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Old 03-09-2007, 02:45 AM
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SBC build questions/comments

I just recently purchased a SBC short block. http://paceperformance.com/index.asp...&ProdID=184534
I'm going to be using 64 cc Vortec heads.
GM composition head gasket .028 Gasket thickness
http://www.crateenginedepot.com/Comp...7-P588C49.aspx
With the above combo my compression works out to be 9.1:1
1st question:
would it be worth it to mill the heads to get it closer to 9.5:1?
And how much would I have to mill them to get them down to 60cc's, which would get me close. I'm guessing around 30 thou?

Not sure on the cam yet. It was going to be a lunati grind.
Advertised Duration IN/EX: 292/292
Duration @.050 IN/EX: 230/230
Gross Valve Lift IN/EX: .480"/.480"
Lobe Sep Angle / Intake Ctr Line: 109/107
RPM Range: 2000-6000
Which will be for sale, so p.m. if interested. I'll post in the classifieds later.
Changed my mind decided I want to go with a roller cam.
Something along the same rpm range or maybe slightly less, 1500-5800.
But, my heads are limited to 480 lift.
So my 2nd question is:
Has anyone done the Crane Cams valve spring swap to gain lift? And will this swap work with a roller set up?

Quote:
The GILBERT CHEVROLET solution is to use Crane Cam�s 10309-1 drop-in valve spring and retainer kit which is good for .550� lift with no machining.The installed height for this Crane Cams kit is taller and the lower part of the retainer is shorter.The �AVERAGE� clearance between the retainer and seal is .575� for this kit.
This combo will be going in a 64 Chevy Nova. Approx. weight 3000+/-, Th350 2500+ stall, 3.08 gears




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Old 03-09-2007, 09:41 AM
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9.0 versus 9.5

commonly accepted that:
each full point compression increase (ex:9.0 to 10.0) can yield "up to" 4% more fwhp at the hp peak "but" more often yields only 2% to 3%

400fwhp x .03 =12fwhp/2 (half a point higher)=6fwhp for 9.0 to 9.5= nothing in a 2800lb car at the rear wheels (6fwhp/2800lbs=.002% power to weight ratio gain before you subtract driveline loss)
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Old 03-09-2007, 10:37 AM
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Unless the heads are used and need to be surfaced to remove rust pitting or ensure flatness I would leave them alone and wait until you get the short block delivered so you can measure the distance from the top of the piston at TDC to the deck. Then select a head gasket with a compressed thickness that gives you .040" - .045" piston to head clearance. This is the quench distance and is VERY important in determining an engines tendency to detonate.

A short block with the piston .025" below the deck and a .039" compressed thickness gasket will have a piston to head distance of ~.064". While it will have a lower compression ratio than the same engine with a .025" piston to deck and a .015" gasket (.040" piston to head distance) the latter will be less detonation prone and timing sensitive. It'll also make more power and be easier to tune.

Do a search on "quench" or "squish" and you'll find some very detailed info on this.

I agree with Red65 completely. You're in the ball park on compression so the power difference won't be noticeable but getting the quench distance right will make a happier engine.

As far as a cam goes, what type of intake and carb do you plan on running? I think you made the right choice in moving to a roller and there are some nice street-able choices out there that will work well with your combo...

Last edited by SlowGTA; 03-09-2007 at 10:44 AM.
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Old 03-09-2007, 10:53 AM
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Why all the engine work, stall converter, and then the "3.08" gears? No offence, but that's like "pushing a rope uphill". You'll see more benefit and drivability in a street car with a gear change to something like 3.55 to 3.73. But, it's your car. BUTCH.
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Old 03-09-2007, 11:44 AM
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Quote:
Originally Posted by junior stocker
Why all the engine work, stall converter, and then the "3.08" gears? No offence, but that's like "pushing a rope uphill". You'll see more benefit and drivability in a street car with a gear change to something like 3.55 to 3.73. But, it's your car. BUTCH.
Maybe, maybe not. I know of Nova running almost this same set up, but with the lunati grind, and runs 12's in the quarter.

But at some point the 3.08's will be changed.
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Old 03-09-2007, 11:46 AM
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Quote:
Originally Posted by SlowGTA
Unless the heads are used and need to be surfaced to remove rust pitting or ensure flatness I would leave them alone and wait until you get the short block delivered so you can measure the distance from the top of the piston at TDC to the deck. Then select a head gasket with a compressed thickness that gives you .040" - .045" piston to head clearance. This is the quench distance and is VERY important in determining an engines tendency to detonate.

A short block with the piston .025" below the deck and a .039" compressed thickness gasket will have a piston to head distance of ~.064". While it will have a lower compression ratio than the same engine with a .025" piston to deck and a .015" gasket (.040" piston to head distance) the latter will be less detonation prone and timing sensitive. It'll also make more power and be easier to tune.

Do a search on "quench" or "squish" and you'll find some very detailed info on this.

I agree with Red65 completely. You're in the ball park on compression so the power difference won't be noticeable but getting the quench distance right will make a happier engine.

As far as a cam goes, what type of intake and carb do you plan on running? I think you made the right choice in moving to a roller and there are some nice street-able choices out there that will work well with your combo...
The intake is Edelbrock Vortec RPM Airgap. I have a holley 3310 750. But I can use anything. Or whatever is best suited to this combo.
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Old 03-09-2007, 12:12 PM
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Quote:
Originally Posted by SlowGTA
Unless the heads are used and need to be surfaced to remove rust pitting or ensure flatness I would leave them alone and wait until you get the short block delivered so you can measure the distance from the top of the piston at TDC to the deck. Then select a head gasket with a compressed thickness that gives you .040" - .045" piston to head clearance. This is the quench distance and is VERY important in determining an engines tendency to detonate.

A short block with the piston .025" below the deck and a .039" compressed thickness gasket will have a piston to head distance of ~.064". While it will have a lower compression ratio than the same engine with a .025" piston to deck and a .015" gasket (.040" piston to head distance) the latter will be less detonation prone and timing sensitive. It'll also make more power and be easier to tune.
So the gasket I'm going to use, which is the one GM uses on this same setup in various apps., will yeild .053 piston to head distance. Which is a little close to the .45. GM has a steel shim gasket that will get me to the magic number, but I'm affraid of it's durablility, or lack there of.
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Old 03-09-2007, 12:36 PM
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just to illustrate how bad the 3.08 gears hurt

12.8 sec ET/3000lb car =334fwhp = a RV cam in a 350?

http://www.speedworldmotorplex.com/calc.htm

Last edited by red65mustang; 03-09-2007 at 01:26 PM.
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Old 03-09-2007, 01:18 PM
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Quote:
Originally Posted by red65mustang
just to illustrate how bad the 3.08 gears hurt

12.8 sec ET/3000lb car =334fwhp = a RV cam in a 350?

http://www.speedworldmotorplex.com/calc.htm

Thanks for the info Red. But to be honest I'm not all that concerned with the gears at this time. OR the 1/4. When the $$$$$$ allows the gears will be changed.
But for now I just want to get a good engine combo with some decent power.
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Old 03-09-2007, 05:15 PM
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In my opinion, with 9.1:1 static c.r., you need to be in the 210-215 range for 0.050" tappet lift duration. The 230 cam will close the intake too late to make decent cylinder pressure. If you want a cam that will make power higher in the range, then you need more static c.r.

To make power to 6,000, you'll need c.r. between 9.5 and 10.75 and a roller cam something like this: Read the recommended compression ratio in the upper right hand corner of the card:
http://www.cranecams.com/?show=brows...tType=camshaft
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Old 03-09-2007, 05:55 PM
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Quote:
Originally Posted by techinspector1
In my opinion, with 9.1:1 static c.r., you need to be in the 210-215 range for 0.050" tappet lift duration. The 230 cam will close the intake too late to make decent cylinder pressure. If you want a cam that will make power higher in the range, then you need more static c.r.

To make power to 6,000, you'll need c.r. between 9.5 and 10.75 and a roller cam something like this: Read the recommended compression ratio in the upper right hand corner of the card:
http://www.cranecams.com/?show=brows...tType=camshaft
Thanks Tech.
The RPM range can be lower. I'm also switching from the 230 cam to a roller cam with less duration. Which was part of my original post. Refer to the first post.
Anyway, I haven't decided on which roller it will be. But that's Part of why I was asking should I mill the heads to get the compression up.
Also this isn't going to be used on the Drag strip very often More Street oriented.
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Old 03-09-2007, 06:15 PM
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Posted by NWayne:
"GM has a steel shim gasket that will get me to the magic number, but I'm affraid of it's durablility, or lack there of."

There are literally millions of small block Chevys all over the world still running with stock steel shim gaskets. There are probably better ways to do it today, but we used to spray 'em with aluminum paint, let it dry, spray on another heavy wet coat and bolt 'em on.

I see that Fel-Pro makes a rubber-coated shim gasket that would preclude the use of any other sealer.
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Old 03-09-2007, 06:42 PM
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Quote:
Originally Posted by techinspector1
Posted by NWayne:
"GM has a steel shim gasket that will get me to the magic number, but I'm affraid of it's durablility, or lack there of."

There are literally millions of small block Chevys all over the world still running with stock steel shim gaskets. There are probably better ways to do it today, but we used to spray 'em with aluminum paint, let it dry, spray on another heavy wet coat and bolt 'em on.

I see that Fel-Pro makes a rubber-coated shim gasket that would preclude the use of any other sealer.

Ok, so if I use the Fel-pro 1094's that gets me .040 piston to head distance. Which, if I understand correctly, gets me the right amount of quench I need? It also raises my compression to 9.35:1. So should I mill the heads to get them up to at least 9.5, or just let it be?
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Old 03-09-2007, 06:47 PM
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I'm gonna have to side with SlowGTA and advise against cutting the heads. These are thin castings in the first place and you need all the meat on them to retain any integrity.

But to answer your question, on 64 cc heads, 0.0065" to 0.007" equals one cc.
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Old 03-09-2007, 06:57 PM
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Quote:
Originally Posted by techinspector1
I'm gonna have to side with SlowGTA and advise against cutting the heads. These are thin castings in the first place and you need all the meat on them to retain any integrity.

But to answer your question, on 64 cc heads, 0.0065" to 0.007" equals one cc.
So .026"-.028"
Can't you safely mill around.030" off of the Vortecs?
If it's not necessary I'm not going to, just curious.

Now that I've solved one part of the equation, I need to find a roller cam for this app. And find out if the Crane Cam's 103091-1 valve spring will solve my Lift problem, and be compatible with a roller cam?
Anybody?
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