgy I suppose).
You're correct in using a .025" in the hole measurement as this is more or less the stock value. Also consider the gasket bore which typically comes in at 4.100". There are other values however that appears to be a standard.
At 9.7:1 you're starting to build some good static compression. The important thing now is to match that to the cam you want to use. 9.7 could be too high or too low depending on the duration of the cam.

 

This compression ratio calculator takes into account the gasket bore diameter as well as lets you calculate the DCR with the cam events in the picture. This gives you a better picture on what octane gas will be needed.
EDIT: use 4.001 for standard cylinder bore diameter. The .025 deck height is the production standard, you might want to measure the actual height as it can range anywhere from .020 to .040. due to the manufacturing tolerances. This can change the C/R picture dramatically.

 

The only .015 gasket I know of is steel shim, not to be used with aluminum heads.

 

I probly would lean toward using a .028" gasket for abit better sealing. .015 is thin

 

I was thinking the same thing. I found quite a few people who used the felpro .015's and had no problems years later. On most websites, they say the .015's can be used on alum or iron heads. But cannot be used on an aluminum block. Damn, the thicker head gasket drops me to 9.44:1.

On that other calculator posted, what would my Piston Head Volume be?

 

The space the piston dome occupies. In the case of dished pistons, it's a negative volume.

 

Since nobody but us old-time racers use domed pistons, the piston head volume is the amount of cc's to fill the valve reliefs on a flat-top or the dish in a dished piston.
For the calculator I posted, it would take 12cc's to fill the piston level so use 12.
If it had a dome it would be say, -5cc's.
Run the DCR numbers. That's borderline 93 octane with a stock cam and a knock sensor.
Need cam info.

 

Thanks guys! I ran the DCR numbers. Not sure if I put the correct data in though:


I haven't picked out a cam yet either. Or what size injectors.

 

if your static is 9.4, then i dont think your dynamic will be that as well.

AFR heads have decent chambers, they are pretty tolerant of timing and air fuel mess ups. I ran mine lean as hell with high timing and didnt see a count of knock. Finally brought the timing down and air fuel up and it made good power on 93. I had a 8.33 to 1 dcr with 11 to 1 static.

with a low mid 9 static you should be fine in the mid high 8's with aluminum heads and pump gas

Oh and use a regular compression calculator for DCR but you have to use your effective dynamic stroke length based on

http://www.empirenet.com/pkelley2/DynamicCR.html

 

Ok, well it appears I plugged something incorrect into that calculator posted. Thanks for the link, I'm going to give it a look over now.


As I said before, I am serious about this build. I'm not trying to waste anyones time. I appreciate all the help. I told Brian at ADperformance what I am ordering. I am just waiting on one last email from him.

 

Do you have the cam specs?

 

Rod length is center-to-center measurement, stock is 5.7 inches for a 350. Some special pistons allow for a 6.0 rod length.
Throw out some cams that you are considering and we'll figure the DCR for ya.
We'll need the intake lobe duration at .050 and the lobe separation angle (LSA) if we can't find the cam tag numbers, to figure the intake closing point.
With this we can figure the DCR number. (which Orr89 has shown can make the DCR much different than the SCR)

 

Here are some of the cams suggested to me. I want a cam that's going to have a nice chop. I also want the cam that's going to give me the best performance also.

GM 846 Cam:
Duration @ .050
Intake: 222
Exhaust: 230
Lift w/ 1.5 rocker arms
Intake: .509
Exhaust: .528
Lift w/ 1.6 rocker arms
Intake: .543
Exhaust: .563
LSA: 112

"XFI" 268 Hydraulic Roller Camshaft
Operating Range: 1800-5800 RPM
Advertised Duration: 268°/276°
Duration @ .050'' Lift: 218° Intake / 224° Exhaust
Lift: .570"/.565" w/1.6 Rockers
Lobe Separation Angle: 113°

XFI 280 Hydraulic Roller Camshaft
Operating Range: 2000-6000 RPM
Duration Advertised: 280° Intake / 288° Exhaust
Duration @ .050'' Lift: 230° Intake / 236° Exhaust
Valve Lift w/1.6 Rockers: .576'' Intake / .570'' Exhaust
Lobe Separation Angle: 113°

CC503
224 int./230 exh. 0.503/0.510 lift 112LSA (1.5 rocker) 1,800-5,800 RPM

Orr89RocZ suggested this when I said I wanted a choppy cam. But he didn't give the name of the cam:
You guys are helping me out a ton! Thank you!

 

I didnt see any engine specs save that its a 350, so i assumed a 4.000" bore, 3.48" stroke, 0.040" quench, and -5cc flat top pistons. That yielded:

GM846 - 10.2:1 static CR, 7.7 Dynamic CR
XFI268 - 8.3:1 Dymanic CR
XFI280 - 7.9:1 dynamic CR

-Zander

 

Its a stock L98 bottom end so the compression will be lucky to make 9.5 to 1. Assuming .020" in the hole, .028" gasket, -12 cc stock 89 L98 pistons, 62 cc

That said I'd still try the CC503 which is that 224/230 cam i mentioned. AKA 276HR from comp. 112 lsa is the 08-503-8 cam hence comp cam 503 or cc503. 110 is the 276hr.
Both are nice cams, the 110 will chop more but not kill that car. it will still be driveable.

GM846 is another nice cam tho. very similar to the 503.

Go on camaroZ28.com and you can just about find either of those two cams for fairly cheap all the time.

XFI 268 is smooth idling but will make good power, just about as much as any of the above two cams

XFI 280 is way tooo big

Another cam thats doing well with LT1's is AI's 226 / 234 - .569/.570 - 110 LSA Primary Operating Range: 2000-6200rpm. It works good from stock block cars to heads/build bottom end higher compression cars.

EDIT: I forget are you running an HSR or similar?

 

Food for thought.
350/ Vortec heads.
XE276HR.
9.97:1 SCR.
8.03:SCR.
Nice chop at idle.
23 mpg hiway and 11" of vacuum at 700rpm.
107mph in the quarter with the wrong spark plugs. Like Orr said, the 110 lsa will give you an nice choppy idle if that's what your after.

 

http://www.compcams.com/Cam_Specs/Ca...?csid=188&sb=2


1,900-5,600 RPM

Hmm, looks good to me. How does everyone feel about it? I finally feel like I have the ball rolling.


Yes sir. Most likely SR. I don't see the BBK being released anytime soon IMO.

 

If you are building the motor I HIGHLY recommend getting the block decked and running a thicker gasket so you can keep your desired compression ratio. I did a head and cam swap and drove 2 miles then had to tear it back apart. The .015 inch steel shim head gaskets are hit of miss if they seal. One of mine didn't and had to take everything off and rebuilt it while I was at it. I replaced it with a FelPro MLS gasket and seems to have done the trick.

Kevin

 

I like this cam...

Kevin

 

[QUOTE=IROCThe5.7L;4076639]http://www.compcams.com/Cam_Specs/Ca...?csid=188&sb=2
1,900-5,600 RPM
Hmm, looks good to me. How does everyone feel about it? I finally feel like I have the ball rolling.QUOTE]


Using that cam (which is what I use)
276/282 adv duration. 110 LSA. 106 LCA.
62 cc heads.
12 cc dished piston.
.025" piston deck.
.026" x 4.10" gasket.
4.00" bore x 3.48" stroke.
9.25:1 SCR
7.45:1 DCR
with .018" x 4.10" gasket.
9.42:1 SCR.
7.58:1 DCR.
Seems a little low.
With .015" gasket.
9.69:1 SCR.
7.8:1 DCR
I'm not sure how the 110 LSA behaves with FI. I'm a carb guy. I believe the same cam is available with a 112 or 114 LSA.
( I see it is.112 LSA. CC503.)
With the CC503. 276/281. 112 LSA. 108 LCA.
.015" x 4.100" shim gasket.
9.69:1 SCR.
7.68:1 DCR.

 

Awesome! Thanks skinnyz! I'm not sure about the .015 gasket. I'm worried about sealing issues. The next smallest one I can find is .028. Orr89 says the cam will be ok with my FI. And won't be terrible to tune.

 

I have used the victor nitroseal head gaskets, they are .025 thick, will not brinell aluminum heads, sealed well on my 12:1 compression motor, and only cost about 15$ a piece, so those are the gaskets I would reccomend.

 

That's what I have in my current build. I had thought they were .026" and had to double check. (.025")

http://www.cnc-motorsports.com/searc...&Keywords=5746

The CC503 with its wider LSA and 108 ICL has 2 degrees later intake valve closing. This lowers the DCR somewhat.

My apologies. I've been using LCA to describe the intake centreline angle rather than ICL. I've edited the previous posts!

 

I wouldn't worry too much about losing a couple of tenths on the compression ratio. You'll never notice it in the real world.

I'll also throw out a voucher for the GMPP .028" composite head gasket if you decide not to go with a thin steel shim. Cheap and tough as nails. I run them in my mild supercharged 383 stroker motor. Putting out about 470 HP (390 to the wheels) and they've been bulletproof so far. In fact, I've blown 3 sets of pistons to smithereens (mostly do to my own tuning mistakes) but the head gaskets have never given me any problems. I also use AFR heads on my motor.

 

 

Which cam is that?

 

XR276HR (Part#: 08-423-8)

http://www.compcams.com/Cam_Specs/Ca...?csid=188&sb=2

 

That's what's in my current engine. Combined with 1.6 Pro Magnum rockers.
It will interesting to see your results.